RosBREED Facilitates Peach Genetic Improvement Via Marker-Assisted Breeding

New cultivar development for peach in the U.S. can be divided into two types according to usage of fruit: fresh market and processing market. Objectives common to all peach breeding programs include improving and maintaining fruit quality (flavor, firmness, and appearance), productivity, size, and season extension. These trait targets are complemented with emphases on ease of processing, disease and pest resistance, a greater diversity of fruit types, and adaptation to low-chill zones in individual programs. Genetic markers associated with some of these traits are available and useful for informing crossing decisions and seedling selection decisions. Despite being one of the best characterized Rosaceae crops with genomic resources including a whole genome sequence, a reference genetic map, EST libraries, and a growing list of marker-locus-trait associations, application of these resources in peach breeding efforts is still limited. The RosBREED project (www.rosbreed.org) aims to bridge this chasm by providing markers and simplified technologies to enable marker-assisted breeding for fruit quality and other critical traits. The four public peach breeding programs in California, Texas, South Carolina, and Arkansas representing a range of breeding objectives, are integral to this project. The peach breeders have established a comprehensive crop reference germplasm set of important breeding parents represented by about 500 popular cultivars, ancestors, breeding selections, and breeding populations. This material is connected through many pedigree linkages, which is characteristic of peach breeding germplasm and can be exploited via the statistical approach of Pedigree-Based Analysis. Pedimap software was used to visualize these pedigree connections, revealing unrealized fractions of shared genomes. Large-scale phenotyping and genotyping of this reference germplasm is underway. Standardized phenotyping protocols for peach fruit quality evaluation were initiated during the 2010 season. High-resolution SNP-based genome scans with a 6K array are providing an unprecedented view of cultivated peach genetic diversity, and, through association with phenotypic performance, functional variation for breeding program-specific predictive marker development. Genetic tests for promising trait targets were recently fast-tracked through RosBREED’s “MAB Pipeline”. Useful outcomes include designation of fruit type (melting and non-softening for fresh market and non-melting for canning; freestone vs. clingstone) for breeding selection decisions.