Abstract: Four types lesions of black tissues type,brown type,black spot type and hardening type were divided in order to determine reasons and infection conditions of black spot disease.The isolation percentage of Alternaria spp.was 89% from black tissues type.The isolation percentage of Trichothecium and Alternaria were 75%,and isolation percentage of A.tenuissima, A.sclerotigenum and T.roseum were the highest.Among them, T.roseum was the most pathogenic pathogen which led to large brown lesion on ripe fruit when infected from wounds.The optimum temperatures for infection by conidia of T.roseum and lesion expansion were 26.8,22.5℃ respectively. A.tenuissima caused large dark or brown lesions on ripe apple fruit when infected from wounds.The optimum temperatures for infection by conidia of A.tenuissima and lesion expansion were 29.4,28.5℃ respectively. A.sclerotigenum owned the highest infection ratio from wounds of mature apple fruit and let to small red-brown lesions on the fruit.The pathogen can fit a wide range of temperature when infection from wounded apple fruit.Conidia of three pathogens could not infected healthy apple.The inoculation with conidia of T.roseum caused significant more lesions on the bagged fruits than the other two pathogens,then the A.tenuissima,and A.sclerotigenum almost did not cause diseased lesions.Pathogens of black spot disease were chance pathogens,and caused disease when met suitable conditions.

Key words: Chance pathogens, Infect, Pathogenic conditions, Types of disease spots, Wound infection

CLC Number: 

• S436.6