Kim Sunggil, Bang Haejeen, Yoo Kil-Sun, Pike Leonard
Vegetable and Fruit Improvement Center, Department of Horticultural Sciences, Texas A&M University, Texas 77843, USA.
Mol Cells. 2007 Apr 30;23(2):192-7.
Bulb color in onions (Allium cepa) is an important trait whose complex inheritance mechanism involves epistatic interactions among major color-related loci. Recent studies revealed that inactivation of dihydroflavonol 4-reductase (DFR) in the anthocyanin synthesis pathway was responsible for the color differences between yellow and red onions, and two recessive alleles of the anthocyanidin synthase (ANS) gene were responsible for a pink bulb color. Based on mutations in the recessive alleles of these two genes, PCR-based markers for allelic selection were developed. In this study, genotype analysis of onions from segregating populations was carried out using these PCR-based markers. Segregating populations were derived from the cross between yellow and red onions. Five yellow and thirteen pink bulbs from one segregating breeding line were genotyped for the two genes. Four pink bulbs were heterozygous for the DFR gene, which explains the continuous segregation of yellow and pink colors in this line. Most pink onions were homozygous recessive for the ANS gene, except for two heterozygotes. This finding indicated that the homozygous recessive ANS gene was primarily responsible for the pink color in this line. The two pink onions, heterozygous for the ANS gene, were also heterozygous for the DFR gene, which indicated that the pink color was produced by incomplete dominance of a red color gene over that of yellow. One pink line and six other segregating breeding lines were also analyzed. The genotyping results matched perfectly with phenotypic color segregation.
洋葱（葱属）的鳞茎颜色是一个重要性状，其复杂的遗传机制涉及主要颜色相关基因座之间的上位性相互作用。最近的研究表明，花青素合成途径中二氢黄酮醇4-还原酶（DFR）的失活导致了黄洋葱和红洋葱之间的颜色差异，而花青素合酶（ANS）基因的两个隐性等位基因导致了粉色鳞茎颜色。基于这两个基因隐性等位基因的突变，开发了基于PCR的等位基因选择标记。在本研究中，使用这些基于PCR的标记对分离群体中的洋葱进行基因型分析。分离群体来自黄洋葱和红洋葱的杂交。对一个分离育种系中的5个黄色鳞茎和13个粉色鳞茎进行了这两个基因的基因分型。4个粉色鳞茎在DFR基因上是杂合的，这解释了该品系中黄色和粉色的连续分离。除了两个杂合子外，大多数粉色洋葱在ANS基因上是纯合隐性的。这一发现表明，纯合隐性ANS基因是该品系中粉色的主要原因。两个在ANS基因上杂合的粉色洋葱在DFR基因上也是杂合的，这表明粉色是由红色基因对黄色基因的不完全显性产生的。还分析了一个粉色品系和其他六个分离育种系。基因分型结果与表型颜色分离完全匹配。
