The role of arbuscular mycorrhizal fungi in enhancing chromium tolerance of common beans

Abstract

Chromium (Cr) is a heavy metal harmful to health and food crop development, impacting food security. Common bean (Phaseolus vulgaris), a crop of national importance, can form symbiotic relationships with arbuscular mycorrhizal fungi (AMF) and adapt to various environmental conditions. This study evaluated the influence of two AMF species on bean plant development in chromium-contaminated soils. The experiment involved growing plants in three-liter pots filled with soil and inoculating them with Rhizophagus clarus or Claroideoglomus etunicatum, with or without chromium. Conducted in a controlled growth chamber, the fourth vegetative stage measured gas exchange, electron transport rate, biochemical analysis, chromium content, mycorrhizal colonization rate, and plant growth. Results showed that plants inoculated with R. clarus had higher CO₂ assimilation rate (Pn) and stomatal conductance (Gs). Plants without chromium had higher superoxide dismutase activity, while those with C. etunicatum had lower catalase and peroxidase activity. Chromium increased malondialdehyde in R. clarus-inoculated plants, decreased peroxide in control plants, and reduced proline in C. etunicatum-inoculated plants. Final analysis indicated that C. etunicatum-inoculated plants had higher soil chromium content and lower pod chromium levels. This study highlights the potential of specific AMF species to improve bean development in chromium-contaminated soils and provides insights into plant-microorganism interactions and physiological responses to chromium tolerance.