4xTrifolium ambiguum and 2xT. occidentale hybridise despite wide geographic separation and polyploidisation: implications for clover breeding

Williams, W. M.; Verry, Isabelle M.; Ansari, H. A.; Hussain, S. W.; Ullah, Ihsan; Ellison, Nicholas W.

doi:10.1007/s00122-019-03395-0

Cited by 4 publications

(21 citation statements)

References 26 publications

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“…Female fertility (OP seed-set) was, however, apparently much lower in the 6 x T. ambiguum x 2 x T. occidentale F 1 s than in the hybrids involving 2 x and 4 x T. ambiguum . One 2 x hybrid produced nearly one (0.8) OP seeds/head [24], while the 3 x hybrid produced 1–2 OP seeds/head [25]. In contrast, the seed-sets obtained in the present study ranged from 0.00–0.14 seeds/head (Table 4).…”

Section: Discussionmentioning

confidence: 60%

“…Of six hybrids checked, five were below 10% in pollen staining. Very low pollen staining (< 3%) was also observed in three F 1 hybrids between 2 x T. ambiguum and 2 x T.occidentale [24] and, similarly, it was approximately 9% in one 3 x F 1 between 4 x T. ambiguum and 2 x T. occidentale [25]. Female fertility (OP seed-set) was, however, apparently much lower in the 6 x T. ambiguum x 2 x T. occidentale F 1 s than in the hybrids involving 2 x and 4 x T. ambiguum .…”

Section: Discussionmentioning

confidence: 94%

“…Previous studies [24, 25] have shown that both 2 x and 4 x T. ambiguum could be hybridized with 2 x T. occidentale and that the F 1 s were inter-fertile with white clover. This indicated that all four taxa were derived from a common ancestor and were part of a species radiation that now covers all of Europe and parts of W Asia.…”

Section: Discussionmentioning

confidence: 99%

“…T. repens is an allotetraploid derivative of hybridization between alpine T. pallescens and coastal T. occidentale and its adaptation spans the habitat range of the whole group. Previous work [24, 25] showed that 2 x and 4 x forms of T. ambiguum formed fertile hybrids with T. occidentale , also after embryo rescue. These inter-fertilities suggested that species divergence had probably not occurred from an accumulation of genetic changes in inter-fertility but rather that such changes had occurred later after the separation and independent development of the ancestral populations [24, 25].…”

Section: Discussionmentioning

confidence: 99%

“…An alternative strategy could be to use the knowledge that white clover is a hybrid between ancestral forms of T. pallescens and T. occidentale [12] and that there has been successful hybridization of 2 x and 4 x T. ambiguum with 2 x T. occidentale . This suggested that T. occidentale could be used as a genetic bridge between white clover and T. ambiguum [24, 25]. In the present case, this would require the generation of not only fertile hybrids between 6 x T. ambiguum and T. occidentale , but also the ability to obtain hybrids of these with a third species, T. repens .…”

Section: Introductionmentioning

confidence: 98%

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A Eurasia-wide polyploid species complex involving 6x Trifolium ambiguum, 2x T. occidentale and 4x T. repens produces interspecific hybrids with significance for clover breeding

et al. 2019

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BackgroundTrifolium ambiguum occurs as a 2x, 4x, 6x polyploid series in W Asia. The 6x form is the most agronomically desirable, having strong rhizomatous spread and drought tolerance. These traits would be potentially very valuable if they could be transferred to white clover (T. repens) which is the most important agronomic clover species. However, to-date, no fertile interspecific hybrids with 6x T. ambiguum are available. Previously, 2x T. occidentale from W Europe has produced synthetic fertile hybrids with both 2x and 4x T. ambiguum and these were inter-fertile with white clover. Here we ask whether 2x T. occidentale can form fertile hybrids with 6x T. ambiguum and act as a genetic bridge to white clover and bring these species together as part of a common gene pool.ResultsTen verified F1 (6x T. ambiguum x 2x T. occidentale) hybrids were produced by embryo rescue and seven were studied further. All four investigated for chromosome number were 2n = 4x = 32 and FISH confirmed the expected 21 T. ambiguum and 8 T. occidentale chromosomes. Hybrid fertility was extremely low but 2n female gametes functioned with white clover pollen to produce seeds. Derived plants were confirmed using FISH and were successfully backcrossed to white clover to produce partially fertile breeding populations.ConclusionsAlthough T. occidentale and 6x T. ambiguum are widely separated by geography and ecological adaptation they have maintained enough genomic affinity to produce partially fertile hybrids. Inter-fertility of the hybrids with allotetraploid T. repens showed that T. occidentale can provide a genetic bridge between 6x T. ambiguum and white clover to produce plants with new phenotypes combining the traits of all three species. Use of this information should enable potentially valuable stress tolerance traits from 6x T. ambiguum to be used in white clover breeding for the first time.

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Section: Discussionmentioning

confidence: 60%

Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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A Eurasia-wide polyploid species complex involving 6x Trifolium ambiguum, 2x T. occidentale and 4x T. repens produces interspecific hybrids with significance for clover breeding

et al. 2019

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Asynapsis and unreduced gamete formation in a Trifolium interspecific hybrid

et al. 2022

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Background Unreduced gametes, a driving force in the widespread polyploidization and speciation of flowering plants, occur relatively frequently in interspecific or intergeneric hybrids. Studies of the mechanisms leading to 2n gamete formation, mainly in the wheat tribe Triticeae have shown that unreductional meiosis is often associated with chromosome asynapsis during the first meiotic division. The present study explored the mechanisms of meiotic nonreduction leading to functional unreduced gametes in an interspecific Trifolium (clover) hybrid with three sub-genomes from T. ambiguum and one sub-genome from T. occidentale. Results Unreductional meiosis leading to 2n gametes occurred when there was a high frequency of asynapsis during the first meiotic division. In this hybrid, approximately 39% of chromosomes were unpaired at metaphase I. Within the same cell at anaphase I, sister chromatids of univalents underwent precocious separation and formed laggard chromatids whereas paired chromosomes segregated without separation of sister chromatids as in normal meiosis. This asynchrony was frequently accompanied by incomplete or no movement of chromosomes toward the poles and restitution leading to unreduced chromosome constitutions. Reductional meiosis was restored in progeny where asynapsis frequencies were low. Two progeny plants with approximately 5 and 7% of unpaired chromosomes at metaphase I showed full restoration of reductional meiosis. Conclusions The study revealed that formation of 2n gametes occurred when asynapsis (univalent) frequency at meiosis I was high, and that normal gamete production was restored in the next generation when asynapsis frequencies were low. Asynapsis-dependent 2n gamete formation, previously supported by evidence largely from wheat and its relatives and grasshopper, is also applicable to hybrids from the dicotyledonous plant genus Trifolium. The present results align well with those from these widely divergent organisms and strongly suggest common molecular mechanisms involved in unreduced gamete formation.

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Interspecific Hybridization in Plant Biology

2022

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4xTrifolium ambiguum and 2xT. occidentale hybridise despite wide geographic separation and polyploidisation: implications for clover breeding

Cited by 4 publications

References 26 publications

A Eurasia-wide polyploid species complex involving 6x Trifolium ambiguum, 2x T. occidentale and 4x T. repens produces interspecific hybrids with significance for clover breeding

A Eurasia-wide polyploid species complex involving 6x Trifolium ambiguum, 2x T. occidentale and 4x T. repens produces interspecific hybrids with significance for clover breeding

Asynapsis and unreduced gamete formation in a Trifolium interspecific hybrid

Interspecific Hybridization in Plant Biology

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