Morphological and Molecular Identification of Fusarium solani Species Complex Causing Root Rot of Bean in Irrigated Fields

Abstract

Root rot is a serious constraint in bean production systems, particularly in irrigated fields where soil moisture conditions favor the proliferation of soil-borne fungal pathogens. Among these, members of the Fusarium solani species complex (FSSC) are recognized as major causal agents, leading to root decay, vascular discoloration, stunted growth, wilting, and significant yield losses. Accurate identification of the pathogen is essential for effective disease management and the development of resistant cultivars. The present study was conducted to characterize and identify Fusarium solani species complex isolates associated with root rot of bean in irrigated agricultural fields using both morphological and molecular approaches. Diseased bean plants showing typical root rot symptoms were collected, and fungal isolates were obtained through standard isolation techniques on selective media. Morphological characterization was performed based on colony features, pigmentation, and microscopic examination of conidia and hyphal structures. Molecular identification was carried out using polymerase chain reaction (PCR) amplification and sequencing of conserved genomic regions, followed by phylogenetic analysis to determine species-level relationships within the complex. Pathogenicity tests were conducted under controlled conditions to confirm the ability of isolates to induce root rot symptoms in healthy bean plants. The results confirmed the consistent association of FSSC isolates with diseased bean roots across surveyed fields. Considerable genetic diversity was observed among isolates, indicating the presence of multiple lineages within the complex. Phylogenetic analysis revealed close relationships with known pathogenic Fusarium strains affecting legume crops worldwide. Pathogenicity assays demonstrated variable virulence among isolates, with highly aggressive strains causing severe root decay and plant mortality. The study highlights the importance of integrating morphological and molecular tools for accurate identification of FSSC pathogens. The findings provide valuable insights into the epidemiology and genetic diversity of Fusarium solani associated with bean root rot and support the development of targeted disease management strategies in irrigated cropping systems.