Cytoplasmic Male Sterility in Russian Dandelion

Russian dandelion (Taraxacum kok-saghyz) is a candidate species for introducing natural rubber production into North America, and its domestication is currently underway to create an economically viable crop. Development of hybrid cultivars is essential to maximize the yield potential of the species, and cytoplasmic male sterility (CMS) is an important breeding tool that can facilitate this process. Male sterility was discovered in two fullsib russian dandelion families, and additional crosses were performed to create F-2, F-3, and backcross generations to assess inheritance of the phenotype. A sterility-inducing cytoplasm (S) that could be restored to fertility by a dominant allele at a single nuclear restorer of fertility (R-f) gene and a fertility-inducing cytoplasm (F) were identified. Characteristics of the CMS system were 1) (S)rfrfx(F)rfif crosses produced only sterile progeny, 2) crosses where the female parents were (F) produced only fertile progeny, and 3) segregation was observed only when the maternal parent had (S). Sterility was not stable in all plants; some with sterility-inducing cytoplasm produced small amounts of pollen or formed both sterile and fertile flowers simultaneously. On the basis of seasonal differences in the frequency of partially sterile plants, sterility was stable at low temperatures and unstable at high temperatures. This germplasm can be of central importance for development of stable CMS lines for hybrid production.