Data_Sheet_1_Untangling the Influence of Heat Stress on Crop Phenology, Seed Set, Seed Weight, and Germination in Field Pea (Pisum sativum L.).docx

The apparent climatic extremes affect the growth and developmental process of cool-season grain legumes, especially the high-temperature stress. The present study aimed to investigate the impacts of high-temperature stress on crop phenology, seed set, and seed quality parameters, which are still uncertain in tropical environments. Therefore, a panel of 150 field pea genotypes, grouped as early (n = 88) and late (n = 62) maturing, were exposed to high-temperature environments following staggered sowing [normal sowing time or non-heat stress environment (NHSE); moderately late sowing (15 days after normal sowing) or heat stress environment-I (HSE-I); and very-late sowing (30 days after normal sowing) or HSE-II]. The average maximum temperature during flowering was about 22.5 ± 0.17°C for NHSE and increased to 25.9 ± 0.11°C and 30.6 ± 0.19°C in HSE-I and HSE-II, respectively. The average maximum temperature during the reproductive period (RP) (flowering to maturity) was in the order HSE-II (33.3 ± 0.03°C) > HSE-I (30.5 ± 0.10°C) > NHSE (27.3 ± 0.10°C). The high-temperature stress reduced the seed yield (24–60%) and seed germination (4–8%) with a prominent effect on long-duration genotypes. The maximum reduction in seed germination (>15%) was observed in HSE-II for genotypes with >115 days maturity duration, which was primarily attributed to higher ambient maximum temperature during the RP. Under HSEs, the reduction in the RP in early- and late-maturing genotypes was 13–23 and 18–33%, suggesting forced maturity for long-duration genotypes under late-sown conditions. The cumulative growing degree days at different crop stages had significant associations (p < 0.001) with seed germination in both early- and late-maturing genotypes; and the results further demonstrate that an extended vegetative period could enhance the 100-seed weight and seed germination. Reduction in seed set (7–14%) and 100-seed weight (6–16%) was observed under HSEs, particularly in HSE-II. The positive associations of 100-seed weight were observed with seed germination and germination rate in the late-maturing genotypes, whereas in early-maturing genotypes, a negative association was observed for 100-seed weight and germination rate. The GGE biplot analysis identified IPFD 11-5, Pant P-72, P-1544-1, and HUDP 11 as superior genotypes, as they possess an ability to produce more viable seeds under heat stress conditions. Such genotypes will be useful in developing field pea varieties for quality seed production under the high-temperature environments.

各类显著气候极端事件会影响冷季型籽粒豆科作物的生长发育进程，其中尤以高温胁迫的影响最为突出。本研究旨在探究高温胁迫对作物物候期、结实率及种子品质参数的影响——这类影响在热带环境中仍存在较大不确定性。为此，本研究选取150份大田豌豆基因型材料，按熟性分为早熟（n=88）与晚熟（n=62）两类，并通过分期播种设置不同高温胁迫环境：正常播种期（非高温胁迫环境，non-heat stress environment, NHSE）、适度晚播（正常播种后15天，即高温胁迫环境I，heat stress environment-I, HSE-I）以及极晚播（正常播种后30天，即高温胁迫环境II，heat stress environment-II, HSE-II）。非高温胁迫环境下，开花期的平均最高气温约为22.5±0.17℃；而在HSE-I与HSE-II中，该数值分别升至25.9±0.11℃与30.6±0.19℃。生殖生长期（从开花至成熟，reproductive period, RP）的平均最高气温排序为HSE-II（33.3±0.03℃）> HSE-I（30.5±0.10℃）> NHSE（27.3±0.10℃）。高温胁迫会降低种子产量（24%~60%）与种子发芽率（4%~8%），且对生育期较长的基因型材料影响更为显著。在生育期超过115天的基因型材料中，HSE-II处理下的种子发芽率降幅最大（>15%），这主要归因于该处理下生殖生长期的环境最高气温更高。在各高温胁迫环境下，早熟与晚熟基因型材料的生殖生长期分别缩短13%~23%与18%~33%，表明晚播条件下生育期较长的基因型会被迫提前成熟。不同作物生育阶段的累积生长度日（growing degree days, GDD）与早、晚熟基因型材料的种子发芽率均存在极显著关联（p<0.001）；研究结果进一步表明，延长营养生长期可提升百粒重与种子发芽率。各高温胁迫环境下均出现结实率（7%~14%）与百粒重（6%~16%）的下降，其中以HSE-II处理的降幅最为明显。晚熟基因型材料中，百粒重与种子发芽率、发芽速率呈正相关；而早熟基因型材料中，百粒重与发芽速率则呈负相关。GGE双标图分析（GGE biplot analysis）筛选出IPFD 11-5、Pant P-72、P-1544-1与HUDP 11为优良基因型，这些材料可在高温胁迫环境下产出更多具有生活力的种子。这类优良基因型材料可用于培育适应高温环境、可高质生产种子的大田豌豆新品种。