Variability of root related traits and its contributions to seed yield in bread wheat (Triticum aestivum L.) under normal condition and terminal drought stress

In Iran where main part of precipitation takes place during winter and spring، wheat is dependent on water conserved in sub soil especially at rain-fed cultivation system. To find the genotypes with good root system at sub soil depth an experiment was conducted with 63 bread wheat genotypes planted in one meter long PVC tubes under non stress and drought stress condition. Under non-stress condition irrigation was conducted regularly while under stress condition it was delayed until soil moisture was depleted to 30 percent of filed capacity. After applying stress and at the end of growth season root related traits in four depth (0-20، 20-40، 40-60 and 60-100 cm) along with yield and its components were measured. The results showed high variation among genotypes for all traits. High significant correlations were observed between total root weights with yield under stress condition (r=0. 58، p=0. 01). A unit increase in root dry weight added 0. 24 g to grain yield in each plant. Separate correlation analysis for each profile showed that the effect of root dry weight at deepest profile on yield was higher than other profiles (r=0. 75، p=0. 01). Under stress condition the effect of root weight at 60-100 cm depth on yield was positive and highly significant. Genotypes of Sardari، Sholeh، Naz and Inia were best genotypes considering root dry weight at this profile with 0. 44، 0. 39، 0. 37 and 0. 37 g/plant، respectively.