A wilt disease was observed during the summer of 1993 in a sunflower field near Peruiga in central Italy. The disease was characterized by yellowing of leaves as plants approached flowering. Large areas of the leaves turned light green, usually beginning at the apex and margins and extending inward. Subsequently, leaf margins turned necrotic, and diseased plants were stunted with smaller heads. Our trials proved that this disease was caused by Phialophora asteris f.sp. helianthi. The fungus was examined for colony morphology, temperature growth responses, and pathogenicity. Significant differences were observed among various culture media. Best growth and profuse sporulation were obtained on carrot and Czapeck agars added with peptone. The optimum temperature fro growth was 25 C; temperatures of 5, 10, 15 and 30 C greatly reduced colony growth and sporulation. No growth was observed at 35C. Significant differences in susceptibility to P.a. helianthi were observed in 17 sunflower cultivars tested in greenhouse trials; sunflower lines HA 335, 803-1 (=DM-5), HA 89, HA-RI, and RHA 274 were the most resistant. This is the first report of the disease in Italy and Europe.
Phialophora asteris f.sp. helianthi a new pathogen of sunflower in Italy
TOSI, Laura;ZAZZERINI, Antonio
1994
Abstract
A wilt disease was observed during the summer of 1993 in a sunflower field near Peruiga in central Italy. The disease was characterized by yellowing of leaves as plants approached flowering. Large areas of the leaves turned light green, usually beginning at the apex and margins and extending inward. Subsequently, leaf margins turned necrotic, and diseased plants were stunted with smaller heads. Our trials proved that this disease was caused by Phialophora asteris f.sp. helianthi. The fungus was examined for colony morphology, temperature growth responses, and pathogenicity. Significant differences were observed among various culture media. Best growth and profuse sporulation were obtained on carrot and Czapeck agars added with peptone. The optimum temperature fro growth was 25 C; temperatures of 5, 10, 15 and 30 C greatly reduced colony growth and sporulation. No growth was observed at 35C. Significant differences in susceptibility to P.a. helianthi were observed in 17 sunflower cultivars tested in greenhouse trials; sunflower lines HA 335, 803-1 (=DM-5), HA 89, HA-RI, and RHA 274 were the most resistant. This is the first report of the disease in Italy and Europe.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
