Inoculation of AM fungi: An effective tool to reduce Cd accumulation in peanut kernel

Abstract

China is an important global peanut producer and exporter. Nevertheless, excessive Cd in peanut kernels has become an important constraint of peanut exportation. Concerns over the heavy metal contamination in food crops have prompted scientists to find ways to solve these problems, including applications of microbiology. In the present research, a greenhouse pot culture experiment was conducted to investigate the effect of arbuscular mycorrhizal fungi (AMF) inoculation on cadmium (Cd) uptake and translocation in peanut plants at different Cd levels. The peanut seeds were sown in pots, where culture substrate was previously mixed with a given amount of Glomus intraradices and 0, 2 and 10 mg kg-1 Cd. In the control plot, G. intraradices was inactivated before mixed into culture substrate. Symbiotic relationships were successfully established between AMF and peanut root at all Cd levels with an average colonization rate of 65.0%. Compared with control plants, AMF inoculation significantly improved phosphorus nutrition supply to peanut plants, increased chlorophyll by 7.5%, photosynthesis by 11.8%, transpiration by 13.9% and root dry weight by 27.0%. In AMF inoculated peanut plants, the concentration and accumulation of Cd were 45.9 and 87.4% higher, respectively, in root system but 31.1 and 31.8% lower, respectively in the aboveground part than in the control plants. At the Cd level of 10 mg kg-1, the translocation rate of Cd in AMF inoculated peanut plants was 51.8% lower than in AMF non-inoculated plants. In summary, AMF inoculation could improve peanut plant growth, result in Cd immobilisation in the peanut root system and inhibit Cd translocation in peanut plants. In conclusion, AMF inoculation may be an effective way to reduce Cd accumulation in peanut kernels.