Innovation
1. Studies on rubber tree powdery mildew infections and the causal pathogenic bacteria are common in the literature. However, research using high-throughput detection techniques to determine the dominant taxa in the community of phyllosphere microorganisms on rubber trees with powdery mildew, and the effect of powdery mildew on these phyllosphere microorganisms, have not yet been reported. This study did so for the first time in order to provide data support for more effective new ideas for the biocontrol of powdery mildew in rubber tree plantations.
2. Most previous reports investigated the relationship between powdery mildew and hosts from a molecular perspective, while this work assessed the influence of pathogenic bacteria on the phyllosphere microorganisms of host leaves from a relatively macroscopic perspective. The results confirm that there is little, if any, difference between the phyllosphere microorganism populations of diseased leaves (Level 3) and healthy leaves at the same plantation site. Based on this finding, it can be inferred that phyllosphere microorganisms may exist in a satisfactory symbiotic relationship with the host plant as well as its pathogenic bacteria. The findings of this study can also confirm, from a fresh perspective, that Erysiphe is a obligate parasitic fungi. In the hostile phyllosphere environment, phyllosphere microorganisms need to maintain robust symbiotic associations with hosts and pathogens to survive and evolve, thus leading to a relatively stable evolutionary relationship between rubber trees, Erysiphe , and their attached phyllosphere microorganisms in tropical and subtropical regions. In the future, this research team will further investigate the interactions between the host, host pathogens, and phyllosphere microorganisms.
3. Few studies have evaluated the effects of foliar pathogens on the phyllosphere microbial community before and after plant infestation, and even fewer studies have examined the impact of obligate parasitic fungi on phyllosphere microorganisms. For example, Dai (2022) investigated the microbial diversity of tobacco leaves infested with Streptomycesand concluded that the relative abundance of Alternaria in healthy leaves increased from the first to the third collection, while the relative abundances of Pseudomonas , Sphingomonas , andMethylobacterium from the same location increased as leaves aged. Huang et al. (2021) reported on the phyllosphere microbial composition and diversity of tobacco leaves infested with subseptate strains ofPhytophthora spp. and found that the relative abundances ofDidymella and Boeremia (Ascomycota ) fungi andPseudomonas and Pantoea (Ascomycota ) bacteria were higher in diseased leaves than in healthy leaves, with healthy tissue harboring a richer and more diverse fungal community. The above-mentioned studies uncovered consistent changes in the abundance and species of microorganisms in the phyllosphere after the pathogenic infection of their hosts. The present study is the first to gauge the effect of the powdery mildew’s obligate parasitic fungi,Erysiphe , on the phyllosphere microorganisms of rubber trees in representative plantation areas in China.

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