2019 ASHS Annual Conference

We report the development of a high-density linkage map for interspecific Malus hybrids based on GBS markers obtained from cross between Malus domestica cultivar ‘Royal Gala’ and seven Malus sieversii accessions as male parents. These populations were used in prior genetic studies of fruit acidity and blue mold resistance. A total of 1,251 progeny among the seven half-sib families yielded 476,000 markers, of which an average 1,799 markers were placed into 17 linkage groups. Separated into pseudo-testcross maps, the average length of was 1420cM and 2178cM, or about 0.48 and 1.1 cM/marker for the ‘Royal Gala’ and M. sieversii maps, respectively. Using this map, we detected major QTLs for two segregating traits among the half-sib families. Burrknot, a pervasive physiological disorder which weakens the trunk and is an entry point for pathogens, segregate in the ‘Royal Gala’ background at LG 11. Likewise, a putative resistance to leafspot-like disease incidence observed in 2017, is strongly associated in the ‘Royal Gala’ background at LG 10. These results provide useful foundations in dissecting the genetic architecture and feasibility of selective breeding for other novel traits in apple.