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

Abstract

Exserohilum leaf spot is a newly arising fungal disease that primarily affects monocots. The isolate collected from diseased wheat leaves produced typical dark brown lesions upon inoculation to healthy plants. Thirty-two plant species of 14 families were evaluated for susceptibility to Exserohilum rostratum as a potential pathogen. The artificial inoculation using detached leaf assay showed symptoms on major cereals like Triticum aestivum, Oryza sativa, Echinochloa esculenta, Panicum miliaceum and Eleusine coracana. The symptoms were reddish-brown in members belonging to Poaceae. Histopathological studies revealed that conidia produce the appressoria within 24 h and penetrate the host through stomata or epidermal cells after germination. Study shows that collateral hosts serve as an infection reservoir, allowing it to survive without its primary host. These secondary hosts aid the pathogen in continuing the infection cycle and spreading the disease. The infections on major cereals like wheat and rice indicate its importance as an emerging plant pathogen.