The 2011 ASHS Annual Conference

Peach is a self-pollinated species with a high level of linkage disequilibrium (LD) conservation for North American and European commercial varieties, LD~13-15cM. The analysis of the University of Florida peach germplasm founding clones, previous releases, and present selections, constitutes the main objective of this report. A total of 198 peach genotypes were fingerprinted with 37 SSRs distributed across the genome (~15-25 cM). Peach germplasm samples included genotypes from the University of Florida, the USDA-UGA-UF moderate-chill breeding effort, North Carolina State University, primitive low chill germplasm, and related species P. dulcis (Mill.) D.A. Webb and P. kansuensis Rehder. Number of alleles per locus (A), effective number of alleles (Ae), observed heterozygosity (Ho), expected heterozygosity (He), Wright’s fixation index (F), power of discrimination (PD), the probability of confusion (C), and Nei’s genetic distance (GD) per locus were calculated.  An unrooted Neighbor-Joining tree was constructed using Nei’s genetic distance. ‘Diamante cling’, ‘Non-melting’, ‘Melting’, ‘High-chill’, and two ‘Nectarine’ clades were identified in the peach germplasm. Genetic diversity values in the range of 0.5 were observed. Past and present peach selections and cultivars developed by the UF breeding program have been determined by breeding strategies, objectives and commercial trends that changed through the years.  To detect potential changes in allele frequencies resulting from the breeding efforts, the genetic diversity of germplasm representing different decades was compared.