Study of relationships among components of resistance to yellow rust (Puccinia striiformis f.sp. tritici) in Iranian Wheat landraces

In order to study the relationships among components of resistance to yellow rust (Puccinia striiformis f.sp. tritici), 47 wheat genotypes of national plant gene bank of Iran were assessed by 4 pathotypes of 6E6A+, 134E134A+, 134E142A+ and 6E4A+ at seedling stage. Correlation Analysis among components of resistance showed that association between latent period and pustule density was not influenced by the pathotype but relationship between latent period and pustule size was affected bythe pathotype of the pathogen. Principal component analysis based on components of resistance, for each pathotype separately, indicated that latent period have the largest effect on the variation of relating principal components. Principal component analysis based on components of resistance for all pathotypes showed that the first 4 components justified 81% of the total variation in the data. Coefficients of traits revealed that the first principal component indicates susceptibility to all pathotypes and the second principal component indicates specific resistance to pathotypes of 134E134A+ and 6E4A+ and sensitivity to pathotypes of 6E6A+ and 134E142A+. Studied genotypes were divided into two groups of resistant and susceptible by cluster analysis through UPGMA method based on principal components. The results of this investigation demonstrated that latent period could be a suitable replacement for other components of resistance to yellow rust in order to select superior genotypes.