In vitro plant regeneration from ovules of Taraxacum officinale and Taraxacum koksaghyz

Taraxacum koksaghyz, the Russian dandelion, produces latex in its taproots and is an alternative to Hevea brasiliensis as a source for rubber. Studying the inheritance of rubber content and yield as well as breeding of T. koksaghyz could strongly benefit from haploid or doubled haploid techniques. Therefore, this study aimed at establishing the conditions to produce haploid and/or double haploid T. koksaghyz plants. This study focused on gynogenesis because analysis of microsporogenesis showed that very small (young) inflorescences already contain mature pollen and that the development of the microspores is not synchronous in different flowers in one inflorescence. Therefore, a surface disinfection protocol, culture media, and culture conditions were established resulting in shoot formation from ovules. Diploid and triploid Taraxacum officinale were also included in the experiments. Depending on the genotype, 0 to 2.6% of the ovules regenerated shoots via callus. These shoots could be rooted and acclimatized to greenhouse conditions without losses. Eleven plants from ovule cultures were analysed for their ploidy level and compared genetically to the donor material using simple sequence repeats (SSRs) to confirm their origin from either haploid or diploid/triploid donor tissues. All regenerated plants had the same ploidy level and were heterozygous at the same loci as their respective donor plants, and thus originated from somatic tissue. Key words: Flow cytometry, gynogenesis, haploids, microsatellite markers, ovule culture, Russian dandelion.