Availability Evaluation and Application of MNP (Multiple Nucleotide Polymorphism) Markers in Variety Identification of Chrysanthemum

In China, PBR (Plant Breeder’s Right) applications of chrysanthemum rank first among all of the applications of ornamental crops in China due to the plant’s significant ornamental, edible, and medicinal values. However, issues of variety infringement and disputes have become increasingly prominent, and traditional molecular markers are difficult to use due to the high heterozygosity and complex ploidy of chrysanthemum. Our study explored the availability of MNP (Multiple Nucleotide Polymorphism) markers in this regard. In total, 30 representative varieties of five types were selected for the screening of MNPs, and another 136 varieties were selected for validation of the screened MNPs. Based on ddRAD-seq (Double Digest Restriction site-associated DNA sequencing) of the 30 varieties, 26,147 SNPs were screened for genetic analysis，and 487 MNPs were screened with a length from 139 to 274 bp, an average of 6.6 SNPs individually, and a repeatability rate of 99.73%. Among the 487 MNPs, 473 MNP markers were found to cover all 27 chromosomes of chrysanthemum. Performance of our MNPs in the 136 varieties was similar to those in the 30 varieties, where the average Ho (observed heterozygosity) was 71.48%, and the average DP (discriminative power) was 82.77%, preliminarily indicating the stability of the 487 MNPs. On the other hand, clustering results based on the 487 MNPs were also generally consistent with those based on the 26,147 SNPs, as well as those based on phenotypic traits, and initial grouping, likewise, further indicating the robust capability of our MNPs in variety discrimination, which is similar to their correspondence with numerous SNPs. Therefore, our MNP markers have great potential in the accurate and rapid identification of chrysanthemum varieties, and, accordingly, in fostering breeding innovation and promoting chrysanthemum marketing.