Evaluation of Relative Resistance in Eleven Apple Rootstocks to Crown Rot Caused by Phytophthora cactorum

An experiment was conducted under normal and post-anthesis drought stress conditions using RCBD with three replications at Karaj, Arak, Mashhad and Miandoab Agricultural Research Stations in 2004-05 and 2005-06 cropping seasons to evaluate the tolerance of 18 facultative and winter wheat genotypes to drought stress. Combined analysis of variance was done on grain yield. Tolerance and susceptibility of the genotypes to drought stress were calculated using Stress Tolerance Index (STI), Stress Susceptibility Index (SSI), Tolerance (TOL), Mean Productivity (MP), Geometric Mean Productivity (GMP), and SDR. Interaction of year × location in normal condition and effect of genotype and interaction of year × location and genotype × year × location were significant in stress condition. Correlation coefficients of indices with grain yield in normal and stress conditions showed MP and STI as the most appropriate indices for selection of tolerant genotypes. Using biplot,, SDR and drought tolerance and susceptibility indices, determined genotypes C-83-6, C-83-7 and C-83-8 as the most tolerant genotypes and genotype C-83-14 as the most susceptible genotype.