Impact of gamma irradiation on growth, yield and physiological attributes of maize

Feeding the increasing global population with adequate supply of cereals for food, particularly with limited agricultural area, is a challenging task. In this context, emphasis on enhancing food producing processes gains attention. Gamma irradiation, up to certain doses, is known to improve crop yield without using chemical fertilizers. Among the cereals, maize is an important crop, which accounts for 9% of total food grain production. Here, we presumed that gamma ray pretreatment to maize seeds would be beneficial and boost the maize productivity and yield. In this study, we conducted field experiments to assess the gamma irradiation induced effect on seedling emergence, plant growth, yield and yield attributes of maize (HQPM-1). Grains of maize were exposed to gamma radiation doses ranging from 0.0025, 0.005, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4 0.50, 1.0 and 2.0 kGy with the help of Co-60 gamma-radiation source facility available in the Centre. The germination of irradiated seeds was assessed in an incubator chamber and the irradiated seeds were sown in the field during kharif (July-October) 2013 and 2014 seasons at the IARI, New Delhi, research farm. The germination was >90% up to 0.1 kGy dose, beyond which, germination of seeds in the incubator as well as in field condition declined significantly. Few seedlings still came out from relatively higher doses of gamma irradiation (>0.5 kGy). However, these seedlings could not survive more than seven days. Results of present study indicated that plant growth parameters, such as plant height, photosynthetic rate, chlorophyll content, leaf area index at 'tasseling' as well as at 'silking' stage affected positively at lower doses (<0.2 kGy). The biological yield, grain weight (g) (cob(-1)), grains (cob(-1)) and 100 grain weights responded positively to the lower doses (approximate to 0.1 kGy) of gamma irradiation. Our results indicated improvement in biological yield by 35.2% at 0.1 kGy as compared to the control (00 kGy). However, maximum reduction (33%) was recorded at 0.5 kGy. Similarly, grain yield (ton ha(-1)) was improved by 8.3% at 0.1 kGy as compared to the control, but reduced the most by 56.9% at 0.5 kGy compared to the respective control.