Wilsonomyces carpophilus as a Pathogen of Shot Hole and Canker Disease in Plum: A Case Study from Himachal Pradesh, India

Abstract

Recently, during routine surveys of plum orchards, Wilsonomyces carpophilus was detected as a causal agent of shot hole and canker in plum in Himachal Pradesh, which induced small, purplish-brown spots that enlarged and turned brown, often with a lighter center. These spots were seen on leaves, buds, and twigs, while infected tissues died and fell out leaving visible holes in the leaves. In severe cases, shoot blight with leaves turning brown and dropping prematurely were observed, where tiny, dark brown bumps (sporodochia), the spore-forming structures developed at the center of twig and leaf lesions. Shot hole was most severe in spring and summer, especially in wet weather. Morphological characterization of shot hole causing agent in plum revealed W. carpophilus, which had septate thin-walled hyphae of 2.0–4.9 mm and sympodial conidiophores. The association of W. carpophilus with shot hole disease in plum has been recorded for the first time in Himachal Pradesh, a North Himalayan state of India, though, other Prunus spp. were found to be infected by this fungus. This was further confirmed through pathogenicity assay in which tested plum shoot exhibited disease symptoms similar to the originally infected plum shoots used for pathogen isolation.