First report of fusarium wilt of cucumber caused by Fusarium oxysporum in Spain

In 2000, cucumber (Cucumis sativus cv. Albatros) in several commercial glasshouses in south-eastern Spain (Almería) exhibited symptoms of wilt, yellowing and necrotic streaks on the stems. Internal, vascular discoloration in affected plants extended from the base of the stem upward. Initial observations were reminiscent of fusarium wilt disease of cucumber, caused by Fusarium oxysporum f. sp. cucumerinum, as described by Owen (1955). Pure colonies of fungi were isolated from surface-disinfested (with flame) stem segments, cut at 0·5 m above the hypocotyl, on potato dextrose agar (PDA) medium. Isolates were identified as Fusarium oxysporum due to occurrence of typical macroconidia with foot-shaped basal cells, microconidia borne in false heads only on monophialides and chlamydospores. To confirm pathogenicity, eight isolates (1-week-old cultures grown on PDA) were used to root-dip inoculate (1 × 106 conidia mL−1) 1-week-old seedlings of cucumber cvs Nevada and Albatros. Seedlings were then transplanted into pots containing vermiculite growth medium and placed in a glasshouse. Of the tested isolates, all but one were pathogenic, causing wilt symptoms or death in 60–100% of dip-inoculated plants, from which F. oxysporum was consistently reisolated. Symptoms observed in inoculated plants were similar to those observed in cucumber plants in commercial glasshouses. This is the first report of F. oxysporum causing wilt of cucumber in Spain.