Structure and Diversity of the Phyllosphere Bacterial Community of Rubber Tree Powdery Mildew
The dominant community at the phylum level was Cyanobacteria , with a relative abundance ranging from 71.24% to 98.29%. This dominance can presumably be explained by the strong viability ofCyanobacteria and their strong symbiosis with some eukaryotes. Because of its widespread presence on the leaf surface of rubber trees, this paper speculates that genera of this bacterial phylum may have colonized the leaf surface via wind dispersal and then multiplied rapidly, thereby fixing nitrogen to help replenish the leaf with nitrogen. In the long term, Cyanobacteria has evolved in a mutually beneficial symbiosis with host leaves, enabling it to occupy an overwhelmingly dominant position in the phyllosphere bacterial community. The increased nitrogen supplies more nutrition for the leaf, which then provides a better parasitic environment for the causal agents of powdery mildew and allows the three actors—the rubber tree leaf,Cyanobacteria , and Erysiphe —to coexist peacefully.
The genus-level community composition and relative abundance of healthy leaves and Level 3-infected leaves at the same site were not significantly different, while community composition and relative abundance at the genus level were significantly different among the four representative regions. This could suggest that Erysiphe had little effect on the overall phyllosphere bacterial community structure, though they may affect the relative abundances of the members of each community. The correlation between OTUs and environmental factors in the four regions demonstrated that certain OTUs were significantly correlated with the ambient temperature and humidity, while the altitude had a negligible influence on OTUs.