Native Bradyrhizobium Enhancing the Growth of Two Peruvian Commercial Varieties of Cowpea

Background: Bradyrhizobium establishes an effective symbiosis with cowpea. This study evaluated the inoculation of seven native strains in two commercial varieties, demonstrating their potential to enhance symbiotic nitrogen fixation (SNF) and contribute to the agronomic utilization of cowpea in degraded soils of the Peruvian arid coast. Methods: We implemented a completely randomized design with ten treatments: seven inoculated with selected Bradyrhizobium strains-four B. yuanmingense (8.1.1, 8.2, 19.3, 20.1), two Bradyrhizobium sp. (1.1, 12.3) and one B. diversitatis 25.1 and three controls-a consortium of effective strains (B. yuanmingense Rc-458-01 and Rc-455-02), a fertilized treatment (40:60:30; N: P: K) and an uninoculated, unfertilized absolute control. Reactivated and purified strains were used to prepare inocula. Two cowpea varieties (Vaina verde INIA-432 and Vaina verde CAR-9) were sown in non-sterile soil and inoculated with standardized cell suspensions. We performed two evaluations: At 45 days post-inoculation, we assessed symbiotic effectiveness through plant height, shoot and root dry weight, nodule dry weight, number of nodules, shoot nitrogen content and nitrogen accumulation; at maturity, we evaluated yield and grain quality, including grain nitrogen, phosphorus and potassium content, number of pods per plant, 100-seed weight, grains per pod and grain yield per plant. Result: Inoculation with native B. yuanmingense strains 19.3 and 20.1, as well as Bradyrhizobium sp. 12.3, significantly increased symbiotic and grain-related parameters in both cowpea varieties.