Wang Ming Li, Tonnis Brandon, Li Xianran, Morris John Bradly
Plant Genetic Resources Conservation Unit, USDA-ARS, 1109 Experiment Street, Griffin, GA 30223, USA.
Wheat Health, Genetics, and Quality Research, USDA-ARS, 291 Clark Hall, Pullman, WA 99164, USA.
Plants (Basel). 2023 Mar 13;12(6):1294. doi: 10.3390/plants12061294.
Sesame is one of the important oilseed crops in the world. Natural genetic variation exists in the sesame germplasm collection. Mining and utilizing the genetic allele variation from the germplasm collection is an important approach for seed quality improvement. The sesame germplasm accession, PI 263470, which has a significantly higher level of oleic acid (54.0%) than the average (39.5%), was identified by screening the entire USDA germplasm collection. The seeds from this accession were planted in a greenhouse. Leaf tissues and seeds were harvested from individual plants. DNA sequencing of the coding region of the fatty acid desaturase gene () confirmed that this accession contained a natural mutation of G425A which may correspond to the deduced amino acid substitution of R142H leading to the high level of oleic acid, but it was a mixed accession with three genotypes (G/G, G/A, and A/A at the position). The genotype with A/A was selected and self-crossed for three generations. The purified seeds were used for EMS-induced mutagenesis to further enhance the level of oleic acid. A total of 635 M plants were generated from mutagenesis. Some mutant plants had significant morphological changes including leafy flat stems and others. M seeds were used for fatty acid composition analysis by gas chromatography (GC). Several mutant lines were identified with high oleic acid (70%). Six M mutant lines plus one control line were advanced to M or M generations. Their high oleate traits from M or M seeds harvested from M or M plants were further confirmed. The level of oleic acid from one mutant line (M 915-2) was over 75%. The coding region of was sequenced from these six mutants, but no mutation was identified. Additional loci may contribute to the high level of oleic acid. The mutants identified in this study can be used as breeding materials for sesame improvement and as genetic materials for forward genetic studies.
芝麻是世界上重要的油料作物之一。芝麻种质资源库中存在自然遗传变异。从种质资源库中挖掘和利用遗传等位基因变异是提高种子品质的重要途径。通过对美国农业部整个种质资源库进行筛选，鉴定出芝麻种质PI 263470，其油酸含量（54.0%）显著高于平均水平（39.5%）。将该种质的种子种植在温室中。从单株植物上收获叶片组织和种子。对脂肪酸去饱和酶基因（）编码区进行DNA测序，证实该种质含有G425A的自然突变，这可能对应于推导氨基酸R142H的替换，从而导致油酸含量高，但它是一个具有三种基因型（该位置为G/G、G/A和A/A）的混合种质。选择A/A基因型并自交三代。纯化后的种子用于甲基磺酸乙酯（EMS）诱变，以进一步提高油酸含量。诱变共产生了635株M1代植株。一些突变植株有明显的形态变化，包括叶片扁平的茎等。M2代种子用于气相色谱（GC）脂肪酸组成分析。鉴定出几个油酸含量高（70%）的突变系。六个M2代突变系加一个对照系进入M3或M4代。从M3或M4代植株收获的M3或M4代种子的高油酸性状得到进一步证实。一个突变系（M915-2）油酸含量超过75%。对这六个突变体的编码区进行测序，但未发现突变。其他位点可能导致油酸含量高。本研究中鉴定出的突变体可作为芝麻改良育种材料和正向遗传学研究的遗传材料。
