Temperature response of Botryotinia fuckeliana sub-population

Botryotinia fuckeliana (de Bary) Whetzel (anamorph: Botrytis cinerea Pers.:Fr.), the causal agent of grapevine grey mould, has two sub-populations (transposa and vacuma) with different combinations of the transposable elements Boty and Flipper: transposa has three combinations (Boty+Flipper+; Boty+Flipper-; Boty- Flipper+), and vacuma lacks transposable elements (Boty-Flipper-). The effect of temperature (5 to 30°C) was determined for a representative isolate of each of the four combinations. The isolates were obtained from the culture collection of the University of Bari. Colony growth rate was lower for the vacuma isolate than the transposa isolates at 30°C but the opposite was true at 5°C. Between 10 and 25°C, colony growth was similar for all four isolates. Only the transposa isolates produced sclerotia between 5 and 20°C, and produced more conidia than the vacuma isolate, with an optimum at 15 and 20°C. Conidial germination after 24 h was lower for the vacuma isolate than for the transposa isolates at 5 and 10°C, did not differ among isolates between 15 and 25°C, and was lower for the Boty+Flipper+ isolate at 30°C. Inoculation of bunches at different growth stages (inflorescence swelling, flowering, groat-sized berries, ripening, and maturation) indicated that the incidence of vacuma isolate was low before flowering while the it was very high and similar for all isolates at flowering. Occurrence of latent infection in berries was also investigated. The observed differences suggest that different sub-populations of B. fukeliana require different infection models.