Triticale vs durum wheat: A performance comparison in a Mediterranean environment

Field Crops Research 180 (2015) 63–71

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Triticale vs durum wheat: A performance comparison in a Mediterranean environment Rosella Motzo a,∗ , Giovanni Pruneddu a , Adriana Virdis b , Francesco Giunta a a b

Dipartimento di Agraria, Sez. Agronomia, Coltivazioni erbacee e Genetica, Via de Nicola 1, 07100 Sassari, Italy Agris Sardegna, Dipartimento per la ricerca nelle produzioni vegetali, Viale Trieste 111, 09123 Cagliari, Italy

a r t i c l e

i n f o

Article history: Received 23 February 2015 Received in revised form 15 May 2015 Accepted 18 May 2015 Keywords: Triticale Durum wheat Mediterranean environment Grain yield G×E

a b s t r a c t The productivity of modern triticales makes them increasingly viable as an alternative small grain cereal crop to durum wheat in the Mediterranean environment. A comparison between the two species was performed, based on a substantial number of cultivars tested in 20 field experiments in Sardinia (Italy). Grain yield per environment ranged from 3.4 to 7.7 t ha−1 ; in 11 of the environments, the triticales as a group out-yielded the durum wheats, while in the remaining nine, the two species yielded equally. The superiority of triticale derived from its combination of setting a higher number of grains per unit area (reflecting greater ear fertility) and a similar per unit grain weight. Triticale is well adapted to the Mediterranean environment, provided that sowing density is no less than 300 seeds per m2 , because ear fertility contributes more than tillering capacity to the number of grains set per m2 . In the 20 environments tested, the generally favourable pre-anthesis period in terms of temperature and water availability assured triticale the possibility of realizing a grain yield at least comparable to that of durum wheat. At the same time triticale out-yielded durum wheat when its flowering time fell within an optimal window, and where the post-anthesis environment was not too stressful. High ear fertility should be treated as an important trait in the breeding of small grain cereals, because of its positive influence over both yield potential and yield stability. © 2015 Elsevier B.V. All rights reserved.

1. Introduction Triticale and durum wheat are both well adapted as small grain cereal crops for the Mediterranean environment. The former has been growing in popularity as a source of livestock feed, and is more recently being promoted as a feedstock for bioethanol production (Beres et al., 2010; Pejin et al., 2009). The characteristic feature of the Mediterranean environment is the high probability of terminal drought, while moisture stress during the winter months is rare (Loss and Siddique, 1994). Total annual rainfall varies widely – from 275 to 900 mm (Aschmann, 1973). A key management decision of farmers to cope with high environmental variability is the correct species and cultivar choice, which can profoundly affect yield levels and stability. Comparisons of the productivity of triticale and wheat have suggested that the former performs better with respect to both overall biomass and grain yield under a range of environmental conditions (Bassu et al., 2011 and papers cited therein). The physiological basis of its advantage lies in its greater

∗ Corresponding author. Tel.: +39 079229330; fax: +39 079229222. E-mail address: [email protected] (R. Motzo). http://dx.doi.org/10.1016/j.fcr.2015.05.007 0378-4290/© 2015 Elsevier B.V. All rights reserved.

ˇ seedling vigour (López-Castaneda and Richards, 1994), its more effective capacity to translocate assimilate from the stem to the ˇ and Richards, 1994), its supedeveloping grain (López-Castaneda rior ear fertility (Giunta et al., 2003; Giunta and Motzo, 2005), its higher radiation use efficiency prior to anthesis (Motzo et al., 2013) and its ability to form a more extensive root system during the early phase of the growing cycle (Zubaidi et al., 1999; Richards et al., 2007). However few attempts have been made to compare the performance of the two species over a wide range of environments. Furthermore comparisons have tested limited numbers of cultivars within each species. This failing is very relevant due to the ample intraspecific variability present within each of the two species. The final grain yield of a cereal crop depends on the development and growth of each of the various yield components (i.e. ears per unit area, grains per ear and the mean grain weight) (Slafer and Rawson, 1994; Slafer et al., 2009). In cereals, variations in grain yield are more associated with changes in grain number than to mean grain weight (Fischer, 2011). However, environmental conditions affect both yield components differently. Grain weight variation is likely to be more sensitive to post-anthesis environmental conditions, whereas pre-anthesis conditions are expected to affect kernel number (Giunta et al., 1993, 1995). The analysis of yield

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R. Motzo et al. / Field Crops Research 180 (2015) 63–71

Table 1 Environments and crop management. Site

Season

Env. code

Sowing date

Preceding crop

Ussana (CA)

2011 1996 1997 1998 1999 2004 2007 2008 2009 2010 1998 1999 2002 2003 2008 2009 2010 2011 2012 2013

CA11 OR96 OR97 OR98 OR99 OR04 OR07 OR08 OR09 OR10 SA98 SA99 SA02 SA03 SA08 SA09 SA10 SA11 SA12 SA13

13-12-2010 20-11-1995 21-01-1997 15-12-1997 23-11-1998 09-12-2003 13-11-2006 21-11-2007 10-03-2009 24-11-2009 09-12-1997 09-12-1998 10-12-2001 23-12-2002 03-12-2007 17-02-2009 18-11-2009 13-12-2010 15-11-2011 27-11-2012

Grain legumes Fallow Flax Fallow Fallow Grain legumes Grain legumes Fallow Grain legumes Fallow Sorghum Maize Maize Wheat Tomato Tomato Fallow Fallow Grain legumes Grain legumes

S. Lucia (OR)

Ottava (SA)

components represents therefore a useful starting point to a more thorough physiological analysis (Porter and Christensen, 2013) of the crop’s ability to cope with environmental variability. In this paper, the process of yield formation in durum wheat and triticale was performed in a Mediterranean environment, based on a substantial set of field experiments involving several well adapted cultivars. In particular, the focus was on how differences between the two species in yield components affected their adaptation to Mediterranean environments.

2. Materials and methods 2.1. Crop management A total of 85 triticale and 131 durum wheat cultivars were included in 20 field trials conducted in Sardinia (Italy) at Sassari (SA; 40◦ 43 N, 80 m asl), S. Lucia (OR; 39◦ 54 N, 15 m asl) and Ussana (CA; 39◦ 24 N, 97 m asl) between 1995/96 and 2012/13. Their long term mean annual rainfall (considering 57 years for SA and OR, and 40 years for CA) was 552 ± 128 mm, 575 ± 139 mm and 444 ± 137 mm, respectively. These values are representative of the Mediterranean environment of South Italy. In all, 20 location × year combinations i.e. “environments”, were tested, with sowing dates varying from November to March (Table 1). Commercial crops of both triticale and durum wheat are generally sown in the period November–December, but sowing can be delayed as late as March if excessive winter rainfall hinders access to the field and this occurred in two environments sampled (OR09 and SA09). The limited resources available did not allow to set out the experiments for both species in all the years of the time interval considered. The trials were part of the National Net for Cereal Varietal Comparison coordinated by the Italian Centre for Agricultural Research (CRA). The durum wheat cultivars (25–29 per year, varying each year) comprised the most widely grown and the highest performing recent releases. The triticale cultivars (12 in 1996, increasing to 28 by 2012/13) were a mixture of spring and facultative types with variable degree of cold requirements. Each plot consisted of eight 9 m length rows separated by 15 cm, and were set out as randomized complete blocks (RCBD) with three/four replicates. The sowing density was 350 grain m−2 . Weeds, pests and diseases were chemically controlled.

Fertilization (kg ha−1 ) N

P

105 80 92 90 82 165 105 105 110 126 130 82 100 120 89 120 120 145 96 145

92 90 0 0 92 92 92 92 92 46 90 92 92 92 92 92 92 91 91 92

2.2. Measurements The number of days to anthesis (DC61, Zadoks et al., 1974) (ANT) was defined by visual inspections of the plots by the day when half of the ears in a plot showed anther exertion. Maturity was considered as the ‘yellow peduncle stage’ (Chen et al., 2010). Grain filling duration (GFD) was approximated as the difference between maturity and ANT. Plant height (PH) was measured from the tip of the ear (awns excluded), based on five randomly chosen plants per plot. At maturity, the number of ears present in three 0.30 m2 samples per plot was counted and the number of ears per m2 (EPM) calculated. Grain yield (GY) was estimated on a whole plot basis. Grain weight (KW) was obtained from the mean of four 250 grain sub-samples per plot. The number of grains per m2 (KNO) was calculated by dividing GY by KW. The number of grains per ear (KPE) was calculated by dividing KNO by EPM. Grain moisture content was determined from three 250 g samples, and used to express both GY and KW on a 13% moisture basis. Different meteorological parameters were collected/calculated at each environment from meteorological stations located 500 m far from the fields with reference to different time intervals: rainfall and evapotranspiration (ETo) from sowing to maturity; the number of days on which the temperature fell below 4 ◦ C (T < 4) and the number of vernal days (VD) in the three months following sowing; the photothermal quotient (QpreA) (Fischer, 1985), the rainfall deficit (RDpreA) and the vapour pressure deficit (VPDpreA) in the 20 days preceding anthesis; the minimum and maximum air temperature, the temperature amplitude, the number of days when the temperature exceeded 25 ◦ C (T > 25), the post anthesis rainfall deficit (RDpostA) and vapour pressure deficit (VPDpostA) during the period from anthesis to maturity. The VPD values were corrected by multiplying the measured ones by 0.75, following Tanner and Sinclair (1983). Vernal days were calculated according to Weir et al. (1984), assuming that full vernalization is obtained between 3 and 10 ◦ C and reduced amounts between −4 and 3 ◦ C and 10 and 17 ◦ C. 2.3. Statistical analysis Comparisons between the two species were made separately for each environment using the cultivar means as random replicates of the ‘species’ treatment and performing a t-test. ANOVA was used to compare the phenological group × species means. A

VPD (kPa) RD (mm)

−103 −95 −134 −91 −139 −24 −112 −110 −87 −67 −107 −137 −135 −127 −61 −139 −61 −164 −109 −48 16 12 23 20 19 1 19 13 28 9 2 9 2 9 6 23 0 10 23 2

T > 25 ◦ C (d) Range T (◦ C)

3. Results

15.4 10.1 13.5 12.2 12.0 9.9 11.5 10.8 13.3 10.3 9.6 10.3 10.4 10.4 10.1 11.6 7.6 11.5 10.6 8.4

principal component analysis (PCA) was performed with the 13 environmental variables to characterize the environments. Genotype × environment interaction (G × E) was subjected to additive main effects and multiplicative interaction (AMMI) analysis based on a sub-set of nine environments (OR08-10, SA08 and 10-13 and CA11) and the 17 cultivars common to those environments (nine durum wheats: ‘Anco Marzio’, ‘Claudio’, ‘Duilio’, ‘Dylan’, ‘Iride’, ‘Maestrale’, ‘Saragolla’, ‘Simeto’ and ‘Svevo’ and eight triticales: the spring types ‘Catria’, ‘Oceania’, ‘Rigel’ and ‘Trica’ and the facultative types ‘Agrano’, ‘Altair’, ‘Bienvenu’ and ‘Magistral’). AMMI-modelled cultivar responses were displayed as ‘nominal yields’ as a function of site IPCA2 scores. Nominal yields are the yields from the AMMI model equation without the environmental deviation. They represent an average environment. All statistical analysis were carried out using routines implemented in either GENSTAT (VSN International, 2011) or R (R Core Team, 2014).

0.8 0.5 1.2 0.6 0.7 0.5 0.6 0.6 1.0 0.5 0.8 0.9 0.8 0.9 1.0 1.3 0.8 1.1 1.2 0.6

R. Motzo et al. / Field Crops Research 180 (2015) 63–71

25.8 23.5 29.4 24.3 25.5 20.1 24.2 23.1 29.4 22.4 20.4 24.2 21.0 23.4 22.1 25.5 19.3 24.0 26.4 18.3 10.4 13.4 15.9 12.2 13.5 10.1 12.7 12.3 16.1 12.1 10.8 14.0 10.5 12.9 12.0 14.0 11.7 12.4 15.8 9.9 0.5 0.4 0.6 0.5 0.4 0.3 0.4 0.4 0.7 0.4 0.6 0.7 0.6 0.8 0.8 0.8 0.7 0.9 0.9 0.6 −28 −38 −56 −28 −28 23 10 −3 −74 −13 0 −37 8 −77 −59 −29 −47 −66 −59 −42

d 1.1 1.8 2.0 2.1 2.5 2.5 2.1 2.4 1.8 2.0 2.3 2.0 2.3 2.0 2.1 1.8 2.0 1.9 1.5 2.4 72 49 36 53 69 73 50 60 28 63 54 73 72 71 58 52 65 63 48 74

Q (MJ m VD (d) T < 4 C (d)

58 9 3 25 41 36 12 26 4 14 8 32 21 29 8 10 9 6 8 16 304 414 454 440 447 373 459 438 419 421 494 502 481 474 515 515 547 626 642 488

ETo (mm) Rainfall (mm)

243 396 331 225 260 402 435 292 292 455 243 230 246 224 377 297 474 380 338 488 CA11 OR96 OR97 OR98 OR99 OR04 OR07 OR08 OR09 OR10 SA98 SA99 SA02 SA03 SA08 SA09 SA10 SA11 SA12 SA13

Anthesis-maturity

Tmin (◦ C) VPD (kPa) RD (mm) ) C

−1 −1 ◦ −2

20 days before anthesis Three months after sowing Sowing-maturity ENV

Table 2 The meteorological conditions prevailing at the 20 environments.

Fig. 1. Biplot of the first two axes of the PCA analysis used to characterize the relationship between the environmental parameters and the 20 environments.

◦

Rainfall during the growing cycle varied from 224 to 488 mm, with a corresponding ETo range of 304–642 mm (Table 2). As a consequence, all but three of the environments suffered from some moisture deficit. The CA11 environment experienced the lowest temperatures over the three months following sowing and the lowest QpreA. OR04 and OR07 benefited from the best water availability together with the lowest VPD pre-anthesis. The parameter RDpreA was particularly variable, ranging from −77 to +23 mm. The minimum temperature experienced during grain filling ranged from 10 to 16 ◦ C, and the maximum from 18 to 29 ◦ C. T > 25 post anthesis was very variable, ranging from 0 to 28 d. RDpostA ranged from −24 to −164 mm, a level substantially greater than RDpreA. The first two axes of a PCA biplot summarizing the relationships between the environmental variables and the environments explained 67% of the total variance (Fig. 1). PC2 (26% of the variance) clearly distinguished the three sites. This PC was mostly related with environmental variables covering either the pre-anthesis

Tmax (◦ C)

3.1. Environments

65

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R. Motzo et al. / Field Crops Research 180 (2015) 63–71

Fig. 2. Boxplots comparing yield and yield components of durum wheat (DW) and triticale (TR) for the whole dataset (cultivar × environment means). The horizontal line indicates the median. The middle 50% of data lie within the box. The whiskers extends beyond the ends of the box to a distance of 1.5 times the interquartile range. Individual outliers are displayed as points.

period or the whole growing cycle. The strongest influence on this axis was exerted by ETo and VPDpreA in the negative direction, and by T < 4 in the positive direction. The averages for these variables were in fact very different between sites. The SA environments experienced a much higher ETo (528 vs 417 mm) and VPDpreA (0.75 vs 0.47 kPa) than the OR and CA environments, and CA11 exhibited the highest T < 4 after sowing. The first principal component (PC1) (41% of the variance) was mainly negatively related with environmental variables relative to the post anthesis period (thermal environment and VPD in particular). 3.2. The relative performance of durum wheat and triticale The variation in performance of the two species across the environments tested is illustrated in Fig. 2. On average, the triticales flowered later and out-performed the durum wheats in terms of GY, KNO, KPE and PH, while the opposite was the case for KW and EPM. With respect to GY, the triticales were superior to durum wheat in 11 of the 20 environments, while in the other nine, the two species performed equally. The superiority of triticale was even more pronounced when the comparison was based on the best 30% of cultivars of each species in each environment (Fig. 3), since here triticale proved superior in 15 of the environments. Based on the full set of cultivars, the GY differential ranged from 0.6 t ha−1 at SA12 to 2.2 t ha−1 at OR07, with an overall mean advantage to triticale of 1.3 t ha−1 . In 13 of the environments, the durum wheats’ KW was higher than that of the triticales by an average of 7 mg, whereas the triticales featured a higher KNO (by an average of 3375 grains per m2 ) in 18 of the environments. The latter reflected a superiority in terms of the number of grains set per ear, rather than in terms of

EPM. The PH of the triticales was greater than that of the durum wheats by an average of about 20 cm, and they reached anthesis 1–7 days later (although this difference was only significant in six of the environments). Most of the environments favouring triticale were amongst the first 13 in terms of GY and also those where the greatest plant heights were recorded. In an attempt to understand the reason for the higher productivity of the triticales, the trials were separated into two groups: one was made up of the 11 environments where triticale out-yielded durum wheat (TR > DW), and the other the nine environments in which there was no yield differential (TR = DW) (Table 3). The TR > DW group comprised the environments where flowering occurred early, consequently allowing a longer period for grain filling which resulted in similar KWs between the two species. Overall, the plants were taller, and sowing was accomplished between November and December. In the TR = DW group, sowing time ranged from November to March. The TR > DW environments were also those where the inter-species difference in KNO was largest. RDpreA was notably lower in the TR > DW than in the TR = DW environments (Table 4), which may well have contributed to the higher KNO, even though QpreA was lower. The values of RDpreA favouring triticales are not rare in this type of Mediterranean environment. Assuming an anthesis date of day 111 (21 April, see Table 3), the RDpreA during the 20 days prior to anthesis calculated from long term meteorological data was <27 mm in 22 out of 55 years at SA (40%), in 47% of years at OR and in 46% at CA. Consistent with the earlier anthesis date and the longer grain filling period, post anthesis conditions tended to be more benign in the TR > DW environments, in terms of both

R. Motzo et al. / Field Crops Research 180 (2015) 63–71

10

a)

9 Grain yield tricale (t ha-1)

8 7 6 5 4 3 2 1 0

0

2

4

6

8

Grain yield durum wheat (t

10

ha-1)

10

b)

Grain yield tricale (t ha-1)

9 8 7 6 5 4 3 2 1 0

0

2

4

6

8

Grain yield durum wheat (t

67

related with minimum and maximum air temperatures, number of days with maximum temperatures above 25 ◦ C and VPD recorded after anthesis. Since the triticales tended to flower later than the durum wheats and the cultivars were more variable for this trait (Fig. 2), three phenological groups were formed by dividing in three equal parts the anthesis period (from the first to the last anthesis date) within each environment. There were more triticale cultivars in the late flowering group and less in the early flowering group, mainly because of the inclusion of facultative types (Table 5). Some species differences in anthesis persisted within the groups, particularly in the late flowering group, where the triticale cultivars were later flowering than the durum wheat ones by about a week. The within group inter species comparison highlighted how the superiority of triticale was reduced as flowering time was delayed, falling from 1.3 t ha−1 in the early flowering group to just 0.11 t ha−1 in the late flowering one. Only those triticale cultivars belonging to the early flowering group were able to produce grains of equivalent weight to the durum wheat cultivars’, explaining why there was such a differential in GY in this group. The effect of flowering time on GY was more marked in triticale than in durum wheat. The inter-species difference for EPM was also affected, since the durum wheats produced only 15 ears more per m2 than triticale in the early flowering group, but 27 more in the late flowering one. In this case the greatest variation among phenological groups was observed in durum wheat. KPE was highly stable across the groups, particularly for durum wheat. The one week difference in ANT between species in the late flowering group was mirrored in less favourable conditions experienced pre-anthesis for triticale in terms of both VPD (0.69 kPa for triticale, 0.55 for durum wheat) and Q (4.2 MJ m−2 d−1 ◦ C−1 for triticale, 7.5 for durum wheat). The result was a penalty on both KPE and KNO for triticale.

10 3.3. Genotype by environment interaction (G × E)

ha-1)

Fig. 3. Relationship between triticale and durum wheat grain yields based on data acquired from all 20 environments (empty symbols: TR = DW environments; full symbols: TR > DW environments, squares: late sowing). Data represent the grand mean at each environment with its related standard error calculated (a) over all the cultivars, (b) over the best 30% of the cultivars of each species. The line stands for the 1:1 ratio.

thermal conditions and moisture stress. An RDpostA of <90 mm over the period 21 April to 31 May occurred in about 30% of years at both OR and SA, and in 22% of years at CA. SA represented a more favourable site for triticale than the other two locations in terms of T > 25 post-anthesis: according to long-term meteorological data, there were fewer than nine hot days in 68% of the years at this site, against only 38% of the years at OR and 29% at CA. All but three of the TR > DW environments mapped to the same right-hand side of PCA1 (Fig. 1), which represented post-anthesis environmental conditions. More precisely, this PCA was negatively

G prevailed over G × E in the determination PH, KW and anthesis date (Table 6). The G × E component of variance was higher than the genotypic one particularly for GY, but also for the duration of grain filling and EPM. The determination of KNO involved an equal contribution of genotype and G × E. The biplot for GY explained about 60% of G × E (Fig. 4a); the durum wheat cultivars were separated from the triticale ones by IPCA2; KW and the duration of grain filling exerted a positive effect on this principal component, while ANT and PH exerted a negative one. The magnitude of the G × E was similar for the two species, although the four facultative triticale cultivars exhibited a higher G × E with regard to the proportion explained by this IPCA, compared to the spring ones (except Rigel). The environments inducing the greatest G × E according to IPCA2 were OR08 and SA08, with the former being more favourable for the durum wheats, and the latter for the triticales. In spite of being 100 km separated, these two

Table 3 Plant performance in the 11 environments where triticale out-yielded durum wheat (TR > DW) compared to the nine where the two species yielded equally (TR = DW). Environment group

Species

TR = DW TR > DW

GY (t ha−1 )

ANT (doy)

Sowing-ANT (d)

GFD (d)

KW (mg)

EPM (no.)

KNO (no.)

KPE (no.)

PH (cm)

5.54a 6.11a

120a 111b

123b 141a

37.2b 41.5a

44.3a 43.5a

331a 320a

12,753a 14,237a

39.9a 45.3a

96b 108a

TR = DW

DW TR

5.58a 5.49a

118a 121a

122a 124a

36.8a 37.6a

48.0a 40.6b

344a 316a

11,692a 13,814a

34.1b 46.4a

84b 109a

TR > DW

DW TR

5.47b 6.76a

110a 113a

140a 144a

41.2a 41.7a

44.8a 42.2a

321a 320a

12,292b 16,182a

39.0b 51.6a

91b 124a

Means with the same letter within group are not statistically different at the t-test for P < 0.05. The analysis was performed on the 40 species × environment means.

68

R. Motzo et al. / Field Crops Research 180 (2015) 63–71

Table 4 Mean values of environmental parameters across the TR = DW and TR > DW environments. 3 months after sowing

20 days before anthesis

Rainfall (mm)

ETo (mm)

T < 4 ◦ C (d)

VD (d)

QpreA (MJ m−2 d−1 ◦ C−1 )

RDpreA (mm)

VPDpreA (kPa)

311a 348a

481a 466a

18a 19a

56a 61a

6.0a 4.8b

−40.6a −27.3b

0.64a 0.60b

Sowing-maturity

Environmentgroup

TR = DW TR > DW

Anthesis-maturity Tmin (◦ C) 13.2a 12.1b

TR = DW TR > DW

Tmax (◦ C) 24.5a 22.7b

Range T (◦ C) 11.3a 10.6b

T > 25 ◦ C (d) 15.6a 9.2b

RDpostA (mm) −118a −91b

VPDpostA (kPa) 0.89a 0.76b

Means with the same letter within a group are not statistically different at the t-test for P < 0.05.

Table 5 Grain yield and its components averaged across the cultivars grouped on the basis of similar flowering time. Phenological group

Species

Cv × env combinations

GY (t ha−1 )

ANT (doy)

GFD (d)

KW (mg)

EPM (no.)

Early

DW TR

293 139

5.39c 6.69a

111c 108c

41b 44a

45.8ab 45.5ab

327bc 312c

Intermediate

DW TR

177 104

5.71bc 6.20ab

117b 119b

37cd 39bc

47.4a 39.4c

Late

DW TR

45 133

5.72bc 5.82bc

118b 125a

35d 37cd

10

7

Root MSE

1.50

KNO (no.)

KPE (no.)

PH (cm)

11,855b 14,819a

37c 50ab

88c 120a

335ab 317bc

12,134b 15,920a

37c 52a

87c 114b

44.3b 38.9c

356a 329ac

12,846b 15,373a

37c 47b

92c 117ab

6.2

59

10

12

3448

Means with the same letter within a column are not significantly different at the LSD test for P < 0.05.

locations represented contrasting environments in the 2008 season, particularly in post anthesis, when lower T > 25 (6 d at SA08 vs 13 d at OR08) and lower water stress (−61 mm of RDpostA at SA08 vs −100 mm at OR08) were recorded at SA. The IPCA1 principal component explained about 32% of the G × E for GY, but did not discriminate between the two species, even though it was strongly associated with KNO (r = 0.75***), one of the most important traits for which the two species differed. Nominal yields were calculated on the basis of the AMMI model equation excluding the environmental deviation (i.e. based on genotype and G × E IPCA2 effects only) across environmental scores for the IPCA2 (Fig. 5). This plot represents the combined sum of squares of genotype (63.4) and IPCA2 (51.8), or 47% of the genotype + G × E sums of squares. Its aim was to interpret GY stability across environments. IPCA2 was chosen rather than IPCA1, because it was the principal component which most effectively discriminated between the two species. ‘Oceania’, a spring triticale cultivar widely grown in Italy, was the most stable and highest yielding cultivar (a consistent GY of ∼7.0 t ha−1 ). The spring triticales ‘Catria’ (6.3–6.5 t ha−1 ) and ‘Trica’ (around 6.0 t ha−1 ) were also stable (although lower yielding). Among the durum wheats, the most stable were ‘Saragolla’ (with a yield comparable to that of ‘Catria’), ‘Dylan’, ‘Maestrale’, ‘Anco Marzio’ and ‘Svevo’. The facultative triticales were the least stable.

Table 6 Results of the AMMI analysis: percent of sum of squares explained by genotype, environment and their interaction. Percent of the interaction variation explained by the first two IPCA. GY

KNO

KW

ANT

GFD

EPM

PH

15.9 78.9 5.2 63.4 14.4

6.2 82.0 11.7 43.6 22.8

26.0 40.9 33.2 29.8 24.3

71.8 22.9 5.3 53.7 19

The first two principal components of the AMMI analysis for KNO (Fig. 4b) explained about 60% of the G × E variance. The environments responsible for the greatest G × E were OR08, CA11 and SS11. OR08 and CA11 mapped on opposite sides of IPCA1. Both experienced low rainfall during the growing season, but differed markedly in the pre-anthesis period: OR08 had the lowest RDpreA (−2.8 mm) and one of the highest Q (2.4 MJ m−2 d−1 ◦ C−1 ), whereas CA11 had the lowest Q (1.1 MJ m−2 d−1 ◦ C−1 ). The main distinguishing environmental parameter for SS1 was its high VPDpreA. The analysis placed the durum wheat cultivars closer to the origin than the triticale ones, indicating a lower interaction. ‘Claudio’, the durum wheat cultivar exhibiting the greatest G × E, has been shown to have a cold requirement (Motzo and Giunta, 2007), in the same way as the facultative triticale cultivars (also showing a large G × E) ‘Agrano’ and ‘Magistral’. The AMMI biplot for KW explained about 70% of the total G × E and the IPCA1 principal component clearly discriminated between the two species (Fig. 4c). Grain filling duration, absolute weight and thermal time to anthesis exerted a positive effect, while PH, ANT and days to maturity exerted a negative one on this IPCA. The durum wheat KW positively interacted with OR08, one of the few environments where the durum wheat GY was comparable to that of triticale. This environment was characterized by a short grain filling period and the least inter-specific difference in PH. The environments positively interacting with triticale were the ones where triticale most clearly out-yielded durum wheat, and where it was able to produce grains as heavy as those set by durum wheat. The KW of the facultative triticale cultivars ‘Agrano’, ‘Altair’ and ‘Magistral’ were particularly well suited to SA10, the environment which provided the longest grain filling duration: here, the T > 25 was zero, the temperature extremes experienced during the grain filling period were modest, and the RD was not severe.

(% Sum of squares) Genotypes Environments Interaction IPCA1 IPCA2

9.3 63.9 26.8 31.7 28.4

18.3 62.0 19.7 40 19.5

34.6 46.7 18.8 54.4 15.7

4. Discussion In the Mediterranean-type environment (annual rainfall of 400–500 mm) where the present trials were carried out, triticale out-yielded durum wheat by around 13%, with the advantage rising

R. Motzo et al. / Field Crops Research 180 (2015) 63–71

1.5

69

(a)

OR08

IPCA2 Grain yield (28.4 %)

1 OR09

0.5

SA11

SA12

OR10

0

CA11

-0.5

SA13

Rigel

-1

SA10

SA08 -1.5 -1.5

-1

-0.5

0

0.5

1

1.5

IPCA1 Grain yield (31.7 %) 80

(b)

60

Agrano

IPCA2 KNO (19.5 %)

40

OR09 OR10

SA08

20

SA12

OR08

0

SA10

Claudio

-20

CA11 SA13

-40

Magistral

-60 SA11

-80 -80

-60

-40

-20

0

20

40

60

80

IPCA1 KNO(40.0 %) 4

(c) OR08

3

IPCA2 KW (15.7 %)

2 1

SA10 Claudio Claudioa Agrano

0

Magistral

Altair SA08

-1

SA11 SA12 SA13

CA11

OR09

OR10

-2 -3 -4 -4

-3

-2

-1

0

1

2

3

4

IPCA1 KW (54.4 %) Fig. 4. AMMI biplots for (a) GY, (b) KNO and (c) KW. Black circles: durum wheats, grey circles: spring triticales, empty circles: facultative triticale, white triangles: environments.

to 23% across a sub-group of eleven of the 20 location/season combinations. A similar level of yield superiority has been cited by Bassu et al. (2011). Compared to the experiments quoted in the latter paper, a much higher number of cultivars of both species including the most productive for this environment were compared here side

Fig. 5. Nominal yields as a function of the environment score on IPCA2. Solid lines: durum wheats, dashed lines: spring triticales; faint dashed lines: facultative triticales.

by side, in 20 different environmental conditions. The higher yield potential of triticale was even more evident when the comparison involved only the best cultivars of each species, or when it involved only spring cultivars of each species which reached flowering at a similar time. The optimal time for anthesis in these environments is in April, as later flowering crops suffer from terminal drought stress. Triticale not only out-performed durum wheat in most of the 20 environments, but also – in spite of the inclusion of several cultivars which flowered after April – in no cases under-yielded durum wheat. Thus it appears able to attain a similar yield as durum wheat even under less favourable conditions, and at the same time be more responsive to favourable conditions. The measurement of the components of yield clarified why the performance of the two species differed. The generally high levels of GY achieved (5.5–6.0 t ha−1 ) were based on an ear density usually below 450 per m2 , which resulted in a maximum of 25,000 grains per m2 , a level which probably represents the threshold below which triticale is not source-limited in the Mediterranean environment (Giunta et al., 1999). There was consequently no correlation between KNO and KW. Similarly there was no evidence for any compensation either between KPE and EPM or between KPE and KW, confirming earlier observations (Giunta et al., 2003). The yield component for which triticale demonstrated a consistent superiority was KNO, which was largely generated by a higher level of KPE at similar levels of EPM. According to Beres et al. (2010), triticales tiller less readily than bread wheat, whereas Giunta et al. (2015) showed that tillering capacity in triticale is highly cultivar-dependent, and is generally superior to that of durum wheat. It is probable that the relatively high sowing density used was not permissive of a full expression of potential species differences in tillering capacity: most of the 450 ears m−2 were borne on the main stem (the mean number of tillers per plant was 0.3). The high ear fertility of triticale reflects its long ears and the formation of many spikelets per ear (Giunta et al., 2001; Estrada-Campuzano et al., 2012). The EPM of the durum wheats, in contrast to that of the triticales, was quite responsive to the prevailing pre-anthesis conditions, confirming the plasticity for this trait highlighted in bread wheat by Sadras and Rebetzke (2013). The capacity to achieve a high KNO via a boost in KPE (as opposed to EPM) may represent an advantage in situations where the grain filling period is characterized by a moisture deficit and soils have a good soil water holding capacity. In these conditions, the water saved in pre-anthesis by a crop with a lower EPM, likely resulting in a lower leaf area index, may be crucial for the subsequent grain filling period. Species differences in the other yield component, KW, were smaller but played a key role in determining species differences in

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grain yield, as triticale out-yielded durum wheat whenever it succeeded in producing KWs comparable to durum wheat ones. The environments in which the triticale KW was comparable to that of durum wheat benefited from favourable post-anthesis conditions in terms of temperature and moisture availability. The KW of triticale was not compromised by its high KPE, as already observed by Giunta et al. (2003). The reason for this lack of compensation is that under favourable pre-anthesis conditions, both KPE and the build-up of translocatable assimilate in the stem are promoted. Triticale is more efficient than durum wheat in the remobilization of assimilate from the stem to the developing grain (López ˇ Castaneda and Richards, 1994). The ability of triticale to attain a KW comparable to that of durum wheat is highly dependent on its phenology, as demonstrated when the cultivars were grouped into classes defined by their flowering time. The early flowering spring triticales, with an anthesis date similar to the durum wheats, were able to exploit the more favourable moisture and temperature regime which prevailed during their grain filling period and to benefit from their potentially longer duration of grain filling (Giunta and Motzo, 2005). Thanks to their higher KNO, they were therefore able to out-yield the durum wheats quite considerably. Thus, the perception that triticale produces small grains is likely based on the use of cultivars with an inappropriate phenology rather than on some inherent inferiority, eventually linked to a higher contribution of smaller grains in relation to its higher KNO (Acreche and Slafer, 2006). On the other hand, the source limitation of triticale (Calderini et al., 2006) is more penalizing for this species when a late anthesis moves the grain filling period to more stressful conditions. The inter-species differences with respect to yield components can explain both their contrasting productivity and their distinct interaction with the environment (Fig. 4). The higher potential for setting grain displayed by the triticales, associated with their greater KPE, allowed them to exploit the generally more favourable environmental conditions prevailing during the preanthesis period. The associated constantly higher KNO of triticale compared to durum wheat was the reason why, also when postanthesis conditions were more limiting, triticale grain yield was not lower than durum wheat’s. The more important contribution of G × E to the variance in KNO displayed by the triticales also implied a greater capacity of this species to respond to benign pre-anthesis conditions. The difference between the two species lay in the responsiveness of triticale to the post-anthesis environment, in that a high KNO amplified any small increase achieved in KW. The AMMI analysis was effective in demonstrating that the different pattern of G × E for GY of the two species mirrored their different G × E for KW and was therefore associated to the prevailing environmental conditions during grain filling, and to species and cultivar (spring vs facultative) differences in phenology. When anthesis is delayed, as is typical of facultative cultivars, the risk of a stressful grain filling period is heightened, resulting in an increase in the G × E component’s contribution to the variance in KW. The AMMI analysis also revealed that the GY of both the durum wheat and the spring triticales was relatively stable, although the greatest stability was combined with the greatest GY in a spring triticale cultivar. A combination of yield stability and high yield potential is attractive, particularly in variable environments such as in the Mediterranean region.

5. Conclusions The identification of the main yield-determining traits of triticale and durum wheat provides a decision-making tool in the choice of species and cultivar. The contrasting ways by which the two species realize their GY have a major impact on their adaptability and yield potential. Triticale is best adapted to

Mediterranean environments – characterized by pre-anthesis periods not limiting in terms of resource availability and environmental stresses–provided that sowing density is in the range 300–350 seeds per m2 . In these conditions tillering capacity contributes much less than ear fertility to the number of grains set per unit area. This assures triticale the possibility of realizing the number of kernels per m2 sufficient to produce a grain yield at least comparable to durum wheat. At the same time triticale is able to out-yield durum wheat whenever its anthesis date falls within the optimal windows for Mediterranean environments, and particularly in seasons with favourable post-anthesis conditions, i.e. in any situation allowing the production of kernel weights similar to durum wheat. High ear fertility should be treated as an important trait in the breeding of small grain cereals, because of its positive influence over both yield potential and yield stability. Acknowledgements We thank Angelo Ara, Agostino Piredda, Paola Fenu, Paolo Manca, Roberto Leri and Giulio Manca for their assistance in field management. References Acreche, M.M., Slafer, G.A., 2006. Grain weight response to increases in number of grains in wheat in a Mediterranean area. Field Crops Res. 98, 52–59. Aschmann, H., 1973. Distribution and peculiarity of Mediterranean ecosystems. In: Di Castri, F., Mooney, D. (Eds.), Mediterranean Type Ecosystem: Origin and Structure. Springer-Verlag, New York. Bassu, S., Asseng, S., Richards, R., 2011. Yield benefits of triticale traits for wheat under current and future climates. Field Crops Res. 124, 14–24. Beres, B.L., Harker, K.N., Clayton, G.W., Bremer, E., Blackshaw, R.E., Graf, R.J., 2010. Weed competitive ability of spring and winter cereals in the Northern Great Plains. Weed Technol. 24, 08116. Calderini, D.F., Reynolds, M.P., Slafer, G.A., 2006. Source-sink effects on grain weight of bread wheat, durum wheat, and triticale at different locations. Aust. J. Agric. Res. 57, 227–233. Chen, Y., Carver, B.F., Wang, S., Cao, S., Yan, L., 2010. Genetic regulation of developmental phases in winter wheat. Mol. Breed. 26, 573–582. Estrada-Campuzano, G., Slafer, G.A., Miralles, D.J., 2012. Differences in yield, biomass and their components between triticale and wheat grown under contrasting water and nitrogen environments. Field Crops Res. 128, 167–179. Fischer, R.A., 1985. Number of kernels in wheat crops and the influence of solarradiation and temperature. J. Agric. Sci. 105, 447–461. Fischer, R.A., 2011. Wheat physiology: a review of recent developments. Crop Pasture Sci. 62, 95–114. Giunta, F., Motzo, R., Fois, G., Bacciu, P., 2015. Developmental ideotype in the context of the dual-purpose use of triticale, barley and durum wheat. Annals Appl. Biol. 166, 118–128, http://dx.doi.org/10.1111/aab.12167 Giunta, F., Motzo, R., Deidda, M., 1993. Effect of drought on yield and yield components of wheat and triticale. Field Crops Res. 33, 399–409. Giunta, F., Motzo, R., Deidda, M., 1995. Effects of drought on leaf area development, biomass production and nitrogen uptake of durum wheat grown in a Mediterranean environment. Aust. J. Agric. Res. 46, 99–111. Giunta, F., Motzo, R., Deidda, M., 1999. Grain yield analysis of a triticale (x Triticosecale Wittmack) collection grown in a Mediterranean environment. Field Crops Res. 63, 199–210. Giunta, F., Motzo, R., Virdis, A., 2001. Development of durum wheat and triticale cultivars as affected by thermo-photoperiodic conditions. Aust. J. Agric. Res. 52, 387–396. Giunta, F., Motzo, R., 2005. Grain yield, dry matter and nitrogen accumulation in the grains of durum wheat and spring triticale cultivars grown in a Mediterranean environment. Aust. J. Agric. Res. 56, 25–32. Giunta, F., Motzo, R., Pruneddu, G., 2003. Comparison of temperate cereals and grain legumes in a Mediterranean environment. Agric. Mediterr. 133, 234–248. ˇ López Castaneda, C., Richards, R.A., 1994. Variation in temperate cereals in rainfed environments. 1. Grain-yield, biomass and agronomic characteristics. Field Crops Res. 37, 51–62. Loss, S.P., Siddique, K.H.M., 1994. Morphological and physiological traits associated with wheat yield increases in Mediterranean environments. Adv. Agron. 52, 229–276. Motzo, R., Pruneddu, G., Giunta, F., 2013. The role of stomatal conductance for water and radiation use efficiency of durum wheat and triticale in a Mediterranean environment. Eur. J. Agron. 44, 87–97. Motzo, R., Giunta, F., 2007. The effect of breeding on the phenology of Italian durum wheats: from landraces to modern cultivars. Eur. J. Agron. 26, 462–470. Pejin, D., Mojovic, L.J., Vucurovic, V., Pejin, J., Dencic, S., Rakin, M., 2009. Fermentation of wheat and triticale hydrolysates: a comparative study. Fuel 88, 1625–1628, http://dx.doi.org/10.1016/j.fuel.2009.01.011

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