strategy for developing representative germplasm sets for systematic QTL validation, demonstrated for apple, peach, and sweet cherry

• Published in: Tree genetics & genomes 2014-12, Vol.10 (6), p.1679-1694
• Main Authors: Peace, C. P, Luby, J. J, van de Weg, W. E, Bink, M. C. A. M, Iezzoni, A. F
• Format: Article
• Language: English
• Subjects: alleles; ancestry; apples; Biomedical and Life Sciences; Biosynthesis; Biotechnology; breeding program; Crop improvement; Crops; Cultivars; fire blight resistance; Forestry; fruit firmness; Fruits; gene; Gene mapping; gene pool; Genomes; Germplasm; Horticultural crops; Horticulture; Life Sciences; Malus domestica; map position; marker-assisted selection; md-acs1; Original Paper; parents; peaches; Performance evaluation; Plant Breeding/Biotechnology; Plant Genetics and Genomics; population-structure; Prunus avium; Prunus persica; pyrus-communis; quantitative trait loci; Statistical power; Tree Biology; x domestica borkh
• ISSN: 1614-2942; 1614-2950
• DOI: 10.1007/s11295-014-0788-z

Horticultural crop improvement would benefit from a standardized, systematic, and statistically robust procedure for validating quantitative trait loci (QTLs) in germplasm relevant to breeding programs. Here, we describe and demonstrate a strategy for developing reference germplasm sets of perennial, clonally propagated crops, especially those with long juvenile periods. Germplasm is chosen to efficiently represent important members of larger pedigree-connected genepools. To facilitate validation of multiple QTLs, genome-wide representation of alleles is optimized for designated important breeding parents (IBPs) by estimating average allelic representation in relatives. The strategy and arising principles were demonstrated in a simulated germplasm set. Strong statistical power can be achieved with a carefully chosen germplasm set composed of IBPs, their numerous unselected progenies and close relatives, and all available founders and intermediate ancestors. Crop Reference Sets were developed in the marker-assisted breeding (MAB)-enabling “RosBREED” project as a base resource for QTL validation in US breeding germplasm of apple (Malus × domestica), peach (Prunus persica), and sweet cherry (Prunus avium) consisting of 467, 452, and 268 individuals, respectively. These sets adequately represent the most designated IBPs, have distinct advantages for QTL validation over other germplasm arrangements of equal size, and are recommended as a base resource for QTL validation by breeders of these US crops. The strategy described here can be used to develop efficient reference germplasm sets suiting other breeding genepools or to calculate the statistical power for QTL validation of germplasm sets already established.