In situ cytophotometric estimation of nuclear DNA in different cultivars of Allium species

The DNA content was determined at intra- and interspecific levels in fourteen diploid and one tetraploid cultivars of Allium covering six species. The 4C DNA values ranged from 67 pg to 71.61 pg in A. cepa, 69.33 pg to 70.25 pg in A. fistulosum, 66.32 pg to 68.67 pg in A. ascalonicum and 73.59 pg to 91.89 pg in A. sativum among the diploid species. The tetraploid A. tuberosum cultivar contained 109.36 pg. Statistical analysis showed significant diversity in the distribution of 4C DNA among the cultivars. A. sativum was quite distinct from other species of Allium studied, all of which maintained a very low range of DNA within the species. The wide differences in the DNA values of A. sativum may be due to the repetitive DNA content. The high DNA value of the tetraploid A. tuberosum was not proportionately double the probable diploid progenitor A. cepa. Autotetraploidy in A. tuberosum has possibly been associated with proportionate lowering of the DNA content through mutational and other changes conferring species stability. Since the DNA values of different cultivars of Allium from diverse ecological zones do not show statistically significant deviation, climatic selection does not appear to be an important factor.