Fertile somatic hybrids of Solanum etuberosum (+) dihaploid Solanum tuberosum and their backcrossing progenies: relationships of genome dosage with tuber development and resistance to potato virus Y

Genetic diversity, as revealed by eighteen Simple Sequence Repeat (SSR) markers in thirty almond [P. dulcis (Mill.) D.A. Webb], twenty fresh-market peach [Prunus persica (L.), Basch], fifteen processing clingstone peach cultivars, and ten rootstocks, established the genetic relatedness among cultivars and characterized the variation within and between species. One accession each of the wild Prunus species, P. davidiana [(Carriere) Franch] and P. webbii [(Spach.) Vieh.], was included in the analysis. The number of presumed alleles revealed by the SSR analysis ranged from one to six in peach whereas almond cultivars showed a range of three to nine. Peach cultivars clustered into ten groups, which are in general agreement with documented origin. Most processing clingstone peach cultivars clustered separately from fresh-market freestone cultivars supporting a distinct origin. Two major clusters were observed in almond with one containing California cultivars and the other containing European cultivars and the important California cultivar Mission. Results establish the value of SSR markers for distinguishing different genetic lineages and characterize an extensive and largely unexploited inter-species gene pool available to peach and almond breeding programs.