Effects of Microbial Agents on Tobacco Root-knot Nematode and Diversity of Rhizosphere Microbial Communities

In order to find a crop protection agent with good control effect on tobacco root-knot nematode disease, and to explore the metabolism of microbial community in tobacco rhizosphere soil and improve the soil micro-ecological environment, using the tobacco variety Honghua Dajinyuan as the experimental material in a field trial, B. subtilis, P. lilacinus, P. fluorescens, T. harzianum and avermectin, avermectin-butyl sulfate were selected for comparison. The effects on tobacco root-knot nematode disease control, metabolic diversity of rhizosphere soil microbial community and tobacco growth were studied. The results showed that P. lilacinus and P. fluorescens could achieve 89% and 76% control effects, respectively. AWCD value, McIntosh index and Simpson index all showed that the application of microbial agents in soil could increase the diversity of soil microbial communities, promote the overall utilization of carbon sources by soil microbial communities, and enhance metabolic activity. Pearson correlation analysis showed that the metabolic utilization of 31 carbon sources in microbial communities in rhizosphere soil was negatively correlated with disease index. The addition of microbial agents such as P. lilacinus, B. subtilis and P. fluorescens in soil can control tobacco root-knot nematode disease, enhance soil microbial community diversity, and promote the growth of tobacco. After treatment with P. lilacinus, the metabolic utilization of carbon sources was improved by increasing the metabolism of carbohydrates (D-galactosidase-γ-lactone) in rhizosphere soil microorganisms to achieve effective control of the disease. The P. lilacinus treatment also brought about the biggest increase in plant height, stem circumference, effective leaf number and maximum leaf width of 44.91%, 20.11%, 11.78% and 39.05%.