Construction of a saturated linkage map for Prunus using an almond x peachF-2 progeny

A map with 246 markers (11 isozymes and 235 RFLPs) was constructed using an interspecific F-2 population between almond (cv Texas) and peach (cv Early gold). RFLPs were obtained using 213 probes from the genomic and cDNA libra ries of different species (almond, peach, P. ferganensis, cherry, plum and apple), including 16 almond probes which correspond to known genes. All mar kers were distributed in eight linkage groups, the same as the basic chromo some number of the genus, covering a total distance of 491 cM. The average map density was 2.0 cM/marker and only four gaps of 10 cM or more were foun d; the two largest gaps were 12 cM each. This map was compared with one con structed previously with an intraspecific almond population sharing 67 anch or loci. Locus order was nearly identical and distances were not significan tly different. A large proportion of the mapped loci (46%) had skewed segre gations; in approximately half of them, the distortion was due to an excess of heterozygotes. One of the distorted regions could be associated with th e position of the self-incompatibility gene of almond.