| Stem rot caused by Sclerotinia sclerotiorum is a great threat to the health and yield of crops including rapeseed plants.The sustainable agricultural development needs friendly biological control stem rot.In this study,microbial resources with strong antagonistic effect against S.sclerotiorum were isolated,identified,and screened from rapeseed-planted field soil in Tibet.We also explored their potential biocontrol application and crop growth promotion.Finally,the potentially effects on rhizosphere microbial community composition of rapeseed were investigated.The following results were obtained:We isolated and identified a biological fungus for the growth promotion of crops.A total of 94 strains,including 32 fungi and 62 bacteria,which belong to 33 different genera,were isolated and purified from rapeseed-planted field soils in a different district in Tibet.The isolated bacteria mainly belong to Bacillus and Streptomyces,and the isolated fungi were mainly assigned to Mortierella and Clonostachys.Based on the dual-cultrue experiments,34 strains with strong antagonistic activity(inhibited bands more than 20mm)to phytopathogenic fungi were screened,including 21 bacterial strains and 13 fungal strains.Among them,strain XZ-90 showed strong biocontrol potential to inhibit S.sclerotiorum growth.Based on the morphological d phylogenetic analyses of ITS-TUB genes,strain XZ-90 was identified as a new species of Clonostachys.The fermentation filtrate of strain XZ-90 showed good characteristics,including thermal stability,acid-base stability,and UV irradiation stability.Strain XZ-90 has a broad-spectrum anti-fungal activity for several important phytopathogenic fungi.The potted experiments showed that the biological effect of strain XZ-90 on S.sclerotiorum was 81.03%,and also the strain XZ-90 could effectively improve the growth of rapeseed.Field experiment showed that strain XZ-90 had 41.47% biocontrol effect on rapeseed rot disease,and increased rapeseed yield by 40.86%.PCR and confocal microscopy showed that strain XZ-90 could be detected from the root,stem,and leaves of rapeseed seedlings after the rape root treated by strain XZ-90,suggesting that SZ-90 could colonize and grow in rapeseed.In addition,strain XZ-90 could also promote the growth of rice,wheat,and tomato.Strain XZ-90 significantly affected the microbial community structure of rapeseed rhizosphere.The results of rape rhizosphere soil microbiome diversity analysis showed that the relative abundance of Proteobacteria increased after the treatment with XZ-90 mycelium suspension.As one of the dominant phyla,the relative abundance of Gemmatimonadetes decreased.11 differential bacterial markers were obtained by LEf Se analysis,which mainly belonged to Proteobacteria.After treatment,the relative abundance of Ascomycota increased,while that of Olpidiomycota,the dominant phylum,decreased.21 fungi markers were obtained,which mainly belonged to the phyla Olpidiomycota,Ascomycota,and Mortierellomycota.The microbial community structure in rape root was more simple,of which the changes were similar to those in the rhizosphere after treatment,except that the relative abundance of Actinobacteria decreased.17 bacterial markers were obtained,and the species were consistent with the rhizosphere soil.7 fungi markers were obtained,of which Olpidiomycota were less than the rhizosphere soil.The changes of microbial community structure in rape rhizosphere may relate to the growth promoting affection of strain XZ-90.In conclusion,as a new species belonging to Clonostachys,strain XZ-90 was screened from the rape field soil in Tibet and had strong antagonistic affection against S.sclerotiorum.The strain had both growth promotion and disease resistance affection on rape and other crops,and could improve the rhizosphere microbial community structure to promote the healthy growth of rape.This study provides a new plant disease control resource and a theoretical basis for the green control of rape diseases,which provides a reference for the exploration of efficient biocontrol agents for plateau environmental conditions. |
