The Potential Effects of Kinetin Implementation on Hybrid Rice Seed Production under Water Deficit

Drought is one of the main abiotic stresses responsible for reducing crop yields worldwide. In hybrid rice production, cytoplasmic male sterility (CMS) displays an alternative plan for producing high-yielding hybrid rice depending on the hybrid vigor. Kinetin (Kin) has an essential role during the early phase of grain setting by regulating cell division, assimilate flow, and osmotic modification under water deficit. Growth, floral, and yield-related traits were evaluated in two CMS lines under five irrigation intervals and two concentrations of the phytohormone kinetin. Our study was conducted to explore the effects of irrigation intervals (continuous flooding (CF), irrigation every six (I6), nine (I9), twelve (I12), and fifteen (I15) days, and kinetin exogenously applied (control, 15 mg L−1, and 30 mg L−1) on growth, floral, and yield-related traits. Growth traits (i.e., number of leaves (NOL), days to complete leaf number (DCLN), days to heading (DTH, 50%), flag leaf area (FLA), and plant height (PH)), floral traits (i.e., duration of spikelet opening (DSO), panicle length (PL), spikelet opening angle (SOA), and panicle exertion (PE)), and seed yield traits (i.e., seed set (SS), panicle weight (PW), seed yield (SY), harvest index (HI), and number of fertile panicles per hill (NFP)) in two CMS lines. Implementation of kinetin displayed the highest significant and positive values for all growth, floral, and yield-related traits when compared to the control (average of applied irrigation intervals). Applying 30 mg L−1 kinetin positively enhanced the growth traits (i.e., NOL, FLA, and PH with 4.1%, 5%, and 3%, respectively), floral traits (i.e., PL, PE, SOA, and DSO with 5.4, 5.7, 5.9, and 5.4%, respectively), and yield-related traits (i.e., PW, SS, SY, HI, and NFP with 22%, 17%, 14%, 14.5%, and 15%, with the same sequence) compared to non-treated plants. Consequently, exogenous foliar spray of kinetin could be an effective process in minimizing the harmful effects (the reduction in PW, SS, SY, HI, and NFP recorded 41%, 61%, 45%, 30%, and 48%, respectively, under I15 conditions when compared to CF) of water deficit in hybrid rice and increasing seed production.