Arbuscular mycorrhizal fungi alleviate negative effects of arsenic-induced stress on crop plants: A meta-analysis

Societal Impact Statement The inoculation with arbuscular mycorrhizal (AM) fungi shows great potential to increase the tolerance of host plants toward toxic arsenic. In many Asian countries and elsewhere, crops are increasingly being irrigated with arsenic-contaminated groundwater, which causes loss of yield and the risk that arsenic enters the food chain. Greenhouse cultivation experiments demonstrated that AM fungi are able to increase the arsenic tolerance in crop plants, but the results are highly variable. This meta-analysis demonstrates that AM fungi significantly reduce the arsenic concentration, and at the same time, positively modify the nutrient supply and the biomass in host crops that are grown under arsenic stress. Thus, the inoculation with AM fungi represents a promising approach to alleviate the negative effects of arsenic on crop growth, which deserves to be developed in future studies. Recent greenhouse experiments showed that the inoculation of crop plants with arbuscular mycorrhizal (AM) fungi does not only improve plant nutrition but also shows great potential to increase the host plants' tolerance toward the toxic metalloid arsenic (As). This approach could alleviate negative effects of crop plants grown under As stress, which causes substantial loss of yield and the risk of As entering the food chain. This is especially relevant in Asian countries and elsewhere where As subsequently accumulates in soil due to irrigation with As-polluted groundwater. Overall effects of AM fungi symbiosis on seven crop plants grown under As stress were assessed by a meta-analysis that included 299 studies obtained from 27 independent publications. Biomass, concentrations of As and phosphorus (P), and P/As ratios in plant tissue were used to evaluate the effects of AM fungi in host crops. Inoculation with AM fungi reduced As concentrations in tissue of host plants by 19% on average, while it increased the P/As ratio and biomass at the same time by 64% and 53%, respectively. With the exception of Helianthus annuus, AM effects were highly significant in all crop plants. The meta-analysis results illustrate that AM fungi are able to significantly reduce As concentration, and at the same time, positively modify the nutrient supply and the biomass in host crops. These promising results strongly encourage the implementation of field trials as a next step toward the development of AM fungi-based approaches to alleviate the negative effects of As stress on crop growth.