Spontaneous chromosome aberrations in diploid solanum

Chromosome aberrations were observed in the tapetum and pollen-mother-cells, generally in form of chromosome bridges, fragments and elimination of univalent chromosomes and fragments. Chromatid bridge formation varied from 13.1 to 10.25% in the first and second anaphases respectively. Endoreduplication with a high degree of ploidy was observed in tapetal cells. Chromosomal reduplication was so marked that the normal diploid chromosome number 24 reached 96. The association of chromosomes in three, four, five and six occurred in 49.4% of the cases observed. The occurrence of high frequency of polyvalents in a diploid seemed to indicate the presence of translocation interchanges inS. venturii. The frequency of univalents varied from 1.3 to 18.7%. Structural changes and gene mutation are probably responsible for failure of pairing among pairable chromosomes. The behaviour of univalents varied, they either pass to poles or lag and divide. The division and elimination of univalents causes unequal distribution of chromosomes on second metaphase plates. Univalents and fragments which failed to be included in the daughter nuclei formed micronuclei. The chromosome irregularities and abortion of pollen grains (45.4%) are presumably due to gene mutation which may have been enhanced in aged seeds.