Chestnut trees (Castanea sativa Mill.) for climate change

As climate changes, getting warmer and drier in countries within the Mediterranean Basin, selection of new chestnut trees to be planted in orchards and forests is needed. In 2015, the Faculty of Forestry at Universidad de Extremadura (Spain) initiated a breeding program aimed to select Castanea sativa genotypes tolerant to global change. This program is currently supported by chestnut growers, regional funds and the Ministry for the Ecological Transition and the Demographic Challenge. Nuts from natural C. sativa stands located in Andalusia (Constantina and Paterna del Río) and Extremadura (Hervás and Valle de Matamoros) were collected and sown under a randomized block design. Circa 500 one-year-old seedlings per population were challenged with drought and Phytophthora cinnamomi. The nine most tolerant plants were selected, established in vitro and micropropagated. Clonal replicates were subjected during two years to drought, heat, waterlogging, and P. cinnamomi conditions (n=8). Commercial 111-1, 2671, 90.044 and 7521 clones, tolerant to P. cinnamomi, were included as controls. Two C. sativa genotypes, ‘Paterna del Río 18’ and ‘Valle de Matamoros 1’, showed resistance to P. cinnamomi, high levels of tolerance to drought and heat stress, and acceptable levels of tolerance to waterlogging. SSR markers confirmed that both clones were C. sativa. Replicates have been planted in two different experimental field plots in order to assess plant performance and adaptation.