Most studies of plant hybridisation are concerned with documenting its occurrence in different plant groups. Many flowering plants are polyploids and seeds developed from crosses between individuals of different ploidies usually show abnormal features and often abort. The success or failure of interploidy crosses is very important to understanding the evolution of plants as well as to agriculture, but much remains to be learned about the nature of hybridisation barriers. Several mechanisms have been proposed to explain postzygotic barriers, including negative interactions between diverged sequences, global genome rearrangements, and widespread epigenetic reprogramming. Some recent advances in our understanding of the process of hybridisation are derived from different experimental studies on a series of A. thaliana ecotypes. Crosses between diploid (2x) and tetraploid (4x) individuals of the same ecotype can result in F1 lethality, and this dosage-sensitive incompatibility plays a major role in polyploidy speciation research. We have performed interploidy crosses between different diploid maternal A. thaliana ecotypes and tetraploid paternal Col-0 ecotype and identified a genetic variation in F1 lethality. We also found that maternal parents of some ecotypes such as Tsu-1 suppressed the F1 lethality caused by paternal-excess interploidy cross of Col-0 ecotype. A preliminary mapping exercise produced advanced backcross populations that are suitable for mapping maternal modifiers and for the identification of modifier genes. Furthermore, we studied the killer effect caused by Col-0 and identified three additive QTL that affect the rate of postzygotic lethality in F1 during interploidy crosses. This information will facilitate the identification of paternal genes that cause F1 lethality and contribute to reproductive isolation. The moa-1 (mosaic aneuploidy 1) mutant of A. thaliana was obtained in a screen of chemically (EMS) mutagenised seeds of Landsberg erecta (Ler). moa-1 has various phenotypic differences to wild type; the preliminary karyotype analysis showed that the cells of individual moa-1 mutant plants have a variable number of chromosomes (usually between 11-18). In contrast, the cells of wild type Arabidopsis plants and conventional aneuploids have a fixed number of chromosomes in each somatic cell. This data showed that all moa-1 plants have an abnormal number of chromosomes and thus they were termed as mosaic aneuploids.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:537702 |
| Date | January 2010 |
| Creators | Bolbol, Ahmed A. E. |
| Contributors | Scott, Roderick |
| Publisher | University of Bath |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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