Study On Screening And Growth Promotion Fuction Of Rhizospheric Antagonistic Actinomycetes From Medical Plants In A'ba Region

Due to plant disease and abiotic stress limit the production of global agriculture extremely, chemical pesticide will alleviate nutrition stress and accelerate the growth of plants. But if chemical pesticide becomes widely used, it would cause the rise of insecticide resistance of insects pests. As the disease inhibitor and plant growth accelerator, microbial inoculants could prevent crop from insects pests and accelerate its growth, then replace chemical pesticide and fertilizer. Separating and searching the diversity of microbes in rhizosphere could provide a reference for development of the source of biocontrol agents for microbes.In this research, I collected 143 samples from the roots and rhizospheres, which came from 36 wild medicinal plants, in A'BA region. Follows the results.(1) My reserach distributed 10 mediums to 400 rhizosperic actinomycetes of roots by the method of dilution plate. According to substrate hypha, aerial hypha, colors, water absorbency of spores,400 actinomycetes could be classified in 10 different groups. Then it showed up the diversity of rhizosperic actinomycetes of medicinal plants in A'BA district. And it provides a large number of microbes sources for follow-up studies.(2) This research used 6 pathogenic fungi to conduct the preliminary screening for antibacterial activity on 400 actinomycetes by flat stand method. The research showed up that for control effect,328 of total actinomycetes worked on at least 1 pathogenic fungi; 206 of total worked on at least 3 pathogenic fungi; 24 of total worked on all 6 fungi. After selecting 60 fungi with broad antimicrobial activity, I conducted growth rate method to test their inhibition rate for pathogenic bacteria of rice blast under shake-flask-fermentation condition, and it indicated different levels of antimicrobial activity.(3) For 60 tested actinomycetes, the positive rate of their PKS ?, PKS ? and NRPS are 45%,60%,10%. While I created the phylogenetic tree, I found the homology of 36 actinomycetes are almost matching to the PKS ? amino acid in Genebank database, some of them are even up to 100%. It showed these actinomycetes are potentially able to synthetic certain polyketide compounds. The homology of some of actinomycetes matching to PKS ? amino acid are less than 93%, so they could synthetic new-structure polyketide compounds. Above all, SCAUG4-15-2 was selected as follow-up experimental subject.(4) The assessment of function of growth promoting indicated in 60 actinomycetes, most of them are able to release heteroauxin and cellulase, and around 25% of them can dissolve iron in soil, meanwhile only 2 of them can dissolve phosphorus bacteria.(5) Based on antagonistic experiment, screening on functional genes, and assessment of function of development promotion, it showed SCAUG4-15-2 has a broad spectrum of antimicrobial activity on six pathogenic fungi, and the inhibition rate for Pyriculariaoryzac cavgra is higher under fermentation condition. SCAUG4-15-2 is able to produce PKS ?, PKS ?, and NRPS simultaneously. The homology of SCAUG4-15-2 is 99% matching to the PKS ? amino acid in Genebank database. It means these actinomycetes are potentially able to synthetic certain polyketide compounds. Therefore, SCAUG4-15-2 has advantage of growth promotion and biocontrol, it can be taken as a potential source for plant growth promotion and biocontrol.(6) The consequence of growth promotion and biocontrol of SCAUG4-15-2 verified by pot experiment showed that taking the method of root-irrigation and reinoculation with pathogenic bacteria of rice blast and SCAUG4-15-2 can effectively reduce rice seedlings of rice blast happening. In the condition of no pathogenic bacteria of rice blast, SCAUG4-15-2 can strongly promote the development of the seedling and rhizome of rice seedlings. After adding pathogenic bacteria of rice blast, it is obvious that SCAUG4-15-2 promotes the disease resistance of rice seedlings. Compared to alone inoculated treatments, there is a significantrise in the index of treatment of co-inoculation of SCAUG4-15-2 and pathogenic bacteria of rice blast, development of rice seedlings, fresh weight and so on, especially the great effect on promotion of root. Change law of rice chlorophyll is basically same after SCAUG4-15-2 alone treating and common treating on SCAUG4-15-2 and pathogenic bacteria of rice blast because content of a,b in chlorophyll of rice seedlings increased and content of chlorophyll increased as well. Pot experiment also showed no matter alone treating or common treating, root vigour enhanced significantly. It means no matter with or without pathogenic bacteria of rice blast, SCAUG4-15-2 can enhance root vigour of rice seedlings, and promote root to absorb water and nutrient, then accelerate the development of rice.(7) The analysis of phylogeny showed that SCAUG4-15-2 is Streptomyces cirratus. The cultural characteristics of both of them are almost same.Above all, SCAUG4-15-2 has advantage of growth promotion and biocontrol, so it can be taken as a potential source for plant growth promotion and biocontrol.