Efficiency Of Paenibacillus Polymyxa Preparations And Chemical Agents On Rhizosphere Microorganisms In Pepper

Pepper phytophthora blight is a global soil-borne disease caused by phytophthora capsici and seriously affects agricultural production.Currently,the main methods to control pepper phytophthora blight are chemical control and biological control.Chemical control has quick effects,but it is not conducive to sustainable agricultural development.Biological control is not only in line with the concept of ecological development,but also promising.Therefore,the application of effective biocontrol agent is an effective way to develop green agriculture.Paenibacillus polymyxa preparation is a kind of widely used biological preparation that can effectively control pepper phytophthora blight and generate a variety of antimicrobial substances.This study collected samples of phytophthora capsici from Hunan.Four highly pathogenic strains of phytophthora capsici were obtained by separating such samples.Their biological morphology,pathogenicity and other aspects were studied.In addition,paenibacillus polymyxa preparation was used to conduct field control experiment on phytophthora capsici to analyze its impacts on the microbial community in the rhizosphere of capsicum.The study results would help to explore the impacts of paenibacillus polymyxa on the rhizosphere microecology of infected pepper and would be of great significance for the clear micro-ecological regulation of pepper phytophthora blight.The study obtained the following results:1.This study obtained 4 highly pathogenic strains of phytophthora capsici were obtained by separating samples collected from Hunan.Two kinds of chemical agents and the sterile filtrate of paenibacillus polymyxa were used to measure the susceptibility of the strain with the highest pathogenicity,strain YY4.The results showed that all of the three agents have inhibitory effects on the growth rate of mycelium,germination of zoospores and other aspects of phytophthora capsici.2.This study used two chemical agents,azoxystrobin 25% SC,metalaxyl?mancozeb 68% and paenibacillus polymyxa preparation to conduct an experiment on the field control efficiency on phytophthora capsici strain YY4.The results showed that the field control efficiency of the three agents on strain YY4 is 71.54%,76.30% and 74.35%,respectively,indicating that the control efficacy of paenibacillus polymyxa preparation has been as high as that of chemical agents and that it can replace chemical agents for control purpose.3.The results of the analysis of the microbial population of pepper rhizosphere soil treated with different agents showed that,at early stage of treatment with paenibacillus polymyxa preparation,it has minor impacts on bacterial microbial communities,but begins to affect the communities as time goes on;and the richness and diversity of species begin to increase.In terms of fungus,paenibacillus polymyxa preparation begins to affect fungi communities at the early stage of treatment;the effects in various aspects reach the highest level at medium stage of treatment and then begin to decrease.Experimental results indicate that the use of paenibacillus polymyxa preparation has slow effects on the bacterial communities in soil rhizosphere,but the effects are long-lasting.Paenibacillus polymyxa preparation has quick effects on fungi communities,but the effects last a short period of time.