Effect of Ionizing Irradiation on Seed Quality, Agronomic Performance and Yield of M1 And M2 Mutant Cowpea Lines

Abstract

The use of mutation breeding in crop improvement is becoming popular in recent times with gamma rays being among the most widely used physical mutagens. However, during gamma-irradiation of seeds to generate desirable traits, certain physiological and biochemical processes are affected. This study sought to examine the effect of irradiation on seed quality, including physiological, seed health, agronomic and yield performance of mutant cowpea lines. Twenty-five (25) cowpea lines were irradiated at five (5) doses of gamma radiation (0, 50, 100, 150 & 200 Gy) at a rate of 330 Gys-1. The results showed significant differences (p<0.05) among the lines in germination parameters, percentage mycoflora infection, agronomic and yield parameters. Increasing irradiation up to 200 Gy led to an increase in percentage hard seeds, mean germination time and uncertainty of germination. However, increasing irradiation led to a decrease in coefficient of variation of germination time, mean germination rate and synchronization index. Irradiation doses up to 200 Gy did not show a significant lethal effect on percentage infections for Cladosporium sphaerospermum, Penicillium and Fusarium moniliforme. The pre-treated irradiated cowpea seeds recorded relatively lower mycoflora infections for saprophytic fungi. Increasing irradiation up to 200 Gy showed decreasing plant height at 21 days after planting and at flowering as well as decreasing pod length and seeds per pod but led to an increase in 100 seed weight. Low doses of irradiation up to 200 Gy affected germination time and synchrony, agronomic performance and yield parameters of both M1 and M2 mutant generations but relatively higher doses would be required to reduce seed-borne mycoflora.