| Strawberry which is known as fragaria nilgerrensis、Cranberry、blackberry, Spread all over the world from the source area South American and Europe. The perennial herb strawbe rry belongs to the rosaceae fragaria that the heart-shaped fruit is delicious with juicy and rich in a variety of nutrients. Its fruits are loved by consumers for its various effects. The plantin g area of strawberry gradually expanded in recent years. However, many adverse factors oft en affect in the process of strawberry growth. The strawberry grey mould is one of the most i mportant disease mainly occurred during strawberry flowering which had a negative effect o n strawberry’s yield and quality and dampen farmers’enthusiasm. Chemically pesticide often used in order to effectively control the expansion and spread of grey mould. Applying a grea t quantity of chemical insecticides especially the wide spectrum insecticides makes the pest f orms resistance to the action of a drug easily not only, and cause environmental pollution an d ecological balance breaking. Therefore, search new method to prevent and control of straw berry grey mould has become a hotspot of research. Biological control technology is an ideal substitute for chemical pesticide to control the strawberry grey mould. The plant source acti ve matter is an important means of controlling strawberry grey mould. Therefore, plate confr ontation and punching method were carried out to study the inhibition effect of pseudomonas aeruginosa SU8 and its product phenazine-1-formamide on strawberry grey mould. The t oxicity in vitro and action mechanism of phenazine-1-formamide were also analyzed. The main research results are as follows:l)The plate confrontation was used to test the antagonistic effect of SU8 on strawberry gre y mould. The results showed that SU8 had antagonistic effect on strawberry grey mould and its antagonistic activity was still strong after 72h culture. The antifungal activities in SU8 fer mentation filtrate -- phenazine-1-formamide had strong antibacterial activity against grey mould which confirmed its potential to develop new biocontrol agents. 2)The toxicity in vitro of phenazine-1-formamide was explored. The results showed that t he concentration of phenazine-1-formamide correlated positively with the inhibition of ph enazine-1-formamide on strawberry grey mould. EC50 value came to 108.1176μg/mL whe n the concentration of phenazine-1-formamide was 69.54%. The equivalent inhibition acti on of phenazine-1-formamide to carbendazim showed that structure transformation, additi ve adding and doses increasing could be used to improve its antibacterial activity for final fie Id application.3)In vitro fruit test showed that phenazine-1-formamide had no toxic effects on strawbe rry fruits; There is an inverse relationship between the concentration of phenazine-1-forma mide and the diameters of lesions, but the concentration of phenazine-1-formamide was pr oportion to its inhibitory effect (between 28.39-75.32), the best inhibitory effect was compar able to carbendazim.4) Phenazine-1-formamide had influence on spore germination. The concentration of phenazine-1-formamide was inversely proportion to spore germination rate. The ratio of c onidia germination was 77～88%when concentration of phenazine-1-formamide was 35-7 0μg/mL, conidia germination ratio was 65% when concentration was 140μg/mL. And when t he concentration reached to 700μg/mL, phenazine-1-formamide showed strong inhibition effect that the conidia germination ratio was only 22%.5)Phenazine-1-formamide had inhibition effect on sclerotia germination. When the conc entration of phenazine-1-formamide reached to 700μg/mL, the sclerotia germination ratio was only 17%, whereas the sclerotia germination of control was unaffected.6)Phenazine-1-formamide had inhibition in growth of hyphae of strawberry grey mould. The concentration of phenazine-1-formamide were directly proportional to the inhibition of hyphae growth. The concentration of phenazine-1-formamide were 35～47μg/mL,70～1 40μg/mL,700μg/mL, the inhibition ratio of hyphae growth were 6.37～7.44%,53.34～74.38 % and 87.32% respectively.7)The action mode of phenazine-1-formamide against strawberry grey mould was deter mined.the colony with 70μg/mL phenazine-1-formamide treatment could not regrow on m edium without agent.The results showed that the phenazine-1-formamide could only act o n hypha when the agent concentration was lower than 47μg/mL, but it could kill the strawber ry grey mould when the agent concentration was above 70μg/mL.8)The effect of phenazine-1-formamide on mycelial morphology was studied. The untre ated colony had straighter and more vigorous growth of hyphae. The treated colony had spar se and distort hyphae, and those decreased hyphae were observed by scanning electron micro scope that the hyphae were deformed and broke into small parts, the intracellular content wer e leaked out.9)Phenazine-1-formamide could change the cell membrane permeability. There was n o significant difference in electrolyte leakage between the test group and control group when agent concentration were 35-140μg/mL, the electrolyte leakage rangeability were significant higher in treated group than those in control at the concentration of 700μg/mL after 60 min t reatment, which showed that phenazine-1-formamide could increase cell membrane penetr ability of the grey mould and cause the leakage of cytoplasm.10)The effects of phenazine-1-formamide on the hypha protein contents were analyzed. At the concentration of 35-70μg/mL, the soluble protein in hypha had been less affected by phenazine-1-formamide after 72h treatment, for a lowest inhibiting rates of 3.04-8.51%. When the concentration of phenazine-1-formamide was 140-700μg/mL, the inhibiting rat es could be over 21%. |
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