Identification of causal organism/s of recently recorded diseases of fishtail palm (Caryota urens)

Abstract

Unreported diseases of fishtail palm (Caryota urens L.) were observed in Sabargamuwa, Western and Southern provinces of Sri Lanka. Infected palms showed leaf spots and leaf blight as symptoms. The present study was conducted to isolate the causal organism/s of these diseases and identify them by morphological and molecular methods and to prove the pathogenicity of the identified causal organism/s. pathogens were isolated from infected leaves on Potato Dextrose Agar (PDA). Two isolated fungal isolates (i.e., A and B) were identified by morphological and molecular identification. Pathogenicity was confirmed for both fungal isolates by detached leaf tests and pot experiments using a spore suspension (1 x 10 5 ml) of each fungal isolates A and B. Sterilized water was sprayed on healthy plants serves as a negative control. Genomic DNA of the fungal isolates were subjected to PCR using ITS1 and ITS4 primers and DNA sequencing and homology search was done. The conidia of fungal isolate A were fusiform, five-celled, with three median versi colored cells and two terminal hyaline cells, and the size ranged from 21.72 -33.03 μm ×5.58-37.78 μm. The basal appendage was hyaline, tubular, and unbranched, whereas there were two to three tubular, unbranched appendages. The conidia of fungal isolate B were bi-celled, one septum, thick-walled, have dark brown pigmentation with longitudinal striations. According to BLAST homology search, isolates A and B were highly homologous with Pestalotiopsisspp. (98.83%), and Lasiodiploidia thermobromae (99%), respectively. Artificial inoculation of detached leaves and pot experiment reproduce the symptoms and inoculated pathogens were reisolated, confirming their pathogenicity. This is the first report of leaf spots and leaf blight on fishtail palm caused by Pestalotiopsis spp and L. thermobromae respectively in Sri Lanka.