Exophiala sp.LHL08 association gives heat stress tolerance by avoiding oxidative damage to cucumber plants

Exophiala sp. LHL08, a gibberellin-producing strain, was investigated to assess its effects on cucumber plant growth and heat (40°C) stress tolerance. The results reveal that Exophiala sp. associated plants had significantly higher plant growth attributes (shoot length, plant biomass, chlorophyll contents, and leaf area) than control under heat stress. Endophytic association helped the plants to obtain adequate water to reduce the leaf electrolytic leakage under stress. High-temperature-induced oxidative stress was less pronounced in Exophiala sp. associated plants as shown by enhanced levels of total polyphenol and reduced activities of glutathione, superoxide anion, and lipid peroxidation. To tolerate heat stress and rescue plant growth, the endophyte association significantly increased catalase and peroxidase activities of the host plants as compared to control plants. Contents of palmitic, stearic, oleic, and α-linolenic were significantly decreased in the Exophiala sp.-inoculated plants than control plants under heat stress. Contents of flavonoids like genistein and daidzein were produced in higher quantities, while glycitein content was almost same in endophyte-associated plants under heat stress than control plants. Contrarily, stress-responsive endogenous abscisic acid and jasmonic acid were significantly activated in non-inoculated control treatments as compared to endophyte-inoculated plants under heat stress. The findings of the study reveal that association of Exophiala sp. with cucumber host plants can modulate heat stress by influencing physiological and biochemical contents of plants under heat stress.