Hybridization of Lycium qingshuiheense and L. ningxiaense revealed using morphological, SSR markers, and chloroplast genomic data

Background: Interspecific hybridization is a common natural phenomenon that plays a crucial role in the formation and maintenance of species. In recent years, the origins of hybrids have been extensively investigated across various plant groups. Lycium has received relatively little attention regarding the occurrence of natural hybrids, despite its economic and ecological significance. In this study, hybridization of L. qingshuiheense and L. ningxiaense was identified based on morphological traits, nuclear simple sequence repeat (SSR) markers, and chloroplast genomic data. Results: We selected 90 specimens of four species across their distributional ranges to examine 12 morphological traits and characterize clusters with distinct phenological traits. Similarly, we genotyped 67 individuals from four species across 10 populations using 10 SSR markers. The morphological analyses revealed a clear division between individuals of L. barbarum and L. ruthenicum while most individuals of L. qingshuiheense and L. ningxiaense were distributed between L. barbarum and L. ruthenicum . The genetic clusters were consistent with the morphological clusters. However, most of the L. ningxiaense samples comprised F1 hybrids, while L. qingshuiheense showed a distinct genetic pattern compared to that of L. ningxiaense due to backcross or interspecific genetic infiltration. Among the four Lycium species, the composition and structureal features of chloroplast genomes from L. qingshuiheense and L. ningxiaense were identical and clustered on a branch with L. ruthenicum in the phylogenetic tree. Conclusion: Combining the morphological, SSR markers, and cp genomes analysis, we affirmed that L. qingshuiheense and L. ningxiaense are hybrids originating from crossing L. ruthenicum (♀) and L. barbarum (♂). This study elucidated the origin of two Lycium species, which contributes to our understanding of the evolutionary mechanisms underlying interspecific hybridization in Lycium . Furthermore, it provides a scientific foundation for the development, utilization, and improvement of Lycium varieties.