Castanea sativa a multipurpose tree: genetic diversity and conservation

Sweet chestnut (Castanea sativa Mill.) is a multipurpose species of Mediterranean region important not only for the production of fruit and timber, but also for its socio-economic and cultural value and for its contribution to the landscape. Owing to environmental changes and anthropogenic factors, which lead habitat fragmentation, there is need of in situ and ex situ conservation plans. For this purpose, all levels of biodiversity should be considered including the intraspecific genetic component, a key factor for the ability of a species to survive under changing environmental conditions. This work aims to evaluate the geographical paterns of genetic diversity of Castanea sativa populations and identify areas that show high values of genetic diversity and divergence. Twenty-three European populations located in three countries (Portugal, Spain, and France) were analyzed by means of 9 functional markers (EST-SSRs) related to water stress and bud burst and 6 neutral markers (SSRs). Observed (Na) and efective (Ne) number of alleles, observed (Ho) and expected (He) heterozygosity and the inbreeding coeficient (Fis) were calculated using GeneAlEx6 sofware. The population structure was investigated using the STRUCTURE 2.3.4 sofware. As shown from AMOVA analysis, the proportion of variation based on genomic microsatellites and EST-SSRs were respectively 1% and 4% among individuals within populations and 14% and 13% among populations. Structure analysis showed diferent grouping of the populations for the two types of markers. Our results suggest the need to combine neutral and functional markers to identify populations and germplasm to be preserved and used in conservation and management programs of genetic resources of this forest species.