2018 ASHS Annual Conference

Piedmont azalea (Rhododendron canescens) is the most common native azalea in the southeast US, ranging from Texas to North Carolina. It is of interest as a landscaping plant because of its adaptability, lace bug resistance, and early flowering. Piedmont azalea is one of the first native azalea species to bloom and could benefit early spring pollinators in urban landscapes. Information on the genetic diversity and population structure of Piedmont azalea would be useful for breeding and conservation biology. We used genotyping-by-sequencing (GBS) to examine 88 genotypes from Georgia and Florida. Bar-coded libraries of MspI/PstI-digested DNA samples were sequenced by Illumina Nextseq 500. Single nucleotide polymorphisms (SNPs) were identified using TASSEL and filtered at a minor allele frequency of 0.05. A total of 5186 SNPs were discovered by GBS, of which 1739 high quality SNPs were retained by TASSEL for further analysis. Since no reference genome was available for alignment, one of the genotypes from the population was selected to create a mock reference genome and all other genotypes were aligned to it. Analysis of population structure using STRUCTURE software showed that the Piedmont azalea genotypes could be grouped in three distinct populations based on delta K=3. Principle component analysis corroborated the STRUCTURE results showing three different population clusters. A neighbor-joining tree was constructed based on the SNP data to determine genetic relationships of the Piedmont azalea genotypes. Information derived from GBS analysis will benefit the breeding of Piedmont azaleas for urban landscapes.