Foliar spraying of Bradyrhizobium and Anabaena improve stress tolerance under deficit irrigation of Cowpea

Abstract

Abstract Water deficit is considered one of the most significant factors limiting cowpea productivity, necessitating sustainable strategies to improve crop tolerance to drought stress. This study investigated the effects of foliar application of Bradyrhizobium and Anabaena on the growth, physiological performance, and productivity of cowpea under different irrigation intervals. Under the 15-day irrigation interval (water-stressed condition), the combined Bradyrhizobium and Anabaena treatment increased total seed yield by more than 30% compared with the stressed untreated control. This confirms the strong role of the consortium in improving drought tolerance and productivity under limited irrigation. Anabaena was identified as Anabaena cylindrica using rpoC1 gene sequence analysis. Phytohormone content of A . cylindrica was quantified by HPLC and bioactive compounds from Bradyrhizobium sp. and A . cylindrica were detected by GC- MS. The study evaluated nodule number, leaf N, K, Na contents, K/Na ratio, chlorophyll, carotenoids, total soluble sugars (TSS), relative water content (RWC), proline concentration, antioxidant enzymes (APX and CAT), and soil enzyme activities (dehydrogenase and urease) along with yield components and total seed yield. Results showed that the consortium treatment significantly improved chlorophyll, carotenoids, TSS, and RWC, while reducing proline accumulation compared with stressed control. It also increased root nodulation, enhanced N and K uptake, reduced Na accumulation, and improved K/Na ratio. It stimulated CAT and APX activities in leaves and enhanced soil enzyme activities, leading to improved yield components and overall productivity under drought stress. These findings highlight the potential of combining Bradyrhizobium and Anabaena cylindrica as an eco-friendly and sustainable biostimulant strategy to enhance cowpea productivity and drought resilience under water-limited conditions.