Biology and epidemiology of Botryotinia fuckeliana sub-populations.

Grey mould, caused by Botryotinia fuckeliana (de Bary) Whetzel (anamorph: Botrytis cinerea Pers.: Fr.), can cause severe yield losses to grapevine. Two sub-populations of the fungus, with different combinations of the transposable elements (Boty and Flipper) have been found: transposa with three combinations (Boty+Flipper+, Boty+Flipper-, Boty-Flipper+) and vacuma with no transposable elements (Boty-Flipper-). A representative isolate of each of the four above mentioned combinations of transposable elements, obtained from the culture collection of the University of Bari, was investigated in relation to the temperature response for colony growth, production of sclerotia, production and germination of conidia. Infection efficiency at different growth stages of bunches (inflorescence swelling, flowering, groat-sized berries, ripening and maturation), temperatures and duration of wetness was also investigated. Colony growth rate was similar for all four isolates between 10 and 25 °C, was lower for the vacuma isolate than for the transposa isolates at 30 °C but the opposite was true at 5 °C. Sclerotia were produced only by transposa isolates between 5 and 20 °C. The transposa isolates produced in vitro more conidia than vacuma isolate, with an optimum at 15 and 20 °C. Conidial germination after 24 h did not differ among isolates between 15 and 25 °C, was lower for the vacuma isolate than for the transposa isolates at 5 and 10 °C, and was lower for the Boty+Flipper+ isolate at 30 °C. The susceptibility of bunches was very high and similar for all isolates at flowering, groat-sized berries and ripening, while before flowering the disease incidence of the vacuma isolate was very low. The incidence of latent infection in berries caused by transposa was higher than the one caused by vacuma. Occurrence of incidence infection in berries at maturation was investigated. The observed differences suggest that B. fuckeliana sub-populations require specific infection models.