Inheritance of antioxidant activity and its association with seed coat color in Cowpea (Vigna unguiculata (l.) walp.)

Analysis of antioxidant activity (AOA) of entries in the 2002 Regional Southernpea Cooperative Trial revealed not only significant differences among entries, but that entries with pigmented (black and red) seed coats were clustered among the highest, cream types were the lowest, while pinkeye and blackeye types were intermediate. Red colored peas were higher in antioxidant activity than black types. These findings provided strong evidence that compounds responsible for pigmentation were involved in AOA. The objectives of the present investigation were to investigate the inheritance of AOA in cowpea and further study the relationship between AOA and seed coat color. Four advanced selections, ARK95-356 (black), ARK98-348 (red), ARK96-918 (cream), and LA92-180 (cream), were crossed in a complete diallel mating design, generating F1, F1', F2, F2', BC1, and BC2 populations. Individual seeds were ground and samples were extracted in methanol and analyzed for AOA using the free radical 2, 2-Diphenyl-1-picrylhydrazyl (DPPH) method. Combining ability tests using Griffing??s Method I Model I indicated presence of highly significant general combining ability (GCA), specific combining ability (SCA), and reciprocal (REC) and maternal (MAT) effects, with pigmented lines exhibiting positive GCA and MAT, while non-pigmented lines exhibited negative GCA and MAT. AOA in the F1 was not significantly different from the maternal parent, with seed coat color also resembling the maternal parent. Segregation for seed coat color was observed in the F2 and F2'. Additive, dominance, and epistatic effects were significant. The broad sense heritability estimate was 0.87. Minimum number of genes responsible for AOA was estimated at about five. Factors governing high AOA appeared to be the same as those responsible for seed coat color, with apparent pleiotropic effects. In conclusion, breeding for high AOA is possible using highly pigmented parental lines.