Schmidt Jennifer E, Lewis Caleb A, Firl Alana J, Umaharan Pathmanathan
Plant Science Center, Mars Wrigley, Davis, CA, USA.
Cocoa Research Centre, The University of the West Indies, St. Augustine Campus, Trinidad and Tobago.
Heliyon. 2025 Jan 10;11(2):e41890. doi: 10.1016/j.heliyon.2025.e41890. eCollection 2025 Jan 30.
Recent regulatory limits on concentrations of cadmium (Cd), an element of concern for human health, have made Cd reduction a key issue in the global chocolate industry. Research into Cd minimization has investigated soil management, cacao genetic variation, and postharvest processing, but has overlooked the cacao-associated microbiome despite promising evidence in other crops that root-associated microorganisms could help reduce Cd uptake. A novel approach combining both amplicon and metagenomic sequencing identified microbial bioindicators associated with leaf and stem Cd accumulation in sixteen field-grown genotypes of . Sequencing highlighted over 200 amplicon sequence variants (ASVs) whose relative abundance was related to cacao leaf and stem Cd content or concentration. The two highest-accumulating genotypes, PA 32 and TRD 94, showed enrichment of four ASVs belonging to the genus , the family , and the order . ASVs whose relative abundance was most negatively associated with plant Cd were identified as sp. (β = -2.21), (β = -2.17), and (β = -2.03) for prokaryotes, and (β = -4.58) and two unidentified ASVs (β = -4.32, β = -3.43) for fungi. Only two ASVs were associated with both leaf and stem Cd, both belonging to the . Of 5543 C d-associated gene families, 478 could be assigned to GO terms, including 68 genes related to binding and transport of divalent heavy metals. Screening for Cd-related bioindicators prior to planting or developing microbial bioamendments could complement existing strategies to minimize the presence of Cd in the global cacao supply.
镉（Cd）是一种关乎人类健康的元素，近期的监管限制已使降低镉含量成为全球巧克力行业的关键问题。对镉最小化的研究已探讨了土壤管理、可可遗传变异和收获后加工，但尽管有其他作物的相关证据表明根系相关微生物有助于减少镉吸收，却忽略了与可可相关的微生物群落。一种结合扩增子测序和宏基因组测序的新方法，鉴定出了与16种田间种植的可可基因型叶片和茎中镉积累相关的微生物生物指标。测序突出显示了200多个扩增子序列变体（ASV），其相对丰度与可可叶和茎中的镉含量或浓度相关。积累量最高的两个基因型PA 32和TRD 94，显示出属于某属、某科和某目的4个ASV的富集。相对丰度与植物镉含量最负相关的ASV，对于原核生物分别鉴定为某菌属（β = -2.21）、某菌属（β = -2.17）和某菌属（β = -2.03），对于真菌分别鉴定为某菌属（β = -4.58）和两个未鉴定的ASV（β = -4.32，β = -3.43）。只有两个ASV与叶片和茎中的镉都相关，二者均属于某菌属。在5543个与镉相关的基因家族中，478个可被归类到基因本体（GO）术语，包括68个与二价重金属结合和转运相关的基因。在种植前筛选与镉相关的生物指标或开发微生物生物改良剂，可以补充现有策略，以尽量减少全球可可供应中镉的存在。
