Morphological and Molecular Characterization of Fusarium verticillioides Causing Stalk Rot and Ear Rot on Maize

Abstract

Severe symptoms of stalk rot and ear rot were observed in maize-growing regions, resulting in reduced grain quality, lodging, and substantial yield losses under field conditions. Diseased stalk and ear tissues exhibiting internal discoloration, mycelial growth, and kernel decay were collected for pathogen isolation and identification. Fungal cultures obtained from infected samples consistently produced fast-growing colonies with whitish to violet aerial mycelia and abundant microconidia formed in chains, characteristic of Fusarium verticillioides. Microscopic examination revealed slender monophialides, oval to cylindrical microconidia, and sparse macroconidia with morphological traits corresponding to descriptions of the species. Pathogenicity tests conducted on healthy maize plants and detached ears reproduced typical stalk and ear rot symptoms, confirming the virulence of the isolates. Re-isolation of the pathogen from inoculated tissues satisfied Koch’s postulates. Molecular characterization was performed through amplification and sequencing of the internal transcribed spacer (ITS) region and translation elongation factor 1-α (TEF1-α) gene. Sequence analysis demonstrated high similarity with authenticated isolates of F. verticillioides deposited in public databases. Phylogenetic analysis grouped the obtained isolates within the F. verticillioides clade with strong bootstrap support, confirming species identity and genetic relatedness among isolates from different maize-growing areas. Environmental conditions characterized by high humidity and moderate temperatures favored disease development and fungal colonization of stalk and ear tissues. The occurrence of F. verticillioides poses a serious threat to maize production because of its capacity to cause yield reduction and contaminate grains with harmful mycotoxins.