Mitigating Drought Stress in Sunflower (Helianthus annuus L.) Through Exogenous Application of β-Aminobutyric Acid

Drought stress is a serious threat for sustainable crop production throughout the world especially in arid and semi-arid regions and one of the main constraints to sunflower (Helianthus annuus L.) production. Different mitigation strategies, including foliar spray of osmolytes such as beta-aminobutyric acid (BABA), help the crop to combat drought conditions. A 2-year field study was conducted to evaluate the effect of exogenous application of BABA on the growth, productivity, and net return of sunflower under drought conditions. The experimental treatments comprised drought levels, viz., control (well watered (WW)); drought stress at vegetative stage (DVS); and drought stress at reproductive stage (DRS). Drought-mitigating treatments comprised foliar application of BABA, viz., 0 mM (control), 25 mM, 50 mM, and 75 mM with three replications. Foliar application of BABA under drought condition had significant effect on physiological traits, yield, and yield-related traits. Foliar application of 75-mM BABA solution improved SPAD-chlorophyll value and membrane stability index and maintained higher relative water contents. It also improved 1000-achene weight and achene yield, and produced about 41% and 44% more achene yield during 2018 and 2019 respectively compared with other treatments. Significant and positive correlations were also observed between yield and yield-contributing traits of sunflower under different water stress conditions. This finding suggests that foliar application of 75-mM BABA may be used as a viable option for sunflower growers to enhance achene yield and net benefit under drought conditions in arid and semi-arid regions.