In 2002, gerbera (Gerbera jamesonii cv. Kaiki) plants that were grown for cut flowers in a soilless cultivation system (rockwool substrate) at Albenga (Savona) in northern Italy were observed exhibiting symptoms of a wilt disease. During the summer of 2002, in a commercial gerbera farm in the province of Imperia (northern Italy), a similar wilt was also observed on cvs. Red Bull, Anedin, and Gud finger that were grown in soil. In both cases, the planting material originated from the Netherlands. During 2003, wilted plants (cvs. Red Bull, Basic, and Cirill) were repeatedly observed in other commercial greenhouses located in the same area. Affected plants were stunted and developed yellowed leaves with initially brown and eventually black streaks in the vascular system. The vascular streaks in the yellow leaves were continuous with a brown discoloration in the vascular system of the crown and upper taproot. In some cases, the leaves of affected plants turned red. From these plants, Fusarium spp. were consistently and readily isolated from symptomatic vascular tissue onto a Fusarium-selective medium (2). Colonies were identified as F. oxysporum after subculturing on potato dextrose agar. Healthy rooted 30-day old plants (cv. Dino) were inoculated by dipping roots into a conidial suspension (5 × 107 conidia per ml) in one of six test isolates of F. oxysporum. Plants were transplanted (1 plant per pot) into pots (3.5 l vol) containing rockwool-based substrate. Noninoculated plants served as control treatments. Plants (21 per treatment) were grown in a glasshouse with an average day temperature of 31°C and night temperature of 25°C (minimum of 20°C and maximum of 42°C). Wilt symptoms and vascular discoloration in the roots, crown, and veins developed within 30 days on each inoculated plant, while noninoculated plants remained healthy. F. oxysporum was consistently reisolated from infected plants. The pathogenicity test was conducted twice. To our knowledge, this is the first report of the presence of F. oxysporum on gerbera in Italy. A wilt of gerbera was described in the Netherlands in 1952 (1) but its presence was not confirmed in further observations (3).
Reference: (1) J. Arx and J. A. von Tijdschr. PlZiekt. 58:5, 1952 (2) H. Komada. Rev. Plant Prot. Res. 8:114, 1975. (3) G. Scholten. Neth. J. Plant Pathol. 76:212, 1970.