Photo by Mongi Zekri, University of Florida Institute of Food and Agricultural Sciences
Beneficial soil fungi known as arbuscular mycorrhizal fungi (AMF) may help citrus trees tolerate toxic levels of manganese, according to new research. The findings could eventually lead to new management strategies for citrus grown in acidic soils where manganese toxicity can limit tree growth and productivity.
An article about the study was published in the journal Tree Physiology. The research was conducted by Cheng-Zhuo Li, Lu-Lu Meng, Fu-Qi Xu, Ying-Ning Zou and Qiang-Sheng Wu of Yangtze University in China; Ren-Hua Huang of Jingchu University of Technology in China; and Abeer Hashem and Elsayed Fathi Abd_Allah of King Saud University in Saudi Arabia.
Researchers studied trifoliate orange seedlings inoculated with the AMF fungus Funneliformis mosseae and exposed them to excessive manganese. High manganese levels can damage roots, reduce photosynthesis and stunt plant growth, particularly in acidic soils.
The researchers found that trees colonized by the beneficial fungus grew better, developed healthier root systems and maintained higher photosynthetic activity than untreated plants. The fungus also reduced the amount of manganese that moved into the roots, stems and leaves.
The study identified two ways the fungus protected citrus. First, it acted as an external barrier, trapping manganese in the soil and fungal structures before it could enter the roots. Second, it provided internal detoxification by helping the plant move manganese into safer storage areas within cells, such as cell walls and vacuoles, where it is less likely to damage important tissues. The fungus also converted manganese into less harmful chemical forms inside the plant.
The findings add to growing evidence that beneficial mycorrhizal fungi can improve citrus resilience to environmental stresses and may have broader applications for maintaining healthy root systems.
While commercial use will require additional field studies on mature trees, the findings suggest these naturally occurring fungi could become part of future strategies to reduce nutrient toxicity and improve citrus performance in challenging soil conditions.
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