A comparative study of European chestnut varieties in relation to adaptive markers

Traditional agroecosystems are considered as main conservatories of landraces biodiversity because they preserve their dynamic processes and farmers' knowledge of selection and management inherent in the development of local cultivars. The Mediterranean region still harbours traditional agroecosystems of particular importance for preserving crop biodiversity, being sweet chestnut (Castanea sativa Miller) a good example. This is one of the multipurpose species of most economic importance in the Mediterranean basin, cultivated extensively for fruit production, and the majority of varieties are the result of the selection of landraces by farmers. In this study, a set of European chestnut traditional varieties were evaluated in order to characterise its genetic resources and detect a possible response in the adaptive potential of this germplasm. Results of Bayesian analysis revealed a clear structure among cultivars from Italy and Spain with a low degree of admixture between them. Furthermore, a strong structure was detected within germplasm from each country congruent with their geographic origin. Statistical analyses did not reveal any significant marker deviating from neutral expectations. Results were discussed considering previous studies carried out on neutral and morphological markers, concluding that information provided by different markers was more powerful in detecting the maximum amount of genetic variation in chestnut varieties, and establishing a baseline to continue identifying markers underlying phenotypic differentiation and/or response to environmental cues among varieties.