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<p>Heat stress poses a serious limitation to spring maize production, particularly when it coincides with the reproductive stage. The present study evaluated the variability for heat tolerance among fifty maize inbred lines derived from different heterotic pools. These inbred lines were grown under two contrasting field conditions viz., a timely sowing (optimal temperature) and a delayed sowing (exposing the plants to high temperatures exceeding &gt; 40&#xa0;°C during anthesis stage) in 2021 and 2022. The results revealed a substantial reduction in plant height, ear height, leaf number, days to 50% silking and 50% anthesis, pollen viability, germination percentage, pollen tube length and grain yield. Conversely, stress indicators such as anthesis-silking interval, tassel blasting and leaf firing significantly increased (<i>p</i> ≤ 0.05), highlighting the adverse effects of high temperatures. At the biochemical level, heat-stressed plants accumulated higher levels of glycine betaine, total soluble sugars, flavonoids, phenols and proline. However, heat stress led to a decline in membrane stability index, chlorophyll a, chlorophyll b, total chlorophyll and carotenoids, alongside a surge in malondialdehyde levels. The analysis revealed that the reproductive traits particularly, pollen viability and tassel blasting were among the most sensitive to heat stress. By integrating physiological, biochemical and reproductive responses, this study identified a set of heat tolerant inbred lines i.e. CML 579, CML 451, LM13, PML 1285, PML 1283, LM16, LM18 and RIL 33 which consistently performed well under both optimal and high temperature environments. The identified heat-tolerant inbred lines included two tropical CIMMYT lines that performed best even under subtropical conditions. Among them, CML579 exhibited the highest grain yield coupled with superior pollen viability, pollen germination and membrane stability index, thereby strongly supporting the hypothesis that maize inbred lines capable of maintaining reproductive efficiency and physiological stability under heat stress are also able to sustain higher grain yield. These findings advance the understanding of how multiple traits collectively contribute to reproductive heat tolerance in maize and also identify promising genetic resource for developing climate-resilient hybrids.</p> Graphical abstract <p></p>

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Evaluation of heat stress responses in maize (Zea mays L.) inbred lines derived from different heterotic pools

  • 期刊论文

  • 发表日期：

    2026年2月14日

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  • Japneet Kaur,
  • Navita Ghai,
  • Surinder Sandhu,
  • Gagandeep Kaur Chahal

摘要

Heat stress poses a serious limitation to spring maize production, particularly when it coincides with the reproductive stage. The present study evaluated the variability for heat tolerance among fifty maize inbred lines derived from different heterotic pools. These inbred lines were grown under two contrasting field conditions viz., a timely sowing (optimal temperature) and a delayed sowing (exposing the plants to high temperatures exceeding > 40 °C during anthesis stage) in 2021 and 2022. The results revealed a substantial reduction in plant height, ear height, leaf number, days to 50% silking and 50% anthesis, pollen viability, germination percentage, pollen tube length and grain yield. Conversely, stress indicators such as anthesis-silking interval, tassel blasting and leaf firing significantly increased (p ≤ 0.05), highlighting the adverse effects of high temperatures. At the biochemical level, heat-stressed plants accumulated higher levels of glycine betaine, total soluble sugars, flavonoids, phenols and proline. However, heat stress led to a decline in membrane stability index, chlorophyll a, chlorophyll b, total chlorophyll and carotenoids, alongside a surge in malondialdehyde levels. The analysis revealed that the reproductive traits particularly, pollen viability and tassel blasting were among the most sensitive to heat stress. By integrating physiological, biochemical and reproductive responses, this study identified a set of heat tolerant inbred lines i.e. CML 579, CML 451, LM13, PML 1285, PML 1283, LM16, LM18 and RIL 33 which consistently performed well under both optimal and high temperature environments. The identified heat-tolerant inbred lines included two tropical CIMMYT lines that performed best even under subtropical conditions. Among them, CML579 exhibited the highest grain yield coupled with superior pollen viability, pollen germination and membrane stability index, thereby strongly supporting the hypothesis that maize inbred lines capable of maintaining reproductive efficiency and physiological stability under heat stress are also able to sustain higher grain yield. These findings advance the understanding of how multiple traits collectively contribute to reproductive heat tolerance in maize and also identify promising genetic resource for developing climate-resilient hybrids.

Graphical abstract