EXPERIMENTAL INSITUTUE FOR CEREAL RESEARCH
via Cassia 176 - 00191 Rome, Italy, and
INSTITUTE OF PHYTOPATHOLOGY
College of Agriculture, Università di Bologna, via filippo Re 8, 40126, Bologna, Italy.
V. Vallega, C. Rubies-Autonell, and C. Ratti.
Wheat soilborne mosaic virus is widespread in the northern and central regions of Italy, causing severe economic losses on both common and durum wheat crops. Yield losses of up to 50 % and 70 % have been recorded on susceptible cultivars of common wheat and durum wheat, respectively. WSBMV also has been detected recently in a number of farms in southern Italy and in Sicily. During the 2000-01 season, 31 durum wheat cultivars were assayed in a severely WSBMV-infested field situated near Minerbio (Bologna) to study their reaction to this virus. The cultivars were grown in 10-m^2^ plots distributed in the field according to a randomized block design with three replicates. As in previous years, resistance to WSBMV was evaluated on the basis of DAS-ELISA readings, symptom severity (on a 0-4 scale), and agronomic performance. Symptom severity (mean score = 1.1; range = 0.1-3.0) and ELISA values (mean = 0.585; range 0.0-1.159) were moderately high. Foliar samples from cultivars Neodur and Colorado had null ELISA values, remained symptomless throughout the season, and produced relatively high grain yields. Cultivars Lloyd and Nefer showed moderately high levels of resistance, confirming their good performance in previous trials, and the same was observed for cultivars Giotto, Meridiano, and Vitron, tested for the first time. The cultivar Provenzal, classified as susceptible in a previous trial, showed a high degree of resistance during the 2000-01 season. All the other cultivars assayed proved at least moderately susceptible to WSBMV. Simple correlation coefficients between agronomic data, ELISA values, and symptom scores were relatively high and mostly statistically significant (Table 1). Regression analysis indicated that the five cultivars representing the highest disease scores (i.e., Vesuvio, Simeto, Cirillo, Claudio, and Portorico) suffered grain losses attributable to WSBMV of about 50 % and a mean plant height reduction of about 10 %.
| Trait | Disease severity | ELISA values |
|---|---|---|
| Grain yield |
- 0.621** |
- 0.570** |
| Test weight |
- 0.315 |
- 0.371* |
| Plant height |
- 0.645** |
- 0.404* |
| 1,000-kernel weight |
- 0.288 |
- 0.079 |
| ELISA value |
0.799** |
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Thirty-five cultivars of common wheat were grown in a severely WSBMV-infested field near Minerbio (Bologna) during the 2000-01 season. Entries were grown in 10-m^2^ plots distributed in the field according to a randomized block design with three replicates. Resistance to WSBMV was evaluated only on the basis of DAS-ELISA readings and symptom severity (on a 0-4 scale). Agronomic data also were collected, but could not be used with sufficient confidence as a resistance parameter because various cultivars were very severely damaged by yellow rust. Symptom severity (mean score = 0.5; range = 0.0-1.7) and ELISA values (mean = 0.656) were relatively low, especially if compared with to those observed on the 33 durum wheats grown in an adjacent field. Eight of the common wheat cultivars analyzed, Belfiore, Colfiorito, Enesco, Etecho, Genio, Pandas, Tremie, and Victo, had null ELISA values and remained nearly asymptomatic throughout the entire season. Belfiore, Etecho, and Victo had not been assayed before, whereas the other five cultivars also had been classed as highly resistant in previous trials. The cultivars Cranklin, Faro, Guadalupe, Marvao, Positano, Ravenna, and Tibet, tested in 2000-01 for the first time, proved susceptible to WSBMV. As might be expected because of the effects of the concomitant yellow rust epidemic, the agronomic data collected were not significantly correlated with either ELISA values or symptom scores (Table 2). Therefore, the damage caused by WSBMV could not be estimated.
| Trait | Disease severity | ELISA values |
|---|---|---|
| Grain yield |
- 0.246 |
- 0.304 |
| Test weight |
- 0.005 |
- 0.058 |
| Plant height |
- 0.352 |
- 0.225 |
| 1,000-kernel weight |
- 0.050 |
- 0.204 |
| ELISA value |
0.834** |
--- |
EXPERIMENTAL INSITUTUE FOR CEREAL RESEARCH
via Mulino, 3 - 26866 S. Angelo Lodigiano (LO), Italy.
M. Perenzin, M. Corbellini, and G. Boggini.
In the present economic and political context where farmers are forced to reduce inputs, bread wheat cultivars able to tolerate a moderate reduction in inputs are needed. The old Italian varieties are not useful for this purpose, mainly because of their low-yielding ability and very poor bread-making quality. Consequently, attention is on the selection of genotypes that can sustain high productivity at reduced rates of chemical applications (fertilizer, herbicides, and pesticides). Field trials in an organic-cropping system allowed the identification of modern genotypes that can provide a satisfactory yield without a high reduction in bread-making quality.
G. Boggini, M. Cattaneo, S. Empilli, and P. Vaccino.
Waxy wheats, characterized by a reduction or an absence of
amylose in the starch, may find a use in the production of
modified food starch, and their flour may be used to extend the
shelf life of baked products. The primary enzyme responsible for
the synthesis of amylose in amyloplast, granule-bound starch synthase
(GBSS), is present in bread wheat in three isoforms encoded by
the structural genes Wx-A1, Wx-B1, and Wx-D1.
We analyzed 288 cultivars of bread wheat, 139 cultivars of durum
wheat, and about 200 accessions from other Triticum species
in order to find genetic variability for the waxy trait. Electrophoretic
separation of GBSS allowed the identification of 63 bread wheats
deficient in the Wx-B1, one in the Wx-A1, and one
in the Wx-D1 protein isoforms, and a T. turgidum
subsp. dicoccum lacking the Wx-A1 isoform. The wheat
accession with Wx mutations were evaluated with a Rapid
Visco Analyser to investigate starch properties. All the analyzed
cultivars showed peak viscosity and final viscosity different
from that of normal wheat. Other analyses to evaluate the amylose-amylopectin
ratio and the rheological characteristics of the partial-waxy
genotypes are under way. A crossing program to select double and
null waxy wheat mutants is in progress.
N.E. Pogna, L. Gazza, G. Boggini, and M. Corbellini.
Puroindolines a (pin A) and b (pin B), two lipid-binding proteins affecting grain texture, were investigated in diploid and hexaploid wheat species by A-PAGE fractionating and PCR amplification. A-PAGE provided a clear separation of pin A and pin B, which occurred as two or four major bands in T. aestivum and T. monococcum, respectively. By A-PAGE analyses, four different puroindoline patterns were identified among the 67 diploid wheat accessions, all of them exhibiting a very soft grain texture as determined by the single-kernel characterization system. Among the 66 bread wheat cultivars analyzed, four A-PAGE patterns, two alleles coding for pin A and four alleles coding for pin B, were identified. Grain softness proved to be associated with the presence of alleles PinaD1a and PinbD1a coding for wild-type pin A and pin B, respectively. On the other hand, medium to hard grain texture was associated with either the absence of pin A (allele PinaD1b) or the occurrence of a single amino acid substitution in wild type pin B (alleles PinbD1b and PinbD1d). Bread wheat cultivars with the same puroindoline composition showed a remarkable variation in grain hardness, suggesting that factors other than pin A and pin B may effect grain texture.
M. Perenzin, M. Corbellini, and M. Cattaneo.
The agronomic and quality performance of the best F1 hybrids produced in Italy in the last years clearly indicate that although a positive trend was observed in yield potential, the level of standard heterosis did not increase because high-yielding cultivars are continuously produced by conventional breeding. Thus, there is concern about the need to develop specific strategies for identifying parental lines characterized by high general-combining ability and specific-combining ability. Among 200 hybrids previously evaluated, one hybrid (A x B) with the highest SCA effects for grain yield was identified. In order to substitute the two parents used with two superior lines, ten cross combinations involving five cultivars with high specific-combining ability effects for parent A and five for parent B were identified. From these ten crosses, a total of 142 lines were selected, crossed with A and B according to a topcross design and fingerprinted with AFLPs. The hybrids obtained were evaluated in replicated plot trials in two locations. Ten lines were identified which, in turn, were crossed according to a diallel mating design. Work is in progress to evaluate the agronomic and quality of the hybrids obtained compared to the best commercial varieties and exploit the use of genetic distances based on molecular markers for the selection of superior parental lines.
A. Brandolini, M. Corbellini, and M. Perenzin.
The breeding program is based on backcrossing and MAS selection and aimed at the introgression of powdery mildew-resistance gene Pm13 in bread wheat cultivars is currently at BC5 stage. Evaluation of lines similar to the recurrent parents also is under way.
A. Brandolini, P. Vaccino, S. Empilli, and M. Corbellini.
An einkorn wheat consensus map, obtained in collaboration with the Max-Planck Institut of Cologne, is completed and in press. The map was used to localize QTLs for quality and agronomic traits. A major QTL for bread-making quality was detected on chromosome arm 1S, and the gene responsible for free threshing was positioned on 2S, in a position compatible with Tg genes of polyploid wheats. Progenies of two-, three- and four-way crosses of lines with good agronomic and quality traits (earliness, free-threshing, short straw, gluten quality, and large kernel) are in evaluation.