Change of microbial community composition in bacterial wilt infected tobacco-planting soils and regulation of the functional bio-organic fertiliser
Bacterial wilt caused by Ralstonia solanacearum is one of main soil-borne diseases during the growth of tobacco. Soil microbes play important roles in tobacco growth and health. Little is known about the differences of soil microbes between healthy and bacterial wilt infected soils. It was found the soil microbial composition and diversity was distinct between healthy and bacterial wilt infected tobacco-planting soils by Illumina-MiSeq sequencing technology. Healthy soils exhibited higher microbial diversity than the bacterial wilt infected soils. Abundance of 36 bacterial genera were significantly different between healthy and bacterial wilt infected soils.
19 bacterial genera were more abundant in the healthy soils, while the rest 17 genera were more abundant in the bacterial wilt infected soils. Interestingly, the beneficial microorganisms (e.g. Bacillus, Bradyrhizobium, Nocardioides and Micromonospora) were more abundant in the healthy soils compared to the bacterial wilt infected soils. Based on the results of Illumina-MiSeq sequencing, three Bacillus strains with strong activity against R. solanacearum, were isolated from the soil planted with tobacco, and then added into organic fertiliser to form functional bio-organic fertiliser (BOF) with resistance to tobacco bacterial wilt. The results showed BOF could reduce the disease index of tobacco bacterial wilt and effectively control the bacterial wilt. After application of BOF the soil microbial community altered dramatically. Abundance of Sphingomonas, Paenibacillus, Thermobacillus and Clostridium increased obviously, which can degrade organic materials and promote growth of benerifical microbes and tobacco. Abundance of Streptomyces and Bacillus also increased obviously in soil treated with BOF, which are antagonists to R. solanacearum by producing antibiotics. The results indicate that BOF positively impacts on the composition and abundance of soil microbial community that are beneficial for control of tobacco bacterial wilt.