Continuous high ambient temperature in hot summer months leads to a sharp decline in turf quality of cool‐season turfgrass. Verticillium dahliae Aspf2‐like protein (VDAL) is a secretory protein of V. dahliae that can improve crop yield and resistance to disease, but its role in improving heat tolerance of cool‐season turfgrass has not been reported so far. The objectives of this study were to explore the effect and mechanism of foliar application of VDAL on improving heat tolerance in cool‐season creeping bentgrass (Agrostis stolonifera) and to further examine the advantage of foliar spraying with VDAL in mitigating summer bentgrass decline (SBD) in the US transition zone or other regions with similar climate. The results demonstrated that the optimal dose of VDAL for improving thermotolerance of two creeping bentgrass cultivars (heat‐tolerant 13 M and heat‐sensitive Seaside II) was screened as 0.2 g L−1 based on analyses of chlorophyll content, photochemical efficiency of PSII, and cell membrane stability under controlled heat stress conditions. Foliar application of the optimal dose of VDAL significantly restricted chlorophyll loss under heat stress and also alleviated heat‐induced declines in net photosynthetic rate, transpiration rate, stomatal conductance, and water use efficiency. In addition, overaccumulations of superoxide anion radical and hydrogen peroxide could be significantly alleviated by the exogenous application of VDAL through improving the activity of antioxidant enzymes including superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase in two cultivars. A further 2‐year field trial showed that foliar application of VDAL improved turf quality, chlorophyll content, photochemical efficiency, and cell membrane stability of the two cultivars during hot summer months of 2022 and 2023. The results indicate that the appropriate dose of VDAL plays a positive role in photosynthetic performance and antioxidant capacity for thermotolerance of creeping bentgrass, and foliar application of VDAL could be considered an effective approach for alleviating SBD.

中文翻译：

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叶面喷施大丽轮枝菌 Aspf2 样蛋白通过调节光合作用和抗氧化能力提高匍匐稷的耐热性


在炎热的夏季，持续的高环境温度导致冷季草坪草的草坪质量急剧下降。大丽轮枝菌 Aspf2 样蛋白 （VDAL） 是大丽轮枝菌的一种分泌蛋白，可以提高作物产量和抗病性，但迄今为止，它在提高冷季草坪草耐热性方面的作用尚未报道。本研究的目的是探讨叶面喷施 VDAL 对提高冷季匍匐禾稷 （Agrostis stolonifera） 耐热性的影响和机制，并进一步研究叶面喷施 VDAL 在缓解美国过渡区或其他类似气候地区的夏季禾本科植物衰退 （SBD） 方面的优势。结果表明，根据叶绿素含量、PSII 的光化学效率和受控热应激条件下细胞膜稳定性的分析，VDAL 提高两个匍匐禾本科品种（耐热 13 M 和热敏 Seaside II）耐热性的最佳剂量筛选为 0.2 g L-1。叶面施用最佳剂量的 VDAL 显着限制了热胁迫下叶绿素的损失，并缓解了热诱导的净光合速率、蒸腾速率、气孔导度和水分利用效率的下降。此外，通过提高两个品种中超氧化物歧化酶、过氧化物酶、过氧化氢酶和抗坏血酸过氧化物酶等抗氧化酶的活性，VDAL 的外源应用可以显著缓解超氧阴离子自由基和过氧化氢的过度积累。 进一步为期 2 年的田间试验表明，在 2022 年和 2023 年炎热的夏季，叶面喷施 VDAL 提高了这两个品种的草坪质量、叶绿素含量、光化学效率和细胞膜稳定性。结果表明，适宜剂量的VDAL对匍匐禾草的光合性能和抗氧化能力起着积极作用，叶面喷施VDAL是缓解SBD的有效途径。