SSR and AFLP markers for germplasm evaluation and cultivar identification in peach

摘要

Using 16 SSR (simple-sequence repeat or microsatellite) markers in a set of 212 peach and nectarine commercial cultivars it was possible to identify 87% of the accessions, and 95% when only one genotype was considered for every group of known sport mutations. Results with 47 AFLPs (Amplified Fragment Length Polymorphism) in a subset of 210 cultivars were very similar: 89% of the cultivars were differentiated from the rest, and 94% when sport duplications were removed. The 43 non-melting flesh cultivars were identified by both marker types as separated from the rest, indicating their value as possible donors of new alleles to the narrow gene pool of the commercial non-melting cultivars. Our data revealed two important aspects to be considered for the test of cultivar identification. First, the existence of marker mutations, detected in both SSRs and AFLPs when comparing the fingerprints of the sports studied. And second, the departures from the assumptions of independence of markers (three pairs of SSRs were linked) and lack of subpopulation structures within the group of cultivars studied, which make the usual calculations of the probability that two cultivars are identical by chance, an underestimation of its real value. These results suggest that a solid test for cultivar identification requires information on mutation rates of the markers used and previous data on a large set of cultivars using highly polymorphic, single-locus markers of known map position. In this context, SSR markers are more adequate than AFLPs for cultivar identification.