Application Effect And Mechanism Of Microbial Inoculants For Regulating Pepper Blight Resistance And Growth In Pepper

Peppers have been widely grown in China for their unique flavour and nutritional value.However,Phytophthora capsica has caused serious damage to the industry in recent years.And long-term application of a large number of chemicals have polluted the environment and even endangered human health.The exploration of green,effective and sustainable biological control techniques is a hot topic of research in pepper blight control.Studies have shown that the application of microbial inoculants to build interroot biological barriers can significantly reduce the occurrence of plant diseases,but there are still problems in the agricultural production of microbial inoculants,such as poor adaptability of single biological control bacteria to the environment,unstable control effect and the best application method.Therefore,it is important to find the best microbial inoculants or combinations of microbial inoculants with good control effect on pepper blight and the best application method to control pepper blight.In this paper,we investigated the effect of four commercially available microbial inoculants on the disease resistance and development of pepper seedlings,and selected two microbial agents,Bacillus subtilis and Trichoderma harzianum,which were significantly resistant to pepper blight and promoted pepper development respectively.On this basis,in order to investigate whether the combination of the microbial inoculant would be more effective,further investigation was carried out to evaluate the effect of the combination of three different mass ratios of microbial inoculants on the growth of pepper and the control of pepper blight,and field verification was carried out to further clarify the effect of the combination of microbial inoculants over the single microbial inoculant.In order to further clarify the role of microbial inoculants in regulating disease resistance and development in pepper,this paper investigates the mechanism of plant growth,immune activation,and soil microbiological regulation,and also used llunina Mi Seq sequencing technology to analyze soil microorganisms in the inter-root environment,and to screen out the core microorganisms that may play a major function in the inter-root environment,with a view to exploring the biocontrol agents with better disease resistance.The results of the study are as follows.The results of the study are as follows:1.Bacillus subtilis,Bacillus polymyxa,Trichoderma harzianum and the microbial compound were used as the test agents,and the effects of different microbial inoculants on the growth of pepper and the control of pepper blight were investigated by pot test and field effect verification.Among them,Bacillus subtilis could significantly promote the growth of pepper.Trichoderma harzianum could significantly control the occurrence of pepper blight.In conclusion: Bacillus subtilis and Trichoderma harzianum can promote the growth and control the pepper blight.2.Different microbial inoculants have different mechanisms of action for regulating the disease resistance and development of pepper,but the application of microbial inoculants can change the inter-root soil microbial community structure and reduce the pathogenic bacteria.Bacillus subtilis significantly promoted the growth of pepper plants,increased the fruit yield and strong seedling index of pepper,and at the same time improved the POD,SOD and CAT activity of the root system after inoculation of P.capsica.Trichoderma harzianum significantly increased the salicylic acid and jasmonic acid content in pepper leaves,thus improving the disease resistance of pepper.3.The diversity of the bacterial community in the inter-rhizosphere soil of pepper changed significantly after the application of Bacillus subtilis and Trichoderma harzianum compared to the non-fungal inter-rhizosphere soil,while the fungal community did not change significantly.Among the bacterial communities,Actinobacteriota and Proteobacteria were the dominant phylum in the inter-rhizosphere bacterial community of pepper at harvest,while Ascomycota,Mortierellomycota and Basidiomycota were the dominant phylum in fungal community.Using linear discriminant analysis effect(LEfse)analysis and Pearson correlation analysis,the initial screening of Agromyces,Gaiella,Massilia,Iamia,MND1,Nocardiopsis,Gibellulopsis,Gibberella,Fusarium,and Microdochium 15 OTUs within nine genera as core species involved in inter-root health and involved in regulating disease resistance and development in pepper.In conclusion,the microbial fungicide application can effectively control the occurrence of pepper blight,and the fungicide application scheme was optimized through the combination of two microbial inoculants.Using 16S/ITS-amplicon sequencing(16S/ITS-amplicon sequencing)and biometric methods,specific beneficial microorganisms were recruited at the root level after fungicide application to lay the foundation for green control of pepper blight.