Study On Diversity And Antagonistic Activity Of Actinobacteria Isolated From Tobacco Soil

In order to understand the actinobacterial diversity and community structure of tobacco soil, and screen excellent biocontrol actinobacteria. A toal of45actinobacteria were isolated from the tobacco soil in Panzhihua City, Yanbian by dilution-plate method. The restriction enzyme Hinf I. Taq I, Hha I and Msp I were used to analyzed the16S rDNA PCR products of the actinobacteria.. For the45isolates of actinomycetes, the plate confrontaton method was used to screen of the strains antagonistic against8kinds of plant pathogenic fungi. And finally B22which had the best effect of antagonistic against maize curvularia disease (Curvularia Lunata) was screened to do the corn pot experiment. The main results are as following:(1) The results of16S rDNA-RFLP indicated that Hinf I was the most effective restriction enzyme to reflect actinomycete16S rDNA sequence difference. All of the strains could be clustered at73%similarity level in the comprehensive clustering tree. And the tree was split into six branches with27taxa at the87%similarity. The clustering results showed that the diversity of actinobacteria in Panzhihua tobacco soil was well.(2) The primary screening results showed that there were13different isolates antagonistic against two or more than two kinds of pathogens, accounting for28.8%of the total number of tested strains. It indicated that antagonistic actinobacteria in the Panzhihua tobacco soils were rich. The secondary screening results showed that the isolate B22could antagonistic against more than5kind plant pathogens and it could strongest antagonistic against maize curvularia disease (Curvularia Lunata) with the inhibition zone width5.4mm. Actinobacteria B22had good potential for biological control.(3) Pot experiment results showed that the disease index group C (plus Curvularia Lunata and actinobacteria B22both) was lower than group A (plus Curvularia Lunata only) by16. The incidence of group C decreased25%than group A after application of actinobacteria B22preparations, indicating that B22could effectively inhibit the occurrence of the maize curvularia disease. Plant height of group B (plus B22only) was higher than group D (CK, no Curvularia Lunata and actinobacteria B22)3.3cm, the difference was significant (p<0.05). Leaf length of group B was longer than group D4cm, the difference was significant (p<0.05). In conclusion, actinobacteria B22could effectively inhibit maize curvularia disease (Curvularia Lunata) and increase the plant growth.(4) The result of16S rDNA complete sequence analysis showed that actinobacteria B22showed more than99%similarity with Streptomyces bungoensis. As the results of the morphological characteristics, cultural characteristics and phylogenetic tree analysis, the actinobacteria B22was identified as Streptomyces bungoensis.