Characterization of Italian Isolates of Fusarium semitectum from Alfalfa (Medicago sativa L.) by AFLP Analysis, Morphology, Pathogenicity and Toxin Production

Fusarium semitectum is a widespread species often isolated from plants with complex disease and also known to be toxigenic. Twenty-seven isolates of F. semitectum obtained from wilted plants of Medicago sativa grown in northern Italy were analysed by Amplified Fragment Length Polymorphisms (AFLP). The isolates were divided in two distinct clusters, coded A and B. Investigations were carried out on morphology, pathogenicity on alfalfa seedlings and toxin production of 18 isolates representative of the two AFLP clusters. Isolates from cluster A showed fast growth and pale peach colour of the colonies on potato-dextrose-agar, whereas those from cluster B showed slow growth and orange pigmentation, changing to brown with age. Length of 5-septate macroconidia was higher in isolates from cluster A and the frequency of classes of conidia septation was statistically different between the two clusters. All isolates from cluster A were pathogenic to alfalfa, whereas those from cluster B were mostly non-pathogenic. The mycotoxigenic profiles were distinct between the two clusters and similar within the same cluster: isolates from cluster A produced zearalenone, alone or together with diacetoxyscirpenol, whereas isolates from cluster B produced deoxyfusapyrone. The results showed that there is a good correspondence between the AFLP clustering and the distinction of F. semitectum isolates from alfalfa into two groups based on morphology, pathogenicity and toxinproduction.