Study On Control Effect And Promote Growth And Fermentation Of The Antagonistic Actinomycetes Of Sclerotinia Sclerotiorum

Sclerotium, a fungal disease, was one of three major diseases which could decrease the production of Chinese rape. It was a disease characters both soil-borne and air-borne. Previous researches had shown that actinomycetes was a main microbial to produce antibiotics, and bio-control actinomycetes could inhibit pathogenic bacteria as well as might produce the plant growth hormone which could promote plants and roots growth. Bio-control actinomyces has a very good prospect, as at present it is still not mature in domestic research and application on sclerotinia stem rot of oilseed rape. Our laboratory experiment gained two bio-control actinomyces,(Streptomyces felleus, YJ1)and (Streptomyces sp., BC32),having good antagonistic activity to the disease, were screened from rhizosphere soil and the plant body. In this study, we carried out a series of researches including control effect, growth-promoting effect, optimization of fermentation conditions, stability and antibacterial spectrum of fermentation broth etc. of the actinomyces. The main results are as follows.1.Bio-control efficiency of strains YJ1and BC32Indoor antibacterial experiments discovered that the inhibition zone wide of biocontrol actinomycetes strains YJ1and BC32were11.5mm and7.3mm, and the antibacterial rate were83.98%and83.24%. Fermented liquid of high levels can inhibit sclerotia germinate and form hyphae and ascospore, while the diluted one’s inhibition effect decreased obviously. In greenhouse, fermentation liquid of actinomycetes daubed on rape leaves or irrigated root could significantly inhibit development lesion at seedling stage, compared with contrast, the reduced rate of lesion were more than70%. In flower phase, it showed different inhibitory action by inoculating Sclerotinia sclerotioroum in different time after spraying fermentation borth, and the3days best.2.Growth-promoting efficiency of strains YJ1and BC32In greenhouse and rape seedling, by fermented liquid root-irrigation, certain biomass such as the plant height, root length, fresh weight of the plant, fresh weight of stem and leaves, and root vigor and chlorophyll content, etc were all improved in varying degrees. And compared with ground part of the growth-promoting, the root growth promoting effects were more apparent, the growth rates of root length were78.9%and63.1%, the plant height were21.92%and21.82%, the dry weight of the plant were30.39%and36.7%, and the growth rates of root vigor were13.49%and56.50%, this showed promoting activities at seedling stage. As it seen, the growth rates of root length were not proportional to the growth rates of root vigor, for plant’s root vigor were not only influenced by root length, but also by many other factors.3.Optimization of fermentation for strains YJ1and BC32In order to improve the fermentation levels of the strains YJ1and BC32, the fermentation media and fermentation conditions were optimized by single factor analysis and orthogonal experiments, respectively. The optimum medium composition (g/L) of strainYJ1were sucrose10.0, soluble starch10.0, soybean meal20.0, K2HPO40.5, MgSO40.5, NaCl1.0and FeSO40.01, the maximum antibiotic activity was obtained at the inoculation volume5%, medium volume in250ml flask75ml, rotary speed of180r/min, fermentation time4days, temperature28℃and initial pH7.0. The optimum medium composition (g/L) of strain BC32were glucose20.0, soybean meal20.0, peptone6.0, NaCl1.0and CaCO34.0, the maximum antibiotic activity was obtained at the inoculation volume3%, medium volume in250ml flask75ml, rotary speed of180r/min, fermentation time6days, temperature28℃and initial pH7.0.4.Fermentation stability and antimicrobial spectrum of strains YJ1and BC32The active substances fermented by YJ1and BC32were stable in inheritance, natural daylight, ultraviolet, neutral or acidic conditions. When pH value was11, the mycelial growth of S. sclerotiorum inhibition rate slumped24.19%and28.87%, respectively. Fermentation broths were treated for90min respectively in60℃and100℃, the inhibition rate fell only0.87%and18.33%for strain YJ1, while fell1.41%and1.79%for strain BC32. So the active substances of BC32had thermal stability, and YJ1only stabilized in low and middle temperatures. The fermentation broths of strains YJ1and BC32were stable when storing in normal temperature, After placed at normal temperature respectively for22d, the inhibition rate fell only4.54%and2.67%.Antibacterial spectrum experiments showed that strains YJ1and BC32had inhibition on many pathogenicbacteria to some extent, such as Fusarium oxysporum, Alternaria solani, Botrytis cinerea, Colletotrichum capsici, Colletotrichum glecosporioides and so on. Overall, the antibacterial spectrum of YJ1was wider than BC32.