Gesteira Gabriel de Siqueira, Ferreira Getulio Caixeta, Mollinari Marcelo, Santos Mateus Figueiredo, Jank Liana, Vilela Mariane de Mendonça, Raposo Andrea, Chiari Lucimara, Zeng Zhao-Bang, Garcia Antonio Augusto Franco
Bioinformatics Research Center, Department of Horticultural Science, North Carolina State University, Raleigh, NC 27607, USA.
Department of Genetics, "Luiz de Queiroz" College of Agriculture, University of Sao Paulo, Piracicaba, SP 13418-900, Brazil.
G3 (Bethesda). 2025 Sep 3;15(9). doi: 10.1093/g3journal/jkaf126.
Megathyrsus maximus (Jacq.), commonly known as guinea grass, is a forage crop widely used to form pastures and feed livestock. The species stands out for presenting high yield and nutritional quality in the leaves and its ability to be clonally propagated by seeds. In this work, we construct a dense and informative genetic linkage map for M. maximus using multiple dosage markers. We sequenced DNA from leaf samples of 224 individuals from a biparental cross between two tetraploid genotypes, then analyzed the raw sequencing data to find variants and call dosage-based genotypes using four related reference genomes. With the multiple dosage genotypes for both parents and all individuals, we constructed a highly informative genetic linkage map using state-of-the-art methods coupled with the multipoint Hidden Markov Model approach. We present the densest and most informative genetic linkage map to date for the species, with 7,095 markers distributed across eight homology groups, spanning 1573.31 cM of the genome. Both parents and all individuals in the mapping population were phased according to the species' ploidy level. There was no evidence of double-reduction or preferential pairing in the studied population. The linkage analysis provided in this work can help unravel the evolutionary pathway of the species, understand the genetic behavior of quantitative traits, assist in the assembly of reference genomes, and support the adoption of genomics-assisted selection strategies in M. maximus breeding programs.
巨须芒草（Megathyrsus maximus (Jacq.)），通常被称为几内亚草，是一种广泛用于形成牧场和饲养牲畜的饲料作物。该物种以其叶片具有高产和优质的营养以及能够通过种子进行克隆繁殖而脱颖而出。在这项工作中，我们使用多剂量标记构建了一个密集且信息丰富的巨须芒草遗传连锁图谱。我们对来自两个四倍体基因型之间双亲杂交的224个个体的叶片样本进行了DNA测序，然后分析原始测序数据以找到变异，并使用四个相关参考基因组来调用基于剂量的基因型。利用双亲及所有个体的多剂量基因型，我们采用最先进的方法结合多点隐马尔可夫模型方法构建了一个信息高度丰富的遗传连锁图谱。我们展示了该物种迄今为止最密集且信息最丰富的遗传连锁图谱，有7095个标记分布在八个同源组中, 跨越基因组的1573.31厘摩。根据该物种的倍性水平对双亲及作图群体中的所有个体进行了定相。在所研究的群体中没有双减数或优先配对的证据。这项工作中提供的连锁分析有助于揭示该物种的进化途径，了解数量性状的遗传行为，协助参考基因组的组装，并支持在巨须芒草育种计划中采用基因组辅助选择策略。
