Effect of water-deficit on stem reserve mobilization for grain filling in wheat (Triticum aestivum L.)

Abstract

The grain filling and development is considered as a key step for wheat yield and is most sensitive to water-deficit. In order to understand the effect of water-soluble carbohydrates (WSC) accumulation and mobilization on water-deficit tolerance, wheat lines viz., check PBW725, parent DS5U^t(5A) and introgression lines (ILs) (5U-24, 5U-26, 5U-27 and 5U-31) were used in this experiment. We examined the pattern of accumulation and mobilization water-soluble carbohydrates in peduncle (Ped), upper internodes (U_int), middle internodes (M_int) and basal internodes (B_int) under water-deficit. B_int showed highest mobilization WSC reserves for grain filling indicating that the lower portions of the stem may exhibit higher remobilization efficiency under water-deficit conditions. Among the ILs, IL 5U-26 showed highest mobilization of WSC in all the internodes. Correlation analysis depicted that increase in mobilization of WSC from U_int, M_int, B_int and Ped enhanced TGW significantly. Highest significant correlation of percent increase in TGW was found with percent change of WSC in Ped (0.97, significant at p<0.01) Also, defoliation studies were carried out under both irrigated and rain-fed conditions to study the mobilization of stem reserves that can provide essential carbon resources for grain-filling to compensate grain weight under defoliated conditions. TGW was reduced after defoliation with significant minimum reduction in IL 5U-26 under irrigated conditions while with non-significant reduction in IL 5U-26 under rain-fed conditions. Also, IL 5U-26 exhibited maximum increase in stem reserve mobilization (SRM) under rain-fed conditions. This indicated that water-deficit considerably increased the remobilization of stem reserves, which enhanced grain filling and contributed significantly to grain weight in 5U-26. Thus, 5U-26 with improved mobilization efficiency can be used in future breeding programmes to enhance grain filling and ultimately yield in wheat.