SSR molecular markers development and fingerprints construction in kohlrabi （Brassica oleracea var. gongylodes L.）

【Objective】To develop SSR molecular markers and construct fingerprints of kohlrabi（Brassica oleracea var. gongylodes L.），in order to understand genetic diversity difference and genetic relationship of kohlrabi varieties at the molecular level and to provide reference for breeding materials selection of kohlrabi.【Method】Based on transcriptomic data，SSR markers were developed and their distribution characteristics were analyzed by bioinformatics methods. PCR method was used to detect validity and polymorphism of SSR primers to screen polymorphic primers that were used to analyze the relationship among 18 kohlrabi materials and construct fingerprints.【Result】A total of 196642 unigenes were obtained by transcriptome sequencing，of which the number of 85468 unigenes contained SSR sites，accounting for 43.46%. The dominant type among the SSR sites was mononucleotides（44.74%），followed by dinucleotides（26.37%） and trinucleotides（27.35%）. The SSR site analysis revealed 112 repeat motifs，of which mononucleotide repeat motifs were mainly A/T（44.16%），and dinucleotide repeat motifs were mainly AG/CT（18.11%）. Through PCR，29 pairs of primers were screened，which could amplify 86 clear bands of high polymorphism and with an average amplification of 3.28 primers per pair. Clustering analysis of 18 kohlrabi materials was conducted with polymorphic bands and the results showed that the kohlrabi materials were divided into 5 categories at the genetic distance of 0.61. At the same time，DNA fingerprint database of 18 kohlrabi materials were constructed based on polymorphic bands and the corresponding identification two-dimensional code was established.【Conclusion】Twenty-nine SSR molecular marker of kohlrabi are developed in this study，and kohlrabis fingerprint based on these molecular marker can be applied in diversity analysis of germplasm resources，variety breeding，development and utilization of kohlrabis.