Acacia nodule-associated bacteria induced plant growth promotion and soil N availability

Abstract

Background and aims Legume-rhizobia symbiotic N fixing potentially contribute to restoring fertility in mined land during rehabilitation efforts. Particularly, Acacia spp. stands out as an important legume of native vegetation, while their symbiotic relationship development and impacts on soil rehabilitation have not been fully understood. Methods In our glasshouse experiment, symbiosis relationship between three Acacia species (A. holosericea, A. ampliceps, and A. auriculiformis) and bacterial inoculum (Acacia nodule-associated bacteria (NAB), Bradyrhizobium diazoefficient CB1809, and Rhizobium leguminosarum bv viciae RLV248) and the effects of seedling ages on nodule formation were investigated. Additionally, the symbiotic nodule development and their the impacts on plant growth, plant N acquisition, and soil N availability were compared. Results The results revealed all three Acacia seedlings successfully formed nodules, with each displaying distinct morphology. Seedlings at 8 weeks demonstrated higher efficacy to form nodules than the those of 12 and 16 weeks old. A. auriculiformis is mostly effective to form nodules with all bacterial inoculums, especially with NAB. Rhizobium in A. auriculiformis nodules are dominated by Bradyrhizobium. Mesorhizobium is predominant in A. ampliceps nodules. Both Bradyrhizobium and Mesorhizobium are highly abundant in the nodules of A. holosericea. Symbiotic nodule development also induced plant growth promotion and N acquisition, with CB1809 the mostly effective. Notably, NAB inoculation could significantly enhanced soil N availability in addition to promoting plant growth. Conclusion These findings underscore the significance of Acacia-NAB symbiosis as a beneficial strategy to boost plant growth, increase soil N availability, and potentially aid in ecological rehabilitation endeavors.