m. zahravi

In order to identify drought tolerant genetic sources in wheat and investigate the changes of traits related to this characteristic, a number of 512 accessions from the wheat collection of the National Plant Gene Bank of Iran along with the drought tolerant cultivars Kavir, Roshan and Mahooti were investigated in the field of Yazd Agriculture and Natural Resources Research Center in the form of two separate augmented statistical design (normal irrigation and drought stress). Drought stress was applied by limiting times of irrigation, i.e. once after planting and the other during seed filling stage. In total, 66 accessions were survived and the evaluation of agronomic traits was carried out according to the international descriptor. The results showed a decrease in the values ​​of all evaluated traits under drought stress condition, and the greatest decrease was in the traits of five-spike seed weight (57.34 %) and number of fertile tillers (48.59 %). A large number of accessions with superior traits compared to the check cultivars were identified under normal and drought stress conditions. Based on the results of principal component analysis under drought stress, the first five components contained 73.84% of the total changes in data. The superior accessions were distinguished based on the characteristics of each component. The studied accessions were separated into four groups with different characteristics using cluster analysis. The results of the present research showed a wide diversity in the evaluated germplasm and the superior accessions identified can be used in future wheat breeding programs to improve tolerance to drought stress.

In order to study changes of agronomic traits under drought stress and identification of tolerant germplasm, a total of 484 accessions of bread wheat collection of National Plant Gene Bank were studied in Yazd field under normal and drought stress conditions by planting tolerant cultivars (Kavir, Roshan and Mahooti). Drought stress was applied by irrigation stoppage after cultivation. Evaluation of agronomic traits was carried out in accordance with international descriptor both for 71 drought survived accessions and the same accessions under normal condition. Analysis of descriptive statistics showed that the grain weight of five spikes under normal condition and the number of fertile tillers under drought stress had the highest coefficient of variation. The highest mean reduction in traits under drought stress was observed for grain weight of five spikes (23.8%) and then for the number of fertile tillers (21.1%). In almost all traits evaluated, some accessions were superior to control cultivars in both normal and drought conditions. Grain weight of five spikes under drought stress was significantly correlated with florets number per spikelet (r = 0.272*), grain number per spike (r = 0.742**), one-hundred-grain weight (r = 0.663**), grain filling period (r = 0.314**) and days to spike emergence (r = -0.238*). The accessions were divided into four groups under drought stress and normal conditions using cluster analysis dendrogram. Distinction among clusters was confirmed by discriminant analysis. The superior accessions identified in this study can be used in drought tolerance wheat breeding programs.

Four advanced lines of wheat which had appeared to be resistant to yellow rust in past years, along with the susceptible cultivar Bolani were intercrossed in one-way diallel cross. Seedlings were grown in greenhouse until the first leaves fully expanded and then inoculated with two pathotypes (race) 6E130A+and 166E42A+of yellow rust, separately. Infection types were scored 18 days after inoculation. Diallel analysis was done by two methods of Griffing, and links and Hayman. Results of analysis of variance of Wr + Vr and Wr - Vr, regression analysis of Vr and Wr and estimates of genetic parameters indicated the importance of additive and dominance effects with pathotype 6E130A+ and importance of additive, dominance and epistatic effects with pathotype 166E42A+. Broad-sense and narrow-sense heritability of infection type were estimated 97% and 58% for pathotype 6E130A+and 99% and 81% for pathotype 166E42A+, respectively. Line M-78-16 possessed the greatest general combining ability to decrease infection type and therefore was suggested to be included in breeding programs for resistance to yellow rust.