A Novel Unequal Reciprocal Translocation in the Karyotype Diversification of Vicia hybrida (Fabaceae)

Abstract

In Viciahybrida (2n = 2x = 12) one out of twenty-five plants analyzed was found to be heterozygote for highly unequal translocation but with a difference and novelty. All the cells analyzed at metaphase I were characterized by the presence of a ring or a chain of four chromosomes. The two derived chromosomes in the heterozygote were of highly unequal size, one being very long metacentric and another very small submetacentric chromosome. The two other ancestral submetacentric and subtelocentric chromosomes were medium sized with little difference in their lengths. The small derived chromosome was not totally heterochromatic, and it was associated with the complex heterozygote by the formation of chiasmata at one or at both ends. No cell was observed to be a trivalent and univalent. Majority (52 %) of cells at anaphase I were characterized by the occurrence of five and six chromosomes at each pole and the small derived chromosome lagging behind. In 64.1 % cells at telophase I, the small derived chromosome was found to lag behind with intact morphology without the process of decondensation. In 48 % cells at telophase II it was seen to divide. A new type of Robertsonian translocation is discussed in relation to the interchanged chromosome.