Development of a second generation linkage map for almond using RAPD and SSR markers

Fifty-four RAPD (random amplified polymorphic DNA) markers and 6 SSRs (simp le sequence repeats) were included in a molecular marker map with 120 RFLPs (restriction fragment length polymorphisms) and 7 isozyme genes previously constructed using the offspring of a cross between the almond (Prunus amyg dalus) cultivars 'Ferragnes' and 'Tuono'. Only highly reproducible RAPDs se gregating 1:1 were used. To identify these markers, a total of 325 primers were screened, from which 41 produced RAPDs useful for mapping. Polymorphis m was detected in six of the eight Prunus SSRs (simple sequence repeats) st udied, thus enabling these to be mapped. All markers were placed on the 8 l inkage groups previously identified. The number of new markers included in the map of 'Ferragnes' was 33 for a total of 126, and 30 in the map of 'Tuo no' for a total of 99. The sizes of the maps of 'Ferragnes' (415 cM) and 'T uono' (416 cM) were similar, representing a 5% increase over the maps const ructed solely with isozymes and RFLPs. The estimated total size of the almo nd map was of 457 cM. Some markers were placed in zones with low density of markers and others in the extreme of linkage groups. The use of RAPD marke rs to complete genetic maps constructed with transferable markers is discus sed.