Cross infectivity and survivability of Colletotrichum gloeosporioides isolated from Papaya

Abstract

Survivability o f Colletotrichum gloeosporioides on papaya petioles was studied under different environmental conditions. Papaya petioles were kept in different places i.e. Attached to the plant and allowing it to fa ll on the ground, in the laboratory room temperature, at 4 °c in the refrigerator, at 28±1 °c and 30±1 °c in bod incubators. Fungal spores collected from petiole lesions at weekly intervals were mounted on cavity slides to count number o f spores per lesion and percentage o f spore germination. Mature fruits ofpapaya, banana, mango, grape and pomegranate were used to assess the cmss-infectivity o f C. gloeosporioides isolatedfrom papaya. Eachfruit was spot inoculated with papaya isolate o f C. gloeosporioides. Number o f fruits infected and the diameter o f lesions were recorded. The cross infectivity o f C. gloeosporioides isolatedfrom banana, mango, grape and pomegranate on papaya, was also studied by spot inoculating each isolate into papaya fruits. Spores o f C. gloeosporioides were fo u n d to be viable under the fie ld condition up to eight weeks since germination percentage was always high in the field ' compared to other treatments. The number o f conidia produced in petiole lesions was high at 4°c which indicated the ability o f the pathogen to survive longer in low temperature conditions. The efficiency o f spore production was reduced after the 5th week in all the treatments. C. gloeosporioides isolated from papaya could cross-infect only mango and banana fruits while isolates o f banana and mango in turn, crossinfected ripened papaya fruits. The cross infection study has shown that the potential exists fo r post-harvest cross infection o f various hosts by C. gloeosporioides.