pca method

In order to compare the efficiency of multivariate statistical methods (cluster analysis and Principal Component Analysis: PCA) with a new method known as "2- step screening method" for selection of wheat genotypes with high yield potential and good drought tolerance, this study was performed. For this, 180 hexaploid wheat genotypes were studied during 2005/2006 cropping season under two conditions of well irrigation and shortage of water (from anthesis on wards) in Karaj. Drought resistance indices including stress susceptibility index (SSI), tolerance index (TOL), mean productivity (MP), stress tolerance index (STI) and geometric mean productivity (GMP) were calculated for all investigated genotypes. Study of correlation coefficients among these indices and grain yield in two conditions for all genotypes showed that STI is better than other indices for screening genotypes with favorable yield in both conditions. But, because the STI value was still significantly affected by higher grain yield in normal conditions, identifying favorable genotypes followed using 3 methods. Study of grain yield under normal and stress conditions and tolerance indices showed that "2-step screening method" is more efficient than the other two methods. This method is based on completing cluster analysis with application of a defined cut off line for SSI index (through establishing a relationship between SI and SSI) to screen out stress susceptible genotypes among first step selected genotypes, hence suggested to be applied in breeding programs.