A phenotypic study of Botrytis bunch rot resistance in Vitis aestivalis-derived ‘Norton’ grape

Botrytis bunch rot, caused by Botrytis cinerea, is one of the most destructive diseases of grapes (Vitis vinifera L.). A phenotyping assay was designed under laboratory conditions to analyze grape-B. cinerea interactions. A conidial suspension of concentration 1 × 105 conidia/ml was prepared and used to inoculate berries from two different grape varieties: V. aestivalis-derived ‘Norton’, a North American hybrid, and V. vinifera ‘Cabernet Sauvignon’, a European grape. The differences in the infection reaction between these two cultivars were visible 10 days after inoculation. Berries from Norton had a low average disease incidence (7.5 %) and disease severity (3.7 %). In contrast, berries from Cabernet Sauvignon were completely susceptible, exhibiting an average disease incidence and severity greater than 90 %. This phenotyping assay can be further applied to evaluate disease progression in a mapping population, developed by crossing V. aestivalis-derived ‘Norton’ and V. vinifera ‘Cabernet Sauvignon’.