genetics of drought tolerance in relation to transpiration response and leaf expansion rate at water vapor pressure deficit in sorghum sorghum bicolor l moench

Abstract

The present investigation was carried out to elucidate the drought tolerance newlinemechanisms in sorghum Recombinant Inbred Lines (RILs) parental pairs with a particular newlinefocus on plant water use and plant developmental characteristics in varying environmental newlineconditions. Limiting transpiration rate (TR) under high vapour pressure deficit (VPD) and/or newlineprogressive soil drying conditions are plant water conservation mechanisms that can play an newlineessential drought-adaptive role if water is limiting to support crops at its full potential. newlineIn this study, two important physiological mechanisms were measured on parental newlinepairs of existing RILs of sorghum mapping populations; In controlled environmental newlineconditions, the parents of RIL 1, RIL 2, RIL 6 and RIL 8 showed contrasting transpiration newlineresponse to increasing VPD. The difference in the soil moisture fractions of transpirable soil newlinewater (FTSW) threshold, where transpiration initiated a decline was high in RIL 1, RIL 3 and newlineRIL 8 parental pairs respectively. The exploration of the variation in the evapotranspiration newlineresponse to VPD was carried out in a high throughput phenotyping facility, in which plants newlinewere grown similar to field density conditions. Under high VPD conditions, the RIL parents newlineshowed usual transpiration peak during the midday period. At this period, genotypic newlinedifferences within parental pairs were observed in RIL 1, RIL 2, RIL 6 and RIL 8. The newlinetolerant parent had lower transpiration than the susceptible parents during the midday/high newlineVPD period. Variation was observed among parental pairs in leaf area normalized with newlinereceived radiation and measured plant architecture traits. Across studied genotypes, RIL 1, newlineRIL 2 and RIL 8 parental pairs showed differences in the plant canopy architecture and the newlinetranspiration response to an increasing VPD. newlineThe limited transpiration rate under high VPD and high FTSW threshold were due to newlinethe difference in hydraulic conductance. The relative hydraulic conductance was studied to newlineidentify the site of limited hydraulic conductance