Biocontrol Mechanisms And Effects Of Bacillus Licheniformis To Some Fruits Postharvest Diseases

Bacillus licheniformis W10 was a new type antagonistic bacterium which could metabolize antifungal protein. The bacterium and its antifungal protein could inhibit Botryosphaeria berengeriana f. sp. piricola, Glomerella cingulata and Penicillium sp., and exhibit some efficacy in control Apple ring rot, Apple anthracnose and Citrus blue mold.The bacterial suspension, the filtrate and the antifungal protein of W10 had obvious damage to the mycelial morphology and inhibitory effects on the growth of the three types pathogens. It was observed that the hyphal cells swelled, expanded into vesicle, the protoplasm of hyphal cells shrinked or leakage from the wound, the hyphae became of twist malformation, and even the cell wall was destroied when those mycelia were incubated in PS amended with the bacterial suspension, filtrate and the antifungal protein of W10. The mode of effect was the same among the bacterial suspension, the filtrate and the antifungal protein, but the damage to the mycelia by the bacterial suspension treating was most serious. When the filtrate and the antifungal protein was diluted 10 times, both the inhibitory rates to the hyphae growth of B. berengeriana were 100%. Meantime, the inhibitory rates to G. cingulata and P. sp. were 90.2% and 94.9%, 50.1% and 77.5% respectively. Otherwise, the bacterium also had some inhibitory impact to sporulation, conidial germination and germ-tube growth. When antifungal protein was diluted 20 times, all inhibitory rates to sporulation, conidial germination and germ-tube growth of B. berengeriana and G. cingulata were 100%. Although the inhibition to P. sp. was weaker than that to B. berengeriana and G. cingulata, the inhibitory rates to sporulation, conidial germination and germ-tube growth reached 75.3%, 86.8% and 68.4% respectively . All the results showed that Bacillus licheniformis W10 had capabilities as a antagonistic becteria to control of the three types of postharvest diseases. The antagonistic bacterium could colonize on the surface of apple and orange fruit, and the colonization time could retain more than 15 days. The colonizing ability of W10 was related to temperature, humidity, introduced bacterial concentration and inoculation pathogen. In 5-15℃range the optimum temperature for colonization was at 15℃, and the optimum relative humidity range was from 95% to 100%. The colonizing capacity of antagonistic bacterium on fruit surface had positive relationship to the introduced bacterial concentration. When bacteria at high concentration (1010cfu/ml) was introduced, 6.19×10~2cfu/cm~2 bacteria was detected from apple surface after 15 days and 1.06×10~2cfu/cm~2 bacteria was detected from orange surface after 30 days. Inoculation B. berengeriana and P. sp. had some influences on the colonization of antagonistic bacterium. The bacterial amount of inoculating pathogens after introducing bacteria was more than that of inoculating pathogens and bacteria together and introducing bacteria after pathogens. Contrasting colonization on apple with that on orange, the more bacterial population were detected from surface of orange fruit and the longer time of bacterial colonization was found on orange surface.It was approved that the bacterial suspension and the antifungal protein could control Apple ring rot, Apple anthracnose and Citrus blue mold, and the effects were as good as that of carbendazim. The inhibitory effect of antifungal protein upon Apple ring rot was the strongest than that of others, reached 66.7% and 50.0% after 15 days and 90 days respectively. Although the inhibitory effect of antifungal protein upon Citrus blue mold was lower, the inhibitory rate was 28.6% after 75 days. The biocontrol impact could be affected by environment conditions. Commonly influence of environment conditions on the antifungal protein was less than that on the bacterial suspension . The bacteria and the antifungal protein could better control of Apple ring rot and Apple anthracnose on condition that at 10℃, RH 35-40% and introducing bacteria at high concentration (1010cfu/ml) or antifungal protein before pathogen colonized on fruit surface. 15℃was the optimum temperature for control for Apple ring rot, Apple anthracnose and Citrus blue mold. The bacteria and the antifungal protein not only could inhibite necrosis spreading but also put off the time of necrosis forming on fitter conditions, which put off the time of necrosis forming than 20 days more.The bacterial suspension and the antifungal protein amended with calcium could enhance the biocontrol effect. The inhibitory rate of antifungal protein with calcium to Apple anthracnose was 100%, which increased by 29.3% than that of antifungal protein alone. The inhibitory rate to Citrus blue mold was increased by 7.7% than that of introducing antifungal protein alone.