DNA MICROSATELLITE IN FRUIT CROPS: ISOLATION, LENGTH POLYMORPHISM, INHERITANCE, SOMATIC STABILITY AND CROSS-SPECIES CONSERVATION

We have isolated and sequenced microsatellites in several fruit crop species, such as grape (Vitis vinifera L.), kiwifruit (Actinidia, chinensis Planch), olive (Olea europea L.), and peach (Prunus persica (L.) Batsch), using microsatellite repeat-enriched genomic libraries. The efficiency of the enrichment procedure was variable (about 50 % of positive plaques in kiwifruit and peach, lower values in grape and olive). The re-amplification from the source genomic DNA was obtained in most cases. The polymorphism was high in all species assayed (5 to 15 alleles/locus in grape, 9 to 17 alleles/locus in kiwifruit, 2 to 8 alleles/locus in peach, data for olive are still being scrutinised). The Mendelian segregation was demonstrated for 8/10 SSR analysed in grape, 99/233 SSR analysed in kiwifruit, and 17/26 SSR analysed in peach. All microsatellites segregated as a single locus in peach, whereas in kiwifruit, grape, and olive several primer pairs amplified two loci each, in agreement with the suspected polyploid origin of the last species. The somatic stability was assayed in peach and olive, using three long-living accessions of cv. 'Redhaven' of different origin and 2-4 centuries-old plants of olive for each of the eight cultivars assayed. No pattern variation of the 26 microsatellites analysed was found in peach, whereas in olive rare intra-variety polymorphisms were observed in several of the 35 microsatellites analysed up to now. The assays on cross-species transportability were carried out in species representative of each genus (14 species of Vitis, 8 species of Actinidia, and 7 species of Prunus) and gave positive amplifications in high percentages (91 % of microsatellites amplified in all Vitis species, 52 % in all Prunus species, and 75 % in all Actinidia species). In some cases, successful amplifications were obtained also in related genera such as Parthenocissus, a genus close to Vitis, and Malus, which together with the genus Prunus belong to the Rosaceae family.