Pathogenicity and Molecular Phylogeny of Fusarium proliferatum Causing Kernel Rot on Maize Under High Humidity Conditions

Abstract

Kernel rot symptoms characterized by discoloration, softening, premature decay, and fungal colonization were observed in maize ears under high humidity and warm environmental conditions, resulting in significant post-flowering yield losses. Diseased kernel samples collected from affected fields were used for pathogen isolation and characterization through morphological, pathogenicity, and molecular approaches. Fungal isolates consistently produced fast-growing cottony colonies with white to violet pigmentation and abundant microconidia and macroconidia typical of Fusarium proliferatum. Considerable variation in colony morphology, sporulation intensity, and growth rate was observed among isolates obtained from different maize-growing regions. Pathogenicity tests conducted on healthy maize ears under controlled conditions reproduced typical kernel rot symptoms, including tissue discoloration and internal decay, whereas control ears remained symptom-free. Re-isolation of the fungus from inoculated kernels fulfilled Koch’s postulates, confirming its pathogenic role. Molecular characterization was performed through amplification and sequencing of internal transcribed spacer (ITS) regions and additional gene loci including translation elongation factor 1-α (TEF1-α). Sequence analysis revealed high similarity with reference F. proliferatum isolates available in international databases. Phylogenetic analysis grouped field isolates within the F. proliferatum clade, while also indicating moderate genetic diversity among populations from different agroecological zones. High humidity conditions significantly enhanced fungal infection, colonization, and disease progression by promoting spore germination and kernel susceptibility. Severe infections resulted in substantial grain quality deterioration and yield reduction, posing a serious threat to maize production.