Efficient Screening Method for Resistance of Cucumber Cultivars to Fusarium oxysporum f. sp. cucumerinum

Abstract

The study was performed to establish an efficient screening method for resistant cucumber to Fusarium oxysporum f. sp. cucumerinum. The isolate KR5 was identified as F. oxysporum f. sp. cucumerinum based on molecular analyses of ITS and TEF genes and host-specificity test on cucurbits including melon, oriental melon, cucumber, and watermelon. Then four cucumber and two rootstock cultivars showing different resistance degrees to the Fusarium wilt pathogen KR5 were selected. And development of Fusarium wilt of the six cultivars according to several conditions, including incubation temperature after inoculation, inoculum concentration, root wounding, and growth stages of seedlings, was investigated. Disease severity of Fusarium wilt on the resistant cultivars was changed with incubation temperatures after inoculation. The resistant cultivars showed the higher resistance when inoculated plants were kept at 25 or 30oC than at 20oC. Among four different growth stages of the seedlings, seven-day-old seedling represented the most difference of resistance and susceptibility to Fusarium wilt. From above results, we suggest that an efficient screening method for resistant cucumber to F. oxysporum f. sp. cucumerinum is to dip the non-cut roots of seven-day-old seedlings in spore suspension of 1.0 × 106-1.0 × 107 conidia/ml and to transplant the seedling into a non-infected soil, and then to incubate the inoculated plants in a growth room at 25oC for 3 weeks to develop Fusarium wilt.

Keywords

• Breeding
• Disease resistance
• Fusarium wilt