Effect of gamma irradiation on seed germination and chromosomal behaviour at meiotic division in bread wheat (Triticum Aestivum L.)

Meiosis was studied in control and seed-irradiated progenies of Triticum aestivum in order to understand the effects of gamma irradiations on chromosomal behavior during meiotic division. The main chromosomal aberrations were stickiness, precocious separations, univalents, multivalents, unoriented bivalents, laggards, bridges, fragments, disturbed polarity, unequal separations of chromosomes and micronuclei. The stickiness, stray bivalents and multivalents at metaphase, laggards, bridges and fragments at anaphase/telophase were the dominant anomalies. The degree of occurrence of all these meiotic abnormalities essentially coincided with the increase in the treatment of gamma irradiations. These chromosomal aberrations also affected the qualitative composition of postmeiotic products, i.e. tetrads and pollen grains. The effect of gamma rays on chiasma frequency and pollen fertility was also studied in which dose dependent decrease was clearly noticeable. Moreover, higher doses (25kR-50kR) markedly decreased seed germination whereas lower dose (5kR-20kR) showed no significant effect (P<0.01) on the germination percentage with respect to the control.