Identification of apple genes Md-Exp7 and Md-PG1 alleles in advanced selections resistant to scab.

The creation of apple varieties with a high level of f lesh f irmness and long shelf life is one of the important goals in breeding. Among the genes controlling these traits, the role of the endogenous ethylene biosynthesis control gene, Md-ACS1, the expansin gene, Md-Exp7, and the polygalacturonase gene, Md-PG1, has been established. The use of DNA marker analysis to solve problems in breeding for fruit quality traits allows one not only to track several target genes simultaneously, but also to cull plants with undesirable alleles at the early stages of development.