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Characterization of development and stem elongation of reed canary grass under northern conditions
Industrial Crops and Products 18 (2003) 155 /169 www.elsevier.com/locate/indcrop
Characterization of development and stem elongation of reed canary grass under northern conditions Mia Sahramaa a,*, Lauri Jauhiainen b a
MTT Agrifood Research Finland, Plant Production Research, FIN-31600 Jokioinen, Finland b MTT Agrifood Research Finland, Research Services, FIN-31600 Jokioinen, Finland
Received 12 August 2002; received in revised form 7 March 2003; accepted 21 March 2003
Abstract Reed canary grass (Phalaris arundinacea L.) is a potential crop for energy and paper production and might also be a useful forage crop under northern growing conditions. Knowledge of phenological traits is needed to adjust the production system according to various end-use requirements. This study aimed at describing variation in plant development, plant height and stem elongation among local and elite populations of reed canary grass. Field experiments were carried out between 1994 and 1997 in Finland. Six developmental stages were determined and plant height was measured at weekly intervals. Differences among groups of reed canary grass were statistically significant. Cultivars developed earlier than local groups, although they needed 3 days more for seed ripening. They were also taller than local populations at time of seed ripening. However, local groups were slightly taller than cultivars during early stages of development. At time of seed ripening some local populations were taller than elite material. Their places of origin could represent potential collection areas for populations showing increased plant height. Seed ripened approximately 95 days from the beginning of the growing season, when the temperature sum was 737 8C days of degree. At time of seed ripening 98% of maximum plant height was reached. A long latent period from reaching maximum plant height to harvest in the following spring is justified for non-food production because biomass continues to increase markedly after seed ripening. Stem elongation was fastest around flag leaf emergence and appearance of inflorescences. Knowledge of the fixed stage of plant development and plant height at each stage provides possibilities to adjust the production system and harvest time according to different end-uses: forage, non-food, and seed production. Information from this study will serve as a basis for further investigations and could be used in breeding reed canary grass. # 2003 Elsevier Science B.V. All rights reserved. Keywords: Local populations; Non-food production; Phenology; Plant height; Variation
1. Introduction
* Corresponding author. Tel.: /358-3-4188-2452; fax: / 358-3-4188-2437. E-mail address: [email protected] (M. Sahramaa).
Reed canary grass (hereafter RCG) has been grown for forage for over a hundred years, especially in North America. In Finland the first forage trials of RCG were documented in 1891 in
0926-6690/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0926-6690(03)00044-X
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Hernia¨inen, south Ha¨me (Essen von, 1913). Although most commonly grown as forage, RCG has been shown to be a potential crop for energy and paper pulp production under northern growing conditions (Landstro¨m et al., 1996; Pahkala, 1997). Although RCG is native to Finland, its cultivation has been limited to date. Currently over 1000 ha of RCG are cultivated for forage and bioenergy at high latitudes in Finland and in Sweden (Leinonen et al., 2000). Foreign forage cultivars are grown for both purposes because no domestic cultivars are available. RCG is preferred in Finland for non-food cultivation because it produces substantial biomass (6 /8 t ha1) under northern, long day conditions (Saijonkari-Pahkala, 2001), and in a delayed harvest system it may use the entire growing season for increasing biomass. At spring harvest the quality of biomass is also better for non-food purposes. Furthermore, RCG has an expansive rhizome and root system (Ka¨tterer and Andre´n, 1999), which enables efficient use of spring moisture for new growth after harvest and good drought tolerance. Non-food cultivation of RCG is also environmentally sound, because RCG has a high storage capacity root system for fertilizer nutrients and only small amounts of N are removed from the field with harvested biomass (Partala et al., 2001). This results in low demand for fertilizers after harvest (Partala et al., 2001). The recommended fertilizer application rate is only 60 /80 kg ha1 on clay soil and about 50 kg ha 1 on an organic soil (Pahkala et al., 2002). Information on the agronomic traits of RCG is needed to adjust both the feed and non-food cultivation practises to northern growing conditions and to evaluate the breeding value of the local material. Knowledge on the extent and nature of variation for agronomic traits is a basic requirement of breeding programmes. Breeding for non-food purposes started in 1993 in Finland with an extensive collection of local populations from all over the country (Fig. 1). The aim of this study, was to evaluate variation in plant development, plant height and stem elongation of local populations and elite material of RCG. Earlier studies from North America and Norway showed that RCG varies for these traits
(Baltensperger and Kalton, 1958; Berg, 1980; Østrem, 1988). Canadian RCG collections, including populations from natural stands, showed significant variation for inflorescence emergence and plant height. High broad-sense heritabilities of 0.94 (inflorescence emergence) and 0.54 (plant height) indicate the possibilities of effective selection in breeding programmes (Sachs and Coulman, 1983). The results of this experiment will furnish new information on variation of phenological traits of RCG that might be used for evaluation of management treatments and for agronomic applications including crop-growth modelling and crop zonation.
2. Material and methods 2.1. Field experiment A trial was conducted in 1994/1997 at MTT Agrifood Research Finland in Jokioinen (60849?N) incorporating 53 wild RCG populations from different regions of Finland; eight cultivars and 14 breeding lines (Fig. 1). The experiment was set up in a randomized complete block design with four replicates. Each plot consisted of 30 individual plants, which were grown from seed in a pot in a greenhouse. Plants were spaced in the field at 25 cm to form a plot of 1.25 m2. The distance between each plot was 2.5 m. The trial was established on an organic soil (replicates 1 and 2) on 29 /30 June 1994 and on clay soil (replicates 3 and 4) on 4 /7 July 1994. Nitrogen fertilizer was applied with a pneumatic applicator (Tume P12, Finland) in the year of establishment at 50 kg N ha1 on the organic soil (trade name TyppirikasY; N:P:K at 20:4:8) and 70 kg N ha1 on the clay soil. Because precipitation was only 1 mm in July 1994, pots were irrigated until the plants were fully established. Harvest was done each year in May by removing the aerial biomass before onset of the new growing season. Nitrogen fertilizer at 40 /70 kg N ha1 was given after the spring harvest. No herbicides were used. Weather data from 1994 to 1997, including accumulated temperature sum at Jokioinen, are shown in Table 1.
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Fig. 1. Origins of the cultivars (8) and breeding lines (14) and geographic origins of the wild populations (53) of reed canary grass included in an experiment conducted at Jokioinen, Finland in 1994 /1997.
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158
Table 1 Deviations from the long-term (1961 /1990) average of monthly air temperature (8C), monthly precipitation (mm) and accumulated temperature sum (8C dd) at Jokioinen (May to September), Finland, in 1994 /1997 May
June
July
August
September
Mean air temperature (8C) 1961 /1990 1994 1995 1996 1997
9.4 /1.6 /0.7 /0.6 /1.7
14.3 /2.2 /2.4 /1.2 /1.8
15.8 /3.2 /0.5 /1.9 /2.0
14.2 /0.9 /0.9 /2.8 /3.6
9.4 /0.6 /0.9 /1.1 /0.6
Precipitation (mm) 1961 /1990 1994 1995 1996 1997
35 /1 /52 /29 /20
47 /19 /74 /6 /55
80 /79 /27 /55 /61
83 /29 /18 /69 /39
65 /40 /21 /45 /13
414 /71 /90 /64 /10
745 /32 /76 /120 /73
1033 /59 /104 /35 /184
1164 /79 /130 /66 /203
Accumulated temperature sum (8C dd)a 1961 /1990 136 1994 /7 1995 /15 1996 /29 1997 /47 a
From the beginning of the growing season.
2.2. Phenology Six developmental stages were determined for RCG and the requirement for effective temperature sum (8C dd, days of degree) was calculated at each stage from the beginning of the growing season (Fig. 2). According to the Finnish Meteorological Institute, the thermal growing season was considered to have begun once the mean daily temperature exceeded /5 8C. Accumulated temperature sum was recorded each day, when temperature was above /5 8C during the growing season. Different stages of development were determined visually for each plot and defined as follows: (1) flag leaf emerged, when flag leaf ligule was visible on 5% of the plants; (2) inflorescence visible, when upper 1/2 cm of the inflorescence was visible on 5% of the plants; (3) inflorescence emerged, when stem below inflorescence was visible on 5% of the plants; (4) beginning of anthesis, when branches of the inflorescence were open and anthers were visible on 5% of the plants; (5) completed anthesis, when branches of the inflorescence were closed along the rachis on
80% of the plants; (6) seed ripened, when inflorescence and stem below it had turned yellow, seeds were fully matured and shattering had started from the top of the inflorescence on 80% of the plants. Seed of RCG matured from top of the panicle downward and first seed matured shattered before most of the crop was ready for harvest. The first two stages were measured in 1995 and 1996, whereas the rest of the measurements were done in 1995 /1997. Thus, most emphasis was directed to analysis of data from 1995 and 1996.
2.3. Plant height In 1994, individual plant height was measured in each plot beginning on 16th of August. As the trial was established less than 2 months earlier, plants had only few panicles at the time of height measurement. In the subsequent years (1995 /97) plant height was measured from soil surface to the top of the panicle of each of three plants in each plot. In 1995 plant heights were measured 10 times at 1-week intervals starting on 23rd May until 14th
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159
Fig. 2. Description for stages of development of reed canary grass in an experiment conducted at Jokioinen, Finland, in 1994 /1997. (Drawing: Helena Ihama¨ki).
July and the last two measurements were done on 1st September and 13th November. In 1996 the height was measured eight times beginning on 30th May until 14th August. The last measurement was done on 11th of October. In 1997, plant height was measured three times: 30th June, 21st July and 1st September. 2.4. Statistical methods All variables were measured more than once during the study. Typically, the repeated measurements were correlated. Correlation was taken into account fitting several covariance structures for repeated-measures. Structures were compared using Akaike’s information criterion and likelihood ratio-test when possible (Wolfinger, 1996). Response variable, yijkl , was analyzed using following model: Yijkl blockl pop(group)ij errorB timek blocktimekl timepop(group)ijk errorW ;
where pop(group)ij , timek and time /pop(group)ijk were fixed effects of population nested group, measurement time and their interaction, respectively. Blockl was a random effect of block while block /timekl was the error term for main-effect of time. ErrorB and errorW were between and within plot errors. All the four previous effects were assumed to be normally distributed. This model and the assumptions on which it is based were presented by Gumpertz and Brownie (1993). In 1994 measurements were done from each plant in a plot and data was analysed using following model: Yijl blockl pop(group)ij errorW errorB Stem elongation of plants was analyzed fitting logistic growth curves. Plant height at the beginning of the different development stage was not measured, but temperature sum at the beginning of different development stage was known for each plot. Therefore, the logistic growth curve was fitted separately for each plot and according to growth curve parameters estimates and tempera-
160
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ture sums the absolute and relative plant height at the different development stages were calculated for each plots. Data for 1995 and 1996 were analyzed separately. The model was: heightijk
b1i ujk o ijk ; 1 exp((xijk b2i )=b3i )
where xijk was a correspondence temperature sum of jth population in ith group at k th measurement time. b1i , b2i and b3i were fixed-effect parameters for maximum height, inflection point (i.e. the point in a curve at which it changes direction from concave to convex to) and slope, respectively. Ujk and oijk were normally distributed random-effect parameters for plot-to-plot variation of maximum height and residual variation, respectively. The assumptions of the models were checked using graphical methods: a box-plot and plots of residuals (Neter et al., 1996). Normality was achieved after arcsine-square root transformation of the data. The parameters of the models were estimated by means of the REML estimation method, using the SAS system for Windows, release 8.2, and MIXED, NLMIXED and CORR procedures. Correlations between variables were measured using Pearson correlation coefficient.
3. Results 3.1. Stages of development The flag leaf emerged approximately 46 days from the beginning of the growing season, when the approximate temperature sum was 266 8C dd. This was 36% of the temperature sum required for seed ripening (Table 2). Inflorescences became visible about 51 days from the beginning of the growing season, when the temperature sum was 305 8C dd (/39 dd). They emerged 58 days from the beginning of the growing season, when the temperature sum was 373 8C dd (/68 dd). Anthesis began 65 days from the beginning of the growing season at 434 8C dd (/62 dd) and was completed 81 days from the beginning of the growing season at 589 8C dd (/155 dd). Anthesis
took approximately 16 days and seed ripening 14 days and lasted much longer than earlier stages. Seed ripened within 95 days from the beginning of the growing season, when the approximate temperature sum was 737 8C dd (/148). Recorded stages of development were reached within 3 months. Flag leaves developed in June and inflorescences emerged in June or early July, depending on the year. In 1995, anthesis began as early as 15th to 26th June, whereas in 1996 it started on 5th July and in 1997 on 25th June. Furthermore, seed ripening took place from the middle of July until mid August, depending on the year. The difference in temperature sum requirement among groups of RCG was significant at each stage of development in 1995 and 1996. Cultivars and breeding lines had the lowest temperature sum requirement. Hence, they reached each stage of development earlier and differed significantly from local groups. Cultivars needed approximately 239 8C dd for flag leaf development (43 days), 275 8C dd for the inflorescence to become visible (48 days), 326 8C dd for inflorescence emergence (54 days), 398 8C dd for anthesis to begin (61 days), 541 8C dd for complete anthesis (76 days) and 697 8C dd for seed ripening (92 days). Inflorescences of local populations emerged approximately 6 days later, they completed anthesis 7 days later and their seeds ripened 4 days later than for cultivars. Plants from groups VIII and X from northern Finland were the latest maturing and they differed significantly from other groups when tested in 1995. The most early ripening populations within the local groups were RH2, RH4, RH13, RH22, RH32, RH33, RH47 and RH49 (Table 3), while the latest maturing populations were RH10, RH81, RH78, RH60 and RH24. Cultivars, breeding lines and the northernmost group X had the lowest temperature sum requirement from flag leaf emergence to the beginning of anthesis, while groups IV, VI and VIII had the highest. Consequently, cultivars and breeding lines needed 2 days less for reaching anthesis compared with local groups. Groups VII and IX had the highest temperature sum requirement for anthesis. However, the situation was vice versa from complete anthesis until seed ripening, when cultivars needed 3 days more for maturing than local
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161
Table 2 Temperature sum requirement (8C dd) of reed canary grass at different developmental stages (1 /6) according to provenance (I /X) in an experiment conducted at Jokioinen, Finland in 1995 /1996 1/4
5/6
1
2
3
4
5
1995 I II III IV V VI VII VIII IX X
238 248 276bc 271b 269ab 262a 276bc 290d 261a 281cd
263 273 298cd 300d 291abc 289ab 297bcd 319 283a 304d
318 345 388cd 382bd 375a 376ab 390c 402 380abc 387cd
382 398 424ab 432c 423a 440de 435ce 457 414a 434bcd
507 523 561ab 561ab 555a 580d 579cd 587d 568bc 554a
661a 666a 709b 712b 688 707b 705b 727d 714bc 725cd
145a 149ab 149ab 161cd 153abc 178e 159bcd 168de 154abc 153abc
125ab 126ab 137cde 129abc 132bcd 140de 143ef 129abc 154f 120a
154d 142c 148cd 151d 133ab 127a 126a 140bc 146cd 171
267
292
374
424
558
701
157
134
144
239 249 267bc 266b 272cd 260a 276d 285e 264ab 278de
286 296 326cd 328de 322bc 310a 323bcd 341f 315ab 336ef
333 346 382d 379cd 376bc 366a 382d 394e 368ab 387de
414 425 451ab 449ab 452b 452b 451ab 461 443a 449ab
575 589 629ab 624a 625a 635bc 640c 635bc 625a 636bc
733 740 785cd 782abcd 779abc 777a 784bcd 798 776ab 788d
175ab 176ab 183cd 183d 180bcd 192 175abc 175ab 179abcd 171a
161a 164a 178bcd 175bc 173b 183de 189e 174bc 183cde 187de
157cd 150be 156ce 158cd 154ce 142a 144ab 163d 150abc 152bc
266
318
371
445
621
774
179
177
153
Mean 1996 I II III IV V VI VII VIII IX X Mean
6
4/5
Group
(1) Flag leaf emerged; (2) inflorescence visible; (3) Inflorescence emerged; (4) beginning of anthesis; (5) completed anthesis; and (6) seed ripened. Between group comparisons: estimated means with the same uppercase letters were not significantly different (P /0.05).
groups. Groups VI and VII from East Finland had the lowest temperature sum requirement for maturing and cultivars and group X the highest. Statistically significant differences among groups are presented in Table 2. 3.2. Plant height Plant height was measured for the first time only 6 weeks after establishment in 1994, when the average plant height was 29 cm, ranging from 14 to 39 cm, depending on group (data not shown). Plant height was greatest in cultivars and least in the northernmost group X. The standard deviation within population was 3.4 /5.7 cm and between population 3.9 and 6.2 cm, when plant height was measured from each plant in a plot.
In 1995 and 1996, measurements of plant height began in May when plants were approximately 22/30 cm tall. Plant height was estimated at each stage of development and also the increment between stages was determined (Table 4). The average stem elongation was less than half (76 cm) of the estimated maximum plant height at the time of flag leaf emergence and more than half (94 cm) from flag leaf emergence to seed ripening. The average plant height was 84 cm at the time of the inflorescence becoming visible in 1995 and 96 cm in 1996. Consequently, at inflorescence emergence the average plant height was almost the same in both years at 116 cm. At the beginning of anthesis average plant height was 135 cm and 79% of the maximum height was reached. At complete anthesis, plant height was 161 cm and 94% of the
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162
Table 3 Seed ripening (days from the beginning of growing season) and plant height (cm) at seed ripening stage of reed canary grass populations in an experiment conducted at Jokioinen, Finland in 1995 /1996 Seed ripening
Seed ripening
Population
1995
Population
SWJ91 SWG63 SWD33 SW5 SW2 Pervenets Motterwitzer SW4 Jo0510 Venturea Venture Barphal Vantage SWB17 SW3 RH4 SWA5 RH2 RH49 RH13
88 88 88 88 88 88 88 88 88 89 89 89 89 89 89 89 90 90 91 91
SWG63 SWB17 SW2 Pervenets SWJ91 SW5 SW4 Motterwitzer Barphal Venture Vantage SWA5 RH47 Venturea RH22 Palaton Jo0510 SW3 SWD33 RH32
RH34 RH30 RH85 RH73 SW91067 RH78 RH60 RH51 RH81 RH10
96 96 97 97 97 97 97 97 98 98
RH30 RH1 RH86 RH80 RH60 RH78 RH46 RH24 RH10 RH81
a
Plant height 1996 93 94 94 94 94 95 95 95 95 95 95 95 95 96 96 96 96 97 97 97 100 100 101 101 101 102 102 102 104 105
Plant height
Population
1995
Population
1996
SW91066 RH79 RH85 Pervenets RH30 Vantage SWG63 RH78 SW2 SW91065 RH33 Jo0510 RH1 RH36 RH47 RH26B SWA5 SWD33 RH77 RH80
196 196 195 195 194 194 193 192 191 191 190 189 189 187 187 187 186 186 186 185
Vantage RH1 RH47 SW91067 RH78 SW91066 SW91065 SWD33 Rival Palaton SWA5 RH83 SW2 Venture Barphal RH85 SW3 RH33 Venturea SW4
193 191 190 188 188 187 187 187 185 185 184 184 184 184 183 182 182 182 182 182
RH15 RH20 RH10 RH32 RH4 RH75 SW1 RH89 RH90 RH109
165 164 163 163 162 161 158 158 154 153
RH52 RH24 RH20 RH17 RH60 RH48 SW1 RH90 RH89 RH109
149 149 148 147 147 145 135 128 128 119
Seed of cultivar Venture bulked once in the field in Jokioinen.
maximum height was reached. At the time of seed ripening plant height was 176 cm in 1995 and 163 cm in 1996. At that time 98% of the maximum plant height was reached. During the six developmental stages studied, stem elongation was most enhanced (26 cm, 15%) between the inflorescence becoming visible and inflorescence emergence as well as during anthesis. During maturation stem elongation was only 5% (9 cm). In 1997, average plant height was 140 cm, ranging from 118 to 148 cm, depending on the group. It was highest with cultivars and lowest with the northernmost group
X (data not shown). Plant height was measured between complete anthesis and seed ripening in mid July (689 8C dd), after which it did not increase significantly. The difference in plant height (cm) and in relative plant height (% of the estimated maximum plant height) was significant among the groups at each developmental stage (Table 4). Local groups were slightly taller than cultivars before emergence of inflorescences. The difference in plant height was most pronounced in 1995 with groups VIII and IX from northern Finland, which were 7 /13
Table 4 Plant height (cm) and relative stem elongation (%) of the maximum height of reed canary grass according to provenance (I /X) at different developmental stages (1 /6) in an experiment conducted at Jokioinen, Finland in 1995 /1996
1995 I II III IV V VI VII VIII IX X Mean 1996 I II III IV V VI VII VIII IX X Mean
1
2
3
cm
%
cm
%
70ab 67a 74cd 76d 72bc 73bc 74cd 80e 81e 72abc
37ab 36a 41de 42e 40cd 39bc 41cde 42e 45f 45f
83bc 79a 82bc 88d 80ab 84c 82abc 91d 89d 79ab
74
41
72e 77bc 75cd 77bc 75cd 77bc 79b 82a 79ab 72de 77
4
5
6
1/4
cm
%
cm
%
cm
%
cm
%
cm
44a 42 46a 48b 44a 44a 45a 48b 49b 49b
111a 114b 118c 120cd 112ab 118c 118c 123de 124e 106
59a 60a 65d 66d 63b 63bc 66d 65cd 69e 66de
139ab 137bc 130de 136c 129de 141a 133cd 141a 135bcd 119
75c 73ab 72ab 75c 72a 75c 74bc 75c 75c 75bc
172a 171a 162cd 165c 159d 171a 164c 169ab 165bc 142
92f 91cde 90ac 90bcd 89a 91ef 91ef 90ab 92fd 89ab
184a 184a 175bc 177b 173c 182a 174bc 182a 176bc 155
98 98a 97abc 97bd 96e 97bcd 97bdf 96cef 97ad 97adef
84
46
116
64
134
74
164
91
176
39 43a 46bc 47cd 46cd 44ab 48d 47cd 51 57
96c 100b 97c 100ab 92 96c 96c 103a 98bc 85
52 56a 59c 61d 57ab 56a 58bc 59c 63d 67
120bc 123a 116d 118cd 111 117d 116d 121ab 115d 95
65 69a 71bc 72cd 68a 68a 71bc 69ab 74de 75e
152a 151a 135cd 137c 131e 142b 135cd 140b 133de 105
83cd 84ef 82bc 83de 81ab 83cd 82cd 80a 85f 83cde
178 174 157bc 158b 155cd 166a 159b 165a 151d 121
97de 97e 96bc 96c 95a 96cd 96cde 95a 97de 95ab
47
96
59
115
70
136
83
158
96
4/5
5 /6
%
cm
%
cm
%
70a 69a 57cd 60bc 57cd 68a 60bc 61b 54d 48
38d 37d 31abc 33bc 32abc 36d 33c 33ac 30ab 30a
32ab 34a 31abc 28c 31bc 30bc 31abc 28c 30abc 23
17d 18d 18bd 15abc 17be 16bd 17de 15a 17cde 14a
12a 13a 13a 13a 13a 11a 10a 14a 11a 13a
6a 7ac 7ac 7ac 7ad 6d 6d 6bcd 5cd 8ab
97
60
33
30
16
12
7
183 179 163b 163b 161b 170a 163b 172a 155 125
99a 99a 99bc 99b 99c 99b 99b 99c 99ab 98c
81 74 59ab 60a 56cd 66 57bcd 57bc 54d 33
44 41 36bc 36c 35a 39 34ab 33 34abc 26
26a 23c 23bc 21cd 23abc 24abc 24abc 26ab 19de 15e
14d 13bc 14bcd 13b 14bc 13bcd 14cd 15bc 12abc 12a
5a 5b 5a 5a 6a 5a 4a 7a 4a 4a
2abc 2bcd 3abcd 3bcd 4ab 3d 3cd 4a 2cd 3bcd
163
99
60
36
22
13
5
3
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Group
(1) Flag leaf emerged; (2) inflorescence visible; (3) inflorescence emerged; (4) beginning of anthesis; (5) completed anthesis; and (6) seed ripened. Between group comparisons: estimated means with the same uppercase letters were not significantly different (P /0.05).
163
164
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cm taller than cultivars before the beginning of anthesis. They differed significantly from plants in other groups, except those in group IV. They were also among the tallest groups in 1996. At flag leaf emergence, plants in local groups reached more of the estimated maximum height than cultivars and breeding lines. The difference was most pronounced with the northernmost groups IX and X until inflorescence emergence. They differed significantly from other groups in most cases. From the beginning of anthesis, the difference in relative plant height among groups was small, although plants of cultivars and breeding lines were taller than those of local groups. At seed ripening they were approximately 16 cm taller than those of local groups, being 183 cm on average. Groups VI and VIII contained the tallest plants among the local groups at seed ripening and they differed significantly from other groups, except cultivars and breeding lines in 1995, and from all other groups in 1996. Group X contained the shortest plants and it differed significantly from the other groups. However, at seed ripening plants of many local populations were among the tallest (in ascending order) (Table 3): Vantage, SW91066, RH78, RH1, SW91065, RH85, RH47, RH79, RH30 and SW2. The shortest populations were RH89, RH90 and RH109 from Lapland and SW1 from Sweden. Considering stem elongation (cm) and relative stem elongation (%) between stages of development, groups differed significantly from each other (Table 4). Cultivars exhibited the highest rate of stem elongation from flag leaf development until the beginning of anthesis, although they were not the tallest group before anthesis. At that time cultivars differed significantly from other groups except breeding lines and group VI in 1995, and in 1996 they differed from all other groups. Relative stem elongation in the same period was highest for cultivars and breeding lines and they differed significantly from other groups. The northernmost group X differed significantly from other groups through containing plants with the lowest rate of stem elongation and also the lowest relative stem elongation. Group X plants had the lowest stem elongation during anthesis and almost all groups differed significantly from it. Group IX was also
characterised by low stem elongation and in 1996 all groups except group IV differed significantly from it. The differences between groups, both in stem elongation and in relative stem elongation, were minor from complete anthesis to seed ripening. 3.3. Parameters for stem elongation The average stem elongation was highest at inflection point, when the requirement for effective temperature sum was approximately 307 8C dd in 1995 and 276 8C dd in 1996 (Table 5). At that point the curve for stem elongation changed from concave to convex (Fig. 3). In 1995, the average stem elongation was 90 cm at the inflection point and 82 cm in 1996. In 1995, the inflection point was achieved around inflorescence emergence and in 1996 after flag leaf emergence. The difference in temperature sum requirement at inflection point was significant among groups. In 1995, cultivars and plants of group IX from northern Finland reached the inflection point earliest, indicating fast stem elongation until that point. They also differed significantly from other groups. In 1996, plants of the northernmost groups (IX, X) reached the inflection point first, differing significantly from all other groups, including cultivars. In both years group VIII plants were the last to reach the inflection point and differed significantly from plants of other groups except group VII in 1995 and all groups in 1996. Estimated maximum plant height was 181 cm in 1995 and 166 cm in 1996 (Table 5). Cultivars, breeding lines and plants of local group VIII had the highest maximum plant height and the northernmost group X the lowest, which also differed significantly from other groups. The maximum difference was 47 cm between cultivars and group X in 1996. Parameter ‘slope’ described the intensity of stem elongation and high values indicated gentle elongation during a long time period, whereas low values indicated sharp, rapid growth. Cultivars and breeding lines differed significantly from other groups through having the steepest growth, whereas plants from groups VIII and X had the highest values for ‘slope’ and showed more gentle growth.
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165
Table 5 Parameters for stem elongation of reed canary grass according to provenance (I /X) in an experiment conducted at Jokioinen, Finland, in 1995 /1996 Maximum value (b1), cm
Inflection point (b2), dd
Slope (b3)
Group
1995
1996
1995
1996
1995
1996
I II III IV V VI VII VIII IX X Mean
187ab 188a 179cd 182abcd 178d 186abc 180bcd 189a 180abcd 159 181
184a 179ab 164e 164e 163e 172cd 165de 175bc 155e 137 166
285a 302b 314c 307bc 314c 311c 316cd 328d 286a 305bc 307
278b 272c 283ab 277bc 287a 282ab 285ab 297 260d 243d 276
91a 96a 110b 113b 113bc 112b 111bc 121c 116bc 117bc 110
87a 92a 109b 107b 113bc 109b 110bc 118cd 106b 131d 108
Between group comparisons: estimated means with the same uppercase letters were not significantly different (P /0.05).
Considerable variation was found among groups according to provenance in stem elongation in 1995 and 1996 (Fig. 3). Cultivars were tallest and reached the maximum plant height sooner than plants of the other groups. Plants of local group VIII were tall, but elongation rate was low. Group IX plants were among the tallest during early development, but maximum plant height was relatively low. The northernmost group X also contained tall plants during early development, especially in 1996, but they reached the lowest maximum plant height.
4. Discussion 4.1. Factors contributing to plant development and height In this study, both anthesis and seed ripening of RCG plant stands lasted for about 2 weeks, indicating large variation in development within and among panicles and individual plants. This is quite typical for other forage grasses: flowering may take place over several weeks (Fairey and Hampton, 1997). Uneven seed ripening of RCG
Fig. 3. Stem elongation (cm) of reed canary grass according to provenance (I-X) as accumulated temperature sum (8C dd) from the beginning of growing season in an experiment conducted at Jokioinen, Finland, in 1995 /1996.
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results in seed losses due to shattering at late harvest and possibly results in decreased germination following early harvest (Sahramaa and Ho¨mmo¨, 2000; Sahramaa et al., 2003a). This has adverse consequences for commercial seed production. In this study, cultivars and breeding lines had 2 days shorter flowering period than plants of local groups, but cultivars needed 3 days more to mature. This is supported by the earlier finding that the most favourable harvest time for cultivars (16 /18 days after anthesis) is somewhat later than that for the local groups (11 /13 days after anthesis) (Sahramaa et al., 2003a). For RCG clones of cultivar ‘Vantage’ tested in Iowa, USA, the pollen shedding period lasted approximately 12 /21 days, depending on the clone (Rincker et al., 1977). In another study estimated genotypic variation among RCG seed lots was 48% (Baltensperger and Kalton, 1958). Temperature sum requirement of RCG was about 737 dd for seed ripening and it occurred from the middle of July until mid August depending on year. This was similar to that recorded for other common forage grasses grown in Finland (Enroth et al., 1997). RCG plant height was high, although it decreased over the study period. During 3 years the average plant height was 160 cm at the seed ripening stage. This was in accordance with results from other studies, where average plant height of RCG collections was 159 cm in Canada in 1979 (Sachs and Coulman, 1983) and 165 cm with RCG cultivar Venture in Finland during 1994/1998 (Saijonkari-Pahkala, 2001). The Canadian study also showed that populations from natural stands were slightly higher than selected material. In this study, groups of cultivars and breeding lines were taller than local groups as a whole, but single populations within a local group, especially from East and North Ostrobothnia (VI, VIII) were taller than cultivars. According to stem elongation parameters determined for the whole growing period, stem elongation was fastest in mid June, around flag leaf emergence and the time of the inflorescence becoming visible. Thereafter the elongation rate started to decrease. Plant height still increased about 15% during inflorescence emergence and anthesis. Thus, this finding agrees with the established finding that flower formation
of grasses is accompanied by rapid elongation of the upper internodes (Langer, 1979). Results from this study showed that RCG reached 98% of its maximum height by seed ripening, after which stem elongation was negligible. Although the time from reaching maximum plant height till harvest carried out the following spring was long, it is well justified for non-food production, because biomass yield increases substantially after seed ripening. Biomass drying is by this means obviated and the quality of raw material is improved. Spring harvested RCG produced on average 6/8 t ha 1 biomass during a 6-year period in Finland, which was about 2 t ha1 higher on average than at autumn harvest (Pahkala and Pihala, 2000). However, in the 1st year after establishment biomass yield was higher at autumn than at spring harvest (Landstro¨m et al., 1996; Ka¨tterer et al., 1998; Saijonkari-Pahkala, 2001). One reason is probably that the slow and irregular germination of RCG seed resulted in a thin plant stand in the 1st year, which was more vulnerable to winter losses than were older leys. Lodging and unfavourable weather conditions have also been suggested as a reason for winter losses (Ka¨tterer et al., 1998; Landstro¨m et al., 1996). However, autumn and spring harvest were not compared or neither winter losses studied, but plant stands were generally well preserved after winter during 4 years of the experiment and DM yield increased at every spring harvest (Sahramaa et al., 2003b). The correlation between plant height and DM yield was statistically significant in this study. However, higher DM yield at spring harvest indicated that plant height was only one trait among several contributing to the total biomass yield. Leafiness, tillering ability and nodal branching were also of great importance. However, information on plant height at different developmental stages is useful in forage production. According to Marten and Donker (1968) RCG should be grazed when it is from 15 to 60 cm tall. If RCG is used for hay or silage, it is recommended to be cut prior to inflorescence emergence (Marten and Heath, 1973). Furthermore, the stage of development at cutting affects the total DM yield of RCG. In a Canadian study, the stand was
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cut three times and DM yield increased if the first cut was done at late maturity (Lawrence and Ashford, 1968). In North America RCG is commonly grown as a forage crop and has aggressively invaded wetland areas, displacing native communities (Merigliano and Lesica, 1998; Gifford et al., 2002). Although RCG is a native species to Finland, its cultivation has been minor to date. Therefore, possible risks associated with cultivation, including invasive character, should be considered before its cultivation takes place on a large-scale. 4.2. Variation among groups of RCG Results from this study showed that there were marked differences in temperature sum requirement at different developmental stages, and in plant height and stem elongation rate among the populations of RCG. Groups of wild populations differed from each other in every trait measured, indicating variation according to provenance. Some variation among populations was expected as RCG is a cross-pollinating species, showing greater variability than many of the self-pollinating species. Cultivars and breeding lines differed from other groups through having the lowest temperature sum requirement at each developmental stage, greatest plant height at seed ripening stage and highest stem elongation rate reflecting the positive impact of breeding. Inflorescences of cultivars emerged approximately 6 days earlier compared with those of local populations and reached complete anthesis 7 days earlier. Furthermore, cultivars ripened 4 days earlier than wild populations. In the study of Berg (1980), vegetatively propagated cultivars also emerged 5 /10 days earlier than Norwegian local populations of RCG. The latitude at which the Norwegian experiment was done was similar to that for this study (above 608N). Although cultivars were the first group to mature, they needed 3 days more than local groups for seed ripening. Plants of the easternmost groups (VI, VII) had a particularly short maturing period. One reason for that might be that wild germplasm tends to secure seed survival with better germination ability before shattering by enhancing the rate
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of maturity. The longer seed ripening period required by cultivars might also result from higher thousand seed weight sought during breeding (Sahramaa et al., 2003a). Earliness was also associated with higher number of panicles in RCG and Festuca arundinacea (Schreb.) (Berg, 1980; Nguyen and Sleper, 1983). High number of stems would be an advantage in non-food production as well as in seed production of RCG. Correlation between seed ripening and panicle number of RCG was found to be weak (/0.11, P B/0.10) in a previous study (Sahramaa et al., 2003b), but high seed yield was clearly associated with many panicles per unit area (Sahramaa et al., 2003a). Cultivars and breeding lines were shorter before anthesis than plants of some of the local groups, especially those from North Ostrobothnia and Kainuu (VIII, IX). The northernmost groups reached the highest rate of growth earlier than other groups, but maximum plant height reached was lowest and rate of elongation low, especially for plants of group X. The northernmost groups were adapted to a short growing season and therefore had higher rates of stem elongation at early growth stages. However, in general, they had lower stem elongation potential and no ability to benefit from the longer growing season of South Finland. These findings were similar to those of Berg (1980) with local Norwegian populations, which grew fast in early summer and stopped growing earlier in the autumn compared with American RCG. Although cultivars were inferior in plant height to local groups during early development, they reached the point of highest stem elongation early, were ultimately taller and reached the maximum height fastest. At seed ripening, groups from North Ostrobothnia (VIII) and East Finland (VI) were tallest among the local groups. Thus, those places could be potential collection areas for tall genotypes. Although group VIII from North Ostrobothnia had high maximum plant height, it had a low stem elongation rate and it was the most late maturing. The northernmost groups IX and X were shortest and group X was among the latest in maturing. The earliest maturing local populations were found from southern parts of Finland, especially within the group V,
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which was nearest to the experimental site, indicating adaptation to local conditions. Promising material from the collections in this study has been selected for further breeding and seed from local populations has been stored in the Nordic Gene Bank.
Lahti and Matti Matilainen at MTT Plant Production Research for their valuable contribution. Professor Pirjo Peltonen-Sainio is warmly thanked for her comments on the manuscript.
References 5. Conclusion Local RCG populations and selected material are characterised by considerable variation in plant development, plant height and stem elongation rate, which creates a basis for improving those traits through plant breeding. According to results of this study, cultivars and breeding lines were the earliest maturing and they should be used primarily in breeding for earliness in Finland. However, North Ostrobothnia and East Finland could be potential areas for collecting tall populations. Furthermore, this study showed that local groups were taller than elite material before inflorescence emergence, which could be useful in forage breeding, where different cutting systems are evaluated. Generally, fastest stem elongation of RCG occurred around flag leaf emergence and at the stage of the inflorescence becoming visible. At seed ripening RCG had almost reached its maximum height. However, plant height was only one trait affecting total biomass, which has been shown to increase markedly after seed ripening. Finally, our study provides possibilities for adjusting RCG management according to different end uses such as forage, non-food or seed production. The results of this experiment yielded new information on variation in phenological traits and how they could serve as a basis for further investigations.
Acknowledgements This study was funded by the Academy of Finland, MTT Agrifood Research Finland and the Finnish Ministry of Agriculture and Forestry. The authors are grateful to Doctor Leena Ho¨mmo¨ at Ministry of Agriculture and Forestry for her implementation of the experiments, and to the technical staff, particularly Helena Ihama¨ki, Aino
Baltensperger, A.A., Kalton, R.R., 1958. Variability in reed canarygrass, Phalaris arundinacea L. I Agronomic characteristics. Agronomy Journal 50, 659 /663. Berg, T., 1980. Investigations in local populations of reed canarygrass (Phalaris arundinacea ) from Western Norway. Forskning og Forsog i Landbruket 31, 433 /447. Enroth, A., Ja¨rvenpa¨a¨, M., Ja¨rvi, A., Nordman, R., Peltonen, J., Ruippo, J., Savela, P., Seppa¨nen, H., 1997. Nurmikasvien siementuotanto, Maaseutukeskusten liiton julkaisuja, Tieto Tuottamaan nro 74. In Finnish. Essen von, M., 1913. Tutkimuksia rehukasviviljelyksen alalta. Tekija¨n kuoltua ja¨rjesta¨nyt Go¨sta Grotenfelt. Kustannusosakeyhtio¨ Otava, Helsinki. In Finnish. Fairey, D.T., Hampton, J.G., 1997. Forage seed production. Volume 1: Temperate species, CAB International, UK. Gifford, A.L.S., Ferdy, J.-B., Molofsky, J., 2002. Genetic composition and morphological variation among populations of the invasive grass, Phalaris arundinacea . Canadian Journal of Botany 80, 779 /785. Gumpertz, M., Brownie, C., 1993. Repeated measures in randomized block and split-plot experiments. Canadian Journal of Forest Research 23, 625 /639. Ka¨tterer, T., Andre´n, O., Petterson, R., 1998. Growth and nitrogen dynamics of reed canarygrass (Phalaris arundinacea L.) subjected to daily fertilization and irrigation in the field. Field Crops Research 55, 153 /164. Ka¨tterer, T., Andre´n, O., 1999. Growth dynamics of reed canarygrass (Phalaris arundinacea L.) and its allocation of biomass and nitrogen below ground in a field receiving daily irrigation and fertilisation. Nutrient Cycling in Agroecosystems 54, 21 /29. Landstro¨m, S., Lomakka, L., Andersson, S., 1996. Harvest in spring improves yield and quality of reed canary grass as a bioenergy crop. Biomass and Bioenergy 11, 333 /341. Langer, R.H.M., 1979. How Grasses Grow. Studies in Biology, vol. 34. Edward Arnold Publishers Ltd, London. Lawrence, T., Ashford, R., 1968. Effect of stage and height of cutting on the dry matter yield and persistence of intermediate wheatgrass, bromegrass, and reed canarygrass. Canadian Journal of Plant Science 49, 321 /332. Leinonen, A., Flyktman, M., Paappanen, T., Sahramaa, M., 2000. Research and development plan for energy crops for the years 2001 /2005. VTT Energy Reports (in Finnish), ENE32/19. Marten, G.C., Donker, J.D., 1968. Determinants of pasture value of Phalaris arundinacea L. vs, Bromus inermis Leyss. Agronomy Journal 60, 703 /705.
M. Sahramaa, L. Jauhiainen / Industrial Crops and Products 18 (2003) 155 /169 Marten, G.C., Heath, M.E., 1973. Reed canarygrass. In: Heath, M.E., Metcalfe, D.S., Barnes, R.F. (Eds.), Forages, The Science of Grassland Agriculture, 3rd ed.. The Iowa State University Press, USA, pp. 263 /276. Merigliano, M.F., Lesica, P., 1998. The native status of reed canarygrass (Phalaris arundinacea L.) in the inland northwest, USA. Natural Areas Journal 18, 223 /230. Nguyen, H.T., Sleper, D.A., 1983. Genetic variability of seed yield and reproductive characters in tall fescue. Crop Science 23, 621 /626. Neter, J., Kutner, M., Nachtsheim, C., Wasserman, W., 1996. Applied Linear Statistical Models, 4th ed.. Irwin, Chicago, p. 1310. Pahkala, K., 1997. Sellua peltokasveista. Peltokasvien soveltuvuus sellun raaka-aineeksi. Lisensiaatintutkimus, University of Helsinki. No 47, pp. 121. In Finnish. Pahkala, K., Pihala, M., 2000. Different plant parts as raw material for fuel and pulp production. Industrial Crops and Products 11, 119 /128. Pahkala, K., Partala, A., Suokannas, A., Klemola, E., Kallioma¨ki, T., Kirkkari, A.-M., Sahramaa, M., Isolahti, M., Lindh, T., Flyktman, M., 2002. Ruokohelven viljely ja korjuu energian tuotantoa varten. Maa-ja elintarviketalous nro 1. In Finnish. Partala, A., Mela, T., Esala, M., Ketoja, E., 2001. Plant recovery of 15N-labelled nitrogen applied to reed canary grass grown for biomass. Nutrient Cycling in Agroecosystems 61, 273 /281.
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Rincker, C.M., Carlson, I.T., Garrison, C.S., 1977. Effects of two diverse environments on seed production characteristics of the parent clones of ‘Vantage’ reed canarygrass. Crop Science 17, 625 /628. Sachs, A.P.W., Coulman, B.E., 1983. Variability in reed canarygrass collections from eastern Canada. Crop Science 23, 1041 /1044. Sahramaa, M., Ho¨mmo¨, L., 2000. Seed production characters and germination performance of reed canary grass in Finland. Agricultural and Food Science in Finland 9, 239 /252. Sahramaa, M., Ho¨mmo¨, L., Jauhiainen, L., 2003a. Variation in seed production traits of reed canary grass germplasm at high latitudes (submitted). Sahramaa, M., Ihama¨ki, H., Jauhiainen, L., 2003b. Variation in biomass related variables of reed canary grass germplasm (submitted). Saijonkari-Pahkala, K., 2001. Non-wood plants as raw material for pulp and paper. Agricultural and Food Science in Finland 10, supplement 1. Wolfinger, R.D., 1996. Heterogeneous variance /covariance structures for repeated measures. Journal of Agricultural, Biological, and Environmental Statistics 2, 205 /230. Østrem, L., 1988. Studies on genetic variation in reed canarygrass, Phalaris arundinacea L. III Seed yield and seed yield components. Hereditas 108, 159 /168.
Characterization of development and stem elongation of reed canary grass under northern conditions Mia Sahramaa a,*, Lauri Jauhiainen b a
MTT Agrifood Research Finland, Plant Production Research, FIN-31600 Jokioinen, Finland b MTT Agrifood Research Finland, Research Services, FIN-31600 Jokioinen, Finland
Received 12 August 2002; received in revised form 7 March 2003; accepted 21 March 2003
Abstract Reed canary grass (Phalaris arundinacea L.) is a potential crop for energy and paper production and might also be a useful forage crop under northern growing conditions. Knowledge of phenological traits is needed to adjust the production system according to various end-use requirements. This study aimed at describing variation in plant development, plant height and stem elongation among local and elite populations of reed canary grass. Field experiments were carried out between 1994 and 1997 in Finland. Six developmental stages were determined and plant height was measured at weekly intervals. Differences among groups of reed canary grass were statistically significant. Cultivars developed earlier than local groups, although they needed 3 days more for seed ripening. They were also taller than local populations at time of seed ripening. However, local groups were slightly taller than cultivars during early stages of development. At time of seed ripening some local populations were taller than elite material. Their places of origin could represent potential collection areas for populations showing increased plant height. Seed ripened approximately 95 days from the beginning of the growing season, when the temperature sum was 737 8C days of degree. At time of seed ripening 98% of maximum plant height was reached. A long latent period from reaching maximum plant height to harvest in the following spring is justified for non-food production because biomass continues to increase markedly after seed ripening. Stem elongation was fastest around flag leaf emergence and appearance of inflorescences. Knowledge of the fixed stage of plant development and plant height at each stage provides possibilities to adjust the production system and harvest time according to different end-uses: forage, non-food, and seed production. Information from this study will serve as a basis for further investigations and could be used in breeding reed canary grass. # 2003 Elsevier Science B.V. All rights reserved. Keywords: Local populations; Non-food production; Phenology; Plant height; Variation
1. Introduction
* Corresponding author. Tel.: /358-3-4188-2452; fax: / 358-3-4188-2437. E-mail address: [email protected] (M. Sahramaa).
Reed canary grass (hereafter RCG) has been grown for forage for over a hundred years, especially in North America. In Finland the first forage trials of RCG were documented in 1891 in
0926-6690/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0926-6690(03)00044-X
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Hernia¨inen, south Ha¨me (Essen von, 1913). Although most commonly grown as forage, RCG has been shown to be a potential crop for energy and paper pulp production under northern growing conditions (Landstro¨m et al., 1996; Pahkala, 1997). Although RCG is native to Finland, its cultivation has been limited to date. Currently over 1000 ha of RCG are cultivated for forage and bioenergy at high latitudes in Finland and in Sweden (Leinonen et al., 2000). Foreign forage cultivars are grown for both purposes because no domestic cultivars are available. RCG is preferred in Finland for non-food cultivation because it produces substantial biomass (6 /8 t ha1) under northern, long day conditions (Saijonkari-Pahkala, 2001), and in a delayed harvest system it may use the entire growing season for increasing biomass. At spring harvest the quality of biomass is also better for non-food purposes. Furthermore, RCG has an expansive rhizome and root system (Ka¨tterer and Andre´n, 1999), which enables efficient use of spring moisture for new growth after harvest and good drought tolerance. Non-food cultivation of RCG is also environmentally sound, because RCG has a high storage capacity root system for fertilizer nutrients and only small amounts of N are removed from the field with harvested biomass (Partala et al., 2001). This results in low demand for fertilizers after harvest (Partala et al., 2001). The recommended fertilizer application rate is only 60 /80 kg ha1 on clay soil and about 50 kg ha 1 on an organic soil (Pahkala et al., 2002). Information on the agronomic traits of RCG is needed to adjust both the feed and non-food cultivation practises to northern growing conditions and to evaluate the breeding value of the local material. Knowledge on the extent and nature of variation for agronomic traits is a basic requirement of breeding programmes. Breeding for non-food purposes started in 1993 in Finland with an extensive collection of local populations from all over the country (Fig. 1). The aim of this study, was to evaluate variation in plant development, plant height and stem elongation of local populations and elite material of RCG. Earlier studies from North America and Norway showed that RCG varies for these traits
(Baltensperger and Kalton, 1958; Berg, 1980; Østrem, 1988). Canadian RCG collections, including populations from natural stands, showed significant variation for inflorescence emergence and plant height. High broad-sense heritabilities of 0.94 (inflorescence emergence) and 0.54 (plant height) indicate the possibilities of effective selection in breeding programmes (Sachs and Coulman, 1983). The results of this experiment will furnish new information on variation of phenological traits of RCG that might be used for evaluation of management treatments and for agronomic applications including crop-growth modelling and crop zonation.
2. Material and methods 2.1. Field experiment A trial was conducted in 1994/1997 at MTT Agrifood Research Finland in Jokioinen (60849?N) incorporating 53 wild RCG populations from different regions of Finland; eight cultivars and 14 breeding lines (Fig. 1). The experiment was set up in a randomized complete block design with four replicates. Each plot consisted of 30 individual plants, which were grown from seed in a pot in a greenhouse. Plants were spaced in the field at 25 cm to form a plot of 1.25 m2. The distance between each plot was 2.5 m. The trial was established on an organic soil (replicates 1 and 2) on 29 /30 June 1994 and on clay soil (replicates 3 and 4) on 4 /7 July 1994. Nitrogen fertilizer was applied with a pneumatic applicator (Tume P12, Finland) in the year of establishment at 50 kg N ha1 on the organic soil (trade name TyppirikasY; N:P:K at 20:4:8) and 70 kg N ha1 on the clay soil. Because precipitation was only 1 mm in July 1994, pots were irrigated until the plants were fully established. Harvest was done each year in May by removing the aerial biomass before onset of the new growing season. Nitrogen fertilizer at 40 /70 kg N ha1 was given after the spring harvest. No herbicides were used. Weather data from 1994 to 1997, including accumulated temperature sum at Jokioinen, are shown in Table 1.
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Fig. 1. Origins of the cultivars (8) and breeding lines (14) and geographic origins of the wild populations (53) of reed canary grass included in an experiment conducted at Jokioinen, Finland in 1994 /1997.
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Table 1 Deviations from the long-term (1961 /1990) average of monthly air temperature (8C), monthly precipitation (mm) and accumulated temperature sum (8C dd) at Jokioinen (May to September), Finland, in 1994 /1997 May
June
July
August
September
Mean air temperature (8C) 1961 /1990 1994 1995 1996 1997
9.4 /1.6 /0.7 /0.6 /1.7
14.3 /2.2 /2.4 /1.2 /1.8
15.8 /3.2 /0.5 /1.9 /2.0
14.2 /0.9 /0.9 /2.8 /3.6
9.4 /0.6 /0.9 /1.1 /0.6
Precipitation (mm) 1961 /1990 1994 1995 1996 1997
35 /1 /52 /29 /20
47 /19 /74 /6 /55
80 /79 /27 /55 /61
83 /29 /18 /69 /39
65 /40 /21 /45 /13
414 /71 /90 /64 /10
745 /32 /76 /120 /73
1033 /59 /104 /35 /184
1164 /79 /130 /66 /203
Accumulated temperature sum (8C dd)a 1961 /1990 136 1994 /7 1995 /15 1996 /29 1997 /47 a
From the beginning of the growing season.
2.2. Phenology Six developmental stages were determined for RCG and the requirement for effective temperature sum (8C dd, days of degree) was calculated at each stage from the beginning of the growing season (Fig. 2). According to the Finnish Meteorological Institute, the thermal growing season was considered to have begun once the mean daily temperature exceeded /5 8C. Accumulated temperature sum was recorded each day, when temperature was above /5 8C during the growing season. Different stages of development were determined visually for each plot and defined as follows: (1) flag leaf emerged, when flag leaf ligule was visible on 5% of the plants; (2) inflorescence visible, when upper 1/2 cm of the inflorescence was visible on 5% of the plants; (3) inflorescence emerged, when stem below inflorescence was visible on 5% of the plants; (4) beginning of anthesis, when branches of the inflorescence were open and anthers were visible on 5% of the plants; (5) completed anthesis, when branches of the inflorescence were closed along the rachis on
80% of the plants; (6) seed ripened, when inflorescence and stem below it had turned yellow, seeds were fully matured and shattering had started from the top of the inflorescence on 80% of the plants. Seed of RCG matured from top of the panicle downward and first seed matured shattered before most of the crop was ready for harvest. The first two stages were measured in 1995 and 1996, whereas the rest of the measurements were done in 1995 /1997. Thus, most emphasis was directed to analysis of data from 1995 and 1996.
2.3. Plant height In 1994, individual plant height was measured in each plot beginning on 16th of August. As the trial was established less than 2 months earlier, plants had only few panicles at the time of height measurement. In the subsequent years (1995 /97) plant height was measured from soil surface to the top of the panicle of each of three plants in each plot. In 1995 plant heights were measured 10 times at 1-week intervals starting on 23rd May until 14th
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Fig. 2. Description for stages of development of reed canary grass in an experiment conducted at Jokioinen, Finland, in 1994 /1997. (Drawing: Helena Ihama¨ki).
July and the last two measurements were done on 1st September and 13th November. In 1996 the height was measured eight times beginning on 30th May until 14th August. The last measurement was done on 11th of October. In 1997, plant height was measured three times: 30th June, 21st July and 1st September. 2.4. Statistical methods All variables were measured more than once during the study. Typically, the repeated measurements were correlated. Correlation was taken into account fitting several covariance structures for repeated-measures. Structures were compared using Akaike’s information criterion and likelihood ratio-test when possible (Wolfinger, 1996). Response variable, yijkl , was analyzed using following model: Yijkl blockl pop(group)ij errorB timek blocktimekl timepop(group)ijk errorW ;
where pop(group)ij , timek and time /pop(group)ijk were fixed effects of population nested group, measurement time and their interaction, respectively. Blockl was a random effect of block while block /timekl was the error term for main-effect of time. ErrorB and errorW were between and within plot errors. All the four previous effects were assumed to be normally distributed. This model and the assumptions on which it is based were presented by Gumpertz and Brownie (1993). In 1994 measurements were done from each plant in a plot and data was analysed using following model: Yijl blockl pop(group)ij errorW errorB Stem elongation of plants was analyzed fitting logistic growth curves. Plant height at the beginning of the different development stage was not measured, but temperature sum at the beginning of different development stage was known for each plot. Therefore, the logistic growth curve was fitted separately for each plot and according to growth curve parameters estimates and tempera-
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ture sums the absolute and relative plant height at the different development stages were calculated for each plots. Data for 1995 and 1996 were analyzed separately. The model was: heightijk
b1i ujk o ijk ; 1 exp((xijk b2i )=b3i )
where xijk was a correspondence temperature sum of jth population in ith group at k th measurement time. b1i , b2i and b3i were fixed-effect parameters for maximum height, inflection point (i.e. the point in a curve at which it changes direction from concave to convex to) and slope, respectively. Ujk and oijk were normally distributed random-effect parameters for plot-to-plot variation of maximum height and residual variation, respectively. The assumptions of the models were checked using graphical methods: a box-plot and plots of residuals (Neter et al., 1996). Normality was achieved after arcsine-square root transformation of the data. The parameters of the models were estimated by means of the REML estimation method, using the SAS system for Windows, release 8.2, and MIXED, NLMIXED and CORR procedures. Correlations between variables were measured using Pearson correlation coefficient.
3. Results 3.1. Stages of development The flag leaf emerged approximately 46 days from the beginning of the growing season, when the approximate temperature sum was 266 8C dd. This was 36% of the temperature sum required for seed ripening (Table 2). Inflorescences became visible about 51 days from the beginning of the growing season, when the temperature sum was 305 8C dd (/39 dd). They emerged 58 days from the beginning of the growing season, when the temperature sum was 373 8C dd (/68 dd). Anthesis began 65 days from the beginning of the growing season at 434 8C dd (/62 dd) and was completed 81 days from the beginning of the growing season at 589 8C dd (/155 dd). Anthesis
took approximately 16 days and seed ripening 14 days and lasted much longer than earlier stages. Seed ripened within 95 days from the beginning of the growing season, when the approximate temperature sum was 737 8C dd (/148). Recorded stages of development were reached within 3 months. Flag leaves developed in June and inflorescences emerged in June or early July, depending on the year. In 1995, anthesis began as early as 15th to 26th June, whereas in 1996 it started on 5th July and in 1997 on 25th June. Furthermore, seed ripening took place from the middle of July until mid August, depending on the year. The difference in temperature sum requirement among groups of RCG was significant at each stage of development in 1995 and 1996. Cultivars and breeding lines had the lowest temperature sum requirement. Hence, they reached each stage of development earlier and differed significantly from local groups. Cultivars needed approximately 239 8C dd for flag leaf development (43 days), 275 8C dd for the inflorescence to become visible (48 days), 326 8C dd for inflorescence emergence (54 days), 398 8C dd for anthesis to begin (61 days), 541 8C dd for complete anthesis (76 days) and 697 8C dd for seed ripening (92 days). Inflorescences of local populations emerged approximately 6 days later, they completed anthesis 7 days later and their seeds ripened 4 days later than for cultivars. Plants from groups VIII and X from northern Finland were the latest maturing and they differed significantly from other groups when tested in 1995. The most early ripening populations within the local groups were RH2, RH4, RH13, RH22, RH32, RH33, RH47 and RH49 (Table 3), while the latest maturing populations were RH10, RH81, RH78, RH60 and RH24. Cultivars, breeding lines and the northernmost group X had the lowest temperature sum requirement from flag leaf emergence to the beginning of anthesis, while groups IV, VI and VIII had the highest. Consequently, cultivars and breeding lines needed 2 days less for reaching anthesis compared with local groups. Groups VII and IX had the highest temperature sum requirement for anthesis. However, the situation was vice versa from complete anthesis until seed ripening, when cultivars needed 3 days more for maturing than local
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161
Table 2 Temperature sum requirement (8C dd) of reed canary grass at different developmental stages (1 /6) according to provenance (I /X) in an experiment conducted at Jokioinen, Finland in 1995 /1996 1/4
5/6
1
2
3
4
5
1995 I II III IV V VI VII VIII IX X
238 248 276bc 271b 269ab 262a 276bc 290d 261a 281cd
263 273 298cd 300d 291abc 289ab 297bcd 319 283a 304d
318 345 388cd 382bd 375a 376ab 390c 402 380abc 387cd
382 398 424ab 432c 423a 440de 435ce 457 414a 434bcd
507 523 561ab 561ab 555a 580d 579cd 587d 568bc 554a
661a 666a 709b 712b 688 707b 705b 727d 714bc 725cd
145a 149ab 149ab 161cd 153abc 178e 159bcd 168de 154abc 153abc
125ab 126ab 137cde 129abc 132bcd 140de 143ef 129abc 154f 120a
154d 142c 148cd 151d 133ab 127a 126a 140bc 146cd 171
267
292
374
424
558
701
157
134
144
239 249 267bc 266b 272cd 260a 276d 285e 264ab 278de
286 296 326cd 328de 322bc 310a 323bcd 341f 315ab 336ef
333 346 382d 379cd 376bc 366a 382d 394e 368ab 387de
414 425 451ab 449ab 452b 452b 451ab 461 443a 449ab
575 589 629ab 624a 625a 635bc 640c 635bc 625a 636bc
733 740 785cd 782abcd 779abc 777a 784bcd 798 776ab 788d
175ab 176ab 183cd 183d 180bcd 192 175abc 175ab 179abcd 171a
161a 164a 178bcd 175bc 173b 183de 189e 174bc 183cde 187de
157cd 150be 156ce 158cd 154ce 142a 144ab 163d 150abc 152bc
266
318
371
445
621
774
179
177
153
Mean 1996 I II III IV V VI VII VIII IX X Mean
6
4/5
Group
(1) Flag leaf emerged; (2) inflorescence visible; (3) Inflorescence emerged; (4) beginning of anthesis; (5) completed anthesis; and (6) seed ripened. Between group comparisons: estimated means with the same uppercase letters were not significantly different (P /0.05).
groups. Groups VI and VII from East Finland had the lowest temperature sum requirement for maturing and cultivars and group X the highest. Statistically significant differences among groups are presented in Table 2. 3.2. Plant height Plant height was measured for the first time only 6 weeks after establishment in 1994, when the average plant height was 29 cm, ranging from 14 to 39 cm, depending on group (data not shown). Plant height was greatest in cultivars and least in the northernmost group X. The standard deviation within population was 3.4 /5.7 cm and between population 3.9 and 6.2 cm, when plant height was measured from each plant in a plot.
In 1995 and 1996, measurements of plant height began in May when plants were approximately 22/30 cm tall. Plant height was estimated at each stage of development and also the increment between stages was determined (Table 4). The average stem elongation was less than half (76 cm) of the estimated maximum plant height at the time of flag leaf emergence and more than half (94 cm) from flag leaf emergence to seed ripening. The average plant height was 84 cm at the time of the inflorescence becoming visible in 1995 and 96 cm in 1996. Consequently, at inflorescence emergence the average plant height was almost the same in both years at 116 cm. At the beginning of anthesis average plant height was 135 cm and 79% of the maximum height was reached. At complete anthesis, plant height was 161 cm and 94% of the
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162
Table 3 Seed ripening (days from the beginning of growing season) and plant height (cm) at seed ripening stage of reed canary grass populations in an experiment conducted at Jokioinen, Finland in 1995 /1996 Seed ripening
Seed ripening
Population
1995
Population
SWJ91 SWG63 SWD33 SW5 SW2 Pervenets Motterwitzer SW4 Jo0510 Venturea Venture Barphal Vantage SWB17 SW3 RH4 SWA5 RH2 RH49 RH13
88 88 88 88 88 88 88 88 88 89 89 89 89 89 89 89 90 90 91 91
SWG63 SWB17 SW2 Pervenets SWJ91 SW5 SW4 Motterwitzer Barphal Venture Vantage SWA5 RH47 Venturea RH22 Palaton Jo0510 SW3 SWD33 RH32
RH34 RH30 RH85 RH73 SW91067 RH78 RH60 RH51 RH81 RH10
96 96 97 97 97 97 97 97 98 98
RH30 RH1 RH86 RH80 RH60 RH78 RH46 RH24 RH10 RH81
a
Plant height 1996 93 94 94 94 94 95 95 95 95 95 95 95 95 96 96 96 96 97 97 97 100 100 101 101 101 102 102 102 104 105
Plant height
Population
1995
Population
1996
SW91066 RH79 RH85 Pervenets RH30 Vantage SWG63 RH78 SW2 SW91065 RH33 Jo0510 RH1 RH36 RH47 RH26B SWA5 SWD33 RH77 RH80
196 196 195 195 194 194 193 192 191 191 190 189 189 187 187 187 186 186 186 185
Vantage RH1 RH47 SW91067 RH78 SW91066 SW91065 SWD33 Rival Palaton SWA5 RH83 SW2 Venture Barphal RH85 SW3 RH33 Venturea SW4
193 191 190 188 188 187 187 187 185 185 184 184 184 184 183 182 182 182 182 182
RH15 RH20 RH10 RH32 RH4 RH75 SW1 RH89 RH90 RH109
165 164 163 163 162 161 158 158 154 153
RH52 RH24 RH20 RH17 RH60 RH48 SW1 RH90 RH89 RH109
149 149 148 147 147 145 135 128 128 119
Seed of cultivar Venture bulked once in the field in Jokioinen.
maximum height was reached. At the time of seed ripening plant height was 176 cm in 1995 and 163 cm in 1996. At that time 98% of the maximum plant height was reached. During the six developmental stages studied, stem elongation was most enhanced (26 cm, 15%) between the inflorescence becoming visible and inflorescence emergence as well as during anthesis. During maturation stem elongation was only 5% (9 cm). In 1997, average plant height was 140 cm, ranging from 118 to 148 cm, depending on the group. It was highest with cultivars and lowest with the northernmost group
X (data not shown). Plant height was measured between complete anthesis and seed ripening in mid July (689 8C dd), after which it did not increase significantly. The difference in plant height (cm) and in relative plant height (% of the estimated maximum plant height) was significant among the groups at each developmental stage (Table 4). Local groups were slightly taller than cultivars before emergence of inflorescences. The difference in plant height was most pronounced in 1995 with groups VIII and IX from northern Finland, which were 7 /13
Table 4 Plant height (cm) and relative stem elongation (%) of the maximum height of reed canary grass according to provenance (I /X) at different developmental stages (1 /6) in an experiment conducted at Jokioinen, Finland in 1995 /1996
1995 I II III IV V VI VII VIII IX X Mean 1996 I II III IV V VI VII VIII IX X Mean
1
2
3
cm
%
cm
%
70ab 67a 74cd 76d 72bc 73bc 74cd 80e 81e 72abc
37ab 36a 41de 42e 40cd 39bc 41cde 42e 45f 45f
83bc 79a 82bc 88d 80ab 84c 82abc 91d 89d 79ab
74
41
72e 77bc 75cd 77bc 75cd 77bc 79b 82a 79ab 72de 77
4
5
6
1/4
cm
%
cm
%
cm
%
cm
%
cm
44a 42 46a 48b 44a 44a 45a 48b 49b 49b
111a 114b 118c 120cd 112ab 118c 118c 123de 124e 106
59a 60a 65d 66d 63b 63bc 66d 65cd 69e 66de
139ab 137bc 130de 136c 129de 141a 133cd 141a 135bcd 119
75c 73ab 72ab 75c 72a 75c 74bc 75c 75c 75bc
172a 171a 162cd 165c 159d 171a 164c 169ab 165bc 142
92f 91cde 90ac 90bcd 89a 91ef 91ef 90ab 92fd 89ab
184a 184a 175bc 177b 173c 182a 174bc 182a 176bc 155
98 98a 97abc 97bd 96e 97bcd 97bdf 96cef 97ad 97adef
84
46
116
64
134
74
164
91
176
39 43a 46bc 47cd 46cd 44ab 48d 47cd 51 57
96c 100b 97c 100ab 92 96c 96c 103a 98bc 85
52 56a 59c 61d 57ab 56a 58bc 59c 63d 67
120bc 123a 116d 118cd 111 117d 116d 121ab 115d 95
65 69a 71bc 72cd 68a 68a 71bc 69ab 74de 75e
152a 151a 135cd 137c 131e 142b 135cd 140b 133de 105
83cd 84ef 82bc 83de 81ab 83cd 82cd 80a 85f 83cde
178 174 157bc 158b 155cd 166a 159b 165a 151d 121
97de 97e 96bc 96c 95a 96cd 96cde 95a 97de 95ab
47
96
59
115
70
136
83
158
96
4/5
5 /6
%
cm
%
cm
%
70a 69a 57cd 60bc 57cd 68a 60bc 61b 54d 48
38d 37d 31abc 33bc 32abc 36d 33c 33ac 30ab 30a
32ab 34a 31abc 28c 31bc 30bc 31abc 28c 30abc 23
17d 18d 18bd 15abc 17be 16bd 17de 15a 17cde 14a
12a 13a 13a 13a 13a 11a 10a 14a 11a 13a
6a 7ac 7ac 7ac 7ad 6d 6d 6bcd 5cd 8ab
97
60
33
30
16
12
7
183 179 163b 163b 161b 170a 163b 172a 155 125
99a 99a 99bc 99b 99c 99b 99b 99c 99ab 98c
81 74 59ab 60a 56cd 66 57bcd 57bc 54d 33
44 41 36bc 36c 35a 39 34ab 33 34abc 26
26a 23c 23bc 21cd 23abc 24abc 24abc 26ab 19de 15e
14d 13bc 14bcd 13b 14bc 13bcd 14cd 15bc 12abc 12a
5a 5b 5a 5a 6a 5a 4a 7a 4a 4a
2abc 2bcd 3abcd 3bcd 4ab 3d 3cd 4a 2cd 3bcd
163
99
60
36
22
13
5
3
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Group
(1) Flag leaf emerged; (2) inflorescence visible; (3) inflorescence emerged; (4) beginning of anthesis; (5) completed anthesis; and (6) seed ripened. Between group comparisons: estimated means with the same uppercase letters were not significantly different (P /0.05).
163
164
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cm taller than cultivars before the beginning of anthesis. They differed significantly from plants in other groups, except those in group IV. They were also among the tallest groups in 1996. At flag leaf emergence, plants in local groups reached more of the estimated maximum height than cultivars and breeding lines. The difference was most pronounced with the northernmost groups IX and X until inflorescence emergence. They differed significantly from other groups in most cases. From the beginning of anthesis, the difference in relative plant height among groups was small, although plants of cultivars and breeding lines were taller than those of local groups. At seed ripening they were approximately 16 cm taller than those of local groups, being 183 cm on average. Groups VI and VIII contained the tallest plants among the local groups at seed ripening and they differed significantly from other groups, except cultivars and breeding lines in 1995, and from all other groups in 1996. Group X contained the shortest plants and it differed significantly from the other groups. However, at seed ripening plants of many local populations were among the tallest (in ascending order) (Table 3): Vantage, SW91066, RH78, RH1, SW91065, RH85, RH47, RH79, RH30 and SW2. The shortest populations were RH89, RH90 and RH109 from Lapland and SW1 from Sweden. Considering stem elongation (cm) and relative stem elongation (%) between stages of development, groups differed significantly from each other (Table 4). Cultivars exhibited the highest rate of stem elongation from flag leaf development until the beginning of anthesis, although they were not the tallest group before anthesis. At that time cultivars differed significantly from other groups except breeding lines and group VI in 1995, and in 1996 they differed from all other groups. Relative stem elongation in the same period was highest for cultivars and breeding lines and they differed significantly from other groups. The northernmost group X differed significantly from other groups through containing plants with the lowest rate of stem elongation and also the lowest relative stem elongation. Group X plants had the lowest stem elongation during anthesis and almost all groups differed significantly from it. Group IX was also
characterised by low stem elongation and in 1996 all groups except group IV differed significantly from it. The differences between groups, both in stem elongation and in relative stem elongation, were minor from complete anthesis to seed ripening. 3.3. Parameters for stem elongation The average stem elongation was highest at inflection point, when the requirement for effective temperature sum was approximately 307 8C dd in 1995 and 276 8C dd in 1996 (Table 5). At that point the curve for stem elongation changed from concave to convex (Fig. 3). In 1995, the average stem elongation was 90 cm at the inflection point and 82 cm in 1996. In 1995, the inflection point was achieved around inflorescence emergence and in 1996 after flag leaf emergence. The difference in temperature sum requirement at inflection point was significant among groups. In 1995, cultivars and plants of group IX from northern Finland reached the inflection point earliest, indicating fast stem elongation until that point. They also differed significantly from other groups. In 1996, plants of the northernmost groups (IX, X) reached the inflection point first, differing significantly from all other groups, including cultivars. In both years group VIII plants were the last to reach the inflection point and differed significantly from plants of other groups except group VII in 1995 and all groups in 1996. Estimated maximum plant height was 181 cm in 1995 and 166 cm in 1996 (Table 5). Cultivars, breeding lines and plants of local group VIII had the highest maximum plant height and the northernmost group X the lowest, which also differed significantly from other groups. The maximum difference was 47 cm between cultivars and group X in 1996. Parameter ‘slope’ described the intensity of stem elongation and high values indicated gentle elongation during a long time period, whereas low values indicated sharp, rapid growth. Cultivars and breeding lines differed significantly from other groups through having the steepest growth, whereas plants from groups VIII and X had the highest values for ‘slope’ and showed more gentle growth.
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165
Table 5 Parameters for stem elongation of reed canary grass according to provenance (I /X) in an experiment conducted at Jokioinen, Finland, in 1995 /1996 Maximum value (b1), cm
Inflection point (b2), dd
Slope (b3)
Group
1995
1996
1995
1996
1995
1996
I II III IV V VI VII VIII IX X Mean
187ab 188a 179cd 182abcd 178d 186abc 180bcd 189a 180abcd 159 181
184a 179ab 164e 164e 163e 172cd 165de 175bc 155e 137 166
285a 302b 314c 307bc 314c 311c 316cd 328d 286a 305bc 307
278b 272c 283ab 277bc 287a 282ab 285ab 297 260d 243d 276
91a 96a 110b 113b 113bc 112b 111bc 121c 116bc 117bc 110
87a 92a 109b 107b 113bc 109b 110bc 118cd 106b 131d 108
Between group comparisons: estimated means with the same uppercase letters were not significantly different (P /0.05).
Considerable variation was found among groups according to provenance in stem elongation in 1995 and 1996 (Fig. 3). Cultivars were tallest and reached the maximum plant height sooner than plants of the other groups. Plants of local group VIII were tall, but elongation rate was low. Group IX plants were among the tallest during early development, but maximum plant height was relatively low. The northernmost group X also contained tall plants during early development, especially in 1996, but they reached the lowest maximum plant height.
4. Discussion 4.1. Factors contributing to plant development and height In this study, both anthesis and seed ripening of RCG plant stands lasted for about 2 weeks, indicating large variation in development within and among panicles and individual plants. This is quite typical for other forage grasses: flowering may take place over several weeks (Fairey and Hampton, 1997). Uneven seed ripening of RCG
Fig. 3. Stem elongation (cm) of reed canary grass according to provenance (I-X) as accumulated temperature sum (8C dd) from the beginning of growing season in an experiment conducted at Jokioinen, Finland, in 1995 /1996.
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results in seed losses due to shattering at late harvest and possibly results in decreased germination following early harvest (Sahramaa and Ho¨mmo¨, 2000; Sahramaa et al., 2003a). This has adverse consequences for commercial seed production. In this study, cultivars and breeding lines had 2 days shorter flowering period than plants of local groups, but cultivars needed 3 days more to mature. This is supported by the earlier finding that the most favourable harvest time for cultivars (16 /18 days after anthesis) is somewhat later than that for the local groups (11 /13 days after anthesis) (Sahramaa et al., 2003a). For RCG clones of cultivar ‘Vantage’ tested in Iowa, USA, the pollen shedding period lasted approximately 12 /21 days, depending on the clone (Rincker et al., 1977). In another study estimated genotypic variation among RCG seed lots was 48% (Baltensperger and Kalton, 1958). Temperature sum requirement of RCG was about 737 dd for seed ripening and it occurred from the middle of July until mid August depending on year. This was similar to that recorded for other common forage grasses grown in Finland (Enroth et al., 1997). RCG plant height was high, although it decreased over the study period. During 3 years the average plant height was 160 cm at the seed ripening stage. This was in accordance with results from other studies, where average plant height of RCG collections was 159 cm in Canada in 1979 (Sachs and Coulman, 1983) and 165 cm with RCG cultivar Venture in Finland during 1994/1998 (Saijonkari-Pahkala, 2001). The Canadian study also showed that populations from natural stands were slightly higher than selected material. In this study, groups of cultivars and breeding lines were taller than local groups as a whole, but single populations within a local group, especially from East and North Ostrobothnia (VI, VIII) were taller than cultivars. According to stem elongation parameters determined for the whole growing period, stem elongation was fastest in mid June, around flag leaf emergence and the time of the inflorescence becoming visible. Thereafter the elongation rate started to decrease. Plant height still increased about 15% during inflorescence emergence and anthesis. Thus, this finding agrees with the established finding that flower formation
of grasses is accompanied by rapid elongation of the upper internodes (Langer, 1979). Results from this study showed that RCG reached 98% of its maximum height by seed ripening, after which stem elongation was negligible. Although the time from reaching maximum plant height till harvest carried out the following spring was long, it is well justified for non-food production, because biomass yield increases substantially after seed ripening. Biomass drying is by this means obviated and the quality of raw material is improved. Spring harvested RCG produced on average 6/8 t ha 1 biomass during a 6-year period in Finland, which was about 2 t ha1 higher on average than at autumn harvest (Pahkala and Pihala, 2000). However, in the 1st year after establishment biomass yield was higher at autumn than at spring harvest (Landstro¨m et al., 1996; Ka¨tterer et al., 1998; Saijonkari-Pahkala, 2001). One reason is probably that the slow and irregular germination of RCG seed resulted in a thin plant stand in the 1st year, which was more vulnerable to winter losses than were older leys. Lodging and unfavourable weather conditions have also been suggested as a reason for winter losses (Ka¨tterer et al., 1998; Landstro¨m et al., 1996). However, autumn and spring harvest were not compared or neither winter losses studied, but plant stands were generally well preserved after winter during 4 years of the experiment and DM yield increased at every spring harvest (Sahramaa et al., 2003b). The correlation between plant height and DM yield was statistically significant in this study. However, higher DM yield at spring harvest indicated that plant height was only one trait among several contributing to the total biomass yield. Leafiness, tillering ability and nodal branching were also of great importance. However, information on plant height at different developmental stages is useful in forage production. According to Marten and Donker (1968) RCG should be grazed when it is from 15 to 60 cm tall. If RCG is used for hay or silage, it is recommended to be cut prior to inflorescence emergence (Marten and Heath, 1973). Furthermore, the stage of development at cutting affects the total DM yield of RCG. In a Canadian study, the stand was
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cut three times and DM yield increased if the first cut was done at late maturity (Lawrence and Ashford, 1968). In North America RCG is commonly grown as a forage crop and has aggressively invaded wetland areas, displacing native communities (Merigliano and Lesica, 1998; Gifford et al., 2002). Although RCG is a native species to Finland, its cultivation has been minor to date. Therefore, possible risks associated with cultivation, including invasive character, should be considered before its cultivation takes place on a large-scale. 4.2. Variation among groups of RCG Results from this study showed that there were marked differences in temperature sum requirement at different developmental stages, and in plant height and stem elongation rate among the populations of RCG. Groups of wild populations differed from each other in every trait measured, indicating variation according to provenance. Some variation among populations was expected as RCG is a cross-pollinating species, showing greater variability than many of the self-pollinating species. Cultivars and breeding lines differed from other groups through having the lowest temperature sum requirement at each developmental stage, greatest plant height at seed ripening stage and highest stem elongation rate reflecting the positive impact of breeding. Inflorescences of cultivars emerged approximately 6 days earlier compared with those of local populations and reached complete anthesis 7 days earlier. Furthermore, cultivars ripened 4 days earlier than wild populations. In the study of Berg (1980), vegetatively propagated cultivars also emerged 5 /10 days earlier than Norwegian local populations of RCG. The latitude at which the Norwegian experiment was done was similar to that for this study (above 608N). Although cultivars were the first group to mature, they needed 3 days more than local groups for seed ripening. Plants of the easternmost groups (VI, VII) had a particularly short maturing period. One reason for that might be that wild germplasm tends to secure seed survival with better germination ability before shattering by enhancing the rate
167
of maturity. The longer seed ripening period required by cultivars might also result from higher thousand seed weight sought during breeding (Sahramaa et al., 2003a). Earliness was also associated with higher number of panicles in RCG and Festuca arundinacea (Schreb.) (Berg, 1980; Nguyen and Sleper, 1983). High number of stems would be an advantage in non-food production as well as in seed production of RCG. Correlation between seed ripening and panicle number of RCG was found to be weak (/0.11, P B/0.10) in a previous study (Sahramaa et al., 2003b), but high seed yield was clearly associated with many panicles per unit area (Sahramaa et al., 2003a). Cultivars and breeding lines were shorter before anthesis than plants of some of the local groups, especially those from North Ostrobothnia and Kainuu (VIII, IX). The northernmost groups reached the highest rate of growth earlier than other groups, but maximum plant height reached was lowest and rate of elongation low, especially for plants of group X. The northernmost groups were adapted to a short growing season and therefore had higher rates of stem elongation at early growth stages. However, in general, they had lower stem elongation potential and no ability to benefit from the longer growing season of South Finland. These findings were similar to those of Berg (1980) with local Norwegian populations, which grew fast in early summer and stopped growing earlier in the autumn compared with American RCG. Although cultivars were inferior in plant height to local groups during early development, they reached the point of highest stem elongation early, were ultimately taller and reached the maximum height fastest. At seed ripening, groups from North Ostrobothnia (VIII) and East Finland (VI) were tallest among the local groups. Thus, those places could be potential collection areas for tall genotypes. Although group VIII from North Ostrobothnia had high maximum plant height, it had a low stem elongation rate and it was the most late maturing. The northernmost groups IX and X were shortest and group X was among the latest in maturing. The earliest maturing local populations were found from southern parts of Finland, especially within the group V,
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which was nearest to the experimental site, indicating adaptation to local conditions. Promising material from the collections in this study has been selected for further breeding and seed from local populations has been stored in the Nordic Gene Bank.
Lahti and Matti Matilainen at MTT Plant Production Research for their valuable contribution. Professor Pirjo Peltonen-Sainio is warmly thanked for her comments on the manuscript.
References 5. Conclusion Local RCG populations and selected material are characterised by considerable variation in plant development, plant height and stem elongation rate, which creates a basis for improving those traits through plant breeding. According to results of this study, cultivars and breeding lines were the earliest maturing and they should be used primarily in breeding for earliness in Finland. However, North Ostrobothnia and East Finland could be potential areas for collecting tall populations. Furthermore, this study showed that local groups were taller than elite material before inflorescence emergence, which could be useful in forage breeding, where different cutting systems are evaluated. Generally, fastest stem elongation of RCG occurred around flag leaf emergence and at the stage of the inflorescence becoming visible. At seed ripening RCG had almost reached its maximum height. However, plant height was only one trait affecting total biomass, which has been shown to increase markedly after seed ripening. Finally, our study provides possibilities for adjusting RCG management according to different end uses such as forage, non-food or seed production. The results of this experiment yielded new information on variation in phenological traits and how they could serve as a basis for further investigations.
Acknowledgements This study was funded by the Academy of Finland, MTT Agrifood Research Finland and the Finnish Ministry of Agriculture and Forestry. The authors are grateful to Doctor Leena Ho¨mmo¨ at Ministry of Agriculture and Forestry for her implementation of the experiments, and to the technical staff, particularly Helena Ihama¨ki, Aino
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