芝麻染色体核型及似近系数分析

芝麻（Sesamum indicum L.）是世界上最古老的油料作物之一,在植物进化中具有重要地位。以8个二倍体栽培种、4个四倍体栽培种以及2个野生种S.radiatum Schum ＆ Thonn和S.schinzianum Asch.为材料,比较分析了芝麻不同种的核型特征。结果表明：栽培种与野生种的核型及结构具有明显的差异,栽培种的着丝点类型有m、sm和st,臂比均值（AAR）为2.11–2.25,核型不对称系数（AKC）为66.05%–66.99%,核型分2B、3A和3B三类;野生种S.radiatum和S.schinzianum仅有M和m两种着丝点类型,AAR值分别为1.09和1.08,AKC为52.12%和51.68%,核型分1B和1A两类。核型聚类结果表明,野生种与栽培种的似近系数范围介于0.027–0.107之间,亲缘关系较远;与地理来源相比,种皮颜色能够显示不同种间的进化地位,推测芝麻进化方向为野生种→栽培种黑芝麻→栽培种白芝麻。

Analysis of Sesame Karyotype and Resemblance-near Coefficient

Sesame is one of the oldest oil crops and has an important place in plant evolution. We compared the chromosome types and karyotypes of 8 diploid and 4 tetraploid materials of Sesamum indicum L. and 2 wild species, S. radiatum Schum ＆ Thonn and S. schinzianum Asch. The species significantly differed in karyotype and chromosome variables. S. indicum centromere types were m, sm and st; the average arm ratio （AAR） was 2.11 to 2.25, asymmetric karyotype coefficients （AKC） were 66.05% to 66.99%, and the karyotypes belonged to 2B, 3A and 3B. However, S. ra- diatum and S. schinzianum exhibited only M and m centromere types; the AAR was 1.09 and 1.08, respectively; AKC was 52.12% and 51.68%, respectively; and karyotypes were 1B and 1A, respectively. Karyotype clustering revealed that the resemblance-near coefficient between S. indicum and the wild species was 0.027 to 0.107, which indicates a remote genetic relationship. Furthermore, seed coat color was more suitable for sesame evolution estimation than was geographic origin. The evolution direction of sesame was from wild species to black cultivars and then white cultivars.