Nutritional Value of Cowpea (Vigna Unguiculata L. Walp) Grain Grown Under Different Soil Moisture as Affected to the Dual Inoculation with Nitrogen Fixing Bacteria and Arbuscular Mycorrhizal Fungi

The study was performed to evaluate the nutritional value and antioxidant properties of cowpea grain, where plants were grown under conditions of tripartite symbiosis (cowpea plants, nitrogen-fixing bacteria (Bradyrhizobium japonicum) and arbuscular mycorrhizal fungi, (Glomus intraradices) without fertilization. Cowpea plants (Vigna unguiculata (L.) Walp) cv. Hrisi were grown in a glasshouse until the full maturity of grain on the Alluvial meadow soil (Eutric Fluvisol) at three levels of water-holding capacity (40, 60 and 80%). Bradyrhizobium japonicum solely and in combination with arbuscular mycorrhizal fungi increased the content of proteins, soluble sugars and total phenols in the cowpea seeds. When dual inoculation has applied the levels of proteins and soluble sugars in the cowpea grain did not reduce at 40%, nor at 80% in comparison with the optimal water-holding capacity level (60%). Antioxidant capacity at 40% water-holding capacity was determined by the increased content of water soluble antioxidants, flavonoid content and increased ferric reducing power activity and increased antioxidant levels was expressed more distinguished in the treatments with dual inoculation. Slight change of antioxidants in the grain of cowpea was established at an elevated level of water supply. Nutritional value of a grain of cowpea after dual inoculation with Bradyrhizobium strains and Glomus intraradices was not determined by the water-holding capacity levels.