Assessment of ⁶⁰Co gamma radiation on early phenological stages of two generations of <i>OFADA</i> rice

Abstract

Traditional Ofada rice varieties from South-West, Nigeria is preferred for its unique taste, aroma and massive potential for export but has low yield. Based on this background, two Ofada rice varieties, FUNAABOR 1 and FUNAABOR 2 were irradiated to create genetic variability as it affects vegetative traits. Seeds from the varieties were exposed to nine levels of ⁶⁰Co gamma irradiation (0, 50, 100, 150, 200, 250, 300, 350 and 400 Gy). The seeds were nursed for 30 days before M₁ seedlings were transplanted into a well tilled soil in a two factorial RCBD with three replicates. Selections from M₁ plants were used to establish M₂ plants generation. The results revealed diverse effects of ⁶⁰Co gamma irradiation treatments on different plant vegetative traits. The establishment rates of M₁ Ofada rice population were unaffected (p > 0.01) by increasing gamma irradiation from 0 to 300 Gy but decreased at 350 Gy. Above 300 Gy, tiller numbers, plant height, lodging incidence, leaf number, leaf length and leaf angle decreased significantly when compared with control (p < 0.01) in both generations (M₁ and M₂). Moderately tillered (10 tillers), tall plant (116.9 cm) obtained from 350 dosage rate recorded highest grain weight of 7.8 g per panicle. High phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) promoted by the irradiation dosages in M₁ selection indicate the extent of environmental influence. High broad sense heritability observed from leaf number, leaf angle, leaf length, leaf blade colour, basal leaf sheath colour and grain weight per panicle shows possibility of rapid genetic improvement of these characters through selection.