Genetic diversity analysis of Tibetan turnip(Brassica rapa L. ssp. rapifera Matzg) revealed by morphological, physiological, and molecular marker

Turnip of the Brassica genus is a traditional crop that is widely cultivated in farming and farming-pastoral regions in Tibet. It is mostly utilized as animal fodder and vegetable around the Tibetan plateau. Given their high altitudes and variable climate types, different regions of Tibet plateau are home to a rich diversity of turnip. A mass of studies related to genetic diversity of highland crops have been carried out in recent years. However, the genetic diversity of Tibetan turnip remains to be elucidated to date. In this study, we performed morphological investigation and simple sequence repeat analysis, to characterize the genetic diversity and population structure of Tibetan turnips. Then, we explored the physiological response of seedlings under low-temperature stress. We also performed a field experiment, to identify clubroot-resistant cultivars. Results showed significant differences in phenotypic traits among different sources of 25 Tibetan turnip accessions. The genetic similarity dendrogram showed that the genetic distance in the 25 accessions was between 0.61 and 0.77. When the similarity coefficient is between 0.644 and 0.646, they can be divided into three subgroups, and they presented a certain relationship between geographical origin and its genetic distance. The central diffusion location suggests that the genetic diversity and population structure of these Tibetan turnip accessions are consistent with their geographical origin. In addition, the potential clubroot resistance accession is 156-13, and the chilling resistance accessions are 156-8 and 156-10. These results suggest the Tibetan turnip is a valuable resource for the genetic analysis and breeding of new clubroot-resistant cultivars.