Screening And Evaluation Of Antagonistic Organisms Against Rhizoctonia Solani

Rice sheath blight is one of the three major diseases of rice, has a serious impact on the yield and quality of rice. Collected from different parts of the plant root around soil isolated and screened against Rhizoctonia solani significant antagonism broad spectrum antibacterial, can inhibit the growth of rice disease pathogens bacteria (mainly Bacillus), The determination of antagonistic bacteria in a pot of rice as well as in the fields of rice sheath blight control effect, revealed its antibacterial mechanism, and laid the foundation for the further use of biocontrol agents against rice diseases.1914bacterial strains were isolated from rice soil,vegetable soil and other wild soil covered by plant in nanjing,shuyang,xuzhou,maoshan mountain and jintan in Jiangsu province. The bacterial from rice soil amount to the most part of the anatagonistic microorganism. Among the tested strains,35strains could inhibit the mycelia growth of Rhizoctonia solani, Ustilaginoidea oryzae, Pyricularia grisea, Xanthomonas oryzae pv.oryzae, Xanthomonas oryzae pv.oryzicola. Strains SF-181had strongest inhibitory activity against Rhizoctonia solani in vitro, with the inhibition rate of89.63%.The control effect of35antagonistic bacteria strains against rice sheath blight was determined in2011. The results showed that11strains showed better control effect, which is greater than48%. MS-48. JM-225. SY-136, SY-143, XZ-7XZ-63JL-217ZS-273and XZ-63,nine bacteria potted control effect is stronger than the Bs-916. JM-225, XF-174compared to the Bs-916the difference was not significant. The following year field experiment,11bacteria control effect of over43%. Two-year experimental result is insignificant, more stable control effect. SY-143pot experiments and field experiments control efficiency of61.26%and61.22%, respectively, anti-efficient and stable effect.The antagonistic Mechanism of bacteria screened were researched.The result showed that the11antagonistic bacteria stains could not produce chitinase.All bacteria produce cellulase except XF-174. proteinase and siderophore was producted by11bacteria stains. It was suggested that the11strains had antibiotic activity against pathogenic fungi because of the producing of proteinase, cellulose, siderophore. It was also possible that other antibiotic materials could play a role in antibiosis.the effect of antagonistic baeterium on rice promotion was researched. The result of showed that compared with the control level,the rice processed by antagonistic bacteria has a higher growth rate of plant height. However, the root length was decreased. Promote biomass research shows that11strains were Phosphatase activity. ZS-273and XF-174does not produce IAA. the remaining9strains can produce IAA. All11strains could produce GA3Based on their morphology, physiological, biochemical characteristics and16S rDNA sequence analysis and gyrB sequence analysis,the strain SF-181was identified to be Bacillus subtilis. The strain XF-174was identified to be Pseudomonas fluorescens. Other9strains were identified to be Bacillus amyloliquefaciens.