Study On The Growth-promoting And Disease-resistant Functions Of Phomopsis Liquidambaris B3-induced Peanut Core Functional Bacterial Assemblage

Peanut is an important oilseed and economic crop in China.There are many poor agricultural management practices with increased demand,such as perennial continuous crop in agricultural farming.For example,the main peanut-producing areas,such as Jiangxi province,have severe problems of continuous crop disorders due to monocropping peanuts.In our previous study,the endophytic fungus Phomopsis liquidambaris B3 was found to be effective in alleviating the continuous crop disorder in peanuts,improving the yield of continuous peanuts,and reducing the occurrence of soil-borne diseases.However,the researches on the underlying mechanism of B3 promoting peanut growth are still incomplete.Our previous studies have indicated that Ph.liquidambaris B3 can promote the establishment of peanutrhizobia symbiosis and affect the bacterial community composition in peanuts’ nodules.However,it remains unclear what the changes in the root endophytic bacterial community induced by Ph.liquidambaris B3 colonization are and whether such changes affect the growth and resistance of peanuts.Therefore,in this study,we investigate the mechanism by which Ph.liquidambaris B3 promotes the healthy growth of peanuts from the perspective of endophytic bacterial community.We first investigated the effects of Ph.liquidambaris inoculation on peanuts’ agronomic traits.Such as peanut plant height,root length,number of nodules,and pod yield under continuous crop conditions through a one-season pot experiment.Secondly,we investigated the incidence and disease index of peanut leaf spot and root rot and quantified the relative abundance of Fusarium oxysporum and Colletotrichum gloeosporioides.Subsequently,we used PCR-DGGE and Biolog-Eco to make preliminary judgments on endophytic bacterial communities’ changes caused by Ph.liquidambaris B3 colonization.The results showed that Ph.liquidambaris B3 was effective in promoting plant height,biomass,and yield of peanut.Compared with the continuous crop control,it significantly reduced root rot at the seedling stage and leaf spot disease at pod and maturity stages.Moreover,the results showed that perennial continuous crop led to changes in endophytic bacterial communities.In contrast,inoculation of Ph.liquidambaris B3 changed root endophytic bacterial communities’ composition.These results suggest that Ph.liquidambaris B3 can well alleviate the stunted development and disease incidence caused by continuous crop,which plays a role in promoting peanuts’ growth under continuous crop conditions.Moreover,prevent plants from soil-borne diseases,significantly affecting the composition of endophytic bacterial communities.To investigate the core microbiome of the peanut endophytic bacterial community,we analyzed the communities’ changes by using the 16 s r RNA sequencing method.Then we combined with the pure culture isolation method to obtain endophytic bacterial isolates.The results showed that endophytic fungi changed the endophytic bacterial community of continuous peanut roots.In detail,increased the abundance of slow-growing Bradyrhizobium sp.and Streptomyces sp.Network analysis based on core microorganisms showed that Streptomyces sp.,Pseudomonas sp.,and Burkholderia sp.were the dominant nodes.Meanwhile,at the pure culture level,Bacillus sp.and Paenibacillus sp.were the dominant genera induced by endophytic fungi.Therefore,combining the results of high-throughput sequencing and pure culture,we selected the genera of Bradyrhizobium sp.,Streptomyces sp.Bacillus sp.,Pseudomonas sp.,Burkholderia sp.,and Paeniacillus sp.are the core genera.To investigate whether the changed microbiome can promote peanuts’ healthy growth and prevent soil-borne diseases,we conducted the following experiments.First,we screened the core microbiome members.Subsequently,we explored the disease-resistant and growth-promoting effects of the core functional bacterial assemblage.Finally,we conducted a preliminary investigation of the diseasepromoting and disease-resistant mechanism of the bacterial assemblage.We screened six bacterial strains as core microorganisms by evaluating endophytic bacterial isolates for in vivo and in vitro probiotic disease resistance characteristics.The results showed that the bacterial assemblage induced by endophytic fungi could significantly promote peanut growth and limit pathogenic bacteria’s abundance.In summary,this paper explored the mechanism of disease resistance of Ph.liquidambaris B3 from the perspective of endophytic bacterial community changes.It provides a theoretical basis for green and effective agricultural management using combinatorial microorganisms.