Marker–Assisted Seedling Selection in Sour Cherry for Fruit Color and Cherry Leaf Spot Resistance

Michigan is the leading producer of sour cherry (Prunus cerasus L.) in the United States. The goal of the sour cherry breeding program at Michigan State University is to develop new cultivars that are resistant to the major disease affecting sour cherry [cherry leaf spot (CLS), Blumeriella jaapii] and have the fruit type desired by the industry.  To increase the efficiency and reduce the number of years to reach these breeding goals, new genetic tests have been developed through RosBREED (www.rosbreed.org) to implement marker-assisted seedling selection (MASS) for these two target traits.  Sour cherry fruit color varies widely from dark purple skin and flesh, to orange skin with colorless flesh due to differences in anthocyanin pigmentation.  The processing industry desires a sour cherry that has brilliant red flesh, as that is the market niche in the U.S.  The genetic test developed for fruit color targets the anthocyanin transcription factor that controls flesh color located on linkage group 3 (LG3). Resistance to CLS is a high industry priority as more pesticides per acre are applied for this disease than any other pest of sour cherry.  One major QTL controlling P. canescens-derived CLS resistance was identified on linkage group 4 (LG4).  Any cherry individual must have this resistance QTL to be CLS resistant. DNA tests, using SSR primers developed to tag the desired alleles for CLS resistance and fruit color, have been developed. Seedling progeny from crosses made in 2013 are anticipated to segregate for fruit color and CLS resistance and DNA tests will be performed on these families for MASS.  This MASS will be able to determine the seedlings that are predicted to be CLS resistance and have brilliant red fruit color. The implementation activities and the results of MASS for these two traits will be presented.