CHROMOSOME ALTERATIONS IN TISSUE-CULTURE CELLS OF ALLIUM-FISTULOSUM

Heterochromatin behaviour and structural alterations in chromosomes of cells derived from callus culture of Allium fistulosum have been studied. The diploid chromosome complement of Allium fistulosum consists of 16 chromosomes with significant amount of heterochromatin mainly of telomeric nature. In eight collections of callus cells analysed, a high rate of numerical and structural chromosome abnormalities was observed. After 12 months in culture about 20% of metaphase chromosomes possessed distinct signs of mutational events. C-banded preparations revealed that many structural alterations involved regions of heterochromatin. Interchromosomal connections and chromatid fusions occurred at telomeric heterochromatin segments. Also formation of the end-to-end associations and polycentric chromosomes often took place without visible loss of telomeric heterochromatin.