Genetic regulation of chromocentres in radish, Raphanus sativus L.

The number and ditribution of chromocentres have been studied in nine varietal populations of radish (Raphanus sativus L.) and their six F1 and two F2 hybrids. The mean number and the distribution of chromocentres in the interphase nuclei were found to be characteristic for a population. The varietal populations differed significantly from each other in this heterochromatin phenotye, indicating different degree of heterochromatinization in them. In the F1 hybrids the number of chromocentres averaged midway between their parents. The population having a narrow range of the distribution of chromocentres showed dominance to those having a wide range of the same. F2 hybrid plants, raised from three F1 families, demonstrated a wider range of distribution for number of chromocentres per nucleus than F1's and parents, though they did not differ significantly from the former in the mean number of chromocentres. It has been concluded that the amount and the distribution of constitutive heterochromatin in radish, as inferred from the chromocentre counts, are under the control of genotypes and regulated polygenically.