Evolutionary trends in morphological, physiological, agronomical and qualitative traits of Triticum aestivum L. cultivars bred in Italy since 1900

Eur. J. Agron., 1994, 3(3), 175-185

Evolutionary trends in morphological, physiological, agronomical and qualitative traits of Triticum aestivum L. cultivars bred in Italy since 1900 M.G. Canevara, M. Romani 1, M. Corbellini, M. Perenzin and B. Borghi* Istituto Sperimentale per la Cerealicoltura, Sezione di S. Angelo Lodigiano, Via Molino, 3; 20079 S. Angelo Lodigiano (Ml), Italy. 1 Present Adress : Istituto Sperimentale perle Colture Foraggere, Lodi, Italy.

Received 5 March 1994 ; accepted 11 March 1994.

* To Abstract

whom correspondence should be addressed.

The agronomical, physiological and qualitative characteristics of 34 representative cultivars of bread wheat belonging to 7 generations (groups) of cultivars produced by Italian breeders over 90 years have been evaluated. Cultivars were grown for three years in replicated trials with two husbandry conditions : old, simulating that in use in the first part of the century, and modern. It was found that there was a reduction of plant height, an increase in harvest index, reduction of the vegetative growth phase associated with a progressive increase of yield potential. With the old husbandry the cultivars did not show a clear positive trend in yield potential, indicating that genetic improvement was largely dependent on or associated with a parallel improvement of growing conditions. The greatest genetic gain was achieved with the last generation of cultivars which, with modern husbandry, produced 830 kg ha- 1 more than those of the previous group. This is an indication that breeding is not approaching a yield plateau and emphasizes its major role in accelerating the increase in yield potential. Moreover, modern cultivars have better quality indices than those of the previous groups, suggesting that Italian breeders were able to manipulate the genes controlling protein composition while selecting genotypes characterized by a shorter straw and an higher yield potential. It is concluded that in the present economic and political context where farmers are forced to optimize and probably to reduce inputs, old cultivars may be used in breeding programmes for low input conditions as donors of specific, useful morphological and physiological traits to be incorporated in future cultivars. Key-words : cultivar comparison, crop management, yield increase, yield components, breadmaking quality.

INTRODUCTION Comparisons of cultivars bred in different periods can throw an interesting light on the evolutionary trend in morphological, physiological, agronomical and qualitative characteristics of the wheats grown in a given region and provide the most direct estimate of breeding progress (Cox et al., 1989 ; Austin et al., 1980a). Comparisons of old and new cultivars have been carried out in different countries : Sweden (McKey, 1979 ; Ledent and Stoy, 1988), United Kingdom (Austin et al., 1980a ; Austin et al., 1989), France (Grignac et al., 1981), Yugoslavia (Borojevic, JSSN II61-0301/94/03!$ 4.001 © Gauthier-Villars - ESAg

1983), Hungary (Balla, 1973), New Zealand (McEwan and Cross, 1978), Australia (Perry and D' Antuono, 1989 ; Lupton and Derera, 1981 ), Argentina (Slafer and Andrade, 1989 ; Slafer et al., 1990a ; 1990b) USA (Cox et al., 1988, 1989 ; Schmidt and Worrall, 1983) Canada (Hucl and Baker, 1987), India (Kulshrestha and Jain, 1982), Mexico (Waddington et al., 1986). This approach is of particular interest in the case of Italy where intensive breeding started at the beginning of the twentieth century (Vallega, 197 4 ; D' Amato, 1989).

M. G. Canevara et al.

176

In this paper we describe the agronomical, physiological and qualitative characteristics of representative cultivars produced by Italian breeders over a 90 year period. The cultivars were grown for three years in two different husbandry conditions : old, as in the first part of the century, and modern, making use of the current high input technology.

group 0, includes local populations ; the second includes cultivars selected from local populations or derived from crosses between local populations ; the third group includes the first cultivars obtained by crossing Italian germplasm with foreign cultivars such as the Japanese Akagomugi or the Dutch Wilhelmina Tarwe. Each of the remaining groups was set up with cultivars having at least one parent belonging to the preceding group.

MATERIALS AND METHODS Agronomical trials Cultivars The cultivars grown in Italy since the beginning of the century were classified in seven groups. The first,

A selected group of 34 cultivars belonging to the seven groups (see Table 1) was grown in the Po Valley at S. Angelo Lodigiano (Milan) during three

Table 1. The 34 cultivars selected to represent the 7 generations of bread wheats cultivated in Italy in diflerent periods from the beginning of the present century.

Group

0

Cultivar No. Name

APULIA 2 *GENTILROSSO 3 *RIETI

Year of introduction or diffusion 1900 1900 1900

4 *INALLETTABILE 961917

5 *FRASSINETO 405

2

3

1927

6 *ARDITO

1916

7 *MENTANA

1918

8 VILLA GLORI

1918

9 AQUILA

1936

10 AUTONOMIA

1930

II FIORELLO

1947

12 *IMPETO

1930

13 LIBERO 14 SALTO

1927 1931

15 S. GIORGIO

1935

16 *S. PASTORE

1940

Origin

Group

Local population Local population Local population

4

Selection from Hatif Inversable Vilmorin Selection from Gentilrosso

5

(Rieti x Wilhelmina T.)-21 X Akagomugi (Rieti x Wilhelmina T.)-21 X Akagomugi (Rieti x Wilhelmina T.)-21 xAkagomugi S. Giovanni x Damiano Frassineto 405 x Mentana Cologna 188 x Damiano Frassineto 405 x Villa Glori Apulia x Ardito (Ardito x Akagomugi) x (Wilhelmina x Rieti) Inallettabile 95 x Ardito Balilla x Villa Glori

6

*

Cultivar No. Name

Year of introduction or diffusion

17 ABBONDANZA

1950

18 LEONE 19 *MARA

1955 1947

20 *PRODUTTORE S.6

1955

21 AQUILEIA

1974

22 * ARGELA TO 23 FARNESE 24 JRNERJO

1959 1970 1970

25 LIBELLULA

1970

26 LONTRA

1970

27 *MARZOTTO 28 ORSO 29 STRAMPELLI N.

1969 1972 1970

30 *CENT AURO 31 GEMINI

1983 1981

32 LEOPARDO

1981

33 *MEC

1974

34 PANDAS

1983

Origin

Autonomia x Fontarronco S. Pastore x Funo Autonomia x Aquila Saito x (Sajtama 27 x Quaderna) (Tevere x Giuliari) x Gallini Mara x Orlandi Funo x S.l Produttore S.6 x Manitoba (Tevere x Giuliari) x S. Pastore (Fortunato x Freccia) x ATM 43 Mara x Impeto Funo x Produttore Libero x (S. Pastore x Jacometti 49) Strampelli x Irnerio (Argelato x Von Rumkers Erly) x (lmpeto x Damiano) -158 (Irnerio x Libellula) x Leone Marzotto x Combine Orso x (Bezostaja 1 X S.l) X (Generoso 7 x Marzotto)

Cultivars included in growth analysis study. Eur. J. A)?ron.

Evolutionary trends among wheat cultivars in Italy

consecutive seasons (1987 -88, 1988-89 and 1989-90) in split - plot trials with four replications. To minimize intergenotypic competition, a very common phenomenon in this kind of agronomic trial (Austin and Blackwell, 1980b ), cultivars differing in plant height or life cycle were allocated to different main plots. The elementary plot consisted of 8 rows, 7.5 m long, corresponding to an area of about 10m2• In each year, two trials were conducted at the Institute experimental farm. The first trial was sown in a poor soil (sand 70 per cent, silt 25 per cent, clay 5 per cent, organic matter 1.1 per cent, exchangeable Pp 5 - Olsen method - 44 p.p.m.) adopting husbandry hereafter referred to as old, as in the first part of the century (sowing 300 kernels m- 2 in 6 rows drilled 25 em apart, 30 kg N ha -I in two top dressings, no herbicide or pesticides) and a second trial in a rich soil (sand 43 per cent, silt 46 per cent, clay 11 per cent, organic matter 2.2 per cent, exchangeable P 2 0 5 - Olsen method - 66 p.p.m.) with modern husbandry (sowing 500 kernels m- 2 in 8 rows drilled 17.5 em apart, 150 kg N ha- 1 in three top dressings, chemical control of weeds and foliar diseases). In the modern husbandry, lodging was reduced by supporting the plants with nets (20 X 20 em mesh). On the day of harvesting, nets were removed from the plots early in the morning to avoid shattering, and culm samples were hand cut from each plot (0.2 m 2 ) at ground level for the estimation of spikes m - 2• A sub-sample of 20 culms was used to provide an estimate of yield components and of harvest index. The plots were then combine harvested and hectolitre weight and grain yield (13 per cent moisture) were determined after seed cleaning. Growth analysis and yield components In 1989-90 a growth analysis of two cultivars in each group (marked with * in Table 1) grown according to the old and modern systems was carried out during grain filling. Plant samples were harvested at four stages : at anthesis, 2 and 4 weeks later, and at maturity. A sub-sample of 20 representative culms was taken at random from the inner rows of each plot and was divided into flag leaf lamina, other leaf laminae, last internode (peduncle), remaining internodes and spike. Green areas were determined as previously described (Borghi et al., 1982). Quality evaluation Seeds of the 4 replications from each cultivar grown under modern husbandry were combined and a sample of 2 kg was milled with a BONA GRB mill. The flour samples were evaluated for protein content with a NIR apparatus ; SDS tests were carried out according to Preston et al. (1982) with minor modifications. Rheological evaluation was performed with Vol. 3.

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3- 1994

177

the Chopin alveograph adopting the method indicated by the manufacturer and with the Brabender farinagraph using a 50 g mixer (AACC method 54-21). Falling number was determined according to the AACC method 56-81B. Baking tests were carried out according to Borghi (1979). Statistical analysis ANOV A analysis was carried out considering husbandry conditions, groups of cultivars and years as fixed effects (factors) and cultivars within groups as random. Thus the cultivar effect was subdivided in group and residual (cultivars within groups). There were only two cultivars belonging to group 1 (selections from local populations) and in the presentation of the agronomic and qualitative results they were included with group 0 (local populations). RESULTS Agronomical characteristics Table 2 summarizes the ANOV As and the means for each level of each factor for grain yield, plant height, heading date and hectolitre weight. All the main effects were statistically significant (p = 0.01) with the exception of plant height for the husbandry factor. About 75 per cent of the variability between cultivars for grain yield and for plant height was accounted for by differences between groups. Grain yield was 3.82 t ha- 1 in local populations and 5.11 t ha- 1 in the most recent cultivars, while plant height decreased from 111.4 em to 80.2 em. Most of the first order interactions were statistically significant. Figure 1 illustrates the year x husbandry interaction for grain yield. Differences between husbandry were highly significant in two years, with the greatest differences in 1989 when the modern husbandry gave twice the yield of the old. The lack of significance in 1988 was due to a late hailstorm which affected the field containing the modern husbandry trial, causing a yield loss of about 30 per cent. The comparison between husbandry conditions as regards grain yield has therefore been based only on the years 1989 and 1990. In Figure 2, which shows the husbandry x cultivar and husbandry x group interactions, it can be seen that the adoption of modern husbandry increased grain yield in all cultivars ; the yield increase was greatest, however, in the most recent cultivars. In contrast, with the old husbandry the yield of the modern cultivars was similar to that of the local populations. Modern husbandry significantly increased plant height in the year 1989 when the cultivars were the shortest (95.9 em against 101.0 em in 1988). Figure 3, illustrative of husbandry x cultivar and husbandry x

M. G. Canevara et al.

178

Table 2. Variance analysis and mean values of agronomic characters of 34 cultivars belonging to 6 groups grown for three years in two husbandry conditions. A) Variance analysis (')

Grain Source of variation d.f.

Year Husbandry Group Residual (')

(y) (h) (g) (r)

y X h h X g h

x r

2

Plant Heading Hectolitre height time weight (em) (days from (kg hl- 1) I April)

29.1** 902.6** 5 30.0** 28 6.3**

1802** 59 25358** 6011 **

706** 401** 525** 245**

2444** 5415** 68** 62**

2 292.5** 15 14.1 ** 28 1.5

3159** 535** 88**

252** 12 3

261** 63** 20*

32 5.8

I

6

3.0

3.2

I

408

Error c.v. %

yield (t ha- 1)

0.4 14.7

group interactions, shows that cultivars of groups 0, 2 and 3 with a plant height of over 1 m did not increase in height with modern husbandry, while the short straw cultivars of groups 4, 5 and 6 reacted positively to the more favourable growing conditions, producing taller canopies. The cultivars differed significantly in life cycle : remarkable differences in heading time were evident among local populations (groups 0 and 1 in Figure 4). For group 3 and later groups the differences between cultivars within a group were limited to 2-4 days and the mean heading time of groups 3-6 was around 6 May, corresponding to a gain of one week in earliness over the local populations. Cultivar differences in hectolitre weight were statistically significant, the greatest values being obtained for group 6, probably because these cultivars were more resistant to lodging in modern husbandry conditions (Figure 5).

B) Mean values

Year 1988 1989 1990 l.s.d. p = 0.05

4.35 4.81 4.17 0.11

101.0 95.9 98.5 0.2

36.9 39.0 35.8 0.2

73.7 76.9 71.0 0.4

Husbandry Old Modern

3.39 5.49

98.2 98.8

37.9 36.5

71.3

3.82 3.81 4.34 4.38 4.74 5.11 0.26

111.4 117.2 108.2 94.0 88.6 80.2 2.3

41.5 36.7 36.1 36.9 36.6 36.3 0.4

73.5 72.6 74.1 73.1 74.0 74.9 1.0

Group 0 2 3 4 5 6 l.s.d. (p

= 0.05)

• oLD DMODERN

I

76.5

CULTIVAR OR GROUP Figure 2. Grain yield, t ha- 1, for the years 1989 and 1990, showing husbandry x cultivar and husbandry x group interactions. Vertical bars represent one l.s.d. (p = 0.05) for the interactions cultivar x h and g x h. See Table 1 for names of cultivars.

1 ( ) Only the most important sources of variation are reported. (') Between cultivars within group.

150 -

"i CIJ ..c

ci' ....J w

>= z

~

:r

~LDOMODERN

E

140

~

-

~ MODER!:Q I I

(.) 130 L I-" I I 120 -

6

0

5

I

4

1--

3

:5

w 110 L

z

a.

2

80 .

0

0

CULTIVAR OR GROUP

c

YEARS Figure 1. Husbandry x year interaction for grain yield, t ha -I. Verticul bur represents one l.s.d. (p = 0.05).

Figure 3. Plant height, em, showing husbandry x cultivar and husbandry x group interactions. Vertical bars represent one l.s.d. (p = 0.05) for the interactions cv x hand g x h. See Table 1 for names of cultivars. Eur. }.

A,~-ron.

179

Evolutionary trends among wheat cultivars in Italy

Figure 4. Heading time of cultivars and groups listed in Table 1. Vertical bars represent on e l.s.d. (p = 0.05) of cultivar and group.

85 L

~

L

~80 X

• OLD 0 MODER; ] -

f-'

:I:

~ 75 -

w

~

between cultivars was accounted for by differences between groups. This suggests that the traits studied had been modified during the 90 years of genetic improvement. However, the number of spikelets per spike and the number of seeds per spikelet fluctuated and in general an increase of the one was associated with a corresponding decrease of the other, revealing mutual compensation. As a result of this compensation, the number of seeds per spike in the last three groups was nearly constant. Kernel weight decreased from 42.1 mg in group 0 to 34.9 mg in group 4 but increased to 36.1 mg in the modern cultivars. Owing to the compensation among these three yield components, grain yield per spike in the recent cultivars was not significantly different from that of the old local populations. In contrast, the number of spikes m - 2 was greater by about 20 per cent in groups 3, 4 and 5 and by about 40 per cent in the last group than in groups I and 2. Culm weight significantly decreased from group 0 to 6 but this decrease was more than compensated by a better dry matter partitioning to kernels (HI increased from 34 up to 44 per cent) and by a gradual increase in the number of culms per unit area of land.

w ~ 70

:::;

Growth analysis

0

f-

f;:l65 :I:

60

0

2

3

4

5

6

GROUP Figure 5. Hectolitre weight, kg h/ - 1, showing husbandry x group intera crion. Vertical bar represents one l.s.d. (p = 0.05).

Yield Components Yield components were determined in the year 1988 in the old husbandry and in 1990 in old and modern . Table 3 gives the ANOV As and the mean values for each level of each factor. Average grain yield was slightly but significantly greater in 1988 and, similarly, yield components were greater in 1988, with the exception of spikelet fe rtility (seeds per spikelet), which was significantly greater in 1990. Yield and yield components differed in the two seasons and several year x group and year x residual interactions were significant : spikelets per spike being the only trait where interactions with the genotypes were not statistically significant. Modern husbandry affected grain yield by increasing the number of spikes m- 2, spikelet fertility and harvest index. With the exception of seeds per spike and seeds per spikelet, the cultivars or their groups reacted similarly to the two husbandry conditions. Cultivars differed in all the traits considered but, as already stated with regard to grain yield and plant height, most of the variation Vol. 3. n' 3- 1994

The study was carried out in 1990 on two representative cultivars of each group and green area parameters were expressed both on the basis of a culm and per unit of ground (Figure 6 and Table 4). Maximum LAI was achieved at heading time : the value remained nearly constant for 2 weeks after flowering and then decreased by 20 per cent during the following 2 weeks. Four weeks after flowering the organs above the last node, including the flag leaf lamina, flag leaf sheath, peduncle and ear structures accounted for 56.7 per cent of total green area while the lamina of the leaves represented only 15 per cent. The ANOV A of green area per culm given in Table 4 shows that with old husbandry, the green parts above the last internode and particularly the flag leaf were significantly larger than with modern husbandry but that the total green area did not differ between the two husbandry treatments, probably because in 1990 plant height, and therefore the green area of the basal internodes, was significantly less with old husbandry (data not shown). No significant husbandry x stage interactions were observed for the different green parts, suggesting that the growing conditions did not affect the rate of senescence. The cultivars differed in rate of senescence but thes;e differences were related to the grouping of cultiv~rs only as regards flag leaf and other leaves ; in the 'case of total green area or green area of the upper parts, the significance of the residual x stage interactions indicates that the cultivars showed patterns of senescence not related to their assignment to the seven groups.

M. G. Canevara et al.

180

Table 3. Variance analysis and mean values of grain yield and yield components of 34 cultivars belonging to 6 groups grown for three years in two husbandry conditions. A) Variance analysis ( 1)

Source of variation

d.f.

(1988 and 1990 old) (y) Year I (g) Group 5 Residual (')(r) 28 y X g y x r Error c.v. % (1990) Husbandry (h) h X g h x r Error c.v. %

5 28 201

Grain yield (t ha- 1)

Spikelets spike-' (No.)

Seeds spikelet-' (No.)

4.44** 22.32** 5.82**

115.0** 37 .2** 6.9**

2.25** 0.79** 0.43**

2.22** 1.28** 0.42 15.1

1.3 2.3 2.0 7.8

0.3 1.1 2.1

Kernel weight (mg)

Seed spike-' (No.)

Yield spike-' (g)

Spike

H.I.

(No.)

Culm weight (g)

m-2

(%)

79.9 366.9** 126.3**

132** 355** 149**

0.414** 0.093 0.354**

670 55292** 14285**

0.07 3.45** 1.27**

368.1** 662.9** 120.9**

0.29* 0.12 0.09 16.3

99.1 ** 38.7 28.4 16.9

44 69** 17 10.9

0.227** 0.116 0.067 21.7

22692* 7086 7316 23.7

0.53 0.48** 0.20 15.1

115.8** 26.9 23.0 12.1

679.6** 70.9 49.2* 25.3 16.3

38 42 28 21 12.4

1.103 0.094 0.112 0.069 22.8

2509** 171 87 94 26.9

0.47 0.32 0.46** 0.21 15.6

824.3** 15.2 32.8 20.2 11.7

I 03.8** 2.1 * 0.6 0.4 16.2

6.9

2.43** 0.26** 0.14* 0.06 14.4

Husbandry (1990) Old Modern

3.73 4.79

17.9 17.8

1.60 1.87

28.7 33.1

36.7 37.7

1.06 1.24

317 403

2.91 3.03

36.1 41.0

Year 1988 1990

4.35 4.17

16.6 17.9

1.92 1.74

32.0 30.9

38.6 37.2

1.23 1.15

363 360

3.01 2.97

40.8 38.5

Group 0 2 3 4 5 6 l.s.d. (p = 0.05)

3.64 3.56 4.11 4.20 4.63 4.92 0.27

16.9 17.6 15.9 17.9 17.5 18.3 0.6

1.56 1.92 1.87 1.86 1.92 1.78 1.12

23.5 34.1 29.6 33.1 33.6 32.6 2.2

42.1 37.3 40.3 34.9 35.9 36.1 1.7

1.12 1.28 1.19 1.19 1.21 1.18 0.11

330 300 358 364 369 421 35

3.28 3.50 3.07 2.92 2.81 2.64 0.18

33.8 35.7 38.4 40.3 42.7 44.0 2.0

I 5 28 67

1.5

B) Mean values

(') Only the most important sources of variation are reported. (') Between cultivars within group.

3CO

280 260 240 220 200 <::; 180 160 1i 140 c. ,.. 120 E u 100 80 60

~a!b 'E

.§

x

'

D

z

<6

UJ

0::

< z

t±J5

0::

4C 20 0

1 ~

UJ

(.!)

4 3

GROUP

5

0

2

4

3

5

6

GROUP

Figure 6. Green area of the different parts of the plant (a) and total green area per unit of ground (h) Table I. Vertical bars represent one l.s.d. (p = 0.05 ).

'~f

the 7 groups listed in Eur. 1. A,Rron.

Evolutionary trends among wheat cultivars in Italy

300 250 ~

a

[ . OLD

0 MODERN

181

I

10 E

'E

x

200

w

::J

0 ~

()

Qj 150

8

b

•oLD

0

2

I

MODERN

6·

<(

a.

w 4 a:

N

E () 100

<(

z

w w

a:

50

(!)

2[ 0

0 0

3

4

5

6

GROUP

3

GROUP

Figure 7. Total green area per culm (a) and per unit area of ground (b) showing husbandry x group interactions. Vertical bars rep· resent one l.s.d. (p = 0.05).

Table 4. Variance analysis and mean values of green areas of 14 cultivars belonging to 7 groups grown in 1990 in two husbandry conditions. A) Variance analysis (')

Green area (cm 2 culm-') Source of variation d.f. Total Superior Spike Flag (4) leaf 37 Husbandry (h) (g) 6 2132** Group Residual (') (r) 7 408** (s) 2 3681 ** Stage h h h y r h h

X g

x r X S X S

x s X C X g X C x r

Error c.v. %

6 7 2 12 14 12 14

61** 244** 132 93 225** !57** 147**

83

41 10.1

Total green Other area leaves m2 m-2

134** 68** 15 18.5** 417** 29** 49** 43** 13.6** 233** 12** 51** 9 8.4** 491 ** 27** 242** 2999** 37.9** 7 2 8 2 6 2 21 43** 7 5 26

4 3 4 9** 6 3 2

37** 10.3** 13* 11.0** 9 0.4 19** 0.5 51** 2.3 II 0.2 0.2 6

15 12.9

13.0

32 21.6

2.2 6 26.6 22.7

202 199

99 93

29 28

28 24

30 28

6.26 6.92

218 214 171 7

86 105 97 5

26 30 29

32 27 19 2

54 26 8 3

7.21 6.90 5.66 0.57

B) Mean values (')

Husbandry Old Modern Stage l anthesis 2 + 2 weeks 3 + 4 weeks l.s.d. (p = 0.05)

1 ( ) Only the most important sources of variation are reported. (2) Between cultivars within group. (') For group see Figure 6. (') Flag leaf lamina, flag leaf sheath, peduncle and ear structures.

Vol. 3, n" 3- 1994

The average group values of the green areas shown in Figure 6 reveal a gradual decrease from group 0 to 6, compensated by a larger number of culms m- 2 in the most recent cultivars (see Table 3), resulting in a greater green area index per unit of ground in modern cultivars. However, the evolutionary trend of the green areas was dramatically different in the two husbandry conditions, as illustrated in Figure 7, where the husbandry x group interactions for green area are shown. All the culti vars of groups 1, 2, 5 and especially those of group 6 were heavily penalized with old husbandry. Qualitative characteristics Protein content gradually decreased from group 0 to 5 (Table 5). This decrease, associated with the increase in yield potential, with the modification of plant architecture and with the better dry matter partitioning to reproductive organs, was compensated by the selection of genotypes with a better protein composition. This is clearly indicated by the quality score listed in the last column. This score reflects the effect of each high molecular weight (HMW) glutenin subunit on gluten quality, principally the alveograph W value. According to Pogna et al. ( 1989), the minimum overall HMW subunit score of a cultivar is 4, the maximum 17. The average quality score of the six groups increased from 5.5 in group 0 to 10.9 in group 6. The SDS sedimentation test, a screening test for breadmaking quality evaluation, did not clearly confirm the evolution in protein composition in the groups and indicated only the statistically significant lower quality of the cultivars of group 2. Alveograph parameters confirmed the poor quality of group 2, characterized by the lowest W value, which gradually increased to 160 ergs in modern cultivars. The increase in W was achieved by incorpo-

M. G. Canevara et al.

182

Table 5. Variance analysis and mean values of quality characters of 34 cultivars belonging to 6 groups grown in the years /989 and 1990 in modern husbandry conditions. A) Variance analysis SDS Sedimentation test Prot.

Source of variation d.f.

(%)

Year (y) Group (g) 5 5 y X g Error (') 56 (28)

total specific ( 1) (ml) (ml)

9.2** 436** 2.3** 14 7 0.1 0.2 8

17.1 ** 1.4* 0.5 0.5

Farino graph

Alveograph

w

G

p

ergs

(%)

(mm)

202** 156 75** 9 II 19 23 17

L (mm)

P/L (mm)

B

(min)

672** 2121** 2.30** 0.23** 0.64 83** 140 0.06 93 15 0.35 0.07 68 16

Loaf volume (ml)

El2 Total Specific (') Falling Quality CD number score(') (min) (B.U.) (sec.)

5.96

63**

42

98.7*

II

4.50

15

30

34.3

41

4.89 1.92 4.61 3.61 3.42 5.15

103 195 141 116 130 76 48

678 603 703 662 649 664

54.8 49.2 59.3 57.0 62.1 61.3 69

392 355 397 367 369 396

B) Mean values

Year

1989 1990

Group 0 2 3 4 5 6 l.s.d. (p = 0.05)

10.9 11.7

67.9 83.9

6.21 7.21

137.5 102.6

24.2 24.3

60.5 40.3

92.6 128.4

0.71 0.34

12.0 11.6 11.5 10.9 10.7 11.2 0.4

76.0 68.2 80.3 74.9 74.3 76.8 7.9

6.3 5.9 6.9 6.8 6.8 6.9 0.6

131.5 65.2 101.8 109.7 126.4 160.0 35.0

23.5 21.3 23.6 22.1 22.3 21.8

50.2 37.1 43.9 46.9 56.1 63.8 10.7

113.8 97.1 124.1 121.8 103.1 100.1

0.47 0.42 0.39 0.46 0.64 0.75 0.22

1.96 1.53 2.15 1.23 1.47 1.65

5.5 5.6 7.2 7.3 8.4 10.9

( 1)

Total/protein content. The quality score represents the average value of all the Italian cultivars included in each group. (') The error includes the variance between cultivars within group and the interaction with years.

e)

rating alleles coding for protein subunits responsible of gluten strength as indicated by the increase of the alveograph P parameter and of the P/L ratio. The farinograph test (carried out in one year only) confirmed that recent cultivars are more tolerant to prolonged mixing (parameters CD and E12) and that this result was achieved without increasing the developing time (B parameter). Bread volume, a trait affected both by protein concentration and protein composition, did not reveal the variations in protein composition occurring in time, while the low specific volume confirmed the poor quality of the cultivars of group 2. The falling number test showed very large values, always over 300 seconds, for all cultivars, indicating that, in the conditions of our experiments, sprouting did not represent a negative factor affecting grain quality. DISCUSSION AND CONCLUSIONS The evolutionary trends within the Italian germplasm are partly similar to those previously observed in the studies mentioned in the Introduction and car-

ried out in several wheat growing areas of the world : gradual reduction in plant height associated with an increase of harvest index, reduction of the vegetative growth phase, all modifications associated with a progressive increase in yield potential. However, some particular aspects of the evolution of the Italian germplasm should be noted. For instance, the first generation of cultivars selected from local populations or from intervarietal crosses within the Italian germplasm (cultivars included in group I) did not furnish outstanding results even though improved cultivars such as Inallettabile 96, Frassineto 405 or Carlotta Strampelli gradually replaced the old local populations. The first spectacular achievement in breeding for high yield was to obtain early ripening cultivars, thus avoiding the late rust attacks which, together with the anticipated termination of the life cycle caused by high temperatures and depletion of the water available in the soil (a complex phenomenon called 'stretta' in Italy, 'echaudage' in France, 'haycuring' in the United States), were responsible for severe yield losses. This goal was achieved by the renowned breeder Nazareno Strampelli with the first generation of cultivars derived from intervarietal crosses between the Italian germplasm and the Japanese cultivar Akagomugi. In fact cultivars such as Eur. 1. A):?"ron.

Evolutionary trends among wheat cultivars in Italy

Ardito, belonging to group 2, were about one week earlier than the old local populations (Figure 4). The optimization of flowering time for the seasonal cycle in a specific environment represents a genetical improvement that, once achieved, cannot be further exploited (Fischer, 1980). It is a matter of record, as observed by Martinic (1980), that, in spite of the great availability of good sources of earliness, no successful cultivar five of more days earlier than San Pastore (number 16 in Figure 4) has ever been put into cultivation in South Europe. The reduction of plant height was achieved as early as 1916 with Ardito, the first cultivar to be widely used, being grown in 1929 over more than 0.5 million ha. However, breeding for short straw become an important selection objective only at the beginning of the 1930s when husbandry conditions improved thanks to a larger availability of mineral fertilizers (nitrogen in particular) and to the mechanization of soil tillage. It is interesting to notice that the cultivars grown during the 1930s such as Mentana (number 7 in Figures 3 and 4), were taller than those used in the 1920s (Dalrymple, 1986). On the other hand, in the reports of cultivar trials published in the first quarter of this century, plant height was not considered by breeders and agronomists a critical trait affecting yield potential (see for instance Bresaola, 1930 ; Michahelles, 1926 ; Bassi, 1924 ). Italian breeders found interesting sources of dwarfism in the Japanese germplasm : Strampelli started using Akagomugi, a culti var carrying Rht8 and Rht9 genes located on chromosomes 2B and 7B respectively (Law, 1983), in his breeding programme in 1912. A second important source of dwarfism was found later in another Japanese cultivar, Saitama 27, introduced into Italy in 1935 by the seed company Produttori Sementi. According to Worland (1986) and Worland and Petrovic (1988) this cultivar carries the Rhtl s dwarfing gene located on chromosome 4A, allelic to Rhtl and Rht3. This gene was introduced into the third generation of cultivars (see for instance Produttore in group 4) at the end of the 1940s, and is present in the majority of the modern cultivars. All the cultivars bred in Italy carry one or more dwarfing genes derived from the two above mentioned Japanese cultivars ; however, the selection for short straw probably involved other minor genes, as indicated by the progressive reduction of plant height, leading to the most recent cultivars of group 6. Law (1983) has indicated that the adoption of the Japanese cultivar Akagomugi as a source of both earliness and dwarfism was a particularly wise decision because each of the two characteristics appears to be controlled by two major genes located on chromosomes 2D and 5B and in both these chromosomes there is a close linkage between the earliness gene and the dwarfing gene. It was therefore relatively easy to incorporate in the new cultivars earliness and Vol. 3, n' 3- 1994

183

short straw, two crucial traits which substantially increased yield potential. According to Cox et al. (1988) the evaluation of cultivars from different periods in common environments provides the most direct estimate of breeding progress ; however, no method for estimating long term breeding progress can completely separate genetic effects from those associated with their interaction effects and, particularly, with improvements in husbandry. Our approach based on the comparison, repeated for three seasons, of cultivars from different periods grown in two contrasting husbandry conditions may facilitate the interpretation of the results and contribute to the separation of genetic and environmental factors affecting the performance of old and modern cultivars. With old husbandry the cultivars did not show a clear positive trend in yield potential ; in fact the highest yield was achieved by the cultivars of group 3 (12.5 per cent more than the local populations) while modern cultivars yielded only 5 per cent more than local populations (Table 6), indicating that genetic improvement was largely dependent on, or associated with, a parallel improvement of growing conditions. With modern husbandry the cultivars belonging to group 6 yielded 46.9 per cent more grain than local populations. However, this estimate of breeding progress does not take into account the improvement of lodging and disease resistance because the old cultivars were supported by a coarse nylon netting and foliar diseases were controlled by chemical treatments. Comparing the yield potential of the cultivars in their optimal growing conditions, i.e. old cultivars with old husbandry and modern cultivars with modern husbandry, the yield advantage of the latter increased to 261 per cent. Table 6 reveals that the greatest genetic gain was achieved with the last generation of cultivars which, on average, produced 830 kg ha- 1 more than those of group 5. This is an indication that the yield plateau has not been reached and emphasizes the continuing role of breeding in increasing yield potential. Moreover, our modern cultivars show better qualitative indices than those of the previous groups. Hucl and Baker (1987) posed the Table 6. Genetic gain in wheat yields (as percentage of local populations) of groups of cultivars of different periods and increase in yield potential under modern husbandry for each group. Group

2 3 4 5 6

kg ha- 1

Husbandry Old

Modern

-

+ + + + +

II

+ 12.5 2.5 + 3.9 + 5.0

6.6 17.1 20.7 30.2 46.9

330 550 180 470 830

M. G. Canevara et al.

184

question of whether the high yield potential of semidwarf cultivars can be combined with the high breadmaking qualities of traditional Canadian cultivars. Apparently the Italian breeders were able to manipulate the genes controlling protein composition while selecting genotypes characterized by a shorter straw and a higher yield potential. Austin et al. ( 1989), on the basis of the results of several studies, calculated the genetic gain in yield. The values ranged from 6-8 kg ha- 1 yeac 1 in regions like Western Australia and the Southern Great Plains in the USA, characterized by very low mean yields, to 59 kg ha- 1 yeac 1 in N.W. Mexico. Our results, relating to a period of 80 years, give an estimate of 29.1 kg ha- 1 yeac 1 if the comparison is based on the results of modern husbandry, increasing to 56.2 kg ha- 1 year- 1 if the comparison is with the performance of the local populations cultivated under old husbandry. In experiments carried out in other wheat growing areas of the world it has been possible to identify the yield components more closely associated with the increase of yield potential : only in a few cases have modern cultivars produced larger kernels ; generally they produce more grains per spikelet, and therefore per spike, and seldom more spikes m- 2 (see Feil, 1992 for a review). Italian breeders were mainly concerned with the improvement of the yield per spike ; in fact the numbers of fertile spikelets per spike and seeds per spike were considered crucial selection traits (Maliani and Michahelles, personal communication). A posteriori evaluation of the breeding work done in Italy does not reveal any clear trend in spike dimensions over time (Figure 8). Breeding progress seems to depend on a gradual modification of complex morpho-physiological traits, mostly but not exclusively associated with the reduction of culm length, leading to a plant type very close to Donald's wheat ideotype (Donald, 1968). One may speculate that visual selection in the nursery on the basis of spike morphology allowed breeders to select those lines with the minimal qualifications for inclusion in preliminary yield trials, the final identification of the new cultivars probably being based mainly on their yield performance in trials sown at normal seed density. Furthermore, the tendency in Italy to adopt heavy seed rates (500-700 seeds m- 2) may have favoured the diffusion of cultivars able to yield well at a very high spike density. The pre-eminent role of yield trials, rather than visual selection, in breeding progress is also revealed by the fact that the largest yield increase was achieved with the last generation of cultivars bred in the 1980's, a period characterized by an intensive mechanization of field experiments consequent on the introduction of plot seeders and harvesters. In conclusion, the evaluation of cultivars bred in different periods in Italy shows the trend common to

0 GROUP 2 0 GROUP 3 0 GROUP 4 D GROUP 5. GROUP 6

l

Figure 8. Variation of grain yield and yield components in the groups 2, 3, 4, 5 and 6 expressed as percentages of the values observed in local populations (group 0).

the history of the genetic improvement of cereals in other regions of the world : optimization of the life cycle in relation to the main environmental constraints, progressive reduction in the size of the vegetative portions of the plant, associated with the modification of plant architecture. The new genotypes are, therefore, adapted to perform best under intensive crop management which includes high seed rates, chemical control of weeds, heavy nitrogen dressings. In fact, in our experiments, modern cultivars did not reveal a great advantage over the local populations when grown in conditions of primitive husbandry. However, the achieved yield level of 3 t ha- 1 with the old system, 50 per cent less than that obtained with modern husbandry and a yield level well below that which is now economic, does not necessarily indicate that modern cultivars could not be grown in a less intensive farming system. For instance Austin et al. (1989), comparing modern and old cultivars over a wide range of nitrogen fertilization in weed-free conditions, found that modern cultivars gave 40 per cent more grain yield than the old ones at all levels of nitrogen fertilization. In the present economic and political context where farmers are forced to optimize and probably to reduce inputs, cultivars able to tolerate a moderate reduction of the inputs are needed. It will be interesting to reconsider old cultivars not as candidates for the future low input agriculture, as has been suggested by some supporters of "biological agriculture", but as donors of specific, useful morphological and physiological traits.

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Evolutionary trends among wheat cultivars in Italy

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