Fungal species causing maize leaf blight in different agro-ecologies in India

Authors: SINGH, VIMLA - Haryana Agricultural University; Lakshman, Dilip; Roberts, Daniel; Ismaiel, Ed - Ed; ABHISHEK, ALOK - Icar-Indian Institute Of Maize Research; HOODA, K.S - National Bureau Of Plant Genetic Resources; PAL, ISHAR - Amity University Mumbai

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2021
Publication Date: 12/14/2021
Citation: Singh, V., Lakshman, D.K., Roberts, D.P., Ismaiel, A.A., Abhishek, A., Hooda, K., Pal, I. 2021. Fungal species causing maize leaf blight in different agro-ecologies in India. Pathogens. 10:1621. https://doi.org/10.3390/pathogens10121621.
DOI: https://doi.org/10.3390/pathogens10121621

Interpretive Summary: Maize is the third leading cereal crop in the world after rice and wheat. Maize leaf blight disease (MLB) causes severe economic loss in India and elsewhere in the world. Leaf samples exhibiting MLB symptoms were collected from six maize ecological growing zones of India and pure cultures of the causal agents of this disease characterized. Cultural and molecular characterization of these cultures revealed that the fungus Bipolaris maydis was the dominant pathogenic species causing this disease, followed by the fungi Carvularia papendorfii and related Carvularia species. One instance each of the fungi B. zeicola and Alternaria sp. were also detected from the MLB samples. This is the first report that B. zeicola, C. papendorfii and related species, and Alternaria sp. cause MLB in India. This information will be useful to plant breeders developing resistant varieties of maize as well as scientists developing MLB disease management strategies.

Technical Abstract: Maize is the third most important cereal crop in India after rice and wheat both in total area under cultivation and yield. Fungal leaf blight disease of maize causes severe economic loss in India and elsewhere in the world. Although Bipolaris maidis is considered the most important pathogen causing maize leaf blight (MLB) in India, several other Bipolaris species and related genera such as Carvularia, Dreschslera, and Exserohilum, and the distant genus Alternaria are also known to infect maize. For investigating the population diversity of MLB in India, 350 symptomatic leaf samples were collected from the Kharif seasons of 2016-17 and 2017-18; this represented 20 MLB hotspots covering nine states and belonged to six maize ecological growing zones of India. Twenty representative pure culture fungal isolates causing MLB symptoms were culturally, pathogenically, and molecularly characterized. Based on morphological and pathological characteristics, Internal Transcribed Spacer (ITS) sequence-based phylogenies were constructed with ex-type strains of Bipolaris and related species. One or more representative isolates from each clade were further verified through GADPH sequence homologies in GenBank. We noted that B. maydis was the dominant pathogenic species, followed by Carvularia papendorfii and related Carvularia species. One instance each of B. zeicola and Alternaria sp. were also detected from the MLB samples. We report for the first time that B. zeicola, C. papendorfii and related species, and Alternaria sp. cause MLB in India. This report provides baseline information for further investigation on MLB disease, diagnosis, and management in India. The increasing severity of maize leaf blight over this decade necessitates more rigorous sampling of maize leaf blight from different maize growing zones to enhance success of resistance breeding programs and the selection of correct disease management strategies.