Screening of Bread Wheat Genotypes for Identifying Tolerance Genetic Resources to Salinity

Salinity is one of the most important environmental stress which limits growth and yield of crops. Breeding and development of tolerant varieties is the most effective approach to confront salinity. Improvement of tolerance to salinity in crops necessitates existence of diverse genetic resources. Genetic variability for salinity tolerance has been reported. Wheat germplasm is a valuable genetic resource for tolerance to abiotic stresses including salinity. This research was performed with the objective of screening and selecting salinity tolerant genotypes in wheat germplasm.

A total of 97 bread wheat genotypes selected from previous studies along with three tolerant check cultivars of Kavir, Roshan and Mahooti were planted in research filed of Karaj (normal condition) and Meybod (saline soil and irrigation water, EC=6.55 ds/m and 5.61 ds/m, respectively) in lattice statistical design with three replications. Agronomical traits were evaluated according to international descriptor. Stress tolerances indices were calculated and the superior genotypes were distinguished by analyses of cluster and principal components. Stepwise regression was used in order to identify effective trits in tolerance to stress.

Grain yield of the check cultivar Kavir was higher than Roshan and Mahooti in stress condition. A total of nine genotypes had higher grain yield in stress condition than Kavir. Genotype KC.4419 had the highest amount of grain yield in normal condition (966.67 g/plot) and the highest values for the indices STI, GMP, HM and HM. The indices STI, GMP and MP had high correlations with grain yield in both normal and stress conditions. The studied genotypes were separated in the biplot of grain yield in normal and salinity stress conditions. A total of 38 genotypes along with all three check cultivars having higher grain yield in normal and salinity stress conditions were located in Region A of biplot. The results of principal component analysis based on the evaluated traits along with STI indicated that three PCs comprised 74.79% of the total variation. While the first PC emphasized on obtaining higher grain yield in stress condition through increasing grain filling period and producing larger seeds, the second PC highlighted the accumulation of dry matter in vegetative tissues. The results of stepwise regression for STI showed that harvest index entered in both models of normal and salinity stress conditions. The trait appeared specifically in regression model of stress condition.

The genotypes KC.1514, KC.4382, KC.4419 and KC.4407 (from Esfahan), KC.142 (from Khoy), KC.3100 (from Mashhad), KC.1143 and KC.388 (from Iran with unknown province) and KC.106 (from USA) with higher grain yield in stress condition than check cultivars were selected as tolerant genotypes. STI, GMP and MP were suggested as the most suitable criteria for selecting superior genotypes in salinity stress condition due to their high correlations with grain yield in both normal and stress conditions.