Production of inbred progenies of diploid potatoes using an S-locus inhibitor (Sli) gene, and their characterization

To develop inbred lines from self-incompatible, cultivated diploid potatoes , an S-locus inhibitor (Sli) gene derived from a self-compatible variant of a wild potato species, Solanum chacoense, was incorporated into various cu ltivated diploid potatoes. The progeny was selfed twice by the action of th e Sli gene to obtain 74 S-2 inbred clones belonging to 8 families. More tha n 40% of them were either non-flowering or pollen sterile. Among the pollen fertile clones, self-compatible clones occurred with a much lower frequenc y (20.9%) than expected (83.3%). The result demonstrated that self-compatib ility was introduced and expressed in the gene pool of cultivated diploid p otatoes by an action of the Sli gene, although serious inbreeding depressio n associated with selfing occurred. The genotypes of S-2 inbreds were surve yed using 46 S. chacoense - specific RFLP (restriction fragment length poly morphism) markers covering the whole potato genome. More than half of the m arkers (67.4%) showed distorted segregation. Particularly, all markers on c hromosome 12 were overrepresented in the S-2 inbreds. This confirms our ear lier finding that the Sli gene locates on chromosome 12 and the alleles lin ked with this gene are preferentially transmitted because of its essential requirement for selfing.