Department of Plant Biology, Rutgers University, New Brunswick, New Jersey, United States of America.
PLoS One. 2024 Jul 25;19(7):e0307326. doi: 10.1371/journal.pone.0307326. eCollection 2024.
Big-bracted dogwoods are popular ornamental trees known for their beautiful spring blooms with showy bracts and four-season appeal. The two most widely grown species are Cornus florida and Cornus kousa, native to Eastern North America and East Asia. Despite their horticultural prominence, there is little information available regarding genetic diversity, population structure, relatedness, and subspecies origins of dogwood cultivars. In this study, 313 cultivars, wild-collected plants, and Rutgers University breeding selections, focusing on C. florida, C. kousa, and interspecific hybrids, were genotyped using restriction-site associated DNA sequencing (RADseq) generating thousands of single nucleotide polymorphism (SNP) and insertion deletion (Indel) markers. The research results showed high genetic diversity among C. florida and C. kousa wild-collected plants and cultivars. For C. florida, pink-bracted plants formed a distinct clade from those with white-bracts with the Mexican C. florida ssp. urbiniana forming an outgroup. For C. kousa, Chinese-collected plants (ssp. chinensis) were a distinct subspecies with clear separation from Japanese and Korean accessions (ssp. kousa) and cultivars were designated as ssp. chinensis, ssp. kousa, or ssp. hybrid. Using this information, a Kompetitive allele specific PCR (KASP) assay genotyping panel was designed to determine C. kousa trees' subspecies makeup. Results revealed many cases of genetically identical cultivars being sold under different names, especially for pink-bracted cultivars of both species. Additionally, reported parent-progeny relationships were evaluated and either validated or discredited. Finally, the hybrid germplasm analysis validated pedigrees of interspecific F1 hybrids and found many of the recent Rutgers breeding selections contain small regions of pacific dogwood (C. nuttallii) DNA introgressed into C. kousa backgrounds. This diversity study elucidates origins, diversity, and relationships of a large population of big-bracted dogwoods. The results can inform plant breeders, arboreta, and the ornamental plant industry, as most modern cultivars and popular historic cultivars are represented.
大花梾木是一种受欢迎的观赏树种，以其美丽的春季花朵而闻名，花朵有鲜艳的苞片，四季皆宜。最广泛种植的两个物种是原产于北美东部和东亚的Cornus florida 和 Cornus kousa。尽管它们在园艺上很突出，但关于狗木品种的遗传多样性、种群结构、亲缘关系和亚种起源的信息却很少。在这项研究中，对 313 个品种、野生植物和罗格斯大学的育种选择进行了基因分型，这些品种主要关注 Cornus florida、Cornus kousa 和种间杂种，使用限制位点相关 DNA 测序（RADseq）生成了数千个单核苷酸多态性（SNP）和插入缺失（Indel）标记。研究结果表明，Cornus florida 和 Cornus kousa 野生植物和品种之间存在高度的遗传多样性。对于 Cornus florida，粉色苞片植物与白色苞片植物形成了一个独特的分支，墨西哥的 Cornus florida ssp. urbiniana 形成了一个外群。对于 Cornus kousa，中国收集的植物（ssp. chinensis）是一个独特的亚种，与日本和韩国的品种（ssp. kousa）有明显的分离，品种被指定为 ssp. chinensis、ssp. kousa 或 ssp. hybrid。利用这些信息，设计了一种竞争性等位基因特异性 PCR（KASP）基因分型检测试剂盒，以确定 Cornus kousa 树木的亚种组成。结果显示，许多遗传上相同的品种以不同的名称出售，特别是对于这两个物种的粉色苞片品种。此外，还评估了报告的亲子关系，要么得到证实，要么被否定。最后，对杂种种质的分析验证了种间 F1 杂种的系谱，并发现许多最近的罗格斯育种选择都含有小部分太平洋梾木（C. nuttallii）的 DNA 渗入到 C. kousa 的背景中。这项多样性研究阐明了大花梾木的起源、多样性和亲缘关系。研究结果可以为植物育种者、树木园和观赏植物产业提供信息，因为大多数现代品种和受欢迎的历史品种都有代表。
