BIOCHEMICAL-CHARACTERIZATION OF PYTHIUM SPP INVOLVED IN CAVITY SPOT OF CARROTS IN FRANCE

The pathogenicity and growth rate in vivo were assessed on 27 isolates of Pythium spp. recovered from cavity spot lesions on carrots grown i n various parts of northwest France. Polyacrylamide gel electrophoresi s of isoesterases was used to identify the Pythium spp. involved. Slow -growing isolates were more aggressive than fast-growing ones when ino culated on carrot tap roots. Isoesterase patterns identified the slow- growing isolates as P. violae and P. sulcatum; P. ultimum and P. inter medium were identified among the less aggressive fast-growing isolate group, in which some isolates were also classed as P. sylvaticum or P. irregulare, which have similar electrophoretic profiles. The incidenc e of Pythium spp. associated with the disease in France is discussed i n regard to cavity spot in other countries.