Seed transmission of Fusarium oxysporum of Eruca vesicaria and Diplotaxis muralis = Samenübertragung von Fusarium oxysporum bei Eruca vesicaria und Diplotaxis muralis

Six seed samples of wild (Diplotaxis muralis) and cultivated (Eruca vesicaria) garden rocket obtained from commercial seed lots used for sowing by farms severely affected by Fusarium wilt of rocket and one commercial sample directly obtained from a seed company, were assayed for the presence of Fusarium oxysporum on a Fusarium-selective medium. Isolations were carried out on subsamples of seeds (500) unwashed or disinfected in 1 % sodium hypochlorite. The pathogenicity of the isolates of Fusarium oxysporum obtained was tested in three trials carried out on wild and cultivated rocket. Five out of seven samples of rocket seeds were contaminated by Fusarium oxysporum. Among the 22 isolates of F. oxysporum obtained, none was isolated from disinfected seeds. Seven of the isolates were pathogenic on wild and cultivated rocket, with cultivated rocket being more susceptible to Fusarium wilt. The results obtained indicate that rocket seeds are a potential source of inoculum for Fusarium wilt of rocket. The possibility of isolating F. oxysporum, although from a low percent of seeds, supports the hypothesis that the rapid spread of Fusarium wilt of rocket recently observed in Italy is due to the use of infected propagative material. Measures for prevention and control of the disease are discussed.