Complex polyploid and hybrid species in an apomictic and sexual tropical forage grass group: genomic composition and evolution in Urochloa ( Brachiaria ) species
Complex polyploid and hybrid species in an apomictic and sexual tropical forage grass group: genomic composition and evolution in Urochloa ( Brachiaria ) species
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无融合生殖和有性热带牧草群中的复杂多倍体和杂种：尾草（臂形草）物种的基因组组成和进化
DOI：
10.1101/2021.02.19.431966
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Tomaszewska P
中科院分区：
文献类型：
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作者：
Tomaszewska P
背景与目的原产于非洲的二倍体和多倍体牧草C4对粮食安全和环境具有重要意义，常被种植在世界各地的边缘土地上。本研究旨在研究其基因组的性质、重复DNA和多倍体的基因组组成，从而建立一个包含许多无融合生殖物种的群体内进化路径模型。方法对来自国际牧草种质资源的362份牧草种质资源进行研究，并采用优化的流式细胞术方法进行倍性鉴定。采用全基因组调查、测序和分子细胞遗传学分析等方法，对尿囊藻的染色体和基因组进行了鉴定。基因组结构复杂多变，物种内有多种倍性和基因组组成，没有明确的地理格局。通过对9个二倍体和多倍体材料的序列分析，鉴定出丰富的基因组特异性重复DNA基序。通过重复DNA和基因组DNA探针的原位杂交，鉴定了进化差异，并使我们能够区分多倍体中存在的不同基因组。结论我们对存在的基因组提出了一个新的统一的命名方法。我们在二倍体和多倍体材料的全基因组水平上建立了一个进化模型，展示了牧草的进化过程。我们支持将狭义的物种概念保留在布氏尾藻、斜纹夜蛾和尾藻上。Ruziziens，不把单一物种的二倍体和多倍体视为细胞型。研究结果和模型对合理选择新杂交种亲本，辅助利用种质资源培育和选择具有较高可持续性和农艺潜力的草地牧草，以及草地生物多样性的测定和保护具有重要的参考价值。
Background and AimsDiploid and polyploidUrochloa(includingBrachiaria,PanicumandMegathyrsusspecies) C4tropical forage grasses originating from Africa are important for food security and the environment, often being planted in marginal lands worldwide. We aimed to characterize the nature of their genomes, the repetitive DNA and the genome composition of polyploids, leading to a model of the evolutionary pathways within the group including many apomictic species.MethodsSome 362 forage grass accessions from international germplasm collections were studied, and ploidy was determined using an optimized flow cytometry method. Whole-genome survey sequencing and molecular cytogenetic analysis were used to identify chromosomes and genomes inUrochloaaccessions belonging to the ‘brizantha’ and ‘humidicola’ agamic complexes andU. maxima.Key ResultsGenome structures are complex and variable, with multiple ploidies and genome compositions within the species, and no clear geographical patterns. Sequence analysis of nine diploid and polyploid accessions enabled identification of abundant genome-specific repetitive DNA motifs.In situhybridization with a combination of repetitive DNA and genomic DNA probes identified evolutionary divergence and allowed us to discriminate the different genomes present in polyploids.ConclusionsWe suggest a new coherent nomenclature for the genomes present. We develop a model of evolution at the whole-genome level in diploid and polyploid accessions showing processes of grass evolution. We support the retention of narrow species concepts forUrochloa brizantha,U. decumbensandU. ruziziensis, and do not consider diploids and polyploids of single species as cytotypes. The results and model will be valuable in making rational choices of parents for new hybrids, assist in use of the germplasm for breeding and selection ofUrochloawith improved sustainability and agronomic potential, and assist in measuring and conserving biodiversity in grasslands.