Fusarium Wilt of Gerbera Caused by a Fusarium sp. in Brazil.

In 2006, gerbera (Gerbera jamesonii) plants, cvs. Basic, Xena, and Olimpia grown for cut flower production in two greenhouse farms in the region of Guarapuava, Paraná, Brazil, exhibited symptoms of a wilt disease. Affected plants (approximately 20, 60, and 50% on cvs. Basic, Xena, and Olimpia, respectively) were stunted and developed yellow leaves unilaterally with initially brown and eventually black streaks in the vascular system. The first symptoms occurred 2 months after transplanting during the hottest period of the summer with an average air temperature of 27°C. Vascular streaks in the yellow leaves were continuous with a brown discoloration in the vascular system of the crown and upper taproot. Occasionally, the leaves of affected plants turned red. A Fusarium sp. was consistently and readily isolated onto a Fusarium-selective medium from symptomatic vascular tissue sampled from the crown of infected plants. Colonies were identified as Fusarium oxysporum on the basis of colony and conidia morphology (1) after subculturing on potato dextrose agar. Since F. oxysporum f. sp. chrysanthemi has been previously reported on Chrysanthemum morifolium, Argyranthemum frutescens, and gerbera (4), pathogenicity tests were carried out by using one monoconidial isolate obtained from wilted plants and one Italian isolate (F. oxysporum f. sp. chrysanthemi MASS 6). The isolates of F. oxysporum were grown in casein hydrolysate in shake culture (90 rpm) for 10 days at 25°C with 12 h of fluorescent light per day. Healthy rooted plants of 30-, 20-, and 45-day-old C. morifolium (cv. Captiva), A. frutescens (cv. Stella 2000), and gerbera (cvs. Jaska, Dalma, and Excellence), respectively, were inoculated by separately dipping roots into a conidial suspension (5 × 10 conidia/ml) of the two isolates of F. oxysporum. Plants were transplanted (one plant per pot) into pots (3.5 liter vol). Noninoculated plants served as control treatments. Plants (15 per treatment) were grown in a glasshouse at an average day temperature of 32°C and night temperature of 23°C (minimum 21°C and maximum 43°C). Wilt symptoms and discoloration of the vascular system in roots, crown, and petioles developed within 29 days on C. morifolium, 26 days on A. frutescens, and 14 days on gerbera. Noninoculated plants remained healthy. F. oxysporum was consistently reisolated from infected plants. The pathogenicity test was carried out twice. Gerbera wilt caused by F. oxysporum f. sp. chrysanthemi was recently reported in Italy (2) and Spain (3). Currently, the wilt of gerbera in the area of Paraná is limited to two farms. To our knowledge, this is the first report of the disease in Brazil as well as in South America. References: (1) C. Booth. Fusarium. CMI, Kew, UK, 1977. (2) A. Garibaldi et al. Plant Dis. 88:311, 2004. (3) A. Garibaldi et al. Plant Dis. 91:638, 2007. (4) A. Minuto et al. J. Phytopathol. 155:373, 2007.