The contribution of rhizobia and arbuscular mycorrhizal fungi co-inoculation on growth and yield of haricot bean (Phaseolus volgaris)

Abstract

The disastrous environmental quality effects of indiscriminate use of commercial fertilizers drive research into natural fertilizer sources and bio-stimulants. As a result, this study aimed to look into the effects of interactions between microbial symbionts Rhizobia(R) and arbuscular mycorrhizal fungi (AMF) on haricot bean growth and biomass output. The haricot bean variety 'Hawassa Dume' was inoculated with a mixture of AMF and indigenous and commercial Rhizobia. The experiment was carried out for 90 days. Inoculation of haricot bean seedlings with the R+AMF resulted in a considerable increase in nodulation (45.0±2.3 in IR and 46.0±7.8 in MBI) compared to uninoculated plants. In the greenhouse trial, dual inoculation of AMF and rhizobia boosted different plant growth parameters: shoot length 12cm in IR and 12.1cm in MBI; shoot dry weight 2.9g in IR and 3.0g in MBI; root dry weight 0.5g in IR and 0.5g in MBI; and number of nodules/plant 4.6 in IR and 4.6 in MBI. The field testing yielded nearly identical results. Similarly, improved nitrogen uptake (0.72% for MBI and 0.56% for IR) and better phosphorus uptake 0.33% and 0.26% for IR and MBI, respectively, were observed compared to single inoculation. Finally, the interactions among the components of the tripartite symbiotic relationship, Rhizobia-AMF-Haricot bean, have boosted plant growth and biomass output. As a result, it is advised that efficient rhizobia and AMF inoculants be produced and distributed to conventional and small-holder agricultural systems, along with more research activities on the efficiency of bio-fertilizers.