[Comprehensive evaluation of resistance to Cd stress in mycorrhizal seedlings formed by different genotypes of <i>Cenococcum geophilum</i> and <i>Pinus massoniana</i>].

To select the mycorrhizal seedlings of <i>Pinus massoniana</i> with excellent Cd-resistance and explore the mechanism of <i>Cenococcum geophilum</i> promoting the resistance to Cd stress of <i>P. massoniana</i>, nine species of <i>C. geophilum</i> isolated from different hosts infected <i>P. massoniana</i> to form mycorrhizal seedlings, were cultured in Cd-contaminated soil for three months. We conducted the principal component analysis (PCA) on biomass, root structure, and photosynthesis, and evaluated the Cd tolerance of mycorrhizal seedlings by membership function. The results showed that dry and fresh weight of mycorrhizal seedlings under Cd stress were 1.0-2.1 and 1.0-1.4 times of that under the control. Root structure of <i>P. massoniana</i> mycorrhizal seedlings was improved by <i>C. geophilum</i>, with root volume and average root diameter being 1.5-2.3 and 1.0-1.3 times of that under the control. Photosynthesis of mycorrhizal seedlings was significantly enhanced by <i>C. geophilum</i>, with photosynthetic rate, stomatal conductance, transpiration rate, and intercellular CO₂ concentration of Cg-HS3 being 11.8, 3.5, 3.0, and 0.4 times of that under the control, respectively. The transport of Cd by mycorrhizal seedlings was significantly reduced by <i>C. geophilum</i>, which was 30.4%-73.0% of that under the control. Based on the <i>D</i> value of comprehensive evaluation of Cd tole-rance of mycorrhizal seedlings, and cluster analysis of inter-group linkage, the mycorrhizal seedlings were classified into Cd-sensitive type (Cg-YS4, Cg-HS2, Cg-YS1, Cg-HS1), low Cd-tolerance type (Cg-HS3, Cg-QQ, Cg-YS3, Cg-YS2), and high Cd-tolerance type (Cg-QG). In conclusion, Cg-QG and Cg-HS3 can be used as excellent materials to resist Cd stress and restore the ecological environment in mining area.