Fruit firmness is an important market driven trait in sweet cherry (Prunus avium L.) as firmness dictates the harvesting, handing and marketing practices. In addition, consumers prefer firm sweet cherries. To investigate the genetic basis of fruit firmness, three different mapping populations were used: an INRA bi-parental F1 population, an INRA sweet cherry diversity population, and the RosBREED pedigreed population. For all three populations, the effects of different genotypes for fruit firmness were highly significant, and the broad-sense heritabilities were high ranging from 0.73 to 0.97. The INRA F1 sweet cherry population exhibited a bimodal distribution for fruit firmness which suggested that this population was segregating for a major locus controlling this trait. A major QTL for fruit firmness, named qP-FF4.1, that has not previously been reported, was identified in all three sweet cherry populations. Thirteen haplotypes (alleles) associated with either soft or firm fruit were identified for qP-FF4.1 in the sweet cherry germplasm. The soft fruit alleles for qP-FF4.1 contributed by the wild ‘mazzard’ sweet cherries were dominant over the firm fruit alleles. The identification of candidate genes for this fruit firmness QTL is underway. These results advance our understanding of the genetic basis of fruit firmness and will help to enable the use of DNA informed breeding for this trait in sweet cherry breeding programs.Read less <