Study On Isolation And Screening Of Soil Actinomycetes With Antagonistic Action To Botrytis Cinerea

The tomato grey mold caused by Botrytis cinerea is one of the important plant diseases in greenhouse tomato produce, might create ruinous harm to greenhouse vegetables frequently specially in tomato. The pathogen Botrytis cinerea is very easy to get antibiotic nature, therefore it is difficult to prevent and control by chemical fungicides, moreover long-term massive use chemical fungicide causes the 3R problem of plant diseases to be more prominent. The purpose of this research is to separate and screen antagonistic actinomycetes to defend Botrytis cinerea from greenhouse tomato soil of Shanxi Yangling, appraisal the strain, optimize fermentation condition, and preliminary study the antagonistic mechanism.The research aimed to find new microbial pesticide resources to control Botrytis cinerea.This experiment separated 2170 actinomycetes from 20 soil samples. Antifungal activity was primarily measured by crossing method using six pathogenic fungi Botrytis cirerea, Alternaria alternate, Rhizoctonia solani, Gaeumannomyces graminis, Bipolaris sorokiniana, and Fusarium oxysporium as indicating microorganism. After primary screening, 13 strains exhibited antagonistic effects, and six of them showed good antagonistic effect after secondary screening. Among them, the WB532 strain had good anti-activeness and stability to Botrytis cirerea. The single spore separation was done and the strongest activeness separate strain WB532-7 was abtained by measuring the antagonistic effect, and inhibition rate of it achieved 91.75% to Botrytis cirerea. So, WB532-7 was screened as the most superior strain.Accorded to the references of streptomycetes classification, different culture medium were used to raise the WB532-7 strain. The colony characteristics, the mycelium morphological characters and the physiological biochemistry characteristics were observed in this study. The results showed that the colour of WB532-7 colony was lavender, the sporophore was helix and the spore was elliptical. And the strain gelatin liquefies, peptonization after coagulates first in milk, and didn't grow on cellulose and so on, accorded to the above characteristics appraises, the WB532-7 strain belongs to Streptomycete Lavendulae.Through experiments to optimized fermentation condition, the best culture conditions were yellow bean cake powder 2%, the glucose 1%, the starch 1.5%, the calcium carbonate 0.25%, the dipotassium hydrogen phosphate 0.05%, under concurrent present initial fermentation medium pH8.0, the fermentation temperature 30℃, the rocker rotational speed 150 r/min, and the fermentation time 72h. Culturing in the above conditions, the strain WB532-7 mycelium metabolism is most exuberant and the antagonistic effect is best.This research had primarily studied on the antagonistic mechanism of WB532-7 strain, the results showed that the WB532-7 strain could inhibit the growth and the spore germination of Botrytis cirerea. The microexamination the cause of disease fungus hypha majority of distortions which is suppressed by WB532-7, is tumescent, is abnormal, the branching increases, the plasma overflow, presents the vesicle which expands; After trade of WB532-7 strain's colony bolt, the spore germination rate of Botrytis cirerea was low, the germ tube or the spore were abnormal, fermentation broth 50x diluent to spore germination suppression rate of Botrytis cirerea is 41%.The pot experiment indicated that WB532-7 fermentation broth exhibited a good prevention and therapeutic action to the tomato grey mold, and the effects reached 83.87% and 79.58%,respectivly. The fermentation broth also could promote the growh of tomato plant, and the treatment plants increased 29.65% comparing with the control, the effect maintains above 20%. The greenhouse field test result showed that WB532-7 fermentation broth 50x diluent may reach 65.16% to control the tomato grey mold, its effect is lower than 50% procymidone WP1500x broth against effect 69.04% and to surpass the comparison medicament 4% agricultural antibiotic 120 300x broth against effect 59.55%, and displays the good stability and the durability.