RAPD markers linked to a gene for resistance to pine needle gall midge in Japanese black pine (Pinus thunbergii)

Linkage of RAPD markers to a single dominant gene for resistance to pine needle gall midge was investigated in Japanese block pine (Pinus thunbergii). Three primers that generated linked markers were found after 1160 primers were screened by bulked segregant analysis. The distances between the resistance gene, R, and the marker genes OPC06(580), OPD01(700), and OPAX19(2100) were 5.1 cM, 6.7 cM and 13.6 cM, respectively. OPC06(580) was in coupling phase to R, whereas OPD01700 and OPAX19(2100) were in repulsion phase to R. A linkage map for a resistant tree was constructed using 96 macrogametophytes. In linkage analysis, 98 out of 127 polymorphic markers were assigned to 17 linkage groups and six linked pairs. The total length of this map was 1469.8 cM, with an average marker density of 15.6 cM. The genome length was estimated to be 2138.3 cM, and the derived linkage map covered 67.5% of the genome. Although the linked markers OPC06580, OPAX19(2100), and OPD01700, belonged to the same linkage group, no precise positions were found for OPC06(580) or OPD01(700).