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.
