Quantifying pearl millet response to high temperature stress: thresholds, sensitive stages, genetic variability and relative sensitivity of pollen and pistil

The objectives were to (1) quantify high temperature (HT) stress impacts at different growth stages (season long, booting to seed‐set and booting to maturity) on various yield components; (2) identify the most sensitive stage(s) to short episodes of HT stress during reproductive development; (3) understand the genetic variations for HT stress tolerance based on cardinal temperatures for pollen germination; and (4) determine relative sensitivity of pollen and pistil to HT stress and associated tolerance or susceptible mechanisms in pearl millet. High temperature stress (≥36/26°C) imposed at different stages and durations caused decrease in number of seeds, individual seed weight and seed yield. Two periods (10–12 days and 2–0 days before anthesis) were identified as most sensitive to short episodes of stress, causing maximum decreases in pollen germination percentage and seeds numbers. HT stresses of ≥36/26°C results in floret sterility. Pistils were relatively more sensitive than pollen grains, causing decreased number of seeds and seed yield. HT stress increased the reactive oxygen species contents and decreased the activity of the antioxidant enzymes in both pollen and pistils. Under HT stress, pistils had relatively higher reactive oxygen species and lower antioxidant enzymes activity compared with pollen grains, which explains greater susceptibility of pistils. We quantified impact of high temperature (HT) stress to determine thresholds, sensitive stages, genetic variability and fertility of pollen and pistil of pearl millet. High temperatures (≥36/26°C) decreased pollen germination, number of seeds and seed yield per panicle. The periods of gametogenesis and anthesis were most sensitive to HT stress affecting seed yield. There were negative impacts on fertility of both pollen and pistil; however, pistil was relatively more sensitive to HT than pollen, which was explained by greater oxidative damage. Pearl millet has relatively higher ceiling temperature compared with other cereals, thus an important climate resilient crop.