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Selva C, Yang X, Shirley NJ, Whitford R, Baumann U, Tucker MR. HvSL1 and HvMADS16 promote stamen identity to restrict multiple ovary formation in barley. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:5039-5056. [PMID: 37279531 PMCID: PMC10498024 DOI: 10.1093/jxb/erad218] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 06/01/2023] [Indexed: 06/08/2023]
Abstract
Correct floral development is the result of a sophisticated balance of molecular cues. Floral mutants provide insight into the main genetic determinants that integrate these cues, as well as providing opportunities to assess functional variation across species. In this study, we characterize the barley (Hordeum vulgare) multiovary mutants mov2.g and mov1, and propose causative gene sequences: a C2H2 zinc-finger gene HvSL1 and a B-class gene HvMADS16, respectively. In the absence of HvSL1, florets lack stamens but exhibit functional supernumerary carpels, resulting in multiple grains per floret. Deletion of HvMADS16 in mov1 causes homeotic conversion of lodicules and stamens into bract-like organs and carpels that contain non-functional ovules. Based on developmental, genetic, and molecular data, we propose a model by which stamen specification in barley is defined by HvSL1 acting upstream of HvMADS16. The present work identifies strong conservation of stamen formation pathways with other cereals, but also reveals intriguing species-specific differences. The findings lay the foundation for a better understanding of floral architecture in Triticeae, a key target for crop improvement.
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Affiliation(s)
- Caterina Selva
- Waite Research Institute, School of Agriculture Food and Wine, University of Adelaide, Waite Campus, Urrbrae 5064, South Australia, Australia
| | - Xiujuan Yang
- Waite Research Institute, School of Agriculture Food and Wine, University of Adelaide, Waite Campus, Urrbrae 5064, South Australia, Australia
| | - Neil J Shirley
- Waite Research Institute, School of Agriculture Food and Wine, University of Adelaide, Waite Campus, Urrbrae 5064, South Australia, Australia
| | - Ryan Whitford
- Waite Research Institute, School of Agriculture Food and Wine, University of Adelaide, Waite Campus, Urrbrae 5064, South Australia, Australia
| | - Ute Baumann
- Waite Research Institute, School of Agriculture Food and Wine, University of Adelaide, Waite Campus, Urrbrae 5064, South Australia, Australia
| | - Matthew R Tucker
- Waite Research Institute, School of Agriculture Food and Wine, University of Adelaide, Waite Campus, Urrbrae 5064, South Australia, Australia
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Würschum T, Zhu X, Zhao Y, Jiang Y, Reif JC, Maurer HP. Maximization through optimization? On the relationship between hybrid performance and parental genetic distance. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2023; 136:186. [PMID: 37572118 PMCID: PMC10423127 DOI: 10.1007/s00122-023-04436-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 07/31/2023] [Indexed: 08/14/2023]
Abstract
Heterosis is the improved performance of hybrids compared with their parental components and is widely exploited in agriculture. According to quantitative genetic theory, genetic distance between parents at heterotic quantitative trait loci is required for heterosis, but how heterosis varies with genetic distance has remained elusive, despite intensive research on the topic. Experimental studies have often found a positive association between heterosis and genetic distance that, however, varied in strength. Most importantly, it has remained unclear whether heterosis increases continuously with genetic distance or whether there is an optimum genetic distance after which heterosis declines again. Here, we revisit the relationship between heterosis and genetic distance and provide perspectives on how to maximize heterosis and hybrid performance in breeding, as well as the consequences for the design of heterotic groups and the utilization of more exotic material and genetic resources.
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Affiliation(s)
- Tobias Würschum
- Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, 70599, Stuttgart, Germany.
| | - Xintian Zhu
- Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, 70599, Stuttgart, Germany
| | - Yusheng Zhao
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), 06466, Stadt Seeland, Germany
| | - Yong Jiang
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), 06466, Stadt Seeland, Germany
| | - Jochen C Reif
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), 06466, Stadt Seeland, Germany
| | - Hans Peter Maurer
- State Plant Breeding Institute, University of Hohenheim, 70599, Stuttgart, Germany
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3
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Genome-Wide Association Analysis for Hybrid Breeding in Wheat. Int J Mol Sci 2022; 23:ijms232315321. [PMID: 36499647 PMCID: PMC9740285 DOI: 10.3390/ijms232315321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 11/24/2022] [Accepted: 11/27/2022] [Indexed: 12/12/2022] Open
Abstract
Disclosure of markers that are significantly associated with plant traits can help develop new varieties with desirable properties. This study determined the genome-wide associations based on DArTseq markers for six agronomic traits assessed in eight environments for wheat. Moreover, the association study for heterosis and analysis of the effects of markers grouped by linkage disequilibrium were performed based on mean values over all experiments. All results were validated using data from post-registration trials. GWAS revealed 1273 single nucleotide polymorphisms with biologically significant effects. Most polymorphisms were predicted to be modifiers of protein translation, with only two having a more pronounced effect. Markers significantly associated with the considered set of features were clustered within chromosomes based on linkage disequilibrium in 327 LD blocks. A GWAS for heterosis revealed 1261 markers with significant effects.
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Millan-Blanquez M, Hartley M, Bird N, Manes Y, Uauy C, Boden SA. A scalable phenotyping approach for female floral organ development and senescence in the absence of pollination in wheat. Development 2022; 149:dev200889. [PMID: 35993314 PMCID: PMC9573784 DOI: 10.1242/dev.200889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 08/15/2022] [Indexed: 11/20/2022]
Abstract
In the absence of pollination, female reproductive organs senesce, leading to an irrevocable loss in the reproductive potential of the flower, which directly affects seed set. In self-pollinating crops like wheat (Triticum aestivum), the post-anthesis viability of unpollinated carpels has been overlooked, despite its importance for hybrid seed production systems. To advance our knowledge of carpel development in the absence of pollination, we created a high-throughput phenotyping approach to quantify stigma and ovary morphology. We demonstrate the suitability of the approach, which uses light-microscopy imaging and machine learning, for the analysis of floral organ traits in field-grown plants using fresh and fixed samples. We show that the unpollinated carpel undergoes a well-defined initial growth phase, followed by a peak phase in which stigma area reaches its maximum and the radial expansion of the ovary slows, and a final deterioration phase. These developmental dynamics were consistent across years and could be used to classify male-sterile cultivars. This phenotyping approach provides a new tool for examining carpel development, which we hope will advance research into female fertility of wheat.
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Affiliation(s)
| | - Matthew Hartley
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Wellcome Genome Campus, Hinxton, Cambridge CB10 1SD, UK
| | | | - Yann Manes
- Syngenta France S.A.S., Le Jardin des Entreprises, 28 000 Chartres, France
| | - Cristobal Uauy
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
| | - Scott A. Boden
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
- School of Agriculture, Food and Wine, Waite Research Institute, University of Adelaide, Glen Osmond 5064, South Australia, Australia
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Li J, Zhou K, Wang Z, Zhou J, Deng X. 基于隐性核雄性不育系的杂交小麦制种技术研究进展、问题与展望. CHINESE SCIENCE BULLETIN-CHINESE 2022. [DOI: 10.1360/tb-2022-0386] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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El Hanafi S, Cherkaoui S, Kehel Z, Sanchez-Garcia M, Sarazin JB, Baenziger S, Tadesse W. Hybrid Seed Set in Relation with Male Floral Traits, Estimation of Heterosis and Combining Abilities for Yield and Its Components in Wheat ( Triticum aestivum L.). PLANTS (BASEL, SWITZERLAND) 2022; 11:508. [PMID: 35214841 PMCID: PMC8880032 DOI: 10.3390/plants11040508] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 01/07/2022] [Accepted: 01/10/2022] [Indexed: 06/14/2023]
Abstract
Breeding hybrids with maximum heterosis requires efficient cross-pollination and an improved male sterility system. Renewed efforts have been made to dissect the phenotypic variation and genetic basis of hybrid floral traits, although the potential of tailoring the appropriate flower design on seed setting is less known. To this end, elite wheat genotypes were crossed using a chemical hybridizing agent at different doses. A total of 23 hybrids were developed from a partial diallel design; and planted in an alpha lattice design with their parents at two locations in Morocco, for two years, to evaluate for yield components, heterosis and combining abilities. The 13.5 L ha-1 dose induced a maximum level of sterility (95%) and seed set showed large phenotypic variation and high heritability. In parallel, seed set showed tight correlation with pollen mass (0.97), visual anther extrusion (0.94) and pollen shedding (0.91) (p < 0.001), allowing direct selection of the associated traits. Using the combined data, mid-parent heterosis ranges were -7.64-14.55% for biomass (BM), -8.34-12.51% for thousand kernel weight (TKW) and -5.29-26.65% for grain yield (YLD); while best-parent heterosis showed ranges of -11.18-7.20%, -11.35-11.26% and -8.27-24.04% for BM, TKW and YLD, respectively. The magnitude of general combining ability (GCA) variance was greater than the specific combining ability (SCA) variance suggesting a greater additive gene action for BM, TKW and YLD. The favorable GCA estimates showed a simple method to predict additive effects contributing to high heterosis and thus could be an effective approach for the selection of promising parents in early generations.
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Affiliation(s)
- Samira El Hanafi
- International Center for Agricultural Research in the Dry Areas, Rue Hafiane Cherkaoui, Rabat-Institutes, Rabat B.P. 6299, Morocco; (Z.K.); (M.S.-G.); (W.T.)
- Physiology Plant Biotechnology Unit, Bio-Bio Center, Faculty of Sciences, Mohammed V University of Rabat, 4 Avenue Ibn Battouta, Rabat B.P. 1014, Morocco;
| | - Souad Cherkaoui
- Physiology Plant Biotechnology Unit, Bio-Bio Center, Faculty of Sciences, Mohammed V University of Rabat, 4 Avenue Ibn Battouta, Rabat B.P. 1014, Morocco;
| | - Zakaria Kehel
- International Center for Agricultural Research in the Dry Areas, Rue Hafiane Cherkaoui, Rabat-Institutes, Rabat B.P. 6299, Morocco; (Z.K.); (M.S.-G.); (W.T.)
| | - Miguel Sanchez-Garcia
- International Center for Agricultural Research in the Dry Areas, Rue Hafiane Cherkaoui, Rabat-Institutes, Rabat B.P. 6299, Morocco; (Z.K.); (M.S.-G.); (W.T.)
| | | | - Stephen Baenziger
- Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE 68588, USA;
| | - Wuletaw Tadesse
- International Center for Agricultural Research in the Dry Areas, Rue Hafiane Cherkaoui, Rabat-Institutes, Rabat B.P. 6299, Morocco; (Z.K.); (M.S.-G.); (W.T.)
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Yang X, Tucker MR. Establishing a regulatory blueprint for ovule number and function during plant development. CURRENT OPINION IN PLANT BIOLOGY 2021; 63:102095. [PMID: 34428719 DOI: 10.1016/j.pbi.2021.102095] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 07/20/2021] [Accepted: 07/21/2021] [Indexed: 06/13/2023]
Abstract
The plant ovule is a fundamentally important organ that is the direct progenitor of the seed. It is one of the last structures to form in the flower and contains relatively few tissues, but undergoes complex developmental transitions that are essential for reproduction. Ovule number and flower fertility are important factors influencing yield, yet studies have identified challenges in trying to increase one without compromising the other. Recent findings in Arabidopsis and cereal crops highlight regulatory pathways that contribute to this yield constraint. Here, we consider the basis for variation in ovule number and development, with a particular focus on hormones and transcriptional regulators that constitute promising targets for the optimisation of reproductive traits and yield.
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Affiliation(s)
- Xiujuan Yang
- Waite Research Institute, School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, Urrbrae, SA, 5064, Australia
| | - Matthew R Tucker
- Waite Research Institute, School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, Urrbrae, SA, 5064, Australia.
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Selva C, Shirley NJ, Houston K, Whitford R, Baumann U, Li G, Tucker MR. HvLEAFY controls the early stages of floral organ specification and inhibits the formation of multiple ovaries in barley. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 108:509-527. [PMID: 34382710 DOI: 10.1111/tpj.15457] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 08/04/2021] [Accepted: 08/06/2021] [Indexed: 06/13/2023]
Abstract
Transition to the reproductive phase, inflorescence formation and flower development are crucial elements that ensure maximum reproductive success in a plant's life cycle. To understand the regulatory mechanisms underlying correct flower development in barley (Hordeum vulgare), we characterized the multiovary 5 (mov5.o) mutant. This mutant develops abnormal flowers that exhibit mosaic floral organs typified by multiple carpels at the total or partial expense of stamens. Genetic mapping positioned mov5 on the long arm of chromosome 2H, incorporating a region that encodes HvLFY, the barley orthologue of LEAFY from Arabidopsis. Sequencing revealed that, in mov5.o plants, HvLFY contains a single amino acid substitution in a highly conserved proline residue. CRISPR-mediated knockout of HvLFY replicated the mov5.o phenotype, suggesting that HvLFYmov5 represents a loss of function allele. In heterologous assays, the HvLFYmov5 polymorphism influenced protein-protein interactions and affinity for a putative binding site in the promoter of HvMADS58, a C-class MADS-box gene. Moreover, molecular analysis indicated that HvLFY interacts with HvUFO and regulates the expression of floral homeotic genes including HvMADS2, HvMADS4 and HvMADS16. Other distinct changes in expression differ from those reported in the rice LFY mutants apo2/rfl, suggesting that LFY function in the grasses is modulated in a species-specific manner. This pathway provides a key entry point for the study of LFY function and multiple ovary formation in barley, as well as cereal species in general.
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Affiliation(s)
- Caterina Selva
- School of Agriculture Food and Wine, Waite Research Institute, University of Adelaide, Waite Campus, Urrbrae, SA, 5064, Australia
| | - Neil J Shirley
- School of Agriculture Food and Wine, Waite Research Institute, University of Adelaide, Waite Campus, Urrbrae, SA, 5064, Australia
| | - Kelly Houston
- James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK
| | - Ryan Whitford
- School of Agriculture Food and Wine, Waite Research Institute, University of Adelaide, Waite Campus, Urrbrae, SA, 5064, Australia
| | - Ute Baumann
- School of Agriculture Food and Wine, Waite Research Institute, University of Adelaide, Waite Campus, Urrbrae, SA, 5064, Australia
| | - Gang Li
- School of Agriculture Food and Wine, Waite Research Institute, University of Adelaide, Waite Campus, Urrbrae, SA, 5064, Australia
- School of Life Sciences and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan, 621010, China
| | - Matthew R Tucker
- School of Agriculture Food and Wine, Waite Research Institute, University of Adelaide, Waite Campus, Urrbrae, SA, 5064, Australia
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Erena MF, Lohraseb I, Munoz-Santa I, Taylor JD, Emebiri LC, Collins NC. The WtmsDW Locus on Wheat Chromosome 2B Controls Major Natural Variation for Floret Sterility Responses to Heat Stress at Booting Stage. FRONTIERS IN PLANT SCIENCE 2021; 12:635397. [PMID: 33854519 DOI: 10.3389/fpls.2021.635397/bibtex] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 02/17/2021] [Indexed: 05/27/2023]
Abstract
Heat stress at booting stage causes significant losses to floret fertility (grain set) and hence yield in wheat (Triticum aestivum L.); however, there is a lack of well-characterized sources of tolerance to this type of stress. Here, we describe the genetic analysis of booting stage heat tolerance in a cross between the Australian cultivars Drysdale (intolerant) and Waagan (tolerant), leading to the definition of a major-effect tolerance locus on the short arm of chromosome 2B, Wheat thermosensitive male sterile Drysdale/Waagan (WtmsDW). WtmsDW offsets between 44 and 65% of the losses in grain set due to heat, suggesting that it offers significant value for marker-assisted tolerance breeding. In lines lacking the WtmsDW tolerance allele, peaks in sensitivity were defined with reference to auricle distance, for various floret positions along the spike. Other (relatively minor) floret fertility response effects, including at the Rht-D1 dwarfing locus, were considered likely escape artifacts, due to their association with height and flowering time effects that might interfere with correct staging of stems for heat treatment. Heat stress increased grain set at distal floret positions in spikelets located at the top of the spike and increased the size of spikelets at the base of the spike, but these effects were offset by greater reductions in grain set at other floret positions. Potentially orthologous loci on chromosomes 1A and 1B were identified for heat response of flowering time. The potential significance of these findings for tolerance breeding and further tolerance screening is discussed.
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Affiliation(s)
- Million F Erena
- School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, Australia
| | - Iman Lohraseb
- School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, Australia
| | - Isabel Munoz-Santa
- School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, Australia
- Department of Statistics and Operations Research, University of Valencia, Valencia, Spain
| | - Julian D Taylor
- School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, Australia
| | - Livinus C Emebiri
- Graham Centre for Agricultural Innovation, Charles Sturt University, Wagga Wagga, NSW, Australia
- New South Wales Department of Primary Industries, Wagga Wagga, NSW, Australia
| | - Nicholas C Collins
- School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, Australia
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10
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Erena MF, Lohraseb I, Munoz-Santa I, Taylor JD, Emebiri LC, Collins NC. The WtmsDW Locus on Wheat Chromosome 2B Controls Major Natural Variation for Floret Sterility Responses to Heat Stress at Booting Stage. FRONTIERS IN PLANT SCIENCE 2021; 12:635397. [PMID: 33854519 PMCID: PMC8040955 DOI: 10.3389/fpls.2021.635397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 02/17/2021] [Indexed: 05/05/2023]
Abstract
Heat stress at booting stage causes significant losses to floret fertility (grain set) and hence yield in wheat (Triticum aestivum L.); however, there is a lack of well-characterized sources of tolerance to this type of stress. Here, we describe the genetic analysis of booting stage heat tolerance in a cross between the Australian cultivars Drysdale (intolerant) and Waagan (tolerant), leading to the definition of a major-effect tolerance locus on the short arm of chromosome 2B, Wheat thermosensitive male sterile Drysdale/Waagan (WtmsDW). WtmsDW offsets between 44 and 65% of the losses in grain set due to heat, suggesting that it offers significant value for marker-assisted tolerance breeding. In lines lacking the WtmsDW tolerance allele, peaks in sensitivity were defined with reference to auricle distance, for various floret positions along the spike. Other (relatively minor) floret fertility response effects, including at the Rht-D1 dwarfing locus, were considered likely escape artifacts, due to their association with height and flowering time effects that might interfere with correct staging of stems for heat treatment. Heat stress increased grain set at distal floret positions in spikelets located at the top of the spike and increased the size of spikelets at the base of the spike, but these effects were offset by greater reductions in grain set at other floret positions. Potentially orthologous loci on chromosomes 1A and 1B were identified for heat response of flowering time. The potential significance of these findings for tolerance breeding and further tolerance screening is discussed.
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Affiliation(s)
- Million F. Erena
- School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, Australia
| | - Iman Lohraseb
- School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, Australia
| | - Isabel Munoz-Santa
- School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, Australia
- Department of Statistics and Operations Research, University of Valencia, Valencia, Spain
| | - Julian D. Taylor
- School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, Australia
| | - Livinus C. Emebiri
- Graham Centre for Agricultural Innovation, Charles Sturt University, Wagga Wagga, NSW, Australia
- New South Wales Department of Primary Industries, Wagga Wagga, NSW, Australia
| | - Nicholas C. Collins
- School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, Australia
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Assessment of hybrid vigour, dominance effect and hybrids regeneration potential in the genus Citrullus. Heliyon 2020; 6:e05005. [PMID: 33005805 PMCID: PMC7511728 DOI: 10.1016/j.heliyon.2020.e05005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 08/17/2020] [Accepted: 09/17/2020] [Indexed: 11/20/2022] Open
Abstract
The current research was directed to explore hybrid vigour for hybrids resulting from crosses among six genotypes of the genus Citrullus, including C. mucosospermus. For such purpose, the mid parent heterosis and the best parent heterosis were assessed. Non parametric method related to homogeneity Chi-square at 5 % likelihood was applied to compare the regeneration potential of progenies. Student's parametric test at 5% was used to separe two means. Six parental genotypes and 16 hybrid families were evaluated for heterosis. The results showed a heterosis effect for all the characters studied nevertheless, this one varies according to the crossing. The observed hybrid vigour would be due to a superdominance or partial dominance effect. In addition, progeny from crosses have the same regenerative potential on both study sites.
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