The domesticated apple (Malus × domestica Borkh.) is one of the most relevant cultivated fruit crops worldwide, in particular in temperate zones, and the fourth most economically important. In order to avoid loss of genetic diversity, germplasm banks have been established to conserve proper genetic diversity, among them we have evaluated five that covers western Iberian Peninsula (the one from Galicia and three from northern to southern Portugal) and Canary Islands.A total of 634 accessions composed of old and local autochthonous apple germplasm, as well as commercial and reference varieties, plus 16 accessions that were collected as wild apples, were studied. Of the total, 484 local accessions were obtained from Spain and 67 from Portugal. The objective of the present study was to analyse the genetic diversity and genetic structure, and define core collection (a small group of cultivars that preserve the allele diversity of the set), by using 13 microsatellite markers (SSRs).Of the total of 634 accessions studied, corresponding to 370 unique genotypes, were grouped into two reconstructed panmictic populations or RPPs; the first RPP included 506 accessions (304 unique genotypes), which belonged to local and autochthonous varieties; and the second RPP clustered the remaining 128 (66 distinct genotypes), which were commercial and reference varieties. In total, 29 new synonyms (74 accessions) were identified between Galicia and the Canary Islands, which indicated the close historical relationship between these two regions located 2000 km apart.A core collection to preserve the whole allelic diversity of the west of the Iberian Peninsula (Galicia and Portugal) and the Canary Islands was defined keeping 10% of the genotypes (63) with respect to total accessions of the complete study, 14% of them (54) from Galicia with wild accessions or 15% (55) from Galicia without wild accessions, 40% (30) from the Canary Islands and 36% (24) from Portugal.The results obtained will allow update of the germplasm banks with correct identification of cultivars, differentiating the autochthonous ones from those derived from commercial cultivars, with the elimination of repetitions (42%), and proposal of the core collection necessary to preserve allele diversity.
The Canary Islands have an enormous richness of crops and varieties, many of them traditional or local, selected for decades by farmers based on the most desirable characteristics. Pear trees were introduced to the Canary Islands presumably in the first years after their Conquest in the 15th century, reaching a high degree of diversification. In this study, to determine the genetic identity of the genus Pyrus in the Canary Islands for conservation purposes, 266 pear accessions from the islands of Tenerife, La Palma and Gran Canaria were characterized with 18 SSRs, in addition to 190 genotypes from Galicia, Asturias, wild and commercial varieties as references to detect possible synonyms, genetic relationships and the possible genetic structure. We identified 310 unique genotypes, both diploid and putative triploid, 120 of them present only in the Canary Islands (39%, with 50% clonality). The population structure of the genotypes was analyzed by STRUCTURE 2.3.4 software (Pritchard Lab, Stanford University, Stanford, CA, USA). The dendrogram, by using the Jaccard coefficient and principal component analysis (PCoA), separated the analyzed genotypes into stable groups. One of these groups was formed only by Canarian varieties present at lower altitudes, showing adaptation to low chilling requirements with a significant positive correlation (0.432, p < 0.01). This first study of the pear germplasm in the Canary Islands reflects the importance of the group of local cultivars and their need for conservation given they are adapted to their peculiar climatic conditions and have a low number of chill units.
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