Selection of vigorous and fertile S-homo- and heterozygous tester clones from self-incompatible diploid potato, Solanum tuberosum L.

Abstract

For the selection of diploid (2n = 2x = 24) potato (Solanum tuberosum) genotypes that are useful for the molecular and genetic analysis of the phenomenon of gametophytic self-incompatibility, three different types of basic populations were investigated. These populations were derived from three primary dihaploid clones, G609, G254 and B16, which possessed the S-allele combinations S1S2, S1S3 and S3S4 respectively. In order to select highly vigorous, profusely flowering, fertile and tuberising progenies, three types of populations, derived from the above mentioned diploid genotypes, were screened for performance and classified for the expression of self-incompatibility. Although the selection for well defined S-genotypes was sometimes complicated due to the occurrence of pseudo-compatibility and of a self-compatibilising factor, the use of a combination of criteria, viz., Iso Electric Focusing (IEF), pollen tube growth in the styles and the extent of berry and seed set made the selection of sufficient representatives of all six types of S-heterozygotes (S1S2, S1S3, S1S4, S2S3, S2S4 and S3S4) possible. After evaluating the strength of the self-incompatibility reaction in these heterozygotes, those with high expression were selfed, and intercrossed within their S-allele incompatibility group through the method of counterfeit pollination. In these progenies, well-performing S-homozygotes (S1S1; S2S2; S3S3; S4S4) for all four S-alleles with high expression of self-incompatibility were selected. As a result, all possible S-homo- and heterozygous genotypes with a predictable type of self-incompatibility are available and maintained both vegetatively and as botanical seed. The development of this material has paved the way for more critical analysis of molecular factors involved in self-incompatibility in diploid potato.