Adaptive genetic diversity of chestnut populations to the impact of Phytophthora cinnamomi

New forest diseases caused by alien invasive pathogens are increasing with the intensification of international trade and global change probability afects their establishment, distribution and virulence. The present forest distribution is influenced by their capacity to adaptation to local environments due to their genetic variability. Molecular technologies ofers new possibilities for population genetic and environmental studies, which can shed light on the evolution and control of forest diseases. There is an interest on loci directly involved in responses to processes related to environmental changes and biotic infestations. Thus, the enlarged availability of DNA sequences has permited the development of molecular markers from EST sequences expressed in diferent physiologic conditions of plants. Chestnut (Castanea sativa Mill.) is a multipurpose species of high economic importance in the Mediterranean basin, and it is an example of integration between natural and man-driven distribution of diversity under changing environmental and historical conditions. In last decades, the species has sufered a strong decline closely associated with ink disease caused by Phytophthora cinnamomi Rands, with dramatic consequences in local mountain economies. In some parts in Europe, the impact of Phytophthora cinnamomi has been mitigated by the use of hybrids rootstocks between C. sativa and two Asian tolerant species (Castanea crenata and Castanea mollissima), although in southern Europe, its use has proved to be unsuitable due to dificulties of adaptation of this resistant material to southern latitudes or local Phytophthora spp. Within an ongoing project funded by the Spanish Ministry of Economy and Competitiveness (AGL-2014-532822-C2-1-R), the adapti - ve diversity in relation to the response of chestnut to Phytophthora cinnamomi was evaluated. One hunderdtwenty chestnut trees from four Spanish regions representative of contrasting ecological and climate conditions (Andalucía, Cataluña, Extremadura and Galicia) and nine polymorphic EST-SSRs were selected. 38 alleles were scored, nine of them exclusive from the Galicia region. Andalusia had the highest level of diversity (uhe= 0.526) whereas Extremadura displayed the lowest (uhe= 0.352). amova analysis showed a high proportion of variation between populations (23%) and population genetic structure using the Bayesian clustering algorithm revealed two distinct gene pools, one formed by Andalucía and Cataluña regions and a second grouping Extremadura and Galicia. Moreover, a dendrogram based on Nei's genetic distances showed slightly diferent grouping separating Andalucía and Cataluña populations. These preliminary results confirm that EST-SSRs are a valuable tool to as - sess adaptive diversity in chestnut and could contribute to a more appropriate gene conservation and assisted breeding strategies.