Testing susceptibility of apple cultivars against Marssonina coronaria

摘要

The apple pathogen Marssonina coronaria (Ellis and Davis, 1914) (teleomorph Diplocarpon mali [Harada, Y. and Sawamura K. 1974]) has recently become a significant problem in Central European organic apple production, causing dark spots on both the leaves and fruit, and early leaf fall. In order to support selection of cultivars for fruit and cider production and to optimise plant protection strategies on these cultivars it is important to know their susceptibility to M. coronaria. In this study 16 commercially important or newly developed apple cultivars were screened for susceptibility to M. coronaria. 1 year old saplings were inoculated using conidia grown in liquid medium and kept at 23°C and under high humidity. The severity of any resulting infection was scored 3 times using a simple scale adapted to visual symptoms. Several cultivars showed good initial resistance to the disease, including Gala, Ariane and Elstar. However, at the last scoring, 21 days after inoculation, Gala had become one ofthe most severely infected cultivars, suggesting that resistance to the disease is complex, and involves a number of mechanisms.