Biological Characteristic Of Hyperparasitic Actinomyces F46 & PR And Control Effect To Postharvest Diseases

Postharvest decay of fruits and greenhouse diseases of vegetables represented one of the most severe causes of losses and reduction in quality all over the world. Synthetic fungicide was the main measure used to control the diseases. As increasing in public concern over the health and environment safety, chemical fungicide has been restricted in vegetables and fruits. Biological control of plant pathogens has became one of the most promising alternatives in agricultural production.The hyperparasites strain F46 was isolated from the leaves of tomato in greenhouse and the strain PR was isolated from the leaves of wheat. On the basis of the morphological features, the physiological and biochemical characteristics and the cell wall chemotype, strain F46 was identified to Streptomyces sp. and strain PR was classified into Streptoverticillium sp..Twelve parasitic fungi, including Pythium aphanidermatum, Mucor piriformis, Ceratocystis fimbriata, Gaeumannomyces graminis, Alternaria spp., Botrytis cinerea, Colletotrichum gloesporioides, Fulvia fulvum, Fusarium oxysporum f. sp. vasinfectum, Penicillium expansum, Trichothecium roseum, Verticillium dahliae, and Gram-negative bacteria Erwinia carotovora pv. carotovora were used to test the antagonistic effects of two hyperparasite strains. The results shown that strain F46 and strain PR have different inhibiting effects on the target pathogens. The inhibiting effect of the strain PR was better than the strain F46. It has been found that lysis phenomena of two hyperparasitic strains on M. piriformis and P. aphanidermatum, and hyperparasitism on others target pathogens. The haustoria and twist hyphae of F46 and PR on target pathogens were observed under the electronic microscopy.The ecological studies with two hyperparasites shown that strain PR did not survive in the soil and strain F46 could survive especially in the soil added with the mycelia of M. piriformis. Two hyperparasites strains were able to colonize in the stern of cucumber seeding, the colony ability of strain PR was better than strain F46. Two hyperparasites had different tolerance to the eight tested fungicides commonly used in greenhous, including carbendazim, chlorothalonil, mancozeb, metalaxyl, procymidone, quintozene, thiophanate -methyl and streptomycin.Biocontrol potential of the hyperparasitic actinomyces strain F46 and strain PR against apple postharvested decay, gray mold of strawberry and tomato were evaluated in the storage condition. The control efficacy of two strains on M. piriformis was more effective than on B. cinerea and P. expansum in apple decay. Comparing the inoculation oftarget pathogens and hyperparasites at the same time, a better control effect was obtained when the biocontrol agents was inoculated at 24h before challenge inoculation. There was significant difference in control efficacy in the different temperature and two biocontrol agents. B. cinerea of strawberry was effectively controlled by strain F46 and strain PR at 10℃. A lower incidence of gray mold in tomato fruit was calculated in challenging with F46 at 10℃ storage condition than at 20℃, but treated by strain PR had not significantly difference between 10℃ and 20℃. The primary results in greenhouse shown that the control efficacy of two strains of hyperparasites against Pseudoperonospora cubensis in cucumber was not up to 50%.