Variation in stomatal conductance responses of cotton cultivars to high vapour pressure deficit under controlled and rainfed environments

Cotton is often negatively impacted by drought periods; thus, plant traits that alleviate the impacts of drought on cotton are highly desirable. The limited-transpiration rate (TRlim) trait under high vapour pressure deficit (VPD) can conserve soil water and prolong crop physiological activity as water deficit progresses. The current research objective was to compare the expression of TR(lim)in cotton cultivars under variable VPD and temperatures by whole-plant transpiration in controlled environments and by leaf-level gas exchange measurements in the field. All cultivars expressed the TR(lim)trait in a controlled environment with high VPD at 32 degrees C; however, at 38 degrees C, only 5 out of 7 commercial and 2 out of 4 conventional cultivars expressed TRlim. Field trials during 2017 and 2018 showed all 4 commercial cultivars that expressed TR(lim)in a controlled environment at 38 degrees C expressed TR(lim,)but shifts in VPD breakpoints were observed. Among conventional cultivars, 2 out of 4 expressed TR(lim)trait. Cultivars that expressed TR(lim)also delayed wilting under rainfed environments when soil water deficits developed and resulted in greater lint yields. Three commercial and two conventional cultivars that expressed the TR(lim)trait in field trials also resulted in greater predawn leaf water potential (LWP). Cultivars that expressed the TR(lim)trait had significantly higher lint yields only during 2017. This study indicates that the impact of TR(lim)trait on yield is relatively small in years with adequate rainfall.

Automated summary

The study illustrates that cotton cultivars with the limited-transpiration rate (TRlim) trait show better drought tolerance and yield performance under drought conditions.