Pathogenicity and infection behaviour of Exserohilum rostratum on wheat and associated collateral hosts.

Abstract Exserohilum leaf spot is a newly arising fungal disease that mostly affects monocots. Thirty-two plant species of 14 families were evaluated for pathogenicity to Exserohilum rostratum as a potential pathogen. The isolate collected from diseased wheat leaves produced typical dark brown lesions upon inoculation to healthy wheat plants and produced similar symptoms. The artificial inoculation of detached leaf assay symptoms appeared on major cereals like Triticum aestivum, Oryza sativa, Echinochloa esculenta, Panicum miliaceum and Eleusine coracana. The symptoms were reddish-brown in most of the genera of Poaceae. Histopathological studies revealed that conidia produce the appressoria within 24 hrs and penetrate the host through stomata or epidermal cells after germination. Study reveals that collateral hosts serve as reservoirs for the infection, allowing it to persist in the absence of its primary host. These secondary hosts aid the pathogen in continuing the infection cycle and spreading the disease.