Genome-wide association study of terpenoids in resin reveals candidate genes for resin yield in Pinus massoniana

Masson pine (Pinus massoniana) is an important species for resin tapping in China. Molecular assisted selection (MAS) has been gradually introduced in to the selection and breeding of masson pine. Until now, the lack of connection between genome information and phenotypic data has hindered the breeding and selection of important chemical compounds of xylem resin. In this study, gas chromatography mass spectrometer (GC-MS) was employed for qualitative and quantitative analysis of chemical compounds of resin collected from 69 masson pine germplasm resources. Then, genome-wide association study (GWAS) was conducted for the terpenoids with higher heritability. A total of 15 primary compounds, including six diterpenes and nine monoterpenes/sesquiterpenes, were detected from xylem resin. By using five GWAS methods, 42 associated SNPs were identified from these masson pines. The P. taeda genome database was used for detecting candidate genes related to the associated SNPs. By using transcriptome data, several members of PKc_like super family, Cytochrome P450, AP2-EFR, F-box, and ABC transporter were found to be highly expressed in the masson pines with higher resin-yielding capacity. The terpenoids associated SNPs can be directly used for MAS. These candidate genes, especially the two F-box members, will contribute to the study of terpenoid biosynthesis mechanisms in the future.