A framework genetic map of Muscadinia rotundifolia

This study presents a framework linkage map based on microsatellite markers for Muscadinia rotundifolia (1n = 20). The mapping population consisted of 206 progeny generated from a cross of two M. rotundifolia varieties, 'Fry' and 'Trayshed'. A total of 884 primers were tested for their ability to amplify markers: 686 amplified and 312 simple sequence repeat (SSR) primer pairs generated 322 polymorphic markers for either one or both parents. The map for the female parent 'Fry' consisted of 212 markers and covered 879 cM on 18 chromosomes. The average distance between the markers was 4.1 cM and chromosome 6 was not represented due to a lack of polymorphic markers. The map for the male parent 'Trayshed' consisted of 191 markers and covered 841 cM on 19 chromosomes. The consensus map consisted of 314 markers on 19 chromosomes with a total distance of 1,088 cM, which represented 66 % of the distance covered by the Vitis vinifera reference linkage map. Marker density varied greatly among chromosomes from 5 to 35 mapped markers. Relatively good synteny was observed across 19 chromosomes based on markers in common with the V. vinifera reference map. Extreme segregation distortion was observed for chromosome 8 and 14 on the female parent map, and 4 on the male parent map. The lack of mapping coverage for the 20th M. rotundifolia chromosome is discussed in relation to possible evolutionary events that led to the reduction in chromosome number from 21 to 19 in the ancestral genome.