Identification of barriers to interspecific crosses in the genus Trifolium
| Authors | |
|---|---|
| Year of publication | 2006 |
| Type | Article in Periodical |
| Magazine / Source | Euphytica |
| MU Faculty or unit | |
| Citation | |
| Field | Animal production |
| Keywords | barriers of crossability - clearing - clover - embryogenesis - interspecific hybridisation - ploidy level - Trifolium |
| Description | Study of pre- and post-fertilisation barriers after interspecific crosses of diploid and tetraploid Trifolium pratense L. and wild species T. alpestre L., T. medium L. and T. sarosiense Hazsl. was aimed to the finding of a cross combination promising for hybrid obtaining. Growth of pollen tubes was arrested in interspecific crosses mainly when T. pratense was on diploid level. To investigate the post-fertilisation barriers in detail, hybrid embryo viability was traced by two clearing treatments of immature seeds, using either chloral hydrate which showed to be most suitable or a mixture of benzyl benzoate and dibutyl phthalate. In interspecific combinations T. pratense (4x) x either T. alpestre or T. sarosiense, enlargement of immature seeds occurred, but no hybrid embryo was traced. Of the wild species used as a male parent for crosses, T. medium was the only exception from the point of view of fertilisation. Globular, heart and early torpedo stages of hybrid embryos were observed 7 days after pollination (DAP) but only when T. pratense was on the tetraploid level. When T. pratense (2x, 4x) was used as a male parent for interspecific crosses with T. alpestre, T. medium and T. sarosiense, strong defects in various stages of embryogenesis were observed, particularly wrinkled and narrowing embryo sacs caused by expansion of endothelial cells. We could conclude the following findings; to make crosses only in one direction with T. pratense as a female parent and T. medium as a male, to use tetraploid plants of T. pratense and to excise hybrid embryos at early torpedo stage, about 7 DAP. |
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