| Strawberry root rot is a serious soil borne disease on strawberry production,and no effective control measure is available yet.Therefore,the objective of this study was to develop a new bio-agent for controlling this disease.The antagonistic strain B04 was isolated from the rhizosphere soil of a healthy strawberry plant,and it strongly inhibited the variety of the growth of phytopathogenic fungi.The antagonistic strain B04 and the preliminary separation of pathogenic Y3 were as experiment materials to carry out the research work in this paper.Firstly,the antagonistic strain B04 and strawberry root rot pathogenic Y3 were classified and identified,respectively.Secondly,the activities of intracellular and extracellular metabolites of strain B04 were researched.Agro-industrial waste materials,specifically wheat bran and vermicompost,were used for solid-state fermentation with strain B04 to produce bio-control agent(BOF-B04).Finally,pot and field experiments were conducted to evaluate the control efficiency of strain B04 solid fermentation preparation against strawberry root rot,the research is as follows:Strain B04 was identified as Streptomyces hygroscopicus by morphological and cultural traits and by 16S rRNA gene sequence analysis.Strain Y3 was tentatively identified as F.oxysporum according to morphological characteristics observed by optical microscope and rDNA-ITS sequences analysis.Strain B04 strongly inhibited the growth of pathogens,especially that of Fusarium oxysporum f.sp.niveum?Verticillium dahliae?Fusarium oxysporum.The research found that the activities of intracellular and extracellular metabolites of the antagonistic strain B04 have stronger antibacterial activity.This paper has optimized the solid material proportion of solid-state fermentation and the culture time of strain B04,and determined the strain B04 solid-state fermentation culture medium formula for comparison:vermicompost 50%and wheat bran 50%.On the seventh day of fermentation at 28?,the number of colony-forming units(CFU)had reached 5.3×1010CFU g-1.The results of the pot experiment showed that application of BOF-B04 significantly increased the fresh weight of strawberry plants compared to the control and also decreased the incidence of root rot.The biocontrol efficiencies of BOF-B04 were 63.35%,and root weight?shoot weight increased 72.41%?43.79%,respectively.Application of BOF-B04 decreased the levels of stress-related enzyme activity and of malondialdehyde compared to the control(activity of SOD?PPO?POD and content of MDA).Moreover,after application of BOF-B04,the number of fungi in rhizosphere soil decreased markedly compared to the control.In contrast,bacterial and actinomycete densities were dramatically higher than in the control.Application of BOF-B04 significantly promoted strawberry growth and reduced disease incidence in field experiments.The root and shoot weights in BOF-B04 treatments were clearly increased,by 77.03%and 64,74%,respectively,the biocontrol efficiency was 56.74%and the strawberry yield was 1.44×104 kg ha-1 and was increased by 55.56%in the first season experiment compared to the control.The biocontrol efficiency of BOF-B04 was 65.63%and yield was 1.53×104 kg ha-1 in the second season experiment.Compared to the first season,the second season reduced disease incidence by 55.25%and increased biocontrol efficiencies by 15.67%in BOF-B04 treament.In addition,application of BOF-B04 also significantly increased the relative abundance of Streptomyces,reduced the relative abundance of Fusarium,altered the microbial community structure of the rhizosphere soil.In conclusion,bio-control(BOF-B04)can control the strawberry root rot effectively,and has a good application prospect. |
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