Purpose Arbuscular mycorrhizal fungi (AMF) aid nutrient uptake and stress tolerance, but their distributions can vary by host genotype, root order, and soil compartment. We investigated how two AMF taxa, Rhizophagus intraradices (Ri) and Funneliformis mosseae (Fm), partition across fine root orders and soil compartments in two Chinese fir (Cunninghamia lanceolata) clones (No. 25 and No. 32) under phosphorus (P) depletion, and whether Ri and Fm abundances covary, indicating complementary colonization. Methods Clonal seedlings grew in P-depleted soils. Fine roots were separated into first (terminal), second (branches from first), and third orders (branches from second). Samples were taken from roots, rhizosphere soil, and bulk soil. AMF abundance was quantified by qPCR targeting Ri and Fm. Amplicon libraries (Illumina MiSeq) profiled AMF community diversity and composition across root orders, compartments, and clones. Reflecting the symbiotic preference of Chinese fir and the differences in the diversity of surrounding AMF. We tested clonal, order, and compartment effects and their interactions, and examined Ri-Fm abundance correlations. Sequencing data were quality-filtered and assigned to taxa with standard pipelines; diversity metrics and community dissimilarities were compared with appropriate statistical models. Results Fm abundance was consistently lower in clone No. 25 than No. 32, with the clearest difference in second-order roots. Across compartments, both taxa peaked in roots versus rhizosphere and bulk soils, indicating preferential intraradical occupancy under P stress. Ri and Fm abundances were positively correlated, suggesting nonexclusive or complementary colonization rather than competition. AMF colonization varies significantly along the gradient from non-rhizosphere soil to rhizosphere soil to within roots, driven by a combination of soil characteristics, root exudates, and host selection. Together, genotype × root order × compartment interactions structure AMF assembly, with second-order roots emerging as a sensitive tier for clonal contrasts. Conclusions AMF distributions in Chinese fir are jointly determined by host genotype, fine-root order, and soil compartment. Lower Fm in clone No. 25 and peak intraradical abundance for both taxa underscore the functional importance of root intrinsic filters under P limitation. Positive Ri-Fm covariation implies complementary colonization. These findings provide a baseline for targeting specific root orders and AMF taxa to enhance P acquisition in P limited forest systems.

Root-zone distribution and arbuscular mycorrhizal associations in Chinese fir clones under phosphorus-depleted soils

期刊论文
发表日期：

2026年5月13日

查看全文

Yue Cao,
Xiaojian Wu,
Yuxin Yao,
Taimoor Hassan Farooq,
Xiangqing Ma,
Yezhou Xu,
Pengfei Wu

摘要

Purpose

Arbuscular mycorrhizal fungi (AMF) aid nutrient uptake and stress tolerance, but their distributions can vary by host genotype, root order, and soil compartment. We investigated how two AMF taxa, Rhizophagus intraradices (Ri) and Funneliformis mosseae (Fm), partition across fine root orders and soil compartments in two Chinese fir (Cunninghamia lanceolata) clones (No. 25 and No. 32) under phosphorus (P) depletion, and whether Ri and Fm abundances covary, indicating complementary colonization.

Methods

Clonal seedlings grew in P-depleted soils. Fine roots were separated into first (terminal), second (branches from first), and third orders (branches from second). Samples were taken from roots, rhizosphere soil, and bulk soil. AMF abundance was quantified by qPCR targeting Ri and Fm. Amplicon libraries (Illumina MiSeq) profiled AMF community diversity and composition across root orders, compartments, and clones. Reflecting the symbiotic preference of Chinese fir and the differences in the diversity of surrounding AMF. We tested clonal, order, and compartment effects and their interactions, and examined Ri-Fm abundance correlations. Sequencing data were quality-filtered and assigned to taxa with standard pipelines; diversity metrics and community dissimilarities were compared with appropriate statistical models.

Results

Fm abundance was consistently lower in clone No. 25 than No. 32, with the clearest difference in second-order roots. Across compartments, both taxa peaked in roots versus rhizosphere and bulk soils, indicating preferential intraradical occupancy under P stress. Ri and Fm abundances were positively correlated, suggesting nonexclusive or complementary colonization rather than competition. AMF colonization varies significantly along the gradient from non-rhizosphere soil to rhizosphere soil to within roots, driven by a combination of soil characteristics, root exudates, and host selection. Together, genotype × root order × compartment interactions structure AMF assembly, with second-order roots emerging as a sensitive tier for clonal contrasts.

Conclusions

AMF distributions in Chinese fir are jointly determined by host genotype, fine-root order, and soil compartment. Lower Fm in clone No. 25 and peak intraradical abundance for both taxa underscore the functional importance of root intrinsic filters under P limitation. Positive Ri-Fm covariation implies complementary colonization. These findings provide a baseline for targeting specific root orders and AMF taxa to enhance P acquisition in P limited forest systems.