Radiation Induced Chromosomal Interchanges in Brassica campestris L.

抄録

The frequency of chromosomal interchanges has been assessed in terms of multivalent associations in self-incompatible and self-compatible Brassica campestris L. var. dichotoma Watt. (cv. Brown Sarson) after irradiation of dry seeds with gamma rays and thermal neutrons. The chromosomal interchanges showed a linear dependence on doses of both these types of irradiation. Gamma rays, compared to thermal neutrons, induced a slightly higher order of segmental interchanges. Pollen and ovule sterility were conditioned by the number and frequency of participating chromosomes. Most multivalents were interchanges of a chain of four chromosomes. Interchanges involving two pairs of non homologous chromosomes were higher in frequency than those involving more chromosomes. Self-compatible types showed a higher degree of resistance to radiation. Apart from interchanges, other aberrations like univalents, laggards, bridges with fragments, unequal anaphase I separation and chromosome stickiness were also observed in low frequency.