PLEIOTROPIC EFFECTS OF GA-INSENSITIVE RHT GENES ON GRAIN-YIELD AND ITS COMPONENT CHARACTERS IN WHEAT

Evaluation of random pairs of near isogenic tall (rht) and dwarf (Rht) lines under late sown conditions indicated that the Rht1, Rht2 and Rh t3 dwarfing genes were associated with 22.25%, 14.19% and 26.73% reduc tion in grain yield, respectively. The negative effect of each of the three Rht genes on grain yield was due to significant reduction in bio logical yield. In turn, the poor biological yield in Rht1 and Rht2 lin es was due mainly to reduced number of lighter tillers while in Rht3 l ines it was due to lighter tillers, less number of grains per floret a nd grains per spike and reduced 100 grain weight. The mechanisms, invo lved in grain yield reduction in the lines containing different Rht ge nes were, thus, different. It is suggested that the poor grain yield a nd biological yield of the Rht lines may arise due to their greater se nsitivity to stress factors, particularly warm conditions, associated with late sowings.