A new virulent strain of Xanthomonas campestris pv. parthenii causing leaf spot of parthenium.

摘要

This paper reports a new virulent strain of Xanthomonas campestris pv. parthenii isolated from parthenium (Parthenium hysterophorus) plant causing leaf spot in Varanasi, Uttar Pradesh, India. This strain produced leaf spot symptoms in parthenium, including the initial appearance of spots as small water-soaked lesions surrounded by characteristic yellow halos on both adaxial and abaxial surfaces of leaves, brown to dark brown spots coalescing to form large necrotic patches, twisting and rolling of leaves. The leaf spot strain was identified as X. campestris pv. parthenii based on morphological, biochemical and physiological characters. Rapid in vitro multiplication, less incubation period and higher disease intensity helped in differentiating the leaf spot strain from earlier reported strain RCXCP8. The new strain was more virulent to cause leaf spot disease on parthenium and may further be exploited as a biological control agent for managing this noxious weed.