Evaluation of genetic diversity of bread wheat genotypes based on physiological traits in non-stress and terminal drought stress conditions

To study genetic variation and terminal drought stress on kernel yield and some physiological traits in bread wheat, an experiment was conducted using 80 irrigated bread wheat genotypes in a randomized complete block design (RCBD) with three replications under normal and terminal drought stress conditions in research farm of the Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran, during 2011-2012 cropping season. The result of combined analysis of variance indicated high significant differences among genotypes for all studied traits except “chlorophyll b” and total chlorophyll. Moreover, effect of the environment on relative water content, kernel yield, kernel filling duration and kernel weight was highly significant. Terminal drought stress reduced “chlorophyll a”, SPAD and relative water contentas much as 3.54%, 2% and 10%, respectively but it increased “chlorophyll b” and total chlorophyll by 6.16 and 2.68%, respectively. In addition, drought stress caused reduction in kernel yield (23.48%), kernel filling duration (19.14%) and kernel weight (18%) but it increased kernel filling rate by 2.20%. There were high negative significant correlation between “chlorophyll a” and “chlorophyll b” and between kernel filling rate and kernel filling duration, whereas, correlation between “chlorophyll b” and total chlorophyll and between kernel filling rate and kernel weight were highly significant and positive. Correlation coefficients exhibited no significant associations between kernel yield and other traits in both normal and drought stress conditions.