The Mode of Integration Between Azotobacter and Rhizobium Affect Plant Growth, Yield, and Physiological Responses of Pea (Pisum sativum L.)

The synergistic action between rhizobia and plant growth-promoting rhizobacteria has been documented. However, the mode of integration that boosts the positive outcomes of the partnership to the host plant is less understood and poorly investigated. The current investigation was carried out to evaluate the effect of pre-sowing versus post-emergence co-inoculation with Azotobacter chroococcum and Rhizobium leguminosarum bv. viceae on growth, yield, and quality attributes of Pisum sativum plants. Pea plants were inoculated as usual with Rhizobium in combination with A. chroococcum either pre- or post-emergence. Pre-emergence co-inoculation was performed by mixing the seeds, either dry or pre-soaked, with peat-based Rhizobium to which the A. chroococcum suspension was added. In the post-emergence inoculation approach, A. chroococcum suspension was injected after cultivation into the pot soil. Application of A. chroococcum and R. leguminosarum bv. viceae significantly improved plant biomass, nutrients uptake, and leaf photosynthetic pigments compared with the corresponding control plants which inoculated solely with Rhizobium. Moreover, inoculation with A. chroococcum enhanced nodulation indices (number of nodules, nodule diameter, and nodule dry weight), as well as the activity of nitrogenase enzyme compared to the control plants. Furthermore, co-inoculation with A. chroococcum resulted in an obvious increase in seed yield and has improved ascorbic acid, protein, and carbohydrates contents in the seeds. Additionally, our results revealed that there were no significant differences between either pre-sowing or post-emergence application. Delivering the A. chroococcum concomitantly with that of Rhizobium to pre-soaked seeds could be adopted as an easy, cost-effective, and efficient inoculation approach to get added benefits to the growth, yield, uptake of nutrient elements, and yield quality traits of pea plants.