Differential analysis on heavy metal cadmium accumulation of Zanthoxylum armatum germplasm resources

【Objective】 To analyze the differences in cadmium（ Cd） accumulation among Zanthoxylum armatum germ-plasm resources, explore the characteristics of cadmium accumulation and enrichment mechanisms, which could provide theoretical reference for the breeding of Z. armatum varieties and cadmium control. 【Method】 Six germplasms with good production traits from the National Forest Tree Germplasm Resource Repository of Zanthoxylum armatum in Jiangjin Dis-trict, Chongqing, including Z. armatum ‘ Jiuyeqinghuajiao’, Z. armatum ‘ Zaoshu Jiuyeqinghuajiao’, Guanling Z. armatum, Sichuan Z. armatum, Yunnan Z. armatum, Yunnan Zanthoxylum sp., were used as experimental materials. The Cd content in 6 parts, including leaves, stems, branch bark, pericarp, seeds and roots, was measured to analyze the charac-teristics of Cd enrichment and transport. And germplasms with great differences in Cd enrichment ability were selected for untargeted metabolomics analysis on root metabolites. 【Result】 Differences in Cd content were observed in the same part among different Z. armatum germplasms, with Yunnan Z. armatum showing higher cadmium content in all parts com-pared to other germplasms. Within the same germplasm, variations in Cd content were also found among different parts. Except for Guanling Z. armatum, the branch bark had the highest Cd content in other germplasms, followed by leaves and roots, which were higher than those in seeds, stems and pericarp. All Z. armatum germplasms had soil Cd enrichment ability in their roots, with enrichment coefficients ranging from 3.470 to 12.780. Yunnan Z. armatum showed significantly stronger enrichment ability than other germplasms（ P＜0.05, the same below）, while Z. armatum‘ Zaoshu Jiuyeqinghua-jiao’ was significantly weaker than other germplasms. The transfer coefficients from root to pericarp, root to leaf, root to stem, root to branch bark, and root to seed were 0.264-0.530, 1.494-3.294, 0.324-0.642, 1.408-3.628 and 0.330-0.943 respectively. Untargeted metabolomics analysis was conducted on the root metabolites of Z. armatum‘ Zaoshu Jiuyeqing-huajiao’ and Yunnan Z. armatum, which had the greatest difference in Cd enrichment ability. A total of 520 differential metabolites were identified, including 196 up-regulated and 324 down-regulated metabolites, with significant differences between the 2 germplasms. Compared with the root metabolites of Z. armatum‘ Zaoshu Jiuyeqinghuajiao’, the root me-tabolites of Yunnan Z. armatum showed an up-regulated trend in organic acids and alkaloids. The results of KEGG meta-bolic enrichment analysis indicated that the differential metabolites were mainly enriched in pathways such as isoflavonoid biosynthesis, phenylalanine metabolism, arginine biosynthesis, taurine and hypotaurine metabolism, and linoleic acid metabolism. 【Conclusion】 There are differences in the accumulation of soil Cd by Z. armatum germplasm resources. Specifically, Z. armatum‘ Zaoshu Jiuyeqinghuajiao’ demonstrated relatively low accumulation ability, whereas Yunnan Z. armatum shows high enrichment ability. This variation in Cd enrichment might be associated with root metabolites.