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

Cyanobacteria Application Ameliorates Floral Traits and Outcrossing Rate in Diverse Rice Cytoplasmic Male Sterile Lines

In rice, cytoplasmic male sterility (CMS) represents an irreplaceable strategy for producing high-yielding hybrid rice based on the commercial exploitation of heterosis. Thereupon, enhancing floral traits and outcrossing rates in CMS lines increase hybrid seed production and ensure global food security. The exogenous application of cyanobacteria could enhance outcrossing rates in CMS lines and, accordingly, hybrid rice seed production. In the present study, we aimed at exploring the impact of cyanobacteria implementation such as Anabaena oryzae, Nostoc muscorum, and their mixture to promote the floral traits, outcrossing rates, and seed production in hybrid rice. The impact of cyanobacteria (Anabaena Oryza (T2), Nostoc muscorum (T3), and their combination (T4) versus the untreated control (T1) was investigated for two years on the growth, floral, and yield traits of five diverse CMS lines, namely IR69625A (L1), IR58025A (L2), IR70368A (L3), G46A (L4), and K17A(L5). The evaluated CMS lines exhibited significant differences in all measured floral traits (days to heading (DTH), total stigma length (TSL), stigma width (SW), duration of spikelet opening (DSO), spikelet opening angle (SOA)). Additionally, L4 displayed the uppermost total stigma length and stigma width, whereas L1 and L5 recorded the best duration of spikelet opening and spikelet opening angle. Notably, these mentioned CMS lines exhibited the highest plant growth and yield traits, particularly under T4 treatment. Strong positive relationships were distinguished between the duration of the spikelet opening, panicle exertion, panicle weight, seed set, grain yield, total stigma length, spikelet opening angle, stigma width, and number of fertile panicles per hill. Cyanobacteria is a potential promising tool to increase floral traits and seed production in hybrid rice

Exogenously Applied Salicylic Acid Boosts Morpho-Physiological Traits, Yield, and Water Productivity of Lowland Rice under Normal and Deficit Irrigation

The main constraint on rice cultivation in the Mediterranean area is the limited irrigation and its large water consumption. In addition, rice is very sensitive to drought conditions because of drought stress on morpho-physiological traits and yield reduction. The application of salicylic acid (SA) has been noticed to be very effective in alleviating the adverse effects of drought stress on rice. The current investigation was conducted as a split-split arrangement under a randomized complete block design with two lowland rice cultivars (Giza177 and Giza179) and SA as a foliar application at four concentrations (0, 400, 700, and 1000 µM) under normal and drought conditions. The results showed that plant growth, leaf photosynthetic pigments, yields, and the most studied traits were significantly affected by irrigation (I), cultivar (C), and SA concentration (p ≤ 0.05 or 0.01). The interaction effect of I × C × SA was only significant on the carotenoids content (p ≤ 0.05). The reduction in grain yield and most studied traits was more pronounced under drought conditions. The Giza179 proved to be a drought-tolerant cultivar under all SA concentrations under drought conditions, while Giza177 was a drought-sensitive cultivar. The application of 700 µM SA gave the best grain yield in both rice cultivars under drought conditions compared to other SA concentrations. Grain yield for normal irrigation (Yp) and drought stress (Ys) conditions were highly positively correlated with indices of the mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI), yield index (YI), yield stability index (YSI), drought resistance index (DI), harmonic mean (HM), and golden mean (GOL). While they are highly negatively correlated with the indices of the stress susceptibility index (SSI), tolerance index (TOL), yield reduction ratio (YR), stress susceptibility percentage index (SSPI), and abiotic tolerance index (ATI). It could be concluded that SA, as a growth regulator, could be used to alleviate the harmful effect of inadequate water availability in soil on rice cultivars as well as to improve the growth, water productivity, and grain yield