Levels of common antigens in determining pathogenicity of Curvularia eragrostidis in different tea varieties

Pathogenicity of Curvularia eragrostidis, a foliar fungal pathogen of tea was studied in 24 commercially cultivated tea varieties by analysing the antigenic patterns of host and pathogen with the help of immunoserological techniques.

Initial testing by cut shoot inoculation technique followed by whole plant inoculation technique showed that among the varieties tested, TV12 was the most susceptible and TV25 most resistant. Antigen preparations from tea varieties, fungal pathogens (C. eragrostidis and Lasiodiplodia theobromae) and a nonpathogen (Gliocladium virens) were compared by immunodiffusion, immunoelectrophoresis and indirect ELISA to detect common antigens shared by host and pathogen. Common antigens were detected by immunodiffusion and immunoelectrophoresis only among susceptible varieties and the pathogens. Such antigens were not found between the pathogens and the resistant varieties and also between nonpathogens and tea varieties. However, ELISA revealed the presence of low level of common antigens between all combinations. A certain minimum level of antigens was present for compatible host-pathogen interaction. Indirect labelling of antibodies with fluorescein isothiocyanate (FITC) showed that cross-reactive antigens were found to be concentrated mainly in the epidermal cells and also spread throughout the cortical cells.

Pathogenicity of C. eragrostidis to different varieties of tea was found to be related to the level of common antigens present between host and pathogen.

Indirect ELISA proved to be valuable in screening commercially cultivated varieties of tea for their susceptibility to C. eragrostidis.