Chromosome constitution of two karyotypes in Vicia macrocarpa.

Abstract

The chromosome complements of two cytotypes of Vicia macrocarpa were investigated and it was observed that the karyotypes changed in relation to the position of centromere, length of chromosome arms and number and nature of nucleolar chromosomes. At the same time changes in some morphological and physiologlcal characters of the plants were also observed. In addition, the two chromosome complements were studied for their banding pattern at the mitotic prophase and metaphase. It was evident that the two cytotypes also showed differences in the amount and distribution of heterochromatin. One of the cytotypes (12E) exhibited a larger number of C-bands than the other (12C). It is concluded that the evolution of V.macrocarpa has been towards a decrease of the amount of heterochromatin, along with the changes of the karyotype. Various multivalents ranging frorn trivalents to hexavalents were observed in some cells at the meiosis in the F1 and F3 of 12Cxl2E. It was thus d.emonstrated that the two cytotypes differed by the presence of two reciprocal translocations. It was possible to identify the parent-derived individual chromosomes at both the mitotic stages and meiosis of the F3 plants based on the differences in the heterochromatic bands ancl centromere position. The extra-chromo some of a trisomic plant in the F3 was identified at the mitotic prophase as well as the chromosomes involvecl in the multivalents at the meiosis of the hybrids.