Department of Agronomy, Iowa State University, Ames, IA, 50011, USA.
KWS SAAT SE & Co. KGaA, Grimsehlstr. 31, 37574, Einbeck, Germany.
Theor Appl Genet. 2024 May 3;137(5):117. doi: 10.1007/s00122-024-04615-y.
A large-effect QTL was fine mapped, which revealed 79 gene models, with 10 promising candidate genes, along with a novel inversion. In commercial maize breeding, doubled haploid (DH) technology is arguably the most efficient resource for rapidly developing novel, completely homozygous lines. However, the DH strategy, using in vivo haploid induction, currently requires the use of mutagenic agents which can be not only hazardous, but laborious. This study focuses on an alternative approach to develop DH lines-spontaneous haploid genome duplication (SHGD) via naturally restored haploid male fertility (HMF). Inbred lines A427 and Wf9, the former with high HMF and the latter with low HMF, were selected to fine-map a large-effect QTL associated with SHGD-qshgd1. SHGD alleles were derived from A427, with novel haploid recombinant groups having varying levels of the A427 chromosomal region recovered. The chromosomal region of interest is composed of 45 megabases (Mb) of genetic information on chromosome 5. Significant differences between haploid recombinant groups for HMF were identified, signaling the possibility of mapping the QTL more closely. Due to suppression of recombination from the proximity of the centromere, and a newly discovered inversion region, the associated QTL was only confined to a 25 Mb region, within which only a single recombinant was observed among ca. 9,000 BC individuals. Nevertheless, 79 gene models were identified within this 25 Mb region. Additionally, 10 promising candidate genes, based on RNA-seq data, are described for future evaluation, while the narrowed down genome region is accessible for straightforward introgression into elite germplasm by BC methods.
一个大效应 QTL 被精细定位，揭示了 79 个基因模型，其中有 10 个有希望的候选基因，以及一个新的倒位。在商业玉米育种中，双单倍体（DH）技术可以说是快速开发新型、完全纯合系的最有效资源。然而，DH 策略，使用体内单倍体诱导，目前需要使用诱变剂，这不仅危险，而且费力。本研究专注于一种替代方法来开发 DH 系-自发单倍体基因组复制（SHGD）通过自然恢复的单倍体雄性育性（HMF）。选择自交系 A427 和 Wf9 进行精细定位与 SHGD-qshgd1 相关的大效应 QTL，前者具有高 HMF，后者具有低 HMF。SHGD 等位基因来自 A427，具有不同水平的 A427 染色体区域恢复的新型单倍体重组群体。感兴趣的染色体区域由 5 号染色体上 4500 万个碱基对（Mb）的遗传信息组成。在 HMF 方面，单倍体重组群体之间存在显著差异，这表明有可能更紧密地定位 QTL。由于近着丝粒重组的抑制，以及一个新发现的倒位区域，相关的 QTL 仅局限于 25 Mb 区域，在大约 9000 个 BC 个体中，只观察到一个重组体。然而，在这个 25 Mb 区域内鉴定出了 79 个基因模型。此外，根据 RNA-seq 数据，描述了 10 个有前途的候选基因，以供未来评估，而缩小的基因组区域可通过 BC 方法直接导入到优良种质中。
