ABSTRACT

Grape downy mildew is a major grape disease that typically occurs when grape leaves are subjected to high temperature. In this study, downy mildew incidence in ‘Red Globe’ grape was investigated. To clarify the effects of grape downy mildew on grape leaves under high-temperature stress. Grape downy mildew infestation and high-temperature treatment alone or combinations were applied to ‘Red Globe’ grape. The gas exchange and chlorophyll fluorescence parameters of grape leaves were measured. The results showed that logistic growth period of grape downy mildew in the Jinzhong, China was from July 20 to August 10. After the combined stress of high temperature and grape downy mildew, photosynthetic rate (Pn), stomatal conductance (G_s), intercellular carbon dioxide concentration (C_i), maximum photochemical efficiency(Fv/Fm), actual photochemical efficiency(ΦPSII), and performance index on absorption basis (PI_ABS) of grape leaves were all decreased more than the sum of those indexes under the two stresses individually. At 28°C, the damage of downy mildew had no significant effect on the degree of photosystem closure of leaves, but it was significantly increased with the combined stresses. The electron transfer efficiency from photosystem II to photosystem I was decreased significantly under the combined stresses. Under 38°C high-temperature stress, the energy dissipated per active reaction center of the leaves affected by grape downy mildew was significantly increased. High temperature aggravated adverse effects of downy mildew on the structure and function of photosystem II (PSII) of grape leaves and then further exacerbated reduction of photosynthesis caused by heat stress.

摘要

葡萄霜霉病是一种主要的葡萄病害，通常在葡萄叶子受到高温时发生。在这项研究中，调查了“红地球”葡萄的霜霉病发病率。阐明高温胁迫下葡萄霜霉病对葡萄叶片的影响。葡萄霜霉病侵染和高温处理单独或组合应用于'红地球'葡萄。测定了葡萄叶片的气体交换和叶绿素荧光参数。结果表明，晋中地区葡萄霜霉病的后勤生长期为7月20日至8月10日。高温和葡萄霜霉病复合胁迫后，光合速率（Pn）、气孔导度（G _s)、细胞间二氧化碳浓度( C _i )、最大光化学效率( Fv/Fm )、实际光化学效率( ΦPSII )、吸收性能指标( PI _{ABS )})葡萄叶片在两种胁迫下的下降幅度均大于这些指标的总和。28℃时霜霉病危害对叶片光合系统关闭程度无显着影响，但随着复合胁迫的增加而显着增加。在联合应力下，从光系统 II 到光系统 I 的电子转移效率显着降低。在38℃高温胁迫下，受葡萄霜霉病影响的叶片单位活性反应中心耗散的能量显着增加。高温加剧了霜霉病对葡萄叶片光系统II( PSII )结构和功能的不利影响，进而加剧了热胁迫引起的光合作用降低。