Effect of Inoculation with Arbuscular Mycorrhizal Fungi and Rhizobium leguminosarum bv. trifolii on Yield of Berseem Clover (Trifolium alexandrium) Under Cadmium Stress

Cadmium is a very mobile element in soil that is absorbed by plant roots and translocation of cadmium from root to shoot deteriorates crop quality. It enters the food chains of humans and animals easily and is a potential threat to human health. The increase of contaminated areas in the country and the existence of farms under cultivation of various forages and the use of these forage products in the animal feed led to this study was carried out with the aim of investigating the effects of arbuscular mycorrhizal fungi and Rhizobium leguminosarum bv. trifolii on the yield of berseem clover (Trifolium alexandrium) under cadmium stress.

A factorial experiment was conducted in the greenhouse of Faculty of Agriculture, University of Zanjan, using a completely randomized design with three replications. In this experiment, the effects of different levels of soil cadmium (0, 5, 10, 25 and 50 mg/kg) and soil inoculation (without inoculation and inoculation with Funneliformis mosseae, Rhizophagus irregularis, Funneliformis mosseae + Rhizobium leguminosarum bv. trifolii, Rhizophagus irregularis + Rhizobium leguminosarum bv. trifolii, Rhizobium leguminosarum bv. trifolii, Funneliformis mosseae + Rhizophagus irregularis and Funneliformis mosseae + Rhizophagus irregularis + Rhizobium leguminosarum bv. trifolii) on growth of berseem clover (Trifolium alexandrium) were assessed.

The results of this study showed a significant effect (1% and 5% probability level) due to soil cadmium levels on dry weights and N, P, K and Cd concentrations of aerial parts and roots of berseem clover. The dry weights and N, P and K concentrations of aerial parts and roots of berseem clover decreased as the levels of soil Cd increased. The highest dry weights of aerial parts and roots, N, P and K concentrations were measured in treatment co-inoculated with Funneliformis mosseae and Rhizobium leguminosarum bv. Trifolii and without Cadmium. Also, the lowest dry weights of aerial parts and roots and macronutrient concentrations were observed in treatment 100 mg Cd/kg and without inoculation with microorganism. Soil contamination with Cd decreased the dry weight of aerial parts and roots by 66.49 and 71.11%, respectively. the highest Cd concentrations in aerial parts and roots were measured 11.25 and 17.80 mg/kg in treatment 100 mg Cd/kg and without inoculation with microorganism and the lowest Cd concentrations in aerial parts and roots were 0.0012 and 0.0046 mg/kg in treatment co-inoculated with Funneliformis mosseae and Rhizobium leguminosarum bv. Trifolii and without Cadmium. The results of the mean comparison of data showed that the Cd concentration in the roots was higher than the aerial parts, and in treatment 100 mg Cd/kg without inoculation with microorganism, Cd concentration of roots was 36.8% higher than the Cd concentration in aerial parts.

Based on the results obtained from this study with the increase in Cd levels of soil, the dry weights and N, P and K concentrations of aerial parts and roots of berseem clover decreased. Soil inoculation with mixture of fungi and bacteria reduced the effect of Cd stress on the growth of clover. Also, the separate inoculation with arbuscular mycorrhizal fungi also reduced the concentration of Cd in the aerial parts and roots. According to the results of this study, in contaminated soils can be used co-inoculated with Funneliformis mosseae and Rhizobium leguminosarum bv. Trifolii to reduce the Cd concentration and increase the yield of plants.