Cytological and Cytogenetic Studies on the Transposition of Centromere and the Karyotype Differentiation in Haplopappus gracilis
II. Genetic behaviour of the new-shaped chromosome
1981 Volume 46 Issue 1-2 Pages 443-449
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1981 Volume 46 Issue 1-2 Pages 443-449
1. The inheritance and genetic influence of the J-shaped chromosome found in Haplopappus gracilis (2n=4) was studied.
2. The frequency of JJ-type progenies obtained from the inbreeding of VJ-type was very low, lower than that of expectation. This suggests that some lethal effects are induced in some of the JJ-homozygotes.
3. From the crossing of VJ-type with VV-type, it is suggested that pollen grains with J-shaped chromosome may be inferior to pollen grains with V-shaped chromosome on VV-homozygous pistile.
4. Karyotype analysis of the clones in the experimental population showed that the VJ-heterozygotes gradually increased, while the VV-homozygotes gradually decreased and very few JJ-homozygotes occurred. This suggests that the VJ-heterozygotes are advantageous than VV-homozygotes, and that the JJ-homozygotes are disadvantageous. Therefore, the J-shaped chromosome is presumed to have a strong influence when combines with V-shaped chromosome.
5. The flowering season of JJ-combination was delayed for about one month as compared with those of VV- and VJ-combinations. This delay of the flowering season may cause the reproductive isolation of JJ-combination from the other combinations, thus resulting in the differentiation of a new karyotype.
