Effect of Gamma Irradiation on Chlorophyll Content in the Cowpea (Vigna unguiculata (L.) Walp)

The experiment was conducted to study the mutagenic effect of gamma rays on chlorophyll content at three different physiological stages in the cowpea: pre-flowering, flowering and post-flowering. Five sets of cowpea seeds were subjected to individual doses of gamma rays: 400 Gy, 450 Gy, 500 Gy, 600 Gy and 0 Gy. The seeds were sown to raise the M1 generation. The M1 generation seeds were collected and sown in the next season to raise the M2 generation. Leaf chlorophyll content was measured for M2 generation plants. Mean chlorophyll content for pre-flowering stage ranged between 38.9 ± 8.17 (control) and 64.2 ± 6.16 (400 Gy). Flowering stage mean chlorophyll content ranged from 48.3 ± 14.4 (600 Gy) to 99.4 ± 6.22 (450 Gy). Post-harvest chlorophyll mean content ranged between 13.1 ±0.98 (600 Gy) and 38.0 ±1.90 (400 Gy). There were significant differences in treatment effects for pre-flowering (P = 0.021), flowering (P = 0.005) and harvest (P = 0.000). At pre-flowering treatment, treatment 400 Gy scored a significant increase of 64 percent (P = 0.02) above the control. The optimum dose for useful induced mutation for increases in chlorophyll concentration in the cowpea was 400 Gy

SSR-Based Genetic Structure Study of Seventy-Eight Cowpea (Vigna unguiculata (L.) Walp) Genotypes

Seventy-eight cowpea accessions were studied using short sequence repeats (SSR) technique. Genetic structure of these accessions was studied using three SSR polymorphic primers, SSR-6206, SSR-6218 and SSR-6219. A total of eight loci were scored for the three primers with a total of ten alleles. Bayesian clustering method grouped the cowpea genotypes into 4 sub-populations. Ancestral allele frequencies ranged between 0.128 and 0.802, while allele frequencies within sub-populations ranged from 0.001 and 0.997. Allele frequency divergence among sub-populations ranged from 0.145 to 0.406. Expected heterozygosity between individuals in the same sub-population ranged from 0.084 and 0.26, Mean genetic differentiation among sub-populations ranged from 0.374 and 0.687, with a mean geneflow ranging from 0.228 and 0.837. There was relative uniformity within the sub-populations which can be accounted for by independent random genetic drift