An association genetics approach was used to examine individual genes and alleles at several loci responsible for complex traits controlling wood traits (cellulose, lignin, and 6C sugar) in European black poplar (Populus nigra). Due to fast growth, clonal propagation and availability of genomic resources have allowed us to investigate further genetic control of wood traits in the species. From thirty-nine candidate genes, 384 SNPs were successfully genotyped in a clonally replicated 288 P. nigra clone population. Only 50.5% of these markers were polymorphic that could be used in association mappings.

The association population (4 ramets per clone) was phenotyped for cellulose, lignin, and 6C sugar contents. Moderately high heritabilities were observed for cellulose and 6C sugar while it was low in lignin. Furthermore, a moderately strong and positive genetic correlation was found between cellulose and lignin which may hinder genetic improvement in cellulose content due to the correlated response on lignin. The LD, across all candidate genes, showed a rapid decay with physical distance. Single-marker-based association tests using GLM and MLM models were implemented to identify associations for cellulose, lignin, and 6C sugar contents.

Eleven unique single marker associations for cellulose, 5 for lignin, and 6C sugar contents were identified from 39 candidate genes, but only one marker for cellulose content (CesA3A-15-456) had a significant association with cellulose and with dominant gene effect after multiple test correction was applied. The percent of total variation explained by significant single marker associations ranged from 3 to 9.2% in cellulose, 2.8 to 3.8% in lignin, and 3.2–5.5% in 6C sugar contents, respectively. Given the rapid decay of within-gene linkage disequilibrium, limitation of sample size, overcorrection for false positives, and intensity of phenotypic selection, it is likely that some of these single marker associations are genuine and deserve to be further investigated with a larger and diverse study population.

使用关联遗传学方法来检查几个位点上的个体基因和等位基因，这些位点负责控制欧洲黑杨（Populus nigra）木材性状（纤维素、木质素和6C糖）的复杂性状。由于生长速度快，克隆繁殖和基因组资源的可用性使我们能够进一步研究该物种木材性状的遗传控制。从 39 个候选基因中，在克隆复制的 288 个P. nigra克隆群体中成功对 384 个 SNP 进行了基因分型。这些标记中只有 50.5% 具有多态性，可用于关联作图。

对关联群体（每个克隆 4 个分株）进行了纤维素、木质素和 6C 糖含量的表型分析。纤维素和 6C 糖的遗传力较高，而木质素的遗传力较低。此外，在纤维素和木质素之间发现了中等强度的正向遗传相关性，这可能由于木质素的相关反应而阻碍纤维素含量的遗传改良。所有候选基因的LD随着物理距离的增加而快速衰减。使用 GLM 和 MLM 模型进行基于单标记的关联测试，以确定纤维素、木质素和 6C 糖含量的关联。

从 39 个候选基因中鉴定出 11 个与纤维素、5 个与木质素和 6C 糖含量相关的独特单标记关联，但在多次研究后，只有一个与纤维素含量相关的标记 (CesA3A-15-456) 与纤维素和显性基因效应具有显着关联。应用了测试校正。由显着的单一标记关联解释的总变异百分比范围分别为纤维素的 3% 至 9.2%、木质素的 2.8% 至 3.8%、6C 糖含量的 3.2% 至 5.5%。考虑到基因内连锁不平衡的快速衰减、样本量的限制、假阳性的过度校正以及表型选择的强度，这些单标记关联中的一些可能是真实的，值得通过更大和多样化的进一步研究研究人群。