Pre-breeding for future challenges in Nordic apples: susceptibility to fruit tree canker and storage diseases

Apple production has a long history in the Nordic countries, but high labour costs and challenging climatic conditions result in production costs that are not competitive on the international market. In addition, access to permitted pre‐harvest chemicals in the orchards has been severely restricted in recent years, and post‐ harvest applications are completely banned. Moreover, grower economy would benefit from being able to forego chemical fungicides altogether, as there is an increasing demand for locally produced, organic fruit. Consequently, climate adaptation and disease resistance/tolerance are major issues for apple breeding programmes in Norway, Sweden and Finland. A public‐private partnership project initiated by the Nordic Council of Ministers and administered by NordGen started in 2012 with the aim of producing and disseminating knowledge concerning levels of susceptibility against some of the most devastating apple diseases in the Nordic countries, namely fruit tree canker (Neonectria ditissima) and storage diseases (Neofabraea spp. and Penicillium expansum), in apple cultivars of potential interest for plant breeding and cultivar development in the Nordic countries. Inoculation of fruit of 81 different apple cultivars with blue mould, P. expansum, has been carried out in Norway and Sweden, whereas evaluation of spontaneous infections of various fungi during storage has been carried out in Finland using fruit of organically produced, local apple cultivars. For fruit tree canker, inoculations have been carried out on detached shoots of 50 different apple cultivars in Norway and Sweden. For both apple canker and blue mould, reproducibility among years and sites was sufficiently high to enable an approximate determination of the level of susceptibility of the studied cultivars.