Phyllosphere microbial transplantation mitigates heat-induced leaf chlorosis in Ginkgo biloba seedlings

Phyllosphere microbiota can enhance plant stress tolerance, but their capacity to alleviate heat-induced chlorosis in Ginkgo biloba seedlings, a woody perennial highly susceptible to heat stress, has not been systematically investigated. Here, we investigated the dynamics of the G. biloba phyllosphere microbiome during seedling development, its response to acute heat stress, and the efficacy of microbiota transplantation in alleviating heat-induced chlorosis. Under controlled environmental conditions, the growth of two-year-old G. biloba seedlings resulted in the maturation of phyllosphere microbiome, indicating by the gradually increased microbial alpha diversity and the increased abundance of potentially beneficial microbes, including Bacillus and Spirosoma species. However, 40/30 °C (day/night) heat regime for two weeks led to drastic compositional shifts, including reduced abundance of Bacillus and Spirosoma, and enrichment of Microbacterium and Chryseobacterium. Heat stress resulted in the chlorosis of leaves, in parallel with reduced leaf soluble sugar content and induced changes of catalase, superoxide dismutase, and peroxidase levels. To test functional rescue, we transplanted leaf microbiota from healthy leaves onto heat-stressed seedlings at two dilution levels. Two-fold dilution inoculation restored Bacillus abundance, reduced catalase and peroxidase activities, and enhanced superoxide dismutase levels, collectively attenuating chlorosis symptoms. Our results demonstrate that native phyllosphere microbiota can re-establish protective microbial assemblages and modulate host oxidative stress responses under extreme heat. This study provides the evidence that targeted microbiome transplantation mitigates heat-induced chlorosis in G. biloba, offering a promising strategy for microbiome-based enhancement of thermotolerance in woody plants.