Sorghum Research Institute, Liaoning Academy of Agricultural Sciences, Shenyang, Shenhe, China.
Institute of Crop Germplasm Resources, Jilin Academy of Agricultural Sciences, Gongzhuling, Kemaoxi Street, China.
PeerJ. 2024 May 27;12:e17438. doi: 10.7717/peerj.17438. eCollection 2024.
The identification and analysis of allelic variation are important bases for crop diversity research, trait domestication and molecular marker development. Grain tannin content is a very important quality trait in sorghum. Higher tannin levels in sorghum grains are usually required when breeding varieties resistant to bird damage or those used for brewing liquor. Non-tannin-producing or low-tannin-producing sorghum accessions are commonly used for food and forage. and , two important cloned genes, regulate tannin biosynthesis in sorghum, and mutations in one or two genes will result in low or no tannin content in sorghum grains. Even if sorghum accessions contain dominant and , the tannin contents are distributed from low to high, and there must be other new alleles of the known regulatory genes or new unknown genes contributing to tannin production.
The two parents 8R306 and 8R191 did not have any known recessive alleles for and , and it was speculated that they probably both had dominant and genotypes. However, the phenotypes of two parents were different; 8R306 had tannins and 8R191 had non-tannins in the grains, so these two parents were constructed as a RIL population. Bulked segregant analysis (BSA) was used to determine other new alleles of and or new Tannin locus. and full-length sequences and tannin contents were detected in wild sorghum resources, landraces and cultivars.
We identified two novel recessive and alleles and four recessive alleles, named as , , , and . These recessive alleles led to loss of function of Tan1 and Tan2, and low or no tannin content in sorghum grains. The loss-of-function alleles of and were only found in Chinese landraces, and other alleles were found in landraces and cultivars grown all around the world. and were detected in foreign landraces, Chinese cultivars and foreign cultivars, but not in Chinese landraces.
These results implied that and recessive alleles had different geographically distribution in the worldwide, but not all recessive alleles had been used in breeding. The discovery of these new alleles provided new germplasm resources for breeding sorghum cultivars for food and feed, and for developing molecular markers for low-tannin or non-tannin cultivar-assisted breeding in sorghum.
等位基因变异的鉴定和分析是作物多样性研究、性状驯化和分子标记开发的重要基础。谷物中单宁含量是高粱的一个非常重要的品质性状。在培育抗鸟害或用于酿造酒的品种时，高粱籽粒中单宁含量通常要求较高。非产单宁或低产单宁的高粱品系通常用于食品和饲料。Tan1 和 Tan2 是两个重要的克隆基因，调节高粱中单宁的生物合成，一个或两个基因的突变会导致高粱籽粒中单宁含量降低或缺失。即使高粱品系含有显性的 Tan1 和 Tan2，单宁含量也从低到高分布，并且一定有其他新的已知调控基因的等位基因或新的未知基因参与单宁的产生。
亲本 8R306 和 8R191 没有任何已知的 Tan1 和 Tan2 隐性等位基因，推测它们可能都具有显性的 Tan1 和 Tan2 基因型。然而，两个亲本的表型不同；8R306 的籽粒中有单宁，8R191 的籽粒中没有单宁，因此这两个亲本被构建为一个 RIL 群体。利用 bulked segregant analysis (BSA) 来确定 Tan1 和 Tan2 或新的 Tannin 基因座的其他新等位基因。对野生高粱资源、地方品种和栽培品种进行了 Tan1 和 Tan2 全长序列和单宁含量的检测。
我们鉴定了两个新的隐性 Tan1 和 Tan2 等位基因和四个隐性 Tan1 等位基因，分别命名为 、 、 、 。这些隐性等位基因导致 Tan1 和 Tan2 功能丧失，高粱籽粒中单宁含量降低或缺失。和 的失活等位基因仅在中国地方品种中发现，而其他等位基因在世界各地的地方品种和栽培品种中发现。和 在国外地方品种、中国品种和国外品种中都有检测到，但在中国地方品种中没有检测到。
这些结果表明，在全世界范围内，和 的隐性等位基因在地理上的分布不同，但并非所有隐性等位基因都被用于育种。这些新等位基因的发现为培育用于食品和饲料的高粱品种以及开发高粱低单宁或无单宁品种辅助育种的分子标记提供了新的种质资源。
