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Sun S, Wang B, Li C, Xu G, Yang J, Hufford MB, Ross-Ibarra J, Wang H, Wang L. Unraveling Prevalence and Effects of Deleterious Mutations in Maize Elite Lines across Decades of Modern Breeding. Mol Biol Evol 2023; 40:msad170. [PMID: 37494285 PMCID: PMC10414807 DOI: 10.1093/molbev/msad170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 07/12/2023] [Accepted: 07/21/2023] [Indexed: 07/28/2023] Open
Abstract
Future breeding is likely to involve the detection and removal of deleterious alleles, which are mutations that negatively affect crop fitness. However, little is known about the prevalence of such mutations and their effects on phenotypic traits in the context of modern crop breeding. To address this, we examined the number and frequency of deleterious mutations in 350 elite maize inbred lines developed over the past few decades in China and the United States. Our findings reveal an accumulation of weakly deleterious mutations and a decrease in strongly deleterious mutations, indicating the dominant effects of genetic drift and purifying selection for the two types of mutations, respectively. We also discovered that slightly deleterious mutations, when at lower frequencies, were more likely to be heterozygous in the developed hybrids. This is consistent with complementation as a potential explanation for heterosis. Subsequently, we found that deleterious mutations accounted for more of the variation in phenotypic traits than nondeleterious mutations with matched minor allele frequencies, especially for traits related to leaf angle and flowering time. Moreover, we detected fewer deleterious mutations in the promoter and gene body regions of differentially expressed genes across breeding eras than in nondifferentially expressed genes. Overall, our results provide a comprehensive assessment of the prevalence and impact of deleterious mutations in modern maize breeding and establish a useful baseline for future maize improvement efforts.
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Affiliation(s)
- Shichao Sun
- Shenzhen Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, China
| | - Baobao Wang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Changyu Li
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Gen Xu
- Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Jinliang Yang
- Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Matthew B Hufford
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, USA
| | - Jeffrey Ross-Ibarra
- Department of Evolution and Ecology, University of California, Davis, CA, USA
| | - Haiyang Wang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, China
| | - Li Wang
- Shenzhen Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, China
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, USA
- Kunpeng Institute of Modern Agriculture at Foshan, Chinese Academy of Agricultural Sciences, Foshan, China
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Arca M, Gouesnard B, Mary-Huard T, Le Paslier MC, Bauland C, Combes V, Madur D, Charcosset A, Nicolas SD. Genotyping of DNA pools identifies untapped landraces and genomic regions to develop next-generation varieties. PLANT BIOTECHNOLOGY JOURNAL 2023; 21:1123-1139. [PMID: 36740649 DOI: 10.1111/pbi.14022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 01/18/2023] [Indexed: 05/27/2023]
Abstract
Landraces, that is, traditional varieties, have a large diversity that is underexploited in modern breeding. A novel DNA pooling strategy was implemented to identify promising landraces and genomic regions to enlarge the genetic diversity of modern varieties. As proof of concept, DNA pools from 156 American and European maize landraces representing 2340 individuals were genotyped with an SNP array to assess their genome-wide diversity. They were compared to elite cultivars produced across the 20th century, represented by 327 inbred lines. Detection of selective footprints between landraces of different geographic origin identified genes involved in environmental adaptation (flowering times, growth) and tolerance to abiotic and biotic stress (drought, cold, salinity). Promising landraces were identified by developing two novel indicators that estimate their contribution to the genome of inbred lines: (i) a modified Roger's distance standardized by gene diversity and (ii) the assignation of lines to landraces using supervised analysis. It showed that most landraces do not have closely related lines and that only 10 landraces, including famous landraces as Reid's Yellow Dent, Lancaster Surecrop and Lacaune, cumulated half of the total contribution to inbred lines. Comparison of ancestral lines directly derived from landraces with lines from more advanced breeding cycles showed a decrease in the number of landraces with a large contribution. New inbred lines derived from landraces with limited contributions enriched more the haplotype diversity of reference inbred lines than those with a high contribution. Our approach opens an avenue for the identification of promising landraces for pre-breeding.
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Affiliation(s)
- Mariangela Arca
- INRAE, CNRS, AgroParisTech, GQE - Le Moulon, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Brigitte Gouesnard
- UMR AGAP Institut, Univ Montpellier, CIRAD, INRAE, Institut Agro, Montpellier, France
| | - Tristan Mary-Huard
- INRAE, CNRS, AgroParisTech, GQE - Le Moulon, Université Paris-Saclay, Gif-sur-Yvette, France
| | | | - Cyril Bauland
- INRAE, CNRS, AgroParisTech, GQE - Le Moulon, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Valérie Combes
- INRAE, CNRS, AgroParisTech, GQE - Le Moulon, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Delphine Madur
- INRAE, CNRS, AgroParisTech, GQE - Le Moulon, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Alain Charcosset
- INRAE, CNRS, AgroParisTech, GQE - Le Moulon, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Stéphane D Nicolas
- INRAE, CNRS, AgroParisTech, GQE - Le Moulon, Université Paris-Saclay, Gif-sur-Yvette, France
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Hale B, Ferrie AMR, Chellamma S, Samuel JP, Phillips GC. Androgenesis-Based Doubled Haploidy: Past, Present, and Future Perspectives. FRONTIERS IN PLANT SCIENCE 2022; 12:751230. [PMID: 35069615 PMCID: PMC8777211 DOI: 10.3389/fpls.2021.751230] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 11/22/2021] [Indexed: 05/03/2023]
Abstract
Androgenesis, which entails cell fate redirection within the microgametophyte, is employed widely for genetic gain in plant breeding programs. Moreover, androgenesis-responsive species provide tractable systems for studying cell cycle regulation, meiotic recombination, and apozygotic embryogenesis within plant cells. Past research on androgenesis has focused on protocol development with emphasis on temperature pretreatments of donor plants or floral buds, and tissue culture optimization because androgenesis has different nutritional requirements than somatic embryogenesis. Protocol development for new species and genotypes within responsive species continues to the present day, but slowly. There is more focus presently on understanding how protocols work in order to extend them to additional genotypes and species. Transcriptomic and epigenetic analyses of induced microspores have revealed some of the cellular and molecular responses required for or associated with androgenesis. For example, microRNAs appear to regulate early microspore responses to external stimuli; trichostatin-A, a histone deacetylase inhibitor, acts as an epigenetic additive; ά-phytosulfokine, a five amino acid sulfated peptide, promotes androgenesis in some species. Additionally, present work on gene transfer and genome editing in microspores suggest that future endeavors will likely incorporate greater precision with the genetic composition of microspores used in doubled haploid breeding, thus likely to realize a greater impact on crop improvement. In this review, we evaluate basic breeding applications of androgenesis, explore the utility of genomics and gene editing technologies for protocol development, and provide considerations to overcome genotype specificity and morphogenic recalcitrance in non-model plant systems.
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Affiliation(s)
- Brett Hale
- Molecular Biosciences Graduate Program, Arkansas State University, Jonesboro, AR, United States
- Arkansas Biosciences Institute, Arkansas State University, Jonesboro, AR, United States
| | | | | | | | - Gregory C. Phillips
- Arkansas Biosciences Institute, Arkansas State University, Jonesboro, AR, United States
- College of Agriculture, Arkansas State University, Jonesboro, AR, United States
- Agricultural Experiment Station, University of Arkansas System Division of Agriculture, Jonesboro, AR, United States
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Würschum T, Weiß TM, Renner J, Friedrich Utz H, Gierl A, Jonczyk R, Römisch-Margl L, Schipprack W, Schön CC, Schrag TA, Leiser WL, Melchinger AE. High-resolution association mapping with libraries of immortalized lines from ancestral landraces. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2022; 135:243-256. [PMID: 34668978 PMCID: PMC8741726 DOI: 10.1007/s00122-021-03963-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 09/29/2021] [Indexed: 05/30/2023]
Abstract
Association mapping with immortalized lines of landraces offers several advantages including a high mapping resolution, as demonstrated here in maize by identifying the causal variants underlying QTL for oil content and the metabolite allantoin. Landraces are traditional varieties of crops that present a valuable yet largely untapped reservoir of genetic variation to meet future challenges of agriculture. Here, we performed association mapping in a panel comprising 358 immortalized maize lines from six European Flint landraces. Linkage disequilibrium decayed much faster in the landraces than in the elite lines included for comparison, permitting a high mapping resolution. We demonstrate this by fine-mapping a quantitative trait locus (QTL) for oil content down to the phenylalanine insertion F469 in DGAT1-2 as the causal variant. For the metabolite allantoin, related to abiotic stress response, we identified promoter polymorphisms and differential expression of an allantoinase as putative cause of variation. Our results demonstrate the power of this approach to dissect QTL potentially down to the causal variants, toward the utilization of natural or engineered alleles in breeding. Moreover, we provide guidelines for studies using ancestral landraces for crop genetic research and breeding.
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Affiliation(s)
- Tobias Würschum
- Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, 70599, Stuttgart, Germany.
| | - Thea M Weiß
- Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, 70599, Stuttgart, Germany
- State Plant Breeding Institute, University of Hohenheim, 70599, Stuttgart, Germany
| | - Juliane Renner
- Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, 70599, Stuttgart, Germany
| | - H Friedrich Utz
- Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, 70599, Stuttgart, Germany
| | - Alfons Gierl
- Genetics, Technical University of Munich, Wissenschaftszentrum Weihenstephan, 85354, Freising, Germany
| | - Rafal Jonczyk
- Genetics, Technical University of Munich, Wissenschaftszentrum Weihenstephan, 85354, Freising, Germany
| | - Lilla Römisch-Margl
- Genetics, Technical University of Munich, Wissenschaftszentrum Weihenstephan, 85354, Freising, Germany
| | - Wolfgang Schipprack
- Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, 70599, Stuttgart, Germany
| | - Chris-Carolin Schön
- Plant Breeding, TUM School of Life Sciences, Technical University of Munich, 85354, Freising, Germany
| | - Tobias A Schrag
- Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, 70599, Stuttgart, Germany
| | - Willmar L Leiser
- State Plant Breeding Institute, University of Hohenheim, 70599, Stuttgart, Germany
| | - Albrecht E Melchinger
- Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, 70599, Stuttgart, Germany.
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