Sensitivity of Verticillium dahliae isolates from chrysanthemum to biofumigant defatted meals.

Verticillium wilt caused by the soilborne pathogen Verticillium dahliae is considered one of the most serious and destructive disease of chrysanthemum. After the ban of noxious chemicals for soil fumigation, including methyl bromide, alternative management strategies for control of V. dahliae such as biofumigation have assumed an increasing importance. This environmental friendly method is based on the glucosinolate-myrosinase system contained in Brassica plant cells which, in the presence of water, produces a number of toxic compounds, especially isothiocyanates, released in the soil after incorporation of brassicaceous green manures. Biofumigant products are also available in form of dry pellet or defatted seed meals (DSM) that contained glucosinolates ten times more concentrated than plant tissues. We tested in vitro the sensitivity of three V. dahliae morphologically distinct strains (10353, 10355, 10360) isolated from infected crysanthyemum plants cv. Veneri to two DSM differing in particle size (0.3 or 1.0 mm). Moreover, we use two different inoculum type: actively growing mycelium and mycelium derived from pathogen colonized seeds. The DL90 values were subjected at ANOVA analysis and results showed that: i) 0.3 mm DSM is more effective than 1 mm DSM, ii) different isolates of Verticillium dahliae show different sensitivity towards biofumigant treatments (10360>10353>10355), iii) mycelium developed from colonized seeds is less sensitive to the biofumigant treatments than active growing mycelium. These data although preliminary, suggest biofumigation can be a valuable tool for soil disinfection against Verticillium dahliae. Further investigation will be performed in order to evaluated sensitivity of sclerotia derived mycelium to DSM.