Identification of a codominant scar marker linked to the seedlessness character in grapevine

The variety Vitis vinifera cv Sultanine presents a type of seedlessness in which fertilization occurs but seeds subsequently fail to develop. It has been suggested that this trait might be controlled by three complementary recessive genes regulated by a dominant gene named I. Bulk segregant analysis was used to search for random amplified polymorphic DNA (RAPD) markers linked to the I gene in progeny obtained by crossing two partially seedless genotypes. One hundred and forty decamer primers were screened using bulks obtained by pooling the DNA of extreme individuals from the phenotypic distribution. We identified two RAPD markers which appeared tightly linked to I(at 0.7 and 3.5 cM respectively). The closest marker was used to develop a codominant SCAR (sequence characterized amplified region), named SCC8. This latter marker appeared of great value either to exclude from the progeny potentially seeded individuals or to select for seedless individuals. Indeed, all the seeded individuals of the progeny were found to be homozygous scc8(-)/scc8(-), and all the individuals homozygous SCC8(+)/SCC8(+) were seedless. Moreover, this marker was successfully applied to other natural seedless varieties where codominance persisted. SCC8 was also used to dissect more precisely the genetics of seedlessness. ANOVA analysis indicated that this SCAR marker accounted for at least 64.9% of the phenotypic variation of the seed's fresh weight and for at least 78.7% of the phenotypic variation of the seed's dry matter. These results confirmed the presence of a major gene, and also the existence of other complementary recessive genes, controlling the expression of seedlessness.