Prada Dario, Romagosa Ignacio, Ullrich Steven E, Molina-Cano Jose L
Centre UdL-IRTA, Av. Alcalde Rovira Roure 191, E-25198 Lleida, Spain.
J Exp Bot. 2005 Jan;56(409):47-54. doi: 10.1093/jxb/eri005. Epub 2004 Oct 22.
Genetic control of seed dormancy in barley (Hordeum vulgare L.) has mostly been described in terms of quantitative variation. Although some molecular markers for dormancy QTL have been identified, the corresponding genes involved in the regulation of the process have not been cloned. Induced barley mutants may constitute useful material to study the physiology and genetics of seed dormancy. The objective of this study was to identify the genetic control of this trait in a mutant (TL43) produced in the barley cv. Triumph. This mutant was selected for reduced dormancy and reduced sensitivity to abscisic acid (ABA). Two sets of F6 barley lines were selected for high and low levels of dormancy from a cross between the original dormant parent and the sodium azide-induced non-dormant TL43 mutant. Unexpectedly, given the near-isogenic nature of these two genotypes, polymorphism was detected for an SSR located in the centromeric region of chromosome 6(6H) out of a total of 92 molecular markers evenly distributed along the genome. Fortunately, upon three cycles of intensive divergent selection, every dormant and non-dormant F5 line consistently showed the genotype for this region identical to Triumph and TL43, respectively. Based on the mutagenic effect presumably attributed to sodium azide, mostly single point mutations, it cannot be clearly established if such extensive genomic variation on chromosome 6(6H) is due to the mutagenic treatment or may be an introgression from an unknown source. The means that could originate such heterogeneity are discussed; however, regardless of its origin, this genomic region shows a strong association with the expression of seed dormancy and provides an additional genetic locus for further studies of the mechanistic basis of this complex trait. In addition, since TL43 shows reduced sensitivity to ABA, the response to this hormone was determined on the F6 seed from the two sets of selected F5 lines. The results confirmed that the initial level of dormancy in the seed lot is the most important factor in determining ABA sensitivity.
大麦（Hordeum vulgare L.）种子休眠的遗传控制大多是从数量变异的角度进行描述的。尽管已经鉴定出一些与休眠数量性状位点（QTL）相关的分子标记，但参与该过程调控的相应基因尚未克隆。诱导产生的大麦突变体可能是研究种子休眠生理和遗传的有用材料。本研究的目的是确定在大麦品种Triumph中产生的一个突变体（TL43）中该性状的遗传控制。该突变体因休眠降低和对脱落酸（ABA）敏感性降低而被选育。从原始休眠亲本与叠氮化钠诱导的非休眠TL43突变体的杂交后代中，选择了两组F6大麦品系，分别具有高休眠水平和低休眠水平。出乎意料的是，鉴于这两种基因型近乎同基因的性质，在总共92个均匀分布于基因组的分子标记中，位于6号染色体（6H）着丝粒区域的一个简单序列重复（SSR）检测到了多态性。幸运的是，经过三轮强化的分化选择，每个休眠和非休眠的F5品系在该区域的基因型分别始终与Triumph和TL43相同。基于可能归因于叠氮化钠的诱变效应，主要是单点突变，尚不能明确确定6号染色体（6H）上如此广泛的基因组变异是由于诱变处理还是可能来自未知来源的基因渗入。文中讨论了可能导致这种异质性的途径；然而，无论其起源如何，该基因组区域与种子休眠的表达显示出强烈的关联，并为进一步研究这一复杂性状的机制基础提供了一个额外的遗传位点。此外，由于TL43对ABA的敏感性降低，对两组选定F5品系的F6种子进行了对该激素的反应测定。结果证实，种子批次的初始休眠水平是决定ABA敏感性的最重要因素。
