Genetic basis of tristyly in tetraploid Oxalis alpina (Oxalidaceae)
The inheritance of style‐morphs was investigated in tetraploid populations of tristylous Oxalis alpina (Oxalidaceae) to determine if alleles controlling style‐morphs are expressed at duplicated loci. In tetraploid populations, a dominant S allele leads to expression of the short‐styled phenotype at...
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| Published in | Botanical journal of the Linnean Society Vol. 179; no. 2; pp. 308 - 318 |
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| Main Authors | , , , , , |
| Format | Journal Article |
| Language | English |
| Published |
Oxford
Blackwell Publishing Ltd
01.10.2015
Oxford University Press |
| Subjects | |
| Online Access | Get full text |
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| Summary: | The inheritance of style‐morphs was investigated in tetraploid populations of tristylous Oxalis alpina (Oxalidaceae) to determine if alleles controlling style‐morphs are expressed at duplicated loci. In tetraploid populations, a dominant S allele leads to expression of the short‐styled phenotype at the short/non‐short locus and is epistatic to the M allele at the mid/long locus. The M allele results in expression of the mid‐styled phenotype but only if the S allele is absent. Long‐styled morphs are homozygous recessive at the short and mid loci. Test crosses of many tetraploid short‐styled individuals resulted in segregations of short‐, mid‐ and long‐styled individuals which, because of linkage between the short and mid loci, can only occur with polyploidy and expression of alleles at duplicated loci. Segregation patterns from three crosses suggest the possibility of disomic inheritance via preferential pairing of chromosomes in tetraploid populations of O. alpina. Segregation patterns in the progeny of mid‐styled individuals indicated that only a few individuals had more than one copy of the M allele, despite the potential for accumulation of M alleles via self‐fertilization of partially self‐compatible mid‐styled morphs in some populations. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179, 308–318. |
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| Bibliography: | Consejo Nacional de Ciencia y Tecnología - No. 47858-Q istex:12C7B239D126EB425543BDB2BEC8A1AC9E27BE1E University of California Institute for Mexico and the United States National Science Foundation - No. DEB-0614164 National Autonomous University of Mexico - No. IN217 803 ark:/67375/WNG-SNKLKZ4S-J File S1. A, populations of Oxalis alpina in the Sky Island region of the Sonoran Desert used for analysis of the genetic basis of style morphs. Style morph frequencies are based on field surveys from Weller et al. 2007. All vouchers are Weller and Sakai unless noted. Asterisks indicate that a gametic chromosome count was obtained (Weller & Denton, 1976); counts were N = 14 in all cases. Geographical coordinates are from Pérez-Alquicira et al. (2010). B, calculation of expected segregation patterns at tristyly loci based on disomic and polysomic inheritance. C, style-morph frequencies in progeny following controlled crosses in seven populations of Oxalis alpina, with expected style-morph segregations, depending on whether inheritance is disomic (diploid case), tetrasomic (all possible chromosome pairing equally likely), or polyploid and disomic (preferential pairing of two sets of homologous chromosomes). Linkage between the S and M loci is assumed in all models of inheritance. In all outcrosses, short- and mid-styled morphs were crossed to homozygous recessive long-styled individuals. Reciprocal crosses using the same short- or mid-styled parents are combined. Progeny of short-styled morphs were grouped by presence or absence of mid-styled morphs. Chi-squared values for segregations following cross pollinations were calculated when 15 or more progeny were scored for style morph; segregations consistent with segregation patterns (from Table 1) are shown under 'Possible modes of inheritance'; a 'yes' indicates the model of inheritance is possible, although in many crosses the number of progeny was too small to calculate χ2 values or differentiate among models. A 'no' in bold type indicates that the observed segregation pattern was inconsistent with the proposed genetic model, either through presence of an unexpected style morph or skewed representation of style morphs that were predicted to occur. Expected segregations are shown for all crosses. Style morphs in progeny are the same as those in the parental cross, unless otherwise noted. For segregations following short- × long-styled crosses, expected 1:1 ratios under the diploid model with linkage could consist either of short- and long-styled progeny, or short- and mid-styled progeny, depending on pattern of linkage. For segregations following mid- × long-styled crosses, ratios were tested against the 1:1 ratio expected for parents with a single M allele, and 3:1 ratios expected for preferential pairing (allopolyploidy) when two M alleles are present. Progeny produced from self-pollinations of short-styled morphs were tested against a 3:1 ratio, unless mid-styled morphs segregated. Progeny produced from self-pollinations of mid-styled morphs were tested against a 3:1 ratio, except for those mid-styled morphs that segregated no long-styled morphs. Asterisks in columns showing χ2 values indicate significance level (*P < 0.05, **P < 0.01, ***P < 0.001). Progeny from self-pollinations using two possible anther whorls were combined. A † in a style morph column indicates presumed contamination. UC-Irvine Undergraduate Research Opportunities Program and Summer Undergraduate Research Program grants ArticleID:BOJ12316 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 0024-4074 1095-8339 |
| DOI: | 10.1111/boj.12316 |