Genotyping of Jujube (Ziziphus spp.) Germplasm in New Mexico and Southwestern Texas

Authors: SAPKOTA, DIKSHYA - New Mexico State University; Zhang, Dapeng; Park, Sunchung - Sun; Meinhardt, Lyndel; YAO, SHENGNGRUI - New Mexico State University

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/17/2023
Publication Date: 6/21/2023
Citation: Sapkota, D., Zhang, D., Park, S., Meinhardt, L.W., Yao, S. 2023. Genotyping of Jujube (Ziziphus spp.) Germplasm in New Mexico and Southwestern Texas. Plants. 12:2405. https://doi.org/10.3390/plants12132405.
DOI: https://doi.org/10.3390/plants12132405

Interpretive Summary: Jujube (Ziziphus jujuba Mill.) is an economically important fruit tree with outstanding adaptability to marginal lands and a broad range of climate conditions. This fruit crop is indigenous to China but is becoming increasingly popular in the US. There are more than one hundred jujube cultivars in the United States. One problem with the jujube community is lack of reliable method for cultivar identification, which affects the effective management and use of jujube germplasm. In our present study, we used 94 Single Nucleotide Polymorphism (SNP) markers to assess genetic integrity of US jujube cultivars. A total of 186 jujube trees from Las Cruces, Gila, Silver City, Tucumcari in New Mexico, and Tornillo and Fabens from Southwestern Texas were analyzed. The result revealed a significant amount of genetic redundancy resulting in fourteen duplicate groups with a total of 48 accessions. Further analysis shows that the US jujube cultivars can be grouped into two major clusters. The first cluster includes mostly the introduced cultivars, whereas the second group comprises of wild jujube (Ziziphus spinosa). Our results also revealed unique jujube populations in the Fabens and Tornillo area and in NMSU Tucumcari Center. These results will be used by jujube researchers and jujube industry to improve the accuracy and efficiency of germplasm management and quality control in and nursery propagation.

Technical Abstract: The Chinese Jujube (Ziziphus jujuba Mill.) is an economically important fruit tree with outstanding adaptability to marginal lands and a broad range of climate conditions. There are more than one hundred jujube cultivars in the United States and most of them were introduced from China. Accurate cultivar identification is essential for effective management of jujube germplasm. In our present study, ninety-four highly polymorphic Single Nucleotide Polymorphism (SNP) markers were used to assess genetic integrity of US jujube cultivars. A total of 186 leaf samples were collected from Las Cruces, Gila, Silver City, Tucumcari in New Mexico, and Tornillo and Fabens from Southwestern Texas. Multi-locus matching of SNP profiles revealed a significant rate of redundancy in this germplasm. Of the 186 examined accessions, fourteen synonymous groups, involving forty-eight samples, were detected. Each synonymous group contained two to eight accessions. Model-based Bayesian clustering revealed two germplasm groups, and their core members showed a significant genetic differentiation (Fst = 0.172, P <0.001). A neighbor-joining phylogenetic tree depicted compatible result with that of the STRUCTURE analysis. The result suggested that the US jujube cultivars can be grouped into two major clusters. The first cluster includes mostly the introduced cultivars. The second cluster comprised of wild jujube (Ziziphus spinosa) and their putative hybrids with cultivated germplasm. The results demonstrated a unique jujube population in the Fabens and Tornillo area and a semi-naturalized population at NMSU Tucumcari Center. These results will guide growers and researchers in jujube cultivar identification and nursery propagation.