Genetic structure and diversity in productive plantations of Monterey (Pinus radiata D. Don.) and maritime (P. pinaster Ait.) pines in Atlantic north-western Spain

Abstract Key message Pine plantations of Pinus radiata and Pinus pinaster in the Atlantic regions of north-western Spain exhibit sufficient genetic diversity to ensure sustainable forests and to establish future breeding programs, although they show lower levels of variation than populations in their native ranges and in other countries. Context Exotic Monterey and native maritime pines are two of the most abundant conifers in north-western Spain and have been widely used for productive objectives. However, the sustainability of these two species has been altered by diseases caused by fungi and insects along with ongoing abiotic stresses. Genetic diversity is a key factor in adaptability as it brings a greater range of functional responses and thus a greater likelihood for a population to resist or recover from a perturbation. Forest management practices may affect the genetic dynamics of tree populations, and therefore European and national regulations are implemented to ensure the long-term sustainability of forest plantations. Aims This research aimed to assess the genetic diversity in Monterey and maritime pines productive plantations across north-western regions of Spain. The goal is to support the adoption of effective management practices to enhance adaptation and breeding potential. Methods In this study, we analyzed the genetic diversity and structure of 52 Monterey and 56 maritime pines plantations spread across north-western Spain, using 12 and 11 nuclear microsatellites, respectively. Results Results exhibited a unique genetic group for Monterey pine plantations, which were genetically uniform and consistent with a single importation provenance in Spain. Conversely, some maritime pine plots were found to be differentiated, suggesting multiple origins. Genetic diversity in both species was slightly lower than reported for their original distribution ranges and for plantations in other countries. Conclusion The relatively small differences in genetic diversity compared with natural populations and other international plantations may indicate sufficient genetic resources to ensure future sustainable management and establish breeding programs. Nonetheless, introducing new genetic material from other provenances to increase overall diversity could broaden the adaptive and productive potential of these two species.