烟草-荞麦轮作对烟草黑胫病防治及土壤微生态的调控作用

【目的】明确烟草—荞麦轮作对烟草黑胫病防治及根际土壤微生物群落结构的调控作用，为利用烟荞轮作缓解烟草连作障碍及烟草黑胫病害提供科学依据。【方法】选择湖北省恩施市宣恩县烟草黑胫病发生较重的连作烟田为试验地点，设烟草—烟草—烟草（连作）和烟草—荞麦—荞麦—烟草（轮作） 2个处理，通过计算田间病情指数评价烟荞轮作对黑胫病发生的影响；运用实时荧光定量PCR（qRT-PCR）检测烟荞轮作下烟草根际黑胫病菌数量的变化；运用Illumina高通量测序分析烟荞轮作对烟草根际微生物丰富度、多样性及群落结构的影响。【结果】烟草移栽后45、60、75和90 d，轮作田烟草黑胫病病情指数分别为2.57、18.03、24.93和75.88，与连作田相比分别下降35.59%、36.22%、46.53%和11.52%；轮作田烟草根际黑胫病菌孢子数量分别为1.05×104、2.19×104、5.25×105和1.32×105个/g，与连作田相比分别降低43.55%、86.81%、95.73%和-43.86%。与连作相比，轮作提高了烟草根际土壤微生物群落的丰富度和多样性，轮作田细菌的Sobs、Shannon和Chao1指数分别上升23.70%、6.38%和24.32%，真菌的Sobs、Shannon和Chao1指数分别上升24.51%、16.57%、41.17%。在门水平上，轮作田中有益细菌门放线菌门（Actinobacteriota）、绿弯菌门（Chloroflexi）、酸杆菌门（Acidobacteriota）的相对丰度分别较连作田提高6.58%、17.79%和38.22%，有益真菌门子囊菌门（Ascomycota）、壶菌门（Chytridiomycota）的相对丰度分别较连作田提高20.47%和420.22%；在属水平上，烟荞轮作显著增加了芽孢杆菌属（Bacillus）、慢生根瘤菌属（Bradyrhizobium）、念珠菌固体杆菌属（Candidatus_Solibacter）、鞘氨醇单孢菌属（Sphingomonas）、芽单胞菌属（Gemmatimonas）和沙壤土杆菌属（Ramlibacter）等有益细菌的丰度，显著减少了致病菌劳尔氏菌属（Ralstonia）的丰度。【结论】烟荞轮作可有效降低田间烟草黑胫病病情指数和根际黑胫病菌数量，提高烟草根际真菌和细菌的群落丰富度和多样性，增加烟草根际多种有益菌的丰度，对改善土壤微生态环境、缓解连作障碍具有积极作用，具有较广的推广应用前景。

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.