Abstract:
Efficient isolation, purification and identification techniques of a new pathogenic fungus of cashew were developed.
In the study, aspects related to identification, characterization of conidial morphology and infection of the Cryptosporiopsis spp
fungus were investigated. Macroscopic observations of symptoms and signs of cashew blight disease as well as isolation,
culturing and morphological characterization of its causative agent were carried out. Cryptosporiopsis spp fungus penetration
and infection mechanisms on susceptible cashew leaves were studied. Cashew leaves were inoculated with fungal suspensions by
pricking with pin, clipping with scissors and painting a fungal suspension onto the leaves with a paintbrush. Pathogenecity assays
were performed on cashew leaves, nuts and apples. Irregular spot lesions, with a brown margin, formed on leaves especially on
the young leaves. Direct conidial transfer was found to be the efficient method of isolation because it was less prone to
contamination. Blight macroconidia are typical of Cryptosporiopsis having ellipsoidal, rounded at the apex, tapering into a scar
at the base. Stomatal penetration of Cryptosporiopsis spp was visible through the simple staining technique using lactophenol
solution. Penetration was by germinating conidia through a cuticle that caused an infection in leaves. Paint brush method of
inoculation was found to be more effective as compared to other two methods based on the lesion size. Leaves inoculated with
Cryptosporiopsis spp isolate began curling after 72 h thereafter developed dark, irregularly shaped spots with brown margins. An
increased understanding of cashew blight is important for developing strategies for its management.
