Association Analysis of the Growth of Black Poplar (Populus Nigra L.) Under Contrasting Nitrogen Levels

The European black poplar (Populus nigra L.) has been used as agermplasm resource for the breeding of new poplar varieties around the world. Theidentification and screening of its high nitrogen use efficiency genotypes couldenable the breeding of new resource-efficient poplar varieties. The accessions werescreened using MALDI-TOF MS genotyping technology for ammoniumtransporter (AMT) and nitrate transporters (NRT) genes against phenotypic data forseedling height and ground diameter traits, in both low and high nitrogenenvironments. Allele re-sequencing of seven genes related to root developmentwas carried out using the minisequencing method. By cluster analysis, 101accessions of black poplar were divided into 4 populations, and it was concludedthat Central Europe is the origin of the evolution of low-nitrogen and highefficiencypopulations of European black poplar. Association study between SNPtyping and seedling height and ground diameter traits showed that there weresignificant correlations between four SNP loci and growth traits under thecontrasting N levels. We found that SNP3 and SNP4 in the PttAMT1;3 gene weresignificantly associated with seedling height traits, and that SNP2 and SNP7 in thePttAMT1;2 and PttAMT1;5 genes, respectively, were significantly associated withground diameter traits. Thus, considerable allelic diversity is present within thecandidate genes studied and can be utilized to develop functional markers to selectfor poplars with improved growth under N stress conditions.