Bouaziz Sifi

Background: Plant-growth-promoting rhizobacteria (PGPR) are a class of beneficial bacteria that colonise the roots of plants and improve projected plant growth through a multivariate process. PGPR application is increasing steadily in the field of agriculture, providing an attractive mechanism to replace pesticides, chemical fertilisers and additional supplements. Methods: In this study, PGPR from rhizospheric soil collected from Abha, a city located in the southern region of the Kingdom of Saudi Arabia (KSA), were isolated and characterised to facilitate verifying the efficacy of using PGPR as a biological control to improve fava bean growth. Four bacterial isolates from the nodules of fava bean plants, S4, S5, S6 and S17, were isolated and characterised. Consequently, an investigation highlighting the impact of PGPR isolates on the preservation of fava bean plants from the root-knot nematode was conducted through a pot culture experiment. Soil infested with the nematode was added to the pots. Two commercial types of fava bean plants (Vicia faba L.) were co-inoculated with PGPR 15 days after planting. Result: The results reveal that the nodule-forming bacteria interact synergistically; this was evidenced by a prominent increase in the shoot length and dry weight of the fava bean plants that had been cultivated in the nematode-infested soil. The results also demonstrate that the overall treatment of the plants did not lead to nodule formation. The results indicate that nodule-forming bacteria could be utilised in leguminous crops to facilitate biocontrol of the root-knot nematode.

Background: Phaseolus vulgaris L. -rhizobia symbiosis has effectively enhanced common bean productivity via multiple biological mechanisms. This study aims to assess the impacts of the strain of Rhizobium on the nodulation, growth, nitrogen (N2) fixation rate and ion accumulation within Phaseolus vulgaris L. under salt stress. Methods: The Coco Blanc cultivar of the common bean was inoculated with the Ar02 rhizobia strain at 15 days after germination. Bean plants were inoculated in perlite culture to which salt was added in concentrations of 0, 25, 50 and 75 mmol L-1 NaCl. Result: Inoculation with the Ar02 rhizobia strain led to infective and effective symbiosis with the common bean plants exposed to saline solutions and non-saline solutions, respectively. Nodule biomass and nitrogen content declined under salt stress but maintained a higher number of nodules and nodule biomass at 75 mM NaCl. Plant root and shoot length increased with higher biomass under saline conditions, significantly more than the non-inoculated plant without salt. However, the progressive addition of NaCl reduced the growth of the root and shoot and the biomass within the inoculated plant. Salinity led to increased Na+ within the plant’s shoot, along with a reduction in Ca+2 and K+ concentrations. The shoot’s Ca+2, Na+ and K+ content were higher in the inoculated plant than the non-inoculated. The salt tolerance in common bean plants inoculated with Ar02 rhizobia was linked with the plant’s capability to sustain nodulation and enhance Na+ concentration in the shoot. Furthermore, salt tolerance within the same variety inoculated with Rhizobium was linked to a decline in the Ca+ and K+ concentrations in the shoot region of salt-exposed plants.