Prevalence of Diseases on Carica papaya L. in Western and Southern Povinces

Abstract

Carica papaya L. is one of the delicious fruits restricted to tropical and sub- tropical regions of the world. Diseases, affecting papaya have become a great threat to the papaya industry in Sri Lanka.Main objectives of this research were 1). to evaluate the incidence of virus and phytoplasma diseases, 2). to identify different bacterial and fungal infections of Carica papaya L. in Western and Southern provinces and 3). to identify papaya phytoplasma disease symptoms. Random sampling of papaya leaves and fruits was done in Western and Southern provinces. Collected samples were directed for the identification of phytoplasma, PRSV, TRSV, TSWV, fungi and bacteria. The suspected virus infections were tested in ELISA for the identification of PRSV, TRSV and TSWV while phytoplasma identification was done by PCR using universal primers. In order to identify fungal pathogens microscopic and macroscopiccolony characters of isolates on PDA were used and their pathogenicity was tested according to Koch's postulates. Bacteria isolated from diseased plant parts on NA medium were basically categorized using Gram's staining. According to the results, phytoplasma diseases can be considered as an emerging threat to the papaya cultivations both in Western and Southern provinces due to high disease prevalence and severe damages leading to plant death. However, still PRSV is the major disease of papaya in both provinces with 48.23% disease incidence in Western province and 62% disease incidence in Southern province. Out of a large number of fungal and bacterial pathogens isolated from diseased leaves, only few isolates were identified and pathogenicity was confirmed. Colletotrichum gloeosporioides and Fusariumsp. were the common fungal pathogens.