White leaf spot: an emerging disease complexity in corn
2023
Mendoza, M.J.C. | Pinili, M.S.
White leaf spot of corn is an emerging disease of corn cultivated in the high elevation of southern part of the Philippines particularly in Bukidnon and Misamis Oriental. The disease has been reported in corn-growing countries including Brazil and South Africa with recorded yield losses of 60%. In the country it was reported only in 2015 in Bukidnon on hybrid corn varieties. Despite the reports abroad on the characterization of the associated fungal and bacterial pathogens causing the disease, there was no studies conducted yet on the etiology of the associated microorganisms causing corn white leaf spot in the country. Thus, the study would like to elucidate the etiology of the associated pathogens through cultural, morphological, and molecular characterization and pathogenicity tests. Isolation from the infected leaf sample showing the different stages of symptom showed varied incidence of bacterial and fungal pathogens. Cultural tests revealed ten fungal colonies and only one bacterial colony type. Morphological characterization of isolates exhibited varied traits of hyphae, spores and fruiting bodies of bodies and the absence or presence of these fungal structures. Molecular characterization of the Internal Transcribed Spacer (ITS) regions of fungal ribosomal DNA (rDNA) using the ITS1 and ITS4 primers unveiled different fungal species including Neopestalotiopsi clavispora, Epicoccum nigrum, Curvularia lunata, Diaporthe guangdongensis, Sordariomycetes sp., Nigrospora oryzae. Pathogenecity tests using susceptible corn variety at third leaf collar vegetative stage displayed the characteristics symptom of white necrotic leaf spots. Results showed that the white leaf spot disease of corn caused by multiple pathogen species. This study is the first to report the etiology of this disease in the country. This disease complex entails appropriate management strategies to prevent its potential threat to our corn industry.
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