Microbial Community From Septobasidium Associated Scale Insects

Septobasidium spp. and scale insects are pathogens or pests of various plants. They have a putative mutualistic association and obtain nutrition from the host plants ultimately, causing great losses in agriculture. However, there are clear evidences for the relationship between Septobasidium spp. and associated scales. The aims of this study are to find out the differences of microbial community of the Septobasidium spp. associated scales and independent scales, to demonstrate the relationship between Septobasidium spp. and associated scales.The microbial community of9scale samples (6with and3samples without the infection of Septobasidium spp.) from Anhui, Beijing and Yunnan, including based on the culture-depedent and independent methods. Low-nutrient media, high-dilution and long-time incubation strategy was used to isolate more slow-growing microbes. Totally360fungal isolates were obtained, of which112isolates were selected by the screening of SSCP and were chosen to be sequenced.57OTUs (Operational Taxonomic Unit) were identified using a≥97%similarity phylotype threshold. A new fungal species, named Knufia aspidiotus, was identified and described based on morphology, rDNA ITS phylogeny analysis. In the mean while,460bacterial isolates were obtained, and43OTUs were identified.Shannon-Wiener index and Margalef index of microbial community from scale insects without association with Septobasidium spp. were much higher than those of the scales assocatied with Septobasidium spp. Methylobacterium sp. was dominant bacterial species from the uninfected scales, while dominant fungal species was not detected. Howver, Septobasidium sp. was dominant fungal species and Sphingomonas sp. was dominant bacterial species from the scales associated with Septobasidium spp. These result indicated that Methylobacterium sp. and Sphingomonas sp. were the key species affecting infection of Septobasidium spp., and Methylobacterium sp. might be as antagonist while Sphingomonas sp. be mutualistic with Septobasidium spp.Each of samples with or without association of Septobasidium spp. was selected for the microbial community based on culture-independent method. Totally492positive clones were analyzed and81clones were selected to be sequenced, and39OTUs were identified. Dominant species in both samples were Candidatus uzinera (80%), which was assumed to be bacteriome-associated endosymbiont.