Pathogenicity confirmation of Ganoderma disease of coconut using early diagnosis technique

The pathogenicity and diagnostic methods were standardized for Ganoderma disease of coconut. The pathogenicity of Ganoderma lucidum isolated from coconut was tested using six types of inoculation techniques. Two diagnostic methods, viz. indirect enzyme-linked immunosorbent assay (ELISA) and polymerase chain reactions (PCR) were applied for the confirmation of pathogenicity in coconut seedlings. Polyclonal antibodies (PAbs) were raised against mycelial, basidiocarp and specific proteins of Ganoderma and used for detection of Ganoderma in inoculated seedlings through indirect ELISA technique. All the three PAbs could detect Ganoderma in diseased coconut root tissues in early stage of the disease before symptom expression by indirect - ELISA at the antiserum dilution of 1: 1000 for mycelial protein, 1: 700 for Ganoderma specific protein and 1: 3000 for basidiocarp protein. Low cross-reactions were observed with saprophytic fungi occurring in coconut roots and also with other basidiomycetous fungi. In PCR, primers Gan1 and Gan2 generated from internal transcribed spacer region of rDNA were used the detection that produced a product of 167-bp size in Ganoderma infected plants. In the present investigation, spawn inoculum responded earlier within 8 weeks compared with other methods of inoculation as expressed by OD value in ELISA test. This was also confirmed by PCR technique. The combination of these two diagnostic methods for detection of Ganoderma infection was highly reliable, rapid and sensitive.