Estudio genético comparativo entre las líneas de girasol T589 y LG-15, con alto contenido de beta-tocoferol en las semillas, y cartografiado del gen responsable del carácter

LG-15 and T589 are sunflower lines with a modified tocopherol profile that includes increased levels of beta-tocopherol. The objectives of the present research are: to conduct a comparative genetic study of the increased beta-tocopherol concentration in both lines, and to identify molecular markers linked to the gene(s) responsible for the modified trait, and to map this gene(s) on the sunflower genetic map. For the genetic study, reciprocal crosses between plants of both high beta-tocopherol lines T589 and LG-15 were made in 2003. Some crosses and backcrosses to T589 seed generations were produced in the same environment in 2004 and analysed for tocopherol profile by high performance liquid chromatography (HPLC). The results indicated a strong environmental effect on the increased levels of beta-tocopherol in LG-15 and T589. The comparison of individual plant means and standard errors of individual plant means for the F2 and Bc1F1 generations with those in the non-segregating parental and F1 generations indicated no transgressive segregation for beta-tocopherol concentration in F2 or BC1F1 seeds. These results suggested that increased beta-tocopherol concentration in both lines is the result of genetic alterations at the same locus, named Tph1. Genetic mapping of the Tph1 gene was conducted evaluating a population derived from the cross between plants of the line T589 and the line CAS-12, with standard seed tocopherol profile. F2 and F3 progenies were evaluated phenotypically for tocopherol profile. A molecular study was conducted. Bulked segregant analysis (BSA) identified two SSR markers on linkage group (LG) 1 of the sunflower genetic map linked to Tph1. A large linkage group was constructed by genotyping additional SSR and INDEL (insertion-deletion polymorphisms) markers from LG 1.The availability of tightly linked PCR-based markers and the location of the Tph1 gene on the sunflower genetic map will be useful for marker-assisted selection in sunflower and provides a basis for the physical mapping and positional cloning of this gene