The main threats to chestnut in Europe are climate change and emerging pathogens. Although many works have separately addressed the impacts on chestnut of elevated temperatures and Phytophthora cinnamomi Rands (Pc) infection, none have studied their combined effect. The objectives of this work were to describe the physiology, secondary metabolism and survival of 6-month-old C. sativa seedlings after plants were exposed to ambient temperature, high ambient temperature and heat wave events, and subsequent infection by Pc. Ten days after the warming scenarios, the biochemistry of plant leaves and roots was quantified and the recovery effect assessed. Plant growth and root biomass under high ambient temperature were significantly higher than in plants under ambient temperature and heat wave event. Seven secondary metabolite compounds in leaves and three in roots were altered significantly with temperature. Phenolic compounds typically decreased in response to increased temperature, whereas ellagic acid in roots was significantly more abundant in plants exposed to ambient and high ambient temperature than in plants subjected to heat waves. At recovery, leaf procyanidin and catechin remained downregulated in plants exposed to high ambient temperature. Mortality by Pc was fastest and highest in plants exposed to ambient temperature and lowest in plants under high ambient temperature. Changes in the secondary metabolite profile of plants in response to Pc were dependent on the warming scenarios plants were exposed to, with five compounds in leaves and three in roots showing a significant ‘warming scenario’ × ‘Pc’ interaction. The group of trees that best survived Pc infection was characterised by increased quercetin 3-O-glucuronide, 3-feruloylquinic acid, gallic acid ethyl ester and ellagic acid. To the best of our knowledge, this is the first study addressing the combined effects of global warming and Pc infection in chestnut.

ISHS VII International Chestnut Symposium Chestnut trees (Castanea sativa Mill.) for climate change

The degradation of riparian ecosystems occurring throughout the past decades has motivated efforts aimed at the restoration of these ecosystems. The success of active revegetation approaches to restoration requires appropriate selection of reproductive material, which in turn requires knowledge of seed traits and germination. Alnus glutinosa (L.) Gaertn. (common alder) is a key riparian tree widely used in restoration projects, and has recently been classified as comprising three species: A. glutinosa; A. lusitanica Vít, Douda, & Mandák; and A. rohlenae Vít, Douda, & Mandák. To help guide restoration species selection, we assessed differences among populations of these species by (1) investigating seed weight, morphology, and germination success from a large population set and (2) modeling germination success in each species in relation to morphological traits and environmental conditions. Seeds were collected from 12 populations encompassing the latitudinal extremes of the species complex, and were then characterized and germinated. Ploidy levels and species were distinguished using cytometric analysis. Site‐level climatic data and seed morphology data were used to model germination success for each species. All seed traits differed between populations and one morphological‐trait (seed weight‐to‐area ratio) differed significantly between the three species. Germination modeling showed that the southwestern species, A. lusitanica, responded positively to high temperature extremes, suggesting tolerance to the climate changes projected for southern Europe. Populations of A. lusitanica located at the latitudinal rear edge of common alder's distribution appear to show establishment‐facilitating adaptations, and therefore may contribute to ecological restoration efforts under a range of environmental conditions.

Increasing temperatures and heat waves decimate the productivity and survival of valuable trees like the European chestnut (Castanea sativa Miller). The main objectives of this study were to assess variation in heat stress tolerance within and between chestnut populations, select molecular markers associated with heat stress tolerance, and to use the selected markers to explore the adaptive potential of C. sativa to tolerate heat stress. Forty-eight trees from three Spanish wild chestnut populations of contrasting climate characteristics were used. Seven out of 20 expressed sequence tag- simple sequence repeat (EST-SSR) markers were selected. To validate the markers, progenies of the 48 trees were subjected to heat stress for 7 days and their heat tolerance was assessed through morphological and physiological changes. Leaf proline content induced by heat was highest in the least thermophilic population. Genetic structure analysis of populations revealed a cluster that included 81 per cent of the seedlings of the most thermophilic population. Signatures of positive selection for heat stress tolerance were detected using VIT099 and POR016 markers, associated with the antioxidant response of plants to heat damage. These markers should be included as candidates for their use in early selection of individuals tolerant to heat stress in C. sativa. Molecular and physiological findings converged in this study to better understand chestnut adaptation to global warming.

Cork oak (Quercus suber L.) is an evergreen tree native to SW Europe and NW Africa. It covers 2·106 ha in the western Mediterranean basin, forms heterogeneous forest ecosystems and represents an im...