Analysis of microbial diversity and niche in rhizosphere soil of healthy and diseased cotton at the flowering stage in southern Xinjiang.

Understanding how microbial community composition and diversity respond to continuous cropping obstacle is not well understood. However, determining the community composition vs assessing the diversity of molecular operational taxonomic units is often difficult. In this study, we focused on the microbial diversity and niche differentiation in rhizosphere soils between healthy and diseased cotton using a molecular approach based on a culture-independent method. A total of 124 operational taxonomic units (OTUs) from 1076 DNA fragments were detected, including 46, 57, and 21 OTUs from fungi, bacteria, and actinomycetes, respectively. The identified OTUs were confirmed by sequencing after polymerase chain reaction-restriction fragment length polymorphism analysis. The number of OTUs from Fusarium species in diseased rhizosphere soils was higher than that in healthy rhizosphere, which was consistent with field observations. Overall, the results showed that microbes in healthy rhizosphere soils were more diverse and occupied a wider niche in the healthy rhizosphere soil environment of the cotton field. Beneficial microbes should further be analyzed in studies examining the soil ecology of fields in which continuous cropping of cotton takes place.

Molecular tracing of white muscardine in Asian corn borer using inter-simple sequence repeat (ISSR) analysis.

Beauveria bassiana is a soil fungus that parasitizes arthropod species, and is used to control the Asian corn borer in Northeast China. In this study, B. bassiana was investigated in Xiaoxian County and Baicheng City, and the results were compared with those of Gongzhuling City, where the fungus was not applied. Using the inter-simple sequence repeat (ISSR) molecular marker technique, 198 isolates were extracted from Asian corn borer and other insect cadavers, and soil and air, and two released strains were analyzed to trace the infection source. In Xiaoxian and Baicheng populations, artificially released B. bassiana subpopulations were more abundant than indigenous fungi, and the released strains were the main cause of disease in those areas. Artificial B. bassiana displayed positive effect on overwintering of Asian corn borers in corn straw stacks in Xiaoxian County. Indigenous populations in Gongzhuling City showed higher genetic variation. In summary, we identified a significant correlation between genetic distance and geographic distance (P < 0.01).