Assessment of meiotic abnormalities induced by gamma irradiations in Zea mays L. (Poaceae)

Maize (Zea mays L.) is an important cereal crop with 2n = 20 chromosomes. For assessing irradiation effects, dry seeds of maize were treated with nine different irradiation doses viz., 5, 10, 15, 20, 25, 30, 35, 40 and 50kR at BARC, Mumbai. The gamma irradiated seed progenies displayed a wide spectrum of meiotic anomalies, the most being lagging chromosomes, chromosome stickiness, multivalents, unoriented bivalents, bridges and micronuclei. Other aberrations identified include chromosome scattering, univalents, disturbed polarity and precocious chromosome movement. The spectrum of these meiotic aberrations was found higher at metaphase than anaphase/telophase. Also, the frequency of aberrations showed positive correlation with the increasing gamma irradiation dose. In addition, gamma irradiation doses decreased germination and survival percentage as well. The irradiation doses ranging from 20-30kR were found beneficial in producing rapid cytogenetic variations and average lethality which could be beneficial in future cytological and mutation breeding programmes.