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Alagna F, Caceres ME, Pandolfi S, Collani S, Mousavi S, Mariotti R, Cultrera NGM, Baldoni L, Barcaccia G. The Paradox of Self-Fertile Varieties in the Context of Self-Incompatible Genotypes in Olive. Front Plant Sci 2019; 10:725. [PMID: 31293602 PMCID: PMC6606695 DOI: 10.3389/fpls.2019.00725] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 05/16/2019] [Indexed: 05/09/2023]
Abstract
Olive, representing one of the most important fruit crops of the Mediterranean area, is characterized by a general low fruit yield, due to numerous constraints, including alternate bearing, low flower viability, male-sterility, inter-incompatibility, and self-incompatibility (SI). Early efforts to clarify the genetic control of SI in olive gave conflicting results, and only recently, the genetic control of SI has been disclosed, revealing that olive possesses an unconventional homomorphic sporophytic diallelic system of SI, dissimilar from other described plants. This system, characterized by the presence of two SI groups, prevents self-fertilization and regulates inter-compatibility between cultivars, such that cultivars bearing the same incompatibility group are incompatible. Despite the presence of a functional SI, some varieties, in particular conditions, are able to set seeds following self-fertilization, a mechanism known as pseudo-self-compatibility (PSC), as widely reported in previous literature. Here, we summarize the results of previous works on SI in olive, particularly focusing on the occurrence of self-fertility, and offer a new perspective in view of the recent elucidation of the genetic architecture of the SI system in olive. Recent advances in research aimed at unraveling the molecular bases of SI and its breakdown in olive are also presented. The clarification of these mechanisms may have a huge impact on orchard management and will provide fundamental information for the future of olive breeding programs.
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Affiliation(s)
- F. Alagna
- Dipartimento Tecnologie Energetiche (DTE), Centro Ricerche Trisaia, ENEA Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile, Rotondella, Italy
| | - M. E. Caceres
- Dipartimento di Scienze Bio Agroalimentari (DiSBA), Istituto di Bioscienze e Biorisorse (IBBR), Consiglio Nazionale Delle Ricerche (CNR), Perugia, Italy
| | - S. Pandolfi
- Dipartimento di Scienze Bio Agroalimentari (DiSBA), Istituto di Bioscienze e Biorisorse (IBBR), Consiglio Nazionale Delle Ricerche (CNR), Perugia, Italy
| | - S. Collani
- Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Umeå, Sweden
| | - S. Mousavi
- Dipartimento di Scienze Bio Agroalimentari (DiSBA), Istituto di Bioscienze e Biorisorse (IBBR), Consiglio Nazionale Delle Ricerche (CNR), Perugia, Italy
| | - R. Mariotti
- Dipartimento di Scienze Bio Agroalimentari (DiSBA), Istituto di Bioscienze e Biorisorse (IBBR), Consiglio Nazionale Delle Ricerche (CNR), Perugia, Italy
| | - N. G. M. Cultrera
- Dipartimento di Scienze Bio Agroalimentari (DiSBA), Istituto di Bioscienze e Biorisorse (IBBR), Consiglio Nazionale Delle Ricerche (CNR), Perugia, Italy
| | - L. Baldoni
- Dipartimento di Scienze Bio Agroalimentari (DiSBA), Istituto di Bioscienze e Biorisorse (IBBR), Consiglio Nazionale Delle Ricerche (CNR), Perugia, Italy
- *Correspondence: L. Baldoni,
| | - G. Barcaccia
- Laboratorio di Genomica, Dipartimento di Agronomia, Animali, Alimenti, Risorse naturali e Ambiente (DAFNAE), Università di Padova, Legnaro, Italy
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Baldwin SJ, Schoen DJ. Genetic variation for pseudo-self-compatibility in self-incompatible populations of Leavenworthia alabamica (Brassicaceae). New Phytol 2017; 213:430-439. [PMID: 27448252 DOI: 10.1111/nph.14109] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 06/15/2016] [Indexed: 05/24/2023]
Abstract
Self-incompatibility (SI) promotes outcrossing, but transitions to self-compatibility (SC) are frequent. Population genetic theory describing the breakdown of SI to SC suggests that, under most conditions, populations should be composed of either SI or SC individuals. Under a narrow range of conditions, theory suggests that SI may persist alongside reduced expression of SI (pseudo-SI, PSI) in mixed-mating populations. We studied genetic variation for PSI segregating in four SI populations of Leavenworthia alabamica by measurement of the heritability of pollen tube number after self-pollination. We tested for the role of the S-locus in this variation by sequencing seven S-alleles from plants with high pseudo-SC (PSC) and testing for the co-segregation of these alleles with PSC. We found a continuous distribution of PSC in all populations and 90% of plants exhibited PSC. The heritability ranged from 0.39 to 0.57. All seven S-alleles from plants with high PSC exhibited trans-specific polymorphism, and no stop codons were observed within the c. 600-bp region sequenced. One of these S-alleles was directly associated with the inheritance of PSC. We conclude that heritable variation in PSC is largely a result of genetic variation in the signaling cascade downstream of the S-locus reaction, together with the presence of one leaky S-allele.
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Affiliation(s)
- Sarah J Baldwin
- Department of Biology, McGill University, Montreal, QC, H3A 1B1, Canada
| | - Daniel J Schoen
- Department of Biology, McGill University, Montreal, QC, H3A 1B1, Canada
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Brennan AC, Tabah DA, Harris SA, Hiscock SJ. Sporophytic self-incompatibility in Senecio squalidus (Asteraceae): S allele dominance interactions and modifiers of cross-compatibility and selfing rates. Heredity (Edinb) 2011; 106:113-23. [PMID: 20372180 PMCID: PMC3183852 DOI: 10.1038/hdy.2010.29] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 11/27/2009] [Accepted: 12/17/2009] [Indexed: 11/08/2022] Open
Abstract
Understanding genetic mechanisms of self-incompatibility (SI) and how they evolve is central to understanding the mating behaviour of most outbreeding angiosperms. Sporophytic SI (SSI) is controlled by a single multi-allelic locus, S, which is expressed in the diploid (sporophyte) plant to determine the SI phenotype of its haploid (gametophyte) pollen. This allows complex patterns of independent S allele dominance interactions in male (pollen) and female (pistil) reproductive tissues. Senecio squalidus is a useful model for studying the genetic regulation and evolution of SSI because of its population history as an alien invasive species in the UK. S. squalidus maintains a small number of S alleles (7-11) with a high frequency of dominance interactions. Some S. squalidus individuals also show partial selfing and/or greater levels of cross-compatibility than expected under SSI. We previously speculated that these might be adaptations to invasiveness. Here we describe a detailed characterization of the regulation of SSI in S. squalidus. Controlled crosses were used to determine the S allele dominance hierarchy of six S alleles and effects of modifiers on cross-compatibility and partial selfing. Complex dominance interactions among S alleles were found with at least three levels of dominance and tissue-specific codominance. Evidence for S gene modifiers that increase selfing and/or cross-compatibility was also found. These empirical findings are discussed in the context of theoretical predictions for maintenance of S allele dominance interactions, and the role of modifier loci in the evolution of SI.
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Affiliation(s)
- A C Brennan
- School of Biology, University of St Andrews, Fife, UK
| | - D A Tabah
- School of Biological Sciences, University of Bristol, Bristol, UK
| | - S A Harris
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | - S J Hiscock
- School of Biological Sciences, University of Bristol, Bristol, UK
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