Pleiotropic effects of Rht dwarfing genes on grain yield and its component traits in wheat under rainfed environment

Evaluation of random dwarf (Rht) and tall (rht) wheat lines under irrigated (nonstress) and rainfed (water stress) environments showed that Rht1 and Rht2 dwarfing genes have negative effect on grain yield under water stress conditions. The greater decline in the grain yield of Rht lines was due to significant and greater reduction in biological yield caused by reduced number of lighter tillers and yield per spike due to reduction in number of florets and grains per spike (Rht1) or grain weight (Rht2) and early maturity. It is concluded that the poor biological and grain yields of Rht dwarf lines under water stress may emanate from their greater sensitivity to the factors associated with diminished soil moisture content. However, in Rht dwarf lines under water stress conditions, variability for stress susceptibility index (S) and its negative association with grain yield were noted. This suggested that it should be possible to select Rht containing semidwarf lines with high yield potential and greater tolerance to water stress conditions.