Bulk segregant analysis for bloom time QTL in sour cherry ( Prunus cerasus L.)

Spring freeze damage to sour cherry (Prunus cerasus L.) flower buds is the major limiting factor to sour cherry production in the U.S. Significant crop reductions from spring freezes occur approximately every three years. In 2002, the losses to spring freeze damage were particularly devastating with 95% of the sour cherry crop in Michigan destroyed. One breeding approach to minimize the potential for freeze injury to sour cherry flowers is to develop late-blooming cultivars that would have an increased chance of avoiding spring freeze damage. Fortunately there is extensive variation for bloom time in sour cherry with extremely late blooming germplasm available.; The goal of this project was to investigate the inheritance of bloom time in tetraploid sour cherry (2n = 4x = 32) using a QTL approach. The progeny population used was from a cross between 'Balaton' and the late blooming sour cherry cultivar 'Surefire'. QTL discovery was done using a bulk segregant approach comparing late and early blooming progeny individuals using SSR and AFLP markers. Using this approach, an AFLP marker was identified that was significantly linked to a putative QTL, termed blm3, controlling bloom time. The late allele, contributed by the late blooming parent 'Surefire', explained 16.5% of the phenotype variance and delayed bloom time by approximately 15 degree days. Future characterization of this QTL and other QTL controlling bloom time may suggest ways to delay bloom in sour cherry and other Rosaceous species, thereby reducing the probability of spring freeze damage and crop loss.