Is a combination of arbuscular mycorrhizal fungi more beneficial to enhance drought tolerance than single arbuscular mycorrhizal fungus in Lallemantia species?

Climate change-induced abiotic stress hinders crop growth, providing a challenge to global food security and agricultural sustainability. An effective approach to safeguard crop production from drought stress is to use either a single species or co-inoculating different native arbuscular mycorrhizal fungi (AMF) species. A pot experiment was carried out to examine the impacts of using single and combined AMF (Claroideoglomus etunicatum, Funneliformis mosseae, and Rhizophagus intraradices) on the growth and physiological-biochemical characteristics of Lallemantia species (Lallemantia iberica and L. royleana) under well-watered, moderate drought, and severe drought conditions. Drought stress had a notable negative impact on growth performance, photosynthetic rate, antioxidant enzyme activities, water use efficiency, nutrient uptake, oil and fatty acid levels, and sugar components, which were associated with restricted root development. In contrast, inoculation with mycorrhizal species, especially Mix 4 treatment (C. etunicatum, F. mosseae, and R. intraradices), significantly boosted root AMF colonization, leading to an increase in mycorrhizal growth response, mycorrhizal dependency, water use efficiency, and seed yield. Seeds produced under Mix 4 inoculation showed the highest levels of mucilage, sugar compounds, oil, and fatty acid compositions, compared with individual AMF and other AMF mixtures. Furthermore, the presence of hydrogen peroxide and lipid peroxidation was significantly reduced by applying Mix 4 treatment under drought stress. It suggested that a combination of AMF species can better promote the growth and yield of Lallemantia species during drought stress by preserving the plants' physiological functions than single arbuscular mycorrhizal fungus.