Morphological and Molecular Characterization of Neocosmospora Species Associated with Root and Crown Rot of Soybean

Abstract

Root and crown rot of soybean caused by Neocosmospora species has emerged as an important soilborne disease complex contributing to significant yield losses in soybean-growing regions. The present study aimed to characterize Neocosmospora spp. associated with symptomatic soybean plants using integrated morphological and molecular approaches. Diseased plants exhibiting root necrosis, crown discoloration, wilting, and reduced vigor were collected from field sites. Fungal isolates were obtained on selective media and examined for colony morphology, pigmentation, growth rate, and microscopic features including macroconidia shape, septation, and chlamydospore formation. Morphological observations indicated variability among isolates, suggesting the presence of multiple species within the Neocosmospora genus complex. Molecular identification was performed using ITS rDNA and translation elongation factor (TEF-1α) gene sequencing, which confirmed the presence of distinct Neocosmospora species associated with soybean root and crown rot. Phylogenetic analysis revealed clear clustering of isolates into separate lineages, demonstrating significant genetic diversity and species-level differentiation. Pathogenicity assays on soybean seedlings confirmed varying levels of virulence among isolates, with some causing rapid root decay and plant collapse, while others induced moderate symptoms. Disease development was favored by warm soil temperatures and high moisture conditions, which enhanced fungal proliferation and infection efficiency. The study highlights the complex etiology of soybean root and crown rot involving multiple Neocosmospora species and underscores the importance of accurate molecular diagnostics for species identification. These findings provide a foundation for improved disease management strategies, including crop rotation, resistant cultivar development, and soil health management practices. Overall, the results contribute to a better understanding of the taxonomy, pathogenicity, and molecular diversity of Neocosmospora spp. in soybean agroecosystems.