Abstract: Clarifying the effects of dry farming of rice on bacterial community diversity and structure, and microsclerotia of Verticillium dahliae in the soil of cotton fields is of great significance to the improvement of ecological prevention and control technology of cotton Verticillium wilt in Xinjiang. The Illumina Miseq highthroughput sequencing platform was used to analyze bacterial diversity and community composition of rhizosphere soils, which were sampled from the cotton fields in July and October. The selective medium method was used to detect the changes in the abundance of microsclerotia of Verticillium dahliae in soil. The results showed that, at the 97% similarity level, ACE index, Chao1 index and OTU quantity of bacteria in rhizosphere soil-between dry-farming rice and cotton were more different in October than in July, but without statistical significance. The abundance and composition of the top 20 bacterial populations ranked by abundance changed greatly between July and October. The abundance of Rhizobium in rhizosphere soil of dry-farming rice (2.15%) was 10.8 times of that in cotton field (0.20%). Results of cluster analysis showed that the difference in bacterial community structure between the dry-farming rice and cotton rhizosphere soil became larger in October. According to LEfSe (LDA Effect Size) analysis, the rhizosphere soil of dry-farming rice was rich in three beneficial bacterial populations: Pseudonocardiaceae, Chryseobacterium, and Ensifer.The abundances of beneficial Pseudomonas, Lysobacter, and Rhizobium in the rhizosphere soil of dry-farming rice increased by 38.7%, 96.8%, and 1433% respectively in October than in July, while the abundances of Pseudomonas, Lysobacter, Bacillus, and Streptomyces in the rhizosphere soil of cotton decreased by 43.3%, 26.3%, 31.3%, and 32.0%, respectively. The relative abundance ratios of Pseudomonas, Lysobacter and Rhizobium in dry-farming rice and cotton rhizosphere soil significantly increased by 157.1%, 177.8%, and 881.8%, respectively, in October than in July. The abundance of microsclerotia of Verticillium dahliae in dry-farming rice and cotton rhizosphere soil was 59.2 and 124.2 ind·g^-1 in July, respectively. By contrast, the abundance was 92.5 and 98.3 ind·g^-1 in October respectively, without significant difference. Our results suggest that, with the extension of growth period, dry-farming rice has a significant effect on soil bacterial community composition in cotton fields, and can obviously enrich beneficial bacterial populations, but has a negative effect on the microsclerotia of Verticillium dahliae.

Key words: dry-farming rice, community diversity, population structure, microsclerotia.