Identification, characterization and pathogenicity of Fusarium species associated with sheath and stem blight - A new...

Pearl millet (Pennisetum glaucum R. Br.) is a vital crop, especially in arid and semi-arid regions, where it serves as a staple food for millions. However, the emergence of sheath and stem blight poses a significant threat to its cultivation, potentially impacting food security. A field survey was conducted during the Kharif 2023 across major pearl millet-growing regions in Tamil Nadu, India led to the collection of diseased samples displaying typical symptoms of sheath and stem blight. A total of 14 pure fungal isolates were obtained and designated as FPM1 to FPM14. Morphological examination revealed the presence of microconidia, macroconidia, and chlamydospores, characteristic of Fusarium species. Molecular identification using ITS and β-tubulin gene sequencing confirmed these isolates as members of the Fusarium fujikuroi species complex (FFSC) and Fusarium incarnatum-equiseti species complex (FIESC). The pathogenicity of these isolates was assessed through in vitro and in vivo tests, revealing significant variability in their ability to induce lesions on pearl millet. Isolate Fusarium pseudonygamai FPM2 demonstrated the highest pathogenicity, producing the largest lesions, while isolates viz., Fusarium proliferatum FPM5 and F. proliferatum FPM10 exhibited minimal infectivity. Additionally, the study evaluated the enzyme activity of the virulent isolate F. pseudonygamai FPM2, identifying strong cellulase, xylanase, and protease activities, which are implicated in the disease progression. This study reported the new disease, sheath and stem blight on pearl millet which was caused by Fusarium pseudonygamai in India and based on pathogenicity test and enzyme assay, its virulence factors were confirmed. It further emphasizes how important it is to implement organic disease management strategies to lessen the negative effects of sheath and stem blight on pearl millet agriculture.