Inheritance of Antioxidant Activity and its Association with Seedcoat Color in Cowpea

The inheritance of antioxidant activity (AOA) and its association with seedcoat color was investigated in cowpea (Vigna unguiculata (L.) Walp. ). Four advanced cowpea lines, ARK95-356 (black seedcoat) and ARK98-348 (red seedcoat), which were high (H) in AOA, and ARK96-918 (cream seedcoat) and LA92-180 (cream seedcoat), which were low (L) in AOA, were selected from the 2002 Regional Southernpea Cooperative Trials. They were crossed in a complete diallel mating design, generating F1, F1´ (1st generation and 1st generation reciprocal cross, respectively), F2, F2´ (2nd generations from F1, F1´), BC1, and BC2 (backcrosses to parents 1 and 2, respectively) populations. Individual seeds were ground and samples were extracted in methanol and analyzed for AOA using the free radical 2,2-diphe- nyl-1-picrylhydrazyl (DPPH) method. Combining ability tests using Griffi ngʼs Method I Model I indicated presence of highly signifi cant general combining ability (GCA), specifi c combining ability (SCA), and reciprocal (RE) and maternal (MAT) effects, with pigmented lines exhibiting positive GCA and MAT, while nonpigmented lines exhibited negative GCA and MAT. AOA in the F1 was not signifi cantly different from the maternal parent, with seedcoat color also resembling the maternal parent. Segregation for seedcoat color was observed in the F2 and F2´. Additive, domi- nance, and epistatic effects were signifi cant. The broad sense heritability estimate was 0.87. Minimum number of genes responsible for AOA was estimated at fi ve. Factors governing high AOA appeared to be the same as those responsible for seedcoat color, with apparent pleiotropic effects. In conclusion, breeding for high AOA in cowpea is possible using highly pigmented parental lines. Cowpea is one of the most ancient food sources, cultivated throughout the world primarily as a pulse and vegetable. It is broadly adapted and grown successfully in extreme environments such as high temperature and low rainfall, and does well on poor soils with few economic inputs. Cowpea is a nutritious source of food, providing proteins, vitamins, minerals, and carbohydrates. The protein profi le complements roots, tubers, or cereals, espe- cially in areas where the population cannot afford higher protein foods such as meat. Several legumes, cowpea included, have been found to contain non-nutrient, bioactive phytochemicals that possess antioxidant capabilities (Beninger et al., 1998; Messina, 1999; Narasinga Rao, 1995; Nzaramba et al., 2003; Warrington et al., 2002). Antioxidants are compounds that inhibit or delay the oxidation of other molecules by inhibiting the initiation or propagation of oxidizing chain reactions (Klein and Kurilich, 2000; Velioglu et al., 1998). The Food and Nutrition Board of the National Academy of Science (1998) defi ned dietary antioxidants as substances in foods that signifi cantly decrease the adverse effects of reactive oxygen species, reactive nitrogen species, or both on normal physiological function in humans. Antioxidant activity (AOA) is a fundamental property im- portant for life. Antioxidants with versatile functions constitute a complex network to overcome oxidative stress suffered by aerobic organisms. Under certain circumstances, however, the natural defenses can be insuffi cient resulting in health problems, hence making administration of exogenous antioxidants as food constituents or therapeutic agents necessary and benefi cial (Niki