Somatic embryogenesis from thin epidermal layers in sunflower and chromosomal regions controlling the response

Somatic embryogenesis of sunflower recombinant inbred lines from the cross ‘PAC-2’ × ‘RHA-266’ was investigated and three QTLs were resolved for the number of embryogenic explants per 100 explants cultured. In order to increase the resolution in our mapping of the QTL regions, two consistently highly embryogenic lines ‘LR35’ and ‘C40’ that have alleles with positive effects at all three loci were crossed to a poorly embryogenic line ‘C149’ having alleles with negative effects at these three QTLs. The genotypes of F2 plants of both crosses were determined using a large number of AFLP and some SSR markers and two linkage maps were constructed. Based on the marker profile at QTL regions, 16 F2 plants, 9 presenting QTLs expected to produce F3 families with high and 7 with low expected embryogenic responses, were selected and somatic embryogenesis of F3 families was studied. In 14 out of 16 cases the phenotype of F3 families agreed with the genotype of their respective F2 plants. Therefore, these three QTLs accounted for most of the embryogenic variations. This study enabled the localization of the QTL regions to much shorter intervals and the identification of four AFLP markers on linkage groups 5 and 13 closely linked to somatic embryogenesis potential.