Effect of arbuscular mycorrhizal fungi on verticillium wilt of artichoke

Arbuscular mycorrhizal fungi (AMF) are known to have beneficial effects on the growth and development of plants and to increase resistance or tolerance to pathogens. Positive effects on plant disease by AMF have been reported in various pathosystems, the most important mechanism of AMF effects on plant disease being the change in the biochemical constituents of plant tissues. The results are reported of studies on the effect of mycorrhizal artichoke offshoot with an isolate of Glomus viscosum Nicolson towards Verticillium wilt, and on changes of the ascorbate system. The severity of external symptoms was significantly lower in mycorrhizal than in non-mycorrhizal artichokes grown in infected soil. No effect was observed on vascular discolouration. Beneficial effects of mycorrhizal plants were evident on the growth, earliness, and marketable yield of artichoke. In healthy mycorrhizal plants there was an increase in ascorbate content with respect to the control, the same as in infected mycorrhizal artichokes as compared with infected non-mycorrhizal. The activity of ascorbate peroxidase, the most efficient scavenger of hydrogen peroxide, showed the same trend as ascorbate. As to dehydroascorbate reductase, the enzyme involved in ascorbate regeneration from its oxidized form, its activity increased equally well in healthy as in infected mycorrhizal plants. These results seem to indicate that, in mycorrhizal artichoke, there is an involvement of the ascorbate system in the defence response to Verticillum wilt