Development of genetic maps of the citrus varieties ‘Murcott’ tangor and ‘Pêra’ sweet orange by using fluorescent AFLP markers

Abstract: The progeny of 87 BC₁ hybrids of ‘Murcott’ tangor and ‘Pêra’ sweet orange, genotyped with fluorescent amplified fragment length polymorphism (fAFLP) markers, was used for the construction of genetic maps for both citrus varieties. Mapping strategies, considering the progeny as a result of backcrossing and cross-pollination, were exploited in Mapmaker 2.0 (LOD score ≥ 3.0 and 9 ≤ 0.40) and JoinMap 3.0 software (LOD score ≥ 3.0 and 9 ≤ 0.25), respectively. Genetic map distances (in cM) between the linked fAFLPs were estimated, in both packages, by the Kosambi’s function. Maps of both parents were constructed in Mapmaker with 121 of the 202 fAFLP markers showing 1:1 Mendelian segregation rates (’Murcott’ map: 65 fAFLPs, average distance between them 29.5 cM, divided into 9 linkage groups (LGs), total size 1651.47 cM; ’Pêra’ map: 55 fAFLPs, average distance between them 31.9 cM, divided into 5 LGs, total size 1596.2 cM). The second ’Murcott’ map, constructed through linkage analysis of 347 fAFLP markers with 3:1 or 1:1 segregation rates by using JoinMap, resulted in the linkage of 227 markers with an average distance of 4.25 cM among them, divided into 9 LGs of 845 cM. fAFLP loci showing distorted segregation and/or clustered were observed in different LGs of the maps generated by all the software. The use of the ’Murcott’ tangor and ’Pêra’ sweet orange genetic maps in research on identification of citrus QRLs (quantitative resistance loci) toXylella fastidiosa and QTLs (quantitative trait loci) related to the productivity and quality of the juice, respectively, is discussed.