Seed-Borne Fungi Associated with Pearl Millet (Pennisetum glaucum): A Study of Seed Health, Transmission, Pathogenicity, Virulence, and Host Susceptibility

Abstract

Pearl millet (Pennisetum glaucum L.) is widely cultivated in Brazil as a succession crop and is also used for forage and as a cover crop in conservation agriculture. However, its productivity is compromised by seed-borne phytopathogenic fungi. This study evaluated the incidence, seed-to-seedling transmission, pathogenicity, and cultivar susceptibility of fungal pathogens associated with the seeds of four pearl millet cultivars. Morphologically, a total of 11 fungal genera were identified, including five genera of storage fungi (Cladosporium, Nigrospora, Aspergillus, Penicillium, and Mucor) and six of phytopathogenic fungi (Alternaria, Colletotrichum, Sclerotium, Exserohilum, Curvularia, and Fusarium). Among these, Curvularia, Exserohilum, and Fusarium were transmitted from seeds to seedlings. Pathogenicity assays revealed variation in virulence among the fungal isolates, with Exserohilum isolate 2 and Curvularia isolate 9 producing disease severity indices exceeding 60%. Evaluation of cultivar susceptibility showed that cultivar ADR 300 was the most susceptible, exhibiting disease severity indices greater than 60% for Exserohilum and 56% for Curvularia. These findings demonstrate that pearl millet seeds can serve as a source of primary ioculum, for the seed transmitted fungal genera identified in this study, particularly Curvularia, Exserohilum, and Fusarium, facilitating their transmission from seed to seeding. Therefore, the use of pathogen-free seeds, routine seed health testing, seed treatment, and integrated disease management strategies is essential to reduce pathogen dissemination in pearl millet production systems.