Study on Crop Growth Rate and Relative Growth Rate in bread wheat genotypes under rainfed and supplementary irrigation conditions

In order to study physiological characteristics of rainfed bread wheat genotypes، an experiment was conducted with 20 genotypes in a randomized complete block design with 4 replications under rainfed and supplementary irrigation conditions. This experiment was carried out at the Dryland Agricultural Research Institute (DARI) in Maragheh during 2007-2008. To determine growth indices، sampling was carried out during growing season. The results revealed that genotype 7 in rainfed and genotypes 1، 7، 12 and 22 in supplementary irrigation conditions had both high CGR and high grain yield. Relative growth rate curve of genotypes 1، 3، 7، 9، 19 and 22 sharply increased than the rest in rainfed condition، so their dry matter accumulation will be faster. This study indicates that high relative growth rate (RGR) cannot be considered the only factor of high grain yield under stress condition، because some high yielding genotypes had low RGR. By contrast، genotypes with high RGR produced high grain yield in supplementary condition.