North American soybean breeders have successfully developed a large number of elite cultivars with diverse maturity groups (MG) from a small number of ancestral landraces. To understand molecular and genetic basis underlying the large variation in their maturity and flowering times, we integrated pedigree and maturity data of 166 cultivars representing North American soybean breeding. Network analysis and visualization of their pedigree relationships revealed a clear separation of southern and northern soybean breeding programs, suggesting that little genetic exchange occurred between northern (MG 0-IV) and southern cultivars (MG V-VIII). We also analyzed the transcript sequence and expression levels of four major maturity genes (E1 to E4) and revealed their allelic variants in 75 major ancestral landraces and milestone cultivars. We observed that e1-as was the predominant e mutant allele in northern genotypes, followed by e2 and e3. There was no allelic variation at E4. Transcript accumulation of the e2 mutant allele was significantly reduced, which might be caused by its premature stop codon triggering the nonsense-mediated mRNA decay pathway. The large DNA deletion generating the e3 mutant allele also created a gene fusion transcript. The e alleles found in milestone cultivars were traced through pedigrees to their ancestral landraces and geographic origins. Our analysis revealed an approximate correlation between dysfunctional alleles and maturity groups for most of the 75 cultivars. However, single e mutant alleles and their combinations were not sufficient to fully explain their maturity diversity, suggesting that additional genes/alleles are likely involved in regulating maturity time.

中文翻译：

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北美南部和北部大豆育种计划的遗传分离及其在四个成熟位点的相关等位基因变异。

北美大豆育种者已经从少数祖先的地方品种中成功地开发出了具有不同成熟群体（MG）的大量优良品种。为了了解其成熟度和开花时间差异很大的分子和遗传基础，我们整合了代表北美大豆育种的166个品种的谱系和成熟度数据。网络分析和他们的血统关系的可视化显示，南部和北部大豆育种计划明显分开，这表明北部（MG 0-IV）和南部品种（MG V-VIII）之间几乎没有基因交换。我们还分析了四个主要成熟基因（E1至E4）的转录序列和表达水平，并揭示了它们在75个主要祖先地方品种和里程碑品种中的等位变体。我们观察到e1-as是北部基因型中主要的e突变等位基因，其次是e2和e3。E4处没有等位基因变异。e2突变体等位基因的转录物积累显着减少，这可能是由于其提前终止密码子触发了无义介导的mRNA衰变途径所致。产生e3突变体等位基因的大DNA缺失也产生了基因融合转录本。在里程碑品种中发现的e等位基因通过谱系追溯到其祖先的地方品种和地理起源。我们的分析显示，对于75个品种中的大多数，功能障碍的等位基因与成熟组之间存在近似的相关性。但是，单个e突变等位基因及其组合不足以充分说明其成熟度多样性，