Assessing Pathogenicity and Cultural Characteristics of Fusarium oxysporum f. sp. ricini Isolates from Major Castor Growing Regions of India

The present study was undertaken to investigate the pathogenicity and cultural characteristics of 20 isolates of Fusarium oxysporum f. sp. ricini, the causal fungus of wilt disease of castor (Ricinus communis L). Pathogenicity tests on the susceptible cultivar JI-35 revealed that all isolates were pathogenic, with symptoms progressing from yellowing and drooping of leaves to marginal necrosis, wilting and root discoloration. The incubation period varied significantly among the isolates, ranging from 10.0 to 22.5 days, while the per cent disease incidence (PDI) ranged from 51.7% to 100%. Cultural characterization that includes mycelial colour, colony morphology, pigmentation, growth habit and sporulation highlighted significant variability among the isolates of F. oxysporum f. sp. ricini. The colour of mycelium among the isolates ranged from white to various shades of pink and yellow, with growth habits observed as fast, moderate, or slow. Sporulation rates varied from very high to sparse among the isolates. The observed diversity in pathogenicity and cultural traits emphasized the presence of genetic variability in F. oxysporum f. sp. ricini isolates. These results are vital for understanding the pathogen virulence and for developing effective management strategies for wilt disease in castor crop.