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The present investigation was conducted in a field experiments at Sakha Agricultural Research Station Farm to evaluate 24 bread wheat genotypes during the two growing seasons 2014/2015 and 2015/2016 under normal and salinity stress conditions. The experimental design used was a randomized complete block design with three replicates. Eleven stress tolerance indices (STI's) were calculated based on average grain yield under normal and stress conditions across the two seasons. Moreover, cluster analysis was performed to identify the similarity/dissimilarity among the tested genotypes for grain yield and salinity tolerance. Results showed large values of broad-sense heritability (hb2) coupled with high values of genetic advance as a percent of mean (GA%) at 5% selection intensity for number of spikes/m2 and number of grains/spike in the adequate site. Concerning the salt stressed soil, the grain yield ratio, number of spikes/m2 and grain yield recorded the highest values of hb2 and GA%. However, there were crucial differences among tested genotypes in respect to grain yield under non-stress and salt stress sites, which demonstrates high genetic diversity among them that enabled us to screen salt tolerant genotypes. Already, the tested wheat genotypes exhibited different responses for salinity stress tolerance indices (STI's). Perfect and positive correlation coefficients (r = 1) were found between three pairs of indices (STI and GMP), (SSPI and TOL) and (CV and SSI) where each one of the previous three pairs occupied one dot on the biplot graph indicating that the three indices are identical for ranking genotypes for salinity tolerance and they could be interchangeably used as a substitute for each other. Therefore, using these pairs of (STI's) together in the same study is considered a waste of time and effort. The cluster analysis classified the tested genotypes into five main groups (clusters) where each group contained the genotypes that showed similar yield potential and salinity tolerance. The fifth cluster contained two promising genotypes namely; lines 2 and 17 that were characterized by moderate grain yield in each of the normal and salt soils recording the lowest grain yield reduction. Also, they occupied the first and second ranks among the tolerant genotypes for salinity stress. Accordingly, results would give a good chance to achieve genotypic improvement of wheat through the hybridization among genotypes taken from different clusters. |
