Development of an Effective Method to Evaluate Resistance of Onion (Allium cepa L.) Cultivars to Fusarium Basal Rot

Fusarium basal rot (FBR), caused by the ascomycete fungus <i>Fusarium oxysporum</i>, is an economically important disease of onion worldwide. The most economical and effective way to manage FBR would be the use of FBR resistant onion cultivars. This study was carried out to develop a rapid screening method for resistant onion cultivars in seedling stage. We used the <i>F. oxysporum</i> 19-385 isolate, which causes damping-off in onion seedlings and basal rot in onion bulbs. We optimized broth incubation and medium composition for the production of inoculum, and determined conidial concentration for the preparation of <i>F. oxysporum</i> infected soil. Ten commercial cultivars of onion were evaluated the seedling survival rates and heights by infected soil inoculation methods. As a result, ‘K-force’ was the most resistant cultivar with 97.4% of relative seedling survival rate against the pathogen, whereas ‘Sunpower’ was the most susceptible cultivar with 20.0% of relative seedling survival rate.