Assembly and maintenance of phyllosphere microbial diversity during rubber tree leaf senescence.

Phyllosphere microorganisms execute important ecological functions including supporting host plant growth, enhancing host resistance to abiotic stresses, and promoting plant diversity. How leaf developmental stages affect plant-microbiome interactions and phyllosphere microbial community assembly and diversity is poorly understood. In this study, we utilized amplicon sequencing of 16S rRNA and ITS genes to investigate the composition and diversity of microbial communities across different leaf developmental stages of rubber trees. Our findings reveal that endophytic microbial communities, particularly bacterial communities, are more influenced by leaf senescence than by epiphytic communities. The high abundance of metabolism genes in the endosphere of yellow leaves contributes to the degradation and nutrient relocation processes. Nutrient loss leads to a higher abundance of α-Proteobacteria (r-selected microorganisms) in the yellow leaf endosphere, thereby promoting stochastic community assembly. As leaves age, the proportion of microorganisms entering the inner layer of leaves increases, consequently enhancing the diversity of microorganisms in the inner layer of leaves. These results offer insights into the mechanisms governing community assembly and diversity of leaf bacteria and fungi, thereby advancing our understanding of the evolving functions of microbial communities during leaf senescence in general, and for an important tropical crop species in particular.