Identification of a new allele of the Dw gene causing brachytic dwarfing in peach

Peach brachytic dwarfism determined by Dwarf gene ( Dw ) is an undesired trait segregating in some peach breeding programs. Recently, a single nucleotide polymorphism (SNP) mutation in the gibberellin insensitive dwarf 1 (GID1) peach gene causing brachytic dwarfism was described. In this research we wanted to validate this marker in an F 2 population of the ‘Nectavantop’ peach cultivar (Nv) to include it as a marker assisted selection tool for peach breeding programs. The observed segregation of the trait was in agreement with that of a recessive gene, the individuals homozygous for the recessive allele ( dwdw ) presenting the dwarf genotype. Dw was mapped to the distal part of linkage group 6 as previously described. The SNP marker based on the causal mutation previously described did not segregate in Nv F 2 population. The sequence of the GID1c gene in Nv revealed a second SNP in its coding sequence which cosegregated with the dwarf phenotype. This SNP was predicted by the SNAP 2 software to cause a major functional change and was validated in the dwarf peach cultivar ‘Small sunning’. These results suggest the existence of at least two independent mutations of the Dw gene causing the peach brachytic dwarf phenotype.