Abstract:

Genetic improvement of fat and fatty acid composition content of soybean seed is interesting to both farmers and processors. The objective of the present study was to aim at constructing a genetic linkage map and mapping QTLs conferring fat and fatty acid composition contents in soybean. The mapping population with 114 BC1F1 plants of the soybean backcross (Essex×ZDD2315)×ZDD2315 was established and tested for their genetic variation, and then used to construct a genetic linkage map by using MAPMAKER 3.0. The genetic linkage map contained 250 SSR markers and one morphological marker, spanning 25 linkage groups (LG) at a total distance of 2 963.5 cM. Each LG contained 2 to 20 markers, with average distance being about 11.8 cM. The methods of composite interval mapping (CIM) and multiple interval mapping (MIM) of Win QTL Cartographer Version 2.5 were used for QTL mapping. With CIM, 18 QTLs conferring the contents of fat and fatty acid composition in soybean seed were mapped on nine LGs, i.e. B2, C1, D1b-1, D2, E, H-1, I, L and N-1, explaining 8.2%–39.3% of the total phenotypic variation, while with MIM nine QTLs were detected on six LGs, i.e. B2, C1, D1b-1, D2, H-1 and N-1, explaining 9.6%–34.5% of the total phenotypic variation. Of which seven QTLs, i.e. fat-1, pal-1, st-1, ole-1, lin-1, lin-4 and lio-2, were located on the same regions as that under CIM, while the other two, i.e. ole-4 and lin-5, were close to those under CIM. The other nine QTLs detected with CIM, but not common with MIM, need to be further verified. The number of major QTLs with large effect conferring the contents of fat and fatty acids appeared not as many as expected, while the minor QTLs with small effect accounted for a certain amount of the variation. Therefore, both major and minor QTLs should be considered in the improvement of fat quantity and quality in soybean seeds.

Key words: Soybean, Fat, Fatty acid composition, QTL mapping