Vol.:(0123456789) 1 3 https://doi.org/10.1007/s11104-021-05007-7 REGULAR ARTICLE Arbuscular mycorrhizal fungi acted synergistically with Bradyrhizobium sp. to improve nodulation, nitrogen fxation, plant growth and seed yield of mung bean (Vigna radiata) but increased the population density of the root‑lesion nematode Pratylenchus thornei Elaine C. Gough · Kirsty J. Owen · Rebecca S. Zwart · John P. Thompson  yield, nodulation, P. thornei population density, AMF colonisation of the roots, and nutrients in the plant shoot, including nitrogen isotope natural abundance (δ 15 N) to quantify fxed nitrogen. Results Arbuscular mycorrhizal fungi and rhizobia acted synergistically to substantially increase nodula- tion, nitrogen fxation, nutrition, seed yield and bio- mass of the plants. The population density of P. thor- nei in roots of the mung bean at 12 weeks increased in plants inoculated with AMF and was positively corre- lated with plant nutrition namely increased phospho- rus, zinc and copper concentrations in the plant shoot. Conclusion Understanding these interactions should inform changes in agronomic practices, to promote the synergism between mycorrhiza and rhizobia for mung bean yield, while managing to limit P. thornei population densities to beneft mung bean itself and subsequent crops in the farming system. Keywords Arbuscular mycorrhizal fungi · Bradyrhizobium · Pratylenchus thornei · Microbiota plant interactions · Vigna radiata · Synergy Introduction Mung bean (Vigna radiata (L.) R. Wilczek) is a high protein, short season legume, with a global production area of 7.3 million ha, predominantly in South Asia (Nair and Schreinemachers 2020). In the subtropical grain region of eastern Australia, mung Received: 10 January 2021 / Accepted: 10 May 2021 © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2021 Abstract Purpose Mung bean is a host of the root-lesion nematode Pratylenchus thornei (Sher & Allen) and the benefcial symbionts arbuscular mycorrhizal fungi (AMF) and nitrogen-fxing Bradyrhizobium bacteria. The purpose of this research was to investigate inter- actions among these organisms afecting their repro- duction and functional impact on mung bean nodu- lation, nutrition, biological nitrogen fxation, growth and seed yield. Methods A glasshouse experiment was conducted with mung bean in pots of a pasteurised vertisol using a factorial design of treatments to investigate the interactive efects of AMF, Bradyrhizobium and P. thornei. The plants were assessed at 6 and 12 weeks after sowing for variables of shoot biomass, seed Responsible Editor: Jan Jansa. Supplementary Information The online version contains supplementary material available at https://doi. org/10.1007/s11104-021-05007-7. E. C. Gough (*) · K. J. Owen · R. S. Zwart · J. P. Thompson  Centre for Crop Health, Institute for Life Sciences and the Environment, University of Southern Queensland, Toowoomba, QLD, Australia e-mail: elaine.gough@usq.edu.au Plant Soil (2021) 465:431–452 Published online: 9 June 2021 /