Diversity Analysis of Ethiopian Mustard Breeding Lines Using RAPD Markers

Ethiopian mustard (Brassica carinata A. Braun) is an oilseed crop less known to the other parts of the world. Utilization of the available germplasm of B. carinata for different breeding purposes requires information on genetic diversity. Random amplified polymorphic DNA (RAPD) was employed to characterize the genetic diversity of 22 B. carinata inbred lines derived from accessions collected from eight different geographic areas in Ethiopia and one from Sweden. Forty-three primers were used for amplification. The resulting RAPD pattern was analysed with respect to size and distribution of fragments, reproducibility, genetic diversity and informativeness of the marker for genotype specific amplification. In total, 371 bands were amplified of which 239 (65%) were polymorphic. Band size ranged from 300 to 4000 kb. The number of bands generated by each primer varied from 3 to 15 with an average of 8.6, while number of polymorphic bands varied from 1 to 12 with an average of 5.6. RAPD patterns were reliably reproducible between replicates. Genetic similarity (GS) calculated from the marker data using Jaccard`s similarity coefficient (JCS) ranged from 0.34 to 0.84. Using cluster analysis based on unweighted pair-group method with arithmetic average (UPGMA) and principal coordinate analysis (PCoA), the 21 Ethiopian inbred lines were grouped into three subgroups and the single genotype introduced from Sweden formed a separate group. The clustering pattern failed to show a clear correspondence between geographic and molecular diversities within the Ethiopian gene pool. Generally, RAPD differentiation was higher for the exotic genotype, thus formation of a gene pool distinct from the Ethiopian gene pool could be possible through introduction. Based on the genetic relatedness, selective parental combinations were earmarked as potential parents for the future breeding work. The RAPD assay generated genotype-specific products in 14 of the genotypes studied which could be used as DNA fingerprint for variety identification.

埃塞俄比亚芥（Brassica carinata A. Braun）是一种在全球其他地区鲜为人知的油料作物。若要将埃塞俄比亚芥的现有种质资源应用于各类育种目标，需先掌握其遗传多样性相关信息。本研究采用随机扩增多态性DNA（Random Amplified Polymorphic DNA, RAPD）标记技术，对22份埃塞俄比亚芥自交系的遗传多样性进行了表征：这些自交系分别源自埃塞俄比亚境内8个不同地理区域的种质，以及1份引自瑞典的种质。实验共使用43条引物进行扩增反应。随后，针对扩增产物的片段大小与分布、扩增重复性、遗传多样性水平，以及该标记用于基因型特异性扩增的信息性等维度，对所得RAPD图谱开展了分析。本研究总计扩增得到371条条带，其中239条（占比65%）具有多态性。条带大小介于300 kb至4000 kb之间。每条引物扩增得到的条带数为3至15条，平均为8.6条；而多态性条带数则为1至12条，平均为5.6条。重复实验间的RAPD图谱具备可靠的可重复性。基于Jaccard相似性系数（Jaccard's similarity coefficient, JCS）计算得到的遗传相似性（Genetic Similarity, GS）取值范围为0.34至0.84。采用非加权配对算术平均法（Unweighted Pair-group Method with Arithmetic Average, UPGMA）进行聚类分析，并结合主坐标分析（Principal Coordinate Analysis, PCoA），结果显示21份埃塞俄比亚本土自交系被划分为3个亚组，而引自瑞典的单份基因型则单独构成一个独立类群。聚类结果未能在埃塞俄比亚芥的本土种质库中呈现出地理多样性与分子多样性之间的明确对应关系。总体而言，外来引种基因型的RAPD分化程度更高，因此通过种质引入，有望构建出区别于埃塞俄比亚本土种质库的独立基因库。基于本次研究得到的遗传相关性数据，本研究筛选出了若干针对性的亲本组合，可作为未来育种工作的潜在亲本。本次RAPD检测在14份供试基因型中获得了基因型特异性扩增产物，此类产物可作为DNA指纹图谱，用于作物品种的鉴定。