Patterns of alleles amplified by 13 SSR markers.

Sweet sorghum is a cereal crop in the grass family belonging to the genus Sorghum bicolor L. Moench. It is known in its sugary juice that is accumulated in its stalk and efficient C4 photosynthetic pathway. Only few molecular genetic diversity studies of Ethiopian sweet sorghum have been carried out. Understanding the genetic diversity of plants is the basis for genetic improvement, effective conservation and efficient utilization of genetic resources. Therefore, the objective of this study was to evaluate the genetic diversity and population structure of Ethiopian sweet sorghum genotypes collected from major growing areas of Ethiopia. In the present study, thirteen SSR markers produced a total of 136 alleles across all the 91 sweet sorghum accessions with an average of 10.46 alleles per marker. The major allele frequency per marker ranged from 0.16 to 0.41 with an average of 0.25. The number of alleles per marker ranged from 6 to 15. The mean PIC value was 0.80. The pair-wise genetic differentiation among the five studied sweet sorghum populations ranged from 0.07 to 0.19. The highest Fst (0.19) and the lowest Fst (0.07) population differentiation were observed between sweet sorghum population of South Wollo and Oromia Liyu Zone, and North Shewa and East Gojam sweet sorghum populations, respectively. The analysis of gene flow across populations showed that the highest gene flow was recorded between North Shewa and East Gojam (2.879), whereas the least gene flow was observed between South Wollo and Oromia Liyu Zone (0.618). The analysis of molecular variance revealed that 16% variation was observed among populations and 84% variation has been observed within populations. Meanwhile, the STRUCTURE and UPGMA methods of clustering suggested that the sampled sweet sorghum populations were clustered into two main groups (K = 2). This comprehensive study of genetic diversity and population structure of sweet sorghum (Sorghum bicolor) in Ethiopia suggests that future sweet sorghum improvement and utilization strategies should take the magnitude and pattern of genetic diversity into consideration.

甜高粱（Sweet sorghum）是隶属于高粱属（Sorghum bicolor L. Moench）的禾本科谷类作物。其以茎秆中积累的含糖汁液以及高效的C4光合途径为显著特征。目前针对埃塞俄比亚甜高粱的分子遗传多样性研究相对匮乏。植物遗传多样性研究是开展遗传改良、有效保护及高效利用遗传资源的核心基础。因此，本研究旨在对从埃塞俄比亚主要种植区收集的埃塞俄比亚甜高粱种质的遗传多样性与群体结构进行评估。
本研究中，13个简单序列重复（SSR, Simple Sequence Repeat）标记在全部91份甜高粱种质中共扩增得到136个等位基因，平均每个标记可扩增出10.46个等位基因。各标记的主等位基因频率范围为0.16至0.41，平均值为0.25。单个标记的等位基因数量介于6至15之间，平均多态性信息含量（PIC, Polymorphism Information Content）值为0.80。5个供试甜高粱群体间的两两遗传分化系数（Fst）范围为0.07至0.19：其中南沃洛（South Wollo）与奥罗米亚利尤区（Oromia Liyu Zone）群体间的遗传分化系数最高（0.19），北舍瓦（North Shewa）与东戈贾姆（East Gojam）群体间的遗传分化系数最低（0.07）。群体间基因流分析结果显示，北舍瓦与东戈贾姆群体间的基因流最高（2.879），而南沃洛与奥罗米亚利尤区群体间的基因流最低（0.618）。分子方差分析（AMOVA, Analysis of Molecular Variance）表明，群体间遗传变异占总变异的16%，群体内遗传变异占总变异的84%。同时，STRUCTURE聚类与非加权组平均法（UPGMA, Unweighted Pair Group Method with Arithmetic Mean）聚类分析结果均显示，供试甜高粱群体可划分为2个主要类群（K=2）。
本项针对埃塞俄比亚甜高粱遗传多样性与群体结构的综合性研究表明，未来甜高粱的改良与利用策略应充分考量遗传多样性的水平与分布模式。