2013 Volume 78 Issue 1 Pages 43-49
Although the occurrence of reciprocal translocation has already been discovered in plants, this is the first report on the striking phenomenon of reciprocal translocation (RT) induced through combined treatment in Brassica campestris L. accession number-IC363713. The seeds were subjected to four doses of gamma rays i.e.15, 30, 45, 60 Kr, followed by 0.3% EMS solution, and were sown in triplicates. Occurrence of RT was identified by the reduced reproductive success of plants, which was authenticated by cytological analysis that revealed the high incidence of multivalent association, forming either a ring or a chain. Rings were discerned to occur in alternate orientation, forming eight-shaped structure while simple loops were noticed erratically when the chromosomes were oriented adjacently. On the other hand, the lack of chiasmata in chromosomes was the cause of chains as multivalent association. No such phenomenon has been observed in non-treated sets. Moreover, the spectrum of multivalent association (MA) and univalents in the pollen mother cells (PMCs) from diakinesis to metaphase-I has been found to be increased in parallel with the dose of treatment, although the frequency of bivalents showed a gradual decline in their percentages. The frequency of quadrivalents has prevailed both in ring and chain forms, other than trivalent, hexavalent and other associations. Meanwhile, pollen fertility drastically decreased with the increasing trend of multivalent association. Notwithstanding RT, various other structural chromosome abnormalities, such as unequal separation, laggards and bridges during meiotic course, were recorded.
