ANALYSIS OF VEGETATIVE COMPATIBILITY GROUPS OF ITALIAN AND DUTCH ISOLATES OF FUSARIUM OXYSPORUM f sp LACTUCAE
I. Pintore, G. Gilardi, M.L. Gullino, A. Garibaldi
Fusarium oxysporum f.sp. lactucae (FOL), the causal agent of lettuce fusarium wilt, has spread to several countries where lettuce is grown. To date, four races of FOL have been identified, but only race 1 has been detected in Europe; race 2 and race 3 have been identified in Japan and in Taiwan. A new physiological race has been isolated in The Netherlands. The vegetative-compatibility group approach has been used to determine genetic diversity within a group of forty-eight FOL strains of different origin, with special attention to the Italian and Dutch isolates of the pathogen, in order to obtain a better understanding of the recent epidemics that have been observed in Europe. On the basis of the complementation pattern, all the Italian isolates of FOL tested were assigned to VCG 0300. FOL isolates belonging to races 2 and 3 belonged to VCG 0301 and 0302, respectively. The isolates obtained from lettuce in The Netherlands belonged to a new VCG, numbered 0303. The results support the hypothesis that FOL race 4 might have been selected locally in Dutch fields.