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Masters LE, Tomaszewska P, Schwarzacher T, Hackel J, Zuntini AR, Heslop-Harrison P, Vorontsova MS. Phylogenomic analysis reveals five independently evolved African forage grass clades in the genus Urochloa. ANNALS OF BOTANY 2024; 133:725-742. [PMID: 38365451 PMCID: PMC11082517 DOI: 10.1093/aob/mcae022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 02/21/2024] [Indexed: 02/18/2024]
Abstract
BACKGROUND AND AIMS The grass genus Urochloa (Brachiaria) sensu lato includes forage crops that are important for beef and dairy industries in tropical and sub-tropical Africa, South America and Oceania/Australia. Economically important species include U. brizantha, U. decumbens, U. humidicola, U. mutica, U. arrecta, U. trichopus, U. mosambicensis and Megathyrsus maximus, all native to the African continent. Perennial growth habits, large, fast growing palatable leaves, intra- and interspecific morphological variability, apomictic reproductive systems and frequent polyploidy are widely shared within the genus. The combination of these traits probably favoured the selection for forage domestication and weediness, but trait emergence across Urochloa cannot be modelled, as a robust phylogenetic assessment of the genus has not been conducted. We aim to produce a phylogeny for Urochloa that includes all important forage species, and identify their closest wild relatives (crop wild relatives). Finally, we will use our phylogeny and available trait data to infer the ancestral states of important forage traits across Urochloa s.l. and model the evolution of forage syndromes across the genus. METHODS Using a target enrichment sequencing approach (Angiosperm 353), we inferred a species-level phylogeny for Urochloa s.l., encompassing 54 species (~40 % of the genus) and outgroups. Phylogenies were inferred using a multispecies coalescent model and maximum likelihood method. We determined the phylogenetic placement of agriculturally important species and identified their closest wild relatives, or crop wild relatives, based on well-supported monophyly. Further, we mapped key traits associated with Urochloa forage crops to the species tree and estimated ancestral states for forage traits along branch lengths for continuous traits and at ancestral nodes in discrete traits. KEY RESULTS Agricultural species belong to five independent clades, including U. brizantha and U. decumbens lying in a previously defined species complex. Crop wild relatives were identified for these clades supporting previous sub-generic groupings in Urochloa based on morphology. Using ancestral trait estimation models, we find that five morphological traits that correlate with forage potential (perennial growth habits, culm height, leaf size, a winged rachis and large seeds) independently evolved in forage clades. CONCLUSIONS Urochloa s.l. is a highly diverse genus that contains numerous species with agricultural potential, including crop wild relatives that are currently underexploited. All forage species and their crop wild relatives naturally occur on the African continent and their conservation across their native distributions is essential. Genomic and phenotypic diversity in forage clade species and their wild relatives need to be better assessed both to develop conservation strategies and to exploit the diversity in the genus for improved sustainability in Urochloa cultivar production.
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Affiliation(s)
- Lizo E Masters
- Department of Genetics and Genome Biology, Institute for Environmental Futures, University of Leicester, Leicester LE17RH, UK
- Accelerated Taxonomy/Trait Diversity and Function, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK
| | - Paulina Tomaszewska
- Department of Genetics and Genome Biology, Institute for Environmental Futures, University of Leicester, Leicester LE17RH, UK
- Department of Genetics and Cell Physiology, University of Wroclaw, 50-328 Wroclaw, Poland
| | - Trude Schwarzacher
- Department of Genetics and Genome Biology, Institute for Environmental Futures, University of Leicester, Leicester LE17RH, UK
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization/Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China
| | - Jan Hackel
- Accelerated Taxonomy/Trait Diversity and Function, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK
- Department of Biology, University of Marburg, Karl-von-Frisch-Straße 8, 35043 Marburg, Germany
| | - Alexandre R Zuntini
- Accelerated Taxonomy/Trait Diversity and Function, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK
| | - Pat Heslop-Harrison
- Department of Genetics and Genome Biology, Institute for Environmental Futures, University of Leicester, Leicester LE17RH, UK
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization/Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China
| | - Maria S Vorontsova
- Accelerated Taxonomy/Trait Diversity and Function, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK
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Martins FB, Aono AH, Moraes ADCL, Ferreira RCU, Vilela MDM, Pessoa-Filho M, Rodrigues-Motta M, Simeão RM, de Souza AP. Genome-wide family prediction unveils molecular mechanisms underlying the regulation of agronomic traits in Urochloa ruziziensis. FRONTIERS IN PLANT SCIENCE 2023; 14:1303417. [PMID: 38148869 PMCID: PMC10749977 DOI: 10.3389/fpls.2023.1303417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 11/15/2023] [Indexed: 12/28/2023]
Abstract
Tropical forage grasses, particularly those belonging to the Urochloa genus, play a crucial role in cattle production and serve as the main food source for animals in tropical and subtropical regions. The majority of these species are apomictic and tetraploid, highlighting the significance of U. ruziziensis, a sexual diploid species that can be tetraploidized for use in interspecific crosses with apomictic species. As a means to support breeding programs, our study investigates the feasibility of genome-wide family prediction in U. ruziziensis families to predict agronomic traits. Fifty half-sibling families were assessed for green matter yield, dry matter yield, regrowth capacity, leaf dry matter, and stem dry matter across different clippings established in contrasting seasons with varying available water capacity. Genotyping was performed using a genotyping-by-sequencing approach based on DNA samples from family pools. In addition to conventional genomic prediction methods, machine learning and feature selection algorithms were employed to reduce the necessary number of markers for prediction and enhance predictive accuracy across phenotypes. To explore the regulation of agronomic traits, our study evaluated the significance of selected markers for prediction using a tree-based approach, potentially linking these regions to quantitative trait loci (QTLs). In a multiomic approach, genes from the species transcriptome were mapped and correlated to those markers. A gene coexpression network was modeled with gene expression estimates from a diverse set of U. ruziziensis genotypes, enabling a comprehensive investigation of molecular mechanisms associated with these regions. The heritabilities of the evaluated traits ranged from 0.44 to 0.92. A total of 28,106 filtered SNPs were used to predict phenotypic measurements, achieving a mean predictive ability of 0.762. By employing feature selection techniques, we could reduce the dimensionality of SNP datasets, revealing potential genotype-phenotype associations. The functional annotation of genes near these markers revealed associations with auxin transport and biosynthesis of lignin, flavonol, and folic acid. Further exploration with the gene coexpression network uncovered associations with DNA metabolism, stress response, and circadian rhythm. These genes and regions represent important targets for expanding our understanding of the metabolic regulation of agronomic traits and offer valuable insights applicable to species breeding. Our work represents an innovative contribution to molecular breeding techniques for tropical forages, presenting a viable marker-assisted breeding approach and identifying target regions for future molecular studies on these agronomic traits.
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Affiliation(s)
- Felipe Bitencourt Martins
- Center for Molecular Biology and Genetic Engineering (CBMEG), University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | - Alexandre Hild Aono
- Center for Molecular Biology and Genetic Engineering (CBMEG), University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | - Aline da Costa Lima Moraes
- Department of Plant Biology, Biology Institute, University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | | | | | - Marco Pessoa-Filho
- Embrapa Cerrados, Brazilian Agricultural Research Corporation, Brasília, Brazil
| | | | - Rosangela Maria Simeão
- Embrapa Gado de Corte, Brazilian Agricultural Research Corporation, Campo Grande, Mato Grosso, Brazil
| | - Anete Pereira de Souza
- Center for Molecular Biology and Genetic Engineering (CBMEG), University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
- Department of Plant Biology, Biology Institute, University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
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Higgins J, Tomaszewska P, Pellny TK, Castiblanco V, Arango J, Tohme J, Schwarzacher T, Mitchell RA, Heslop-Harrison JS, De Vega JJ. Diverged subpopulations in tropical Urochloa (Brachiaria) forage species indicate a role for facultative apomixis and varying ploidy in their population structure and evolution. ANNALS OF BOTANY 2022; 130:657-669. [PMID: 36112370 PMCID: PMC9670755 DOI: 10.1093/aob/mcac115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 09/13/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND Urochloa (syn. Brachiaria) is a genus of tropical grasses sown as forage feedstock, particularly in marginal soils. Here we aimed to clarify the genetic diversity and population structure in Urochloa species to understand better how population evolution relates to ploidy level and occurrence of apomictic reproduction. METHODS We explored the genetic diversity of 111 accessions from the five Urochloa species used to develop commercial cultivars. These accessions were conserved from wild materials collected at their centre of origin in Africa, and they tentatively represent the complete Urochloa gene pool used in breeding programmes. We used RNA-sequencing to generate 1.1 million single nucleotide polymorphism loci. We employed genetic admixture, principal component and phylogenetic analyses to define subpopulations. RESULTS We observed three highly differentiated subpopulations in U. brizantha, which were unrelated to ploidy: one intermixed with U. decumbens, and two diverged from the former and the other species in the complex. We also observed two subpopulations in U. humidicola, unrelated to ploidy; one subpopulation had fewer accessions but included the only characterized sexual accession in the species. Our results also supported a division of U. decumbens between diploids and polyploids, and no subpopulations within U. ruziziensis and U. maxima. CONCLUSIONS Polyploid U. decumbens are more closely related to polyploid U. brizantha than to diploid U. decumbens, which supports the divergence of both polyploid groups from a common tetraploid ancestor and provides evidence for the hybridization barrier of ploidy. The three differentiated subpopulations of apomictic polyploid U. brizantha accessions constitute diverged ecotypes, which can probably be utilized in hybrid breeding. Subpopulations were not observed in non-apomictic U. ruziziensis. Sexual Urochloa polyploids were not found (U. brizantha, U. decumbens) or were limited to small subpopulations (U. humidicola). The subpopulation structure observed in the Urochloa sexual-apomictic multiploidy complexes supports geographical parthenogenesis, where the polyploid genotypes exploit the evolutionary advantage of apomixis, i.e. uniparental reproduction and clonality, to occupy extensive geographical areas.
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Affiliation(s)
- J Higgins
- Earlham Institute, Norwich Research Park, Norwich NR4 7UZ, UK
| | - P Tomaszewska
- Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK
- Department of Genetics and Cell Physiology, Faculty of Biological Sciences, University of Wroclaw, 50-328 Wroclaw, Poland
| | - T K Pellny
- Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
| | - V Castiblanco
- International Center for Tropical Agriculture (CIAT), 6713 Cali, Colombia
| | - J Arango
- International Center for Tropical Agriculture (CIAT), 6713 Cali, Colombia
| | - J Tohme
- International Center for Tropical Agriculture (CIAT), 6713 Cali, Colombia
| | - T Schwarzacher
- Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK
| | - R A Mitchell
- Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
| | - J S Heslop-Harrison
- Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization/Guangdong Provincial, Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China
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