Evidence for the existence of endosperm balance number in the true clovers (<i>Trifolium</i> spp.)

Parrott, W. A.; Smith, R. R.

doi:10.1139/g86-085

Cited by 27 publications

(25 citation statements)

References 14 publications

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“…Endosperm development was shown to be normal (Chen and Gibson, 1974). Subsequently, T. nigrescens was correctly allocated an EBN of 4 and T. occidentale an EBN of 2 (Parrott and Smith, 1986). Consideration of EBN would therefore predict endosperm failure in crosses between the diploid parents to give diploid progeny, and these would occur only very rarely, if at all.…”

Section: Discussionmentioning

confidence: 99%

Hybridization and Introgression between Two Diploid Wild Relatives of White Clover, Trifolium nigrescens Viv. and T. occidentale Coombe

et al. 2008

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Trifolium nigrescens Viv. and T. occidentale Coombe are diploid (2n = 2x = 16) clover species with contrasting habits and geographic distributions. Trifolium nigrescens is a nonstoloniferous annual with widespread distribution in the Mediterranean countries of Europe and northern Africa, Turkey, the Middle East, and the Caucasus region. By contrast, T. occidentale is a stoloniferous perennial and is strictly coastal, occurring on the Gulf Stream coasts of Portugal, Spain, France, Ireland, and the United Kingdom. Here we report for the first time that both 2x T. nigrescens ssp. nigrescens and ssp. petrisavii can be hybridized with 2x T. occidentale. No special techniques are required, and advanced generation hybrid populations can be produced. Furthermore, backcrosses to T. nigrescens are easily obtained, and introgression of genes from T. occidentale occurs. The chromosomes of the two species show perfect pairing and regular disjunction at meiosis. The biological separation (reproductive isolation) of these species is incomplete. This incomplete isolation is paralleled by a partial breakdown of the genetic mechanism that would normally prevent endosperm development in these crosses. Observations on the life history of one hybrid and its progeny showed that two traits involved in perenniality were inherited in opposite ways. These species are close relatives of white clover and are potentially important sources of traits for plant breeding. This work raises the likelihood of simultaneous introgression of traits from both diploid species into white clover.

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Section: Discussionmentioning

confidence: 99%

Hybridization and Introgression between Two Diploid Wild Relatives of White Clover, Trifolium nigrescens Viv. and T. occidentale Coombe

et al. 2008

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“…Indeed, even though new polyploids are often reproductively isolated from their diploid congeners, referred as the "triploid block" (20), polyploidization is also associated with the bypass of interspecific reproductive barriers (21)(22)(23)(24)(25). Postzygotic interspecific reproductive barriers rely on similar mechanisms as the triploid block; both affect hybrid seed survival as a consequence of endosperm developmental failure.…”

Section: Significancementioning

confidence: 99%

“…According to the endosperm balance number (EBN) hypothesis, the effective ploidy of a species must be in a 2:1 maternal to paternal ratio in the endosperm to allow normal endosperm development (21)(22)(23)40). It has been proposed that species can have different effective ploidies, explaining the quantitative nature of hybrid seed failure.…”

Section: Significancementioning

confidence: 99%

Endosperm-based hybridization barriers explain the pattern of gene flow between Arabidopsis lyrata and Arabidopsis arenosa in Central Europe

Lafon‐Placette

Johannessen

Hornslien

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

113

128

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Based on the biological species concept, two species are considered distinct if reproductive barriers prevent gene flow between them. In Central Europe, the diploid species Arabidopsis lyrata and Arabidopsis arenosa are genetically isolated, thus fitting this concept as "good species." Nonetheless, interspecific gene flow involving their tetraploid forms has been described. The reasons for this ploidy-dependent reproductive isolation remain unknown. Here, we show that hybridization between diploid A. lyrata and A. arenosa causes mainly inviable seed formation, revealing a strong postzygotic reproductive barrier separating these two species. Although viability of hybrid seeds was impaired in both directions of hybridization, the cause for seed arrest differed. Hybridization of A. lyrata seed parents with A. arenosa pollen donors resulted in failure of endosperm cellularization, whereas the endosperm of reciprocal hybrids cellularized precociously. Endosperm cellularization failure in both hybridization directions is likely causal for the embryo arrest. Importantly, natural tetraploid A. lyrata was able to form viable hybrid seeds with diploid and tetraploid A. arenosa, associated with the reestablishment of normal endosperm cellularization. Conversely, the defects of hybrid seeds between tetraploid A. arenosa and diploid A. lyrata were aggravated. According to these results, we hypothesize that a tetraploidization event in A. lyrata allowed the production of viable hybrid seeds with A. arenosa, enabling gene flow between the two species.interspecies hybrid seed failure | Arabidopsis | reproductive isolation | endosperm cellularization | EBN

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“…Evidence for EBN-like systems has been also reported in other species such as Trifolium spp. (Parrott and Smith 1986), Glycine spp. (Zhang and Palmer 1990), Lycopersicon spp.…”

Section: Endosperm Barriersmentioning

confidence: 99%

Substitutes for genome differentiation in tuber-bearing Solanum: interspecific pollen-pistil incompatibility, nuclear-cytoplasmic male sterility, and endosperm

2004

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The cultivated potato, Solanum tuberosum L. (2n=4x=48), has a very large number of related wild and cultivated tuber-bearing species widely distributed in the Americas. These species, grouped in 16 taxonomic series, range from the diploid to the hexaploid level. Polyploid species are either disomic or polysomic, and sexual polyploidization via genetically controlled 2 n gametes has played a major role in their evolution. Species are separated in nature by geographical and ecological barriers. However, there are several examples of sympatric species that share the same niches but do not readily cross (i.e., the diploids S. commersonii and S. chacoense in certain areas of Argentina). External barriers alone are, therefore, not sufficient to explain species integrity. In addition, there is no strong evidence indicating that genome differentiation is important in the group. In this review we present evidence supporting the assertion that interspecific pollen-pistil incompatibility, nuclear-cytoplasmic male sterility, and the endosperm are major forces that strengthen the external hybridization barriers allowing, at the same time and under specific circumstances, a certain amount of gene exchange without jeopardizing the integrity of the species.

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Evidence for the existence of endosperm balance number in the true clovers (Trifolium spp.)

Cited by 27 publications

References 14 publications

Hybridization and Introgression between Two Diploid Wild Relatives of White Clover, Trifolium nigrescens Viv. and T. occidentale Coombe

Hybridization and Introgression between Two Diploid Wild Relatives of White Clover, Trifolium nigrescens Viv. and T. occidentale Coombe

Endosperm-based hybridization barriers explain the pattern of gene flow between Arabidopsis lyrata and Arabidopsis arenosa in Central Europe

Substitutes for genome differentiation in tuber-bearing Solanum: interspecific pollen-pistil incompatibility, nuclear-cytoplasmic male sterility, and endosperm

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