Variation in adaptive traits among and within Spanish and European populations of Castanea sativa: selection of trees for timber production

Mediterranean and Northern Iberian gene pools of wild Castanea sativa Mill. are two differentiated ecotypes originated under natural divergent selection

“…The results obtained from our study of genetic variation confirmed the high level of genetic differentiation among Iberian chestnut populations for most adaptive traits related to annual growth rhythm and an increasing population effect for phenology and growth over the years, as previously reported by Míguez-Soto and Fernández-López [52] in six European and six geographically distant Spanish populations. This population differentiation followed a north–south, or wet–xeric, pattern as indicated the significant correlations of flushing, BS and H with the xerothermic index and the latitude of the origin of provenances.…”

“…The result obtained in the drought-stress experiment indicated that, in general terms, xeric populations developed larger root systems under drought conditions, which is a characteristic adaptation to drought by forest trees [78]. The higher survival observed in xeric populations under water stress conditions in our study also supported previous suggestions relating to the greater adaptive ability of the central and southern Iberian populations to drought [49, 52]. The between treatment comparisons of the BLUP values of our study populations for the traits more affected by the drought-stress treatment provided additional information on the behavior of each population (Fig 5).…”

“…Clinal geographic pattern was reported previously for provenance trials of C . sativa in Spain, in which populations with low xerothermic indices and higher latitudes showed later flushing [49, 51, 52], later BS and faster growth [52]. This pattern was also observed in provenance trials of European populations from Spain, Italy and Greece for phenology and growth [50, 52] and for functional expressed sequence tag-SSR markers [73].…”

“…Several provenance studies based on the genetic variation of adaptive traits related mainly to phenology and growth, reported important differences among natural European and Iberian populations of C . sativa [48–52]. Specifically, provenance trials conducted in Iberian Peninsula indicated a latitudinal clinal variation for several adaptive traits; northern populations showed later flushing and bud set, more vigorous growth, higher stem straightness and higher resistance to frost than central and southern Spanish populations [49, 51, 52] This north-south variation has been related to drought and frost as relevant factors in the natural selection that shaped the actual structure of C .…”

“…All these patterns of geographical variation identified in these adaptive traits seem to indicate, in general terms, a natural origin of the Iberian chestnut populations. In relation to the genetic variation within natural populations, fewer studies have been carried out but the general observation is that among-population differences were greater than within population differences [51, 52].…”