Differences in the physiological responses of Rht13 and rht wheat lines to short-term osmotic stress

Abstract

GA-insensitive dwarfing genes e.g. Rht-B1b and Rht-D1b have been widely used to reduce plant height, increase grain yield and improve harvest index values. GA-responsive dwarfing genes, such as Rht13, have potential for wheat improvement but are not used in commercial breeding. Here, a set of recombinant inbred lines (RILs) of varying height was developed from a cross of Rht13-containing Magnif M1 and Rht8-containing Jinmai 47. These RILs (Rht13 and rht) were used to evaluate the effects of Rht13 on wheat drought resistance under hydroponics conditions simulated by polyethylene glycol-6000 (10% PEG). Under osmotic stress, Rht13 seedlings showed significantly lower transpiration rates than rht lines. The Rht13 seedlings also had relatively higher photosynthetic rates and lower leaf water loss rates and higher leaf relative water content than rht lines. While investigating the reasons underlying these differences, we found that the Rht13 lines’ root system could reduce the decrease in root hydraulic conductance (Lp) via osmotic adjustment and via modulating the expression of plasma membrane aquaporins (TaPIPs). Because of the reduced transpiration rate, severely reduced shoot water loss and improved water uptake ability of roots under short-term osmotic stress, the Rht13 seedlings maintained their overall water balance more effectively than did the rht seedlings. These findings demonstrate that the dwarfing allele is a potential candidate for wheat breeding programs aiming to improve performance in arid and semi-arid regions.