内生甲基营养型芽孢杆菌对罗汉果斑枯病的拮抗作用.

【Objective】Biological control effects of Bacillus methylotrophicus strain bjq-a against on Siraitia grosvenorii leaf blight was tested to provide reference for green control of S. grosvenorii leaf blight and development of antibiological inoculant.【Method】The antagonism of bjq-a on Stagonosporopsis cucurbitacearum were studied via the plate confrontation test, the hyphae mixed fermentation cultivation test, the concave slide method and microscope examination. Mycelial morphology, mycelial growth inhibition rate and spore germination inhibition rate were detected.The control efficacy against S.cucurbitacearum on S. grosvenorii was analyzed by inoculation of leaves in vitro. By detecting the contents of protease,cellulase and chitinase in bjq-a fermentation liquid,the antibacterial mechanism of bjq-a was preliminarily studied.【Result】The results showed that bjq-a had obvious antagonistic activity against S. cucurbitacearum,after 30 days confront culture,the growth inhibition rate of bjq-a against S. cucurbitacearum was 62.5 %. 40 % and 20 % bjq-a fermentation liquid had strong antimicrobial effects,the growth inhibition rates were 99.5 % and 96.2 % respectively.50 % bjq-a fermentation could inhibit the spore germination with the inhibitory ratio of 90.5 %. Hyphae and spore treated by fermentation liquid of bjq-a were swelled and deformed. When 20 % bjq-a fermentation liquid was used to control S. grosvenorii leaf blight, the result showed that the onset time was delayed for 1 day,the incidence of diseases was reduced by 60.0 %,the enlargement of lesions was inhibited,and the inhibition rate was 82.2 %.The result of antibiosis mechanism indicated that strain bjq-a could produce protease,chitinase and cellulose, and was one of the mechanisms that produced antagonistic activity.【Conclusion】This study indicated that bjq-a with broad spectrum antifungal activity had brilliant control efficacy on S. grosvenorii leaf blight.The strain could be exploited so as to become effective biological agents in the future. [ABSTRACT FROM AUTHOR]