Genetic Rules of Heterosis in Plants

Birchler, James A.

doi:10.1002/9781118552872.ch19

Cited by 6 publications

(2 citation statements)

References 72 publications

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“…Patterns like Fig. 1a are most often observed with closely related lines, but with the level of heterosis increasing with divergence (Birchler, 2013 ). By contrast, Fig.…”

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confidence: 98%

The diverse effects of phenotypic dominance on hybrid fitness

et al. 2022

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When divergent populations interbreed, their alleles are brought together in hybrids. In the initial F1 cross, most divergent loci are heterozygous. Therefore, F1 fitness can be influenced by dominance effects that could not have been selected to function well together. We present a systematic study of these F1 dominance effects by introducing variable phenotypic dominance into Fisher's geometric model. We show that dominance often reduces hybrid fitness, which can generate optimal outbreeding followed by a steady decline in F1 fitness, as is often observed. We also show that "lucky" beneficial effects sometimes arise by chance, which might be important when hybrids can access novel environments. We then show that dominance can lead to violations of Haldane's Rule (reduced fitness of the heterogametic F1) but strengthens Darwin's Corollary (F1 fitness differences between cross directions).Taken together, results show that the effects of dominance on hybrid fitness can be surprisingly difficult to isolate, because they often resemble the effects of uniparental inheritance or expression. Nevertheless, we identify a pattern of environment-dependent heterosis that only dominance can explain, and for which there is some suggestive evidence. Our results also show how existing data set upper bounds on the size of dominance effects. These bounds could explain why additive models often provide good predictions for later-generation recombinant hybrids, even when dominance qualitatively changes outcomes for the F1.

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“…Patterns like Fig. 1a are most often observed with closely related lines, but with the level of heterosis increasing with divergence (Birchler, 2013 ). By contrast, Fig.…”

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confidence: 98%

The diverse effects of phenotypic dominance on hybrid fitness

et al. 2022

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“…The mechanism of heterosis is less known, and it is generally believed that the degree of genetic distance contributes to heterosis. 79 However, recent studies have shown that epigenetic involvement also contributes to heterosis, 80 , 14 re-sequenced the whole genome of parent plants and clonal plants and reported the reliable transmission of genetic information, which demonstrated that epigenetic information was also transferred normally across generations. Although epigenetic modification cannot be ruled out, the modifications were too minor to induce detectable phenotypic changes in rice under field conditions.…”

Section: Limitations To Synthetic Apomixismentioning

confidence: 99%

Apomixis and strategies to induce apomixis to preserve hybrid vigor for multiple generations

et al. 2020

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Hybrid seeds of several important crops with supreme qualities including yield, biotic and abiotic stress tolerance have been cultivated for decades. Thus far, a major challenge with hybrid seeds is that they do not have the ability to produce plants with the same qualities over subsequent generations. Apomixis, an asexual mode of reproduction by avoiding meiosis, exists naturally in flowering plants, and ultimately leads to seed production. Apomixis has the potential to preserve hybrid vigor for multiple generations in economically important plant genotypes. The evolution and genetics of asexual seed production are unclear, and much more effort will be required to determine the genetic architecture of this phenomenon. To fix hybrid vigor, synthetic apomixis has been suggested. The development of MiMe (mitosis instead of meiosis) genotypes has been utilized for clonal gamete production. However, the identification and parental origin of genes responsible for synthetic apomixis are little known and need further clarification. Genome modifications utilizing genome editing technologies (GETs), such as clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (cas), a reverse genetics tool, have paved the way toward the utilization of emerging technologies in plant molecular biology. Over the last decade, several genes in important crops have been successfully edited. The vast availability of GETs has made functional genomics studies easy to conduct in crops important for food security. Disruption in the expression of genes specific to egg cell MATRILINEAL (MTL) through the CRISPR/Cas genome editing system promotes the induction of haploid seed, whereas triple knockout of the Baby Boom (BBM) genes BBM1, BBM2, and BBM3 cause embryo arrest and abortion, which can be fully rescued by maletransmitted BBM1. The establishment of synthetic apomixis by engineering the MiMe genotype by genome editing of BBM1 expression or disruption of MTL leads to clonal seed production and heritability for multiple generations. In the present review, we discuss current developments related to the use of CRISPR/Cas technology in plants and the possibility of promoting apomixis in crops to preserve hybrid vigor. In addition, genetics, evolution, epigenetic modifications, and strategies for MiMe genotype development are discussed in detail.

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Polyploids as a “model system” for the study of heterosis

Washburn

Birchler

2013

Plant Reprod

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Heterosis research over the past century has focused primarily on diploid plants and animals. This is despite the fact that most heterotic organisms contain polyploid events in their recent and/or ancient past and various important crop species are heterotic polyploids. We present an argument for the study of heterosis within polyploid systems and give examples of how their study can improve current hypotheses and generate new ones. Polyploid systems allow experiments not possible in diploids but the insights gained must be incorporated into models to explain heterosis at all levels.

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Genetic Rules of Heterosis in Plants

Cited by 6 publications

References 72 publications

The diverse effects of phenotypic dominance on hybrid fitness

The diverse effects of phenotypic dominance on hybrid fitness

Apomixis and strategies to induce apomixis to preserve hybrid vigor for multiple generations

Polyploids as a “model system” for the study of heterosis

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