Effects of tobacco-buckwheat rotation on regulation of tobacco black shank prevention and control and soil microenvironment

【Objective】 To investigate the effects of tobacco-buckwheat rotation on regulation of tobacco black shank occurrence and rhizosphere soil microbial community，so as to provide a basis for alleviating continuous cropping obstacle of tobacco by tobacco-buckwheat rotation.【Method】 A continuous cropped tobacco field with severe tobacco black shank disease in Xuan’ en County，Enshi City，Hubei Province was selected as the experimental site，and 2 treatments were set： tobacco-tobacco-tobacco（continuous cropping）and tobacco-buckwheat-buckwheat-tobacco（buckwheat-tobacco rotation）.The disease index of the field was calculated to evaluate the effect of tobacco-buckwheat rotation on black shank disease occurrence.The change of the number of tobacco black shank bacteria in rhizosphere under rotation was detected by quantitative real-time PCR（qRT-PCR）.Effects of tobacco-buckwheat rotation on richness，diversity and microbial community structure were analyzed through Illumina high-throughput sequencing.【Result】 Seem from 45，60，75 and 90 d after tobacco transplantation，tobacco black shank disease indexes of rotation cropping field were 2.57，18.03，24.93 and 75.88，decreased by 35.59%，36.22%，46.53% and 11.52% compared with those of continuous cropping field，respectively； the rhizosphere black shank spore of tobacco in the rotation cropping field were 1.05×104，2.19×104，5.25×105 and 1.32×105 conidia/g，respectively，43.55%，86.81%，95.73% and-43.86% lower than those of continuous cropping field，respectively.Compared with continuous cropping，rotation cropping increased the richness and diversity of the tobacco rhizosphere soil microbial community.Sobs，Shannon and Chao1 indexes of bacteria in the rotation cropping field were increased by 23.70%，6.38% and 24.32% respectively.Sobs，Shannon and Chao1 indexes of fungi increased by 24.51%，16.57% and 41.17%，respectively.At the phylum level，the relative abundance of beneficial bacteria Actinobacteriota，Chloroflexi and Acidobacteriota in the rotation field increased by 6.58%，17.79% and 38.22% respectively，while relative abundance of beneficial fungi Ascomycota and Chytridiomycota increased by 20.47% and 420.22%，respectively.At the genus level，the proportions of beneficial bacteria of Bacillus，Bradyrhizobium，Candidatus_Solibacter，Sphingomonas，Gemmatimonas and Ramlibacter were significantly increased in rotation field and the proportion of pathogenic bacteria of Ralstonia was significantly reduced.【Conclusion】 Tobacco-buckwheat rotation can lower the tobacco black shank disease index and reduce the number of rhizosphere black shank pathogenic bacterium，increase the abundance，diversity of tobacco rhizosphere fungi and bacteria community and raise abundance of tobacco rhizosphere beneficial bacteria，thereby improving soil microenvironment and alleviating continuous cropping obstacles，bringing a great popularization and application prospect.