The Research Of Hypovirulence In Botrytis Cinerea CanBC-3

Botrytis cinerea CanBC-3 is a pathogenic strain. However, when it was successively cultured on media for a period of time, many characteristics altered, including reduced virulence (hypovirulence), slow growth and abnormal colony. Those changes involved in interference of pathogenic elements in Botrytis cinerea. We hypothesized that these abnormal strains could be used to disclose pathogenesis mechanisms of B. cinerea. In this study, CanBC-3HV, a derivative of CanBC-3, was characterized for pathogenicity, cultural features and the nature of the "hypovirulent element".Firstly, the pathogenicity, culture characteristics and biomass of CanBC-3V, CanBC-3HV and CanBC-2 of Botrytis cinerea were compared. Results showed that CanBC-3V and CanBC-2 were strong pathogenic type (SPT)strain, they grew rapidly, formed normal colonies and had high biomass; CanBC-3HV was a weak pathogenic type(WPT) strain, it grew slowly, formed abnormal colonies and had low biomass .Secondly, the vertical transmission rule and horizontal transmission of CanBC-3HV were analyzed. Results showed that the hypovirulence trait could be vertically transferred to derivatives from scleratia, conidia and protoplasts, and horizontally to CanBC-3V, but not CanBC-2, through hyphal contact.Thirdly, production of acids, toxins, protease, amylase, polygalacturonase (PG), and infection structrues between Botrytis cinerea strains CanBC-3HV (WPT) and CanBCoV (SPT) was compared. Results showed that CanBC-3HV could normally produce acids and the extra-cellular enzymes mentioned above. Production of PG was suppressed slightly.Fourthly, the mechanisms involved in hypovirulence of CanBC-3HV were analyzed. Results showed that the hypovirulence of CanBC-3HV was not associated with dsRNA elements, endophytic bacteria and transposons. TEM observation showed an abnormal phenomenon in hyphae of CanBC-3HV. This phenomenon has not been reported so far.