PGPR菌剂对辣椒的促生效应及根际土壤细菌的响应研究

Growth-promoting effects of PGPR microbial agent on chilli and response of rhizosphere soil bacteria

研究田间条件下PGPR菌剂灌根对辣椒根际土壤细菌数量及群落结构的影响,为深入探究PGPR菌剂的田间促生机制提供理论依据。以4株PGPR菌株制成PGPR菌剂,对辣椒进行灌根,并采用Illumina-MiSeq平台对辣椒根际土壤细菌V3-V4区进行Paired-end测序,结合细菌及功能菌群数量、辣椒产量指标,比较分析菌剂灌根配施全量化肥(PGPR-CF1)、菌剂灌根配施80%化肥(PGPR-CF2)和全量化肥(CK)处理后对辣椒根际土壤细菌数量及群落结构特征的影响。结果表明:PGPR菌剂灌根后辣椒根际土壤细菌及包含固氮、解磷及解钾等功能菌群的数量显著提高,且物种丰度和多样性均高于对照,细菌优势度则表现为PGPR-CF1和CK组高于PGPR-CF2。所有土样共得到有效序列573 896条,在相似水平为97%下聚类分析得到OTUs数分别为2 153个(CK)、2 337个(PGPR-CF1)、2 358个(PGPR-CF2);各处理辣椒根际土壤中的优势门为酸杆菌门、放线菌门、拟杆菌门、绿弯菌门、浮霉菌门和变形菌门,相对丰度总占比分别为83.7%(PGPR-CF1)、79.55%(PGPR-CF2)和79.77%(CK)。PGPR菌剂灌根后增加了伯克霍尔德氏菌目、芽孢杆菌目、鞘脂单胞菌目等的相对丰度,降低了芽单胞菌目、酸杆菌目的相对丰度。Pearson指数表明,辣椒产量和单果重与根际土壤细菌多样性和丰度正相关。研究显示,PGPR菌剂处理,可以提高根际土壤细菌和功能菌群的数量,同时影响了物种多样性和群落结构,并促进了辣椒增产。

The effects of PGPR inoculants on the number and community structure of bacteria in chilli rhizosphere soil under field conditions are investigated to provide a theoretical basis for further exploring growth-promoting mechanism of these inoculants.Three treatments are designed,including PGPR inoculants plus 100%chemical fertilizer(PGPR-CF1),PGPR inoculants plus 80%chemical fertilizer(PGPR-CF2)and 100%chemical fertilizer(CK).The PGPR inoculants,consisted of four bacterial strains,are irrigated to chilli’s roots.And then V3-V4 region of 16S rRNA gene in the rhizosphere is sequenced by Paired-end using Illumina-MiSeq platform,combining with measurements of functional bacteria numbers and yield indexes of chilli.The effects on bacteria numbers and community structure in chilli rhizosphere soil are compared and analyzed based on above results.The result shows that the number of bacteria and functional bacteria,including nitrogenfixing bacteria,phosphorus-dissolving bacteria and potassium-insolubing bacteria,increase significantly after root irrigation with PGPR,the bacterial abundance and diversity in group treated with PGPR inoculants are higher than control group,but the bacterial dominance of PGPR-CF1 and CK are higher than PGPR-CF2.Under the similarity level of 97%,the OTUs number of CK,PGPR-CF1 and PGPR-CF2 are 2153,2337 and 2358,respectively,by cluster analysis of 573896 valid sequences;The dominant phylum in the chilli rhizosphere soil of all treatments are Acidobacteria,Actinobacteria,Bacteroidetes,Chloroflexi,Planctomycetes,Proteobacteria.The relative abundance ratios were 83.7%(PGPR-CF1),79.55%(PGPR-CF2)and 79.77%(CK),respectively.However,the relative abundance of orders such as Bacillales,Burkholderiales,Sphingobacteriales,etc.,are increased after the irrigation with PGPR inoculants,the other orders,such as Gemmatimonadales,Actinomycetes,etc.,are the opposite.Chilli yield and weight of single fruit are positively correlated with the diversity and abundance of bacteria in the chilli rhizosphere soil based on Pearson indexes.PGPR inoculants improve numbers of bacteria and functional bacteria in rhizosphere soil,impact on the rhizobacterial diversity and community structure,and increase the yields of chilli.