Objective This study is carried out to establish an efficient and convenient method that can replace Fusarium oxysporum to evaluate the fusarium wilt resistance in cucurbits including cucumber and bitter gourd, and to facilitate the relevant breeding and basic research.

Method Cucumber and bitter gourd were selected as cucurbitaceous representatives with flat and uneven cotyledons, respectively. Cucumber and bitter gourd materials with consistent resistance/susceptibility to F. oxysporum and fusarium acid were selected, and the cotyledon discor the first true leaf were treated with appropriate fusarium acid solution (FA). The FA induced different chlorotic phenotypes in the cotyledon discs and true leaves were evaluated, wich reflected the corresponding palnts having different resistance/susceptibility to F. oxysporum.

Result Under the treatment with appropriate fusaric acid solution, the leaf discs of cucumber cotyledons and the true leaves of bitter gourd resistant or susceptible to fusarium wilt showed different degrees of yellowing and chlorotic phenotypes within 24 h. Obviously, the yellowing and chlorotic degrees of susceptible accessions were more serious than those of the resistant accessions, which were consistent with their fusarium wilt susceptibility/resistance traits. According to the color difference, one could accurately distinguish the resistance/susceptibility of the cucumber and bitter gourd accessions, but also their progeny in the derived F2 segregated population.

Conclusion Fusaric acid can be used for rapid and accurate evaluation of the resistance to fusarium wilt in cucumber, bitter gourd and other crops. It is especially suitable for the accesstions with consistent resistance traits to fusarium acid and F. oxysporum.