Paternity analysis using SSR markers reveals that the anthocyanin-rich tea cultivar 'Ziyan' is self-compatible

Most tea plants (Camellia sinensis) are self-incompatible. Self-incompatibility is critical for preventing inbreeding depression and maintaining genetic diversity, but it can hinder breeding and genetic studies. Originally, the propose of this study was to identify fathers of 16 elite F-1 individuals derived from open-pollinated seeds of an anthocyanin-rich tea cultivar 'Ziyan'. In order to achieve this, 41 candidate parents and 16 F-1 individuals were genotyped with 15 polymorphic SSR markers. Using exclusion and likelihood methods, fathers of 12 individuals were identified at 95% level of confidence. Surprisingly, the results showed that eight individuals were from self crossing of 'Ziyan'. Additional 36 SSR markers were used to further confirm selfing and the results were consistent, demonstrating that 'Ziyan' is self-compatible. As expected, the degrees of heterozygosity of the eight selfing individuals were significantly lower than 'Ziyan' and other tea accessions. This is the first report of a clonal cultivar of C. sinensis being self-compatible under open-pollination conditions and verified using DNA based markers. Therefore, 'Ziyan' and its selfing offspring will be valuable materials for both genetic studies and breeding in C. sinensis.