Cytological Effects of Gamma Radiation and Its Impact on Growth and Yield of M1 and M2 Plants of Cowpea Cultivars

Abstract

This study aimed at investigating the changes imposed by gamma radiation in mitotic activities and the chromosomes as well as the vegetative criteria and yield of M1 and M2 plants of five cowpea cultivars. Seeds of cultivars (Kaha 1, Dokki 331, Azmerly, Cream 7 and Giza 6) were exposed to levels of γ-radiation ranging from 50 to 300 Gy. Low levels of γ-radiation enhanced mitotic activity and resulted in significant increase in chromosomal abnormalities in the root tip cells of M1 and M2 plants. The percentage of abnormalities varied among the varieties and was generally lower in M2 plants compared to M1 plants. The 50-Gy and 100-Gy doses of γ-radiation induced positive effects on plant growth and yield of M1 plants, while the 300 Gy of γ-radiation caused detrimental damage on three cultivars (Dokki 331, Azmerly and Cream 7), which failed to grow to flowering. More pronounced improvements in growth and yield were recorded in M2 plants; the increase in growth and yield was often associated with increased mitotic activity and the occurrence of chromosomal abnormalities, indicating that γ-radiation-induced chromosomal abnormalities are not likely to be associated with negative effects on growth or yield. Based on the calculated yield index, 50 Gy of γ-radiation may be used to improve the yield of three varieties (Dokki 331, Azmerly and Cream 7) and the 100 Gy dose may be recommended for improving the yield of the two varieties, Kaha 1 and Giza 6.