Exogenous Application of β-aminobutyric Acid Improved Water Relations, Membrane Stability Index, and Achene Yield in Sunflower Hybrids Under Terminal Drought Stress

Sunflower (Helianthus annuus L.) is a major oilseed crop grown for edible oil throughout the world, including Pakistan. Drought stress is the most significant constraint to crop production in a changing climate scenario, and its severity is increasing day by day. Less rainfall and rising temperatures, particularly during the seed-filling phase, reduce achene yield in sunflower hybrids. Exogenous application of β aminobutyric acid (BABA) is effective in reducing the severity of terminal drought stress in many crop plants. Therefore, the present study was conducted to assess the effect of foliar BABA application on the membrane stability, growth, and productivity of sunflower hybrids under induced terminal drought conditions. A pot experiment was carried out to compare the growth and yield potential of two sunflower hybrids, Hysun-33 and NK-Senji, to two levels of water application: normal irrigation (NI) and terminal drought (TD). To combat terminal drought, four BABA concentrations (0, 20, 40, and 60 mM) were used. When compared to NK-Senji, Hysun-33 had the highest SPAD-chlorophyll value, head weight, 100-achene weight, and achene yield. In comparison to normal irrigation terminal drought increased proline content while lowering relative water content, SPAD-Chlorophyll, 100-achene weight, and achene yield. However, under terminal drought, foliar application of β-aminobutyric acid improved relative water content, SPAD-chlorophyll value, head weight, 100-achene weight, and achene yield. When different levels of BABA were used, the application of 60 mM produced 46% more achene yield than the control. A reduced achene yield was obtained under terminal drought which was improved by foliar spraying of 60 mM β-aminobutyric acid which increased in SPAD-chlorophyll value, membrane stability index, relative water content, and 100-achene weight. Overall, the exogenous application of BABA improved water relations, membrane stability index, and achene yield in sunflower hybrids under terminal drought stress.