Isolation And Screening Of Actinomyces From The Rhizosphere Soil Of Pigeon Pea [Cajanus Cajan(Linn.)Millsp] And Analysison The Plant-Growth Promoting Activity Of Strain CCRS8

Pigeon pea [Cajanus cajan(Linn.)Millsp.] is a medicinal and edible woody legume plant,which has important application value in many fields such as medicine,food and ecological restoration.The demand for pigeon pea is gradually increasing in various regions of the world,especially in developing regions.In order to meet the market demand,farmers in various planting areas inevitably increase the yield of pigeon pea by increasing the amount of chemical fertilizers.However,excessive dependence on chemical fertilizers will lead to a series of problems,such as decreased soil fertility,water pollution,destruction of microbial communities and increased susceptibility to crop diseases.The use of biofertilizers containing microorganisms that can promote plant growth to replace chemical fertilizers is considered to be a feasible strategy to solve a series of problems caused by chemical fertilizers.Plant growth promoting rhizobacteria is the main source of microorganisms in biofertilizers.However,there are few reports on the research of plant growth promoting rhizobacteria,especially plant growth promoting rhizosphere actinomycetes of pigeon pea.The purpose of this study was to evaluate the plant growth promoting function of rhizosphere actinomycetes of pigeon pea,study their growth promoting effect on pigeon pea and other crops and provide new strain resources for the development of biofertilizers.The main research results are as follows:1.Forty-five actinomycetes were isolated from the rhizosphere soil of pigeon pea by gradient dilution coating method.In order to preliminarily classify these actinomyces,fifteen representative strains were selected and identified by morphological observation and 16 S r RNA sequence analysis.Among them,fourteen strains were Streptomvces sp.,one strain was Glycomyces sp.,indicating that the isolated actinomyces in the rhizosphere of pigeon pea were mainly Streptomyces sp..2.Through colorimetric method and specific growth promoting screening medium,strain CCRS8 with the ability of producing auxin,siderophore,phosphate solubilization,ammonia production and producing a variety of extracellular hydrolytic enzymes(chitinase,pectinase,protease,amylase)was obtained.The inhibitory activity against pathogenic fungi and bacteria was detected by plate confrontation method and filter paper diffusion method,and it was found that it could inhibit the growth of various pathogens.It was identified as Streptomyces sp.by observing its morphological and combining with 16 S r RNA sequence analysis.3.In order to study the material basis for plant growth of strain CCRS8,the types of plant hormones produced by strain CCRS8 were qualitatively analyzed by ultra performance liquid chromatography-mass spectrometry/mass spectrometry,and the results showed that strain CCRS8 could produce auxin and salicylic acid.Then,gas chromatography-mass spectrometry combined with NIST 11.0 database retrieval and ultra performance liquid chromatography-high resolution mass spectrometry combined with mz Cloud database retrieval were used to further explore other growth promoting related active substances produced by strain CCRS8 in addition to plant hormones.It was found that strain CCRS8 may produce a variety of metabolites with antifungal,antibacterial,insecticidal and plant growth regulation effects.Finally,the nonribosomal peptide synthase,polyketide synthase and d TDP-4-ketone-6-deoxy-D-glucose synthase genes of strain CCRS8 were amplified by PCR to evaluate the ability of strain CCRS8 to synthesize antibiotics and other substances at the gene level,and it was found that strain CCRS8 had the potential to synthesize non-ribosomal peptides,polyketide antibiotics.4.In order to study the in vivo promoting effect of strain CCRS8 on host plant pigeon pea and important food crops wheat and maize,the pot experiment was conducted to observe the effects of strain CCRS8 on the growth indicators of three crops.Plant height,root length,fresh weight,dry weight and nodule number of pigeon pea increased by 67.36%,77.21%,72.08%,89.75% and 145%,respectively,while that of wheat increased by 59.91%,63.99%,55.14% and60.81%,respectively.Plant height,root length,fresh weight and dry weight of maize increased by 35.75%,25.82%,69.15% and 72.59%,respectively.These results showed that strain CCRS8 significantly promoted the growth of pigeon pea,wheat and maize(P<0.05),and had the potential to be developed as biofertilisers.