Genetic relationship and source species identification of 58 Qi-Nan germplasms of Aquilaria species in China that easily form agarwood

Abstract

Recently, Qi-Nan germplasm, the germplasm ofAquilariaspecies that easily forms agarwood, has been widely cultivated in Guangdong and Hainan Provinces in China. Since the morphological characteristics of Qi-Nan germplasm are similar to those ofAquilariaspecies and germplasm is bred by grafting, it is difficult to determine the source species of this germplasm by traditional taxonomic characteristics. In this study, we performed a DNA barcoding analysis of 58 major Qi-Nan germplasms as well asAquilaria sinensis,A.yunnanensis,A.crassna,A.malaccensisandA.hirtawith 5 primers (nuclear gene internal transcribed spacer 2 (ITS2) and the chloroplast genesmatK,trnH-psbA,rbcLandtrnL-trnF). This field survey in the Qi-Nan germplasm plantations in Guangdong and Hainan Provinces aimed to accurately identify the source species of Qi-Nan germplasm. According to the results, ITS2 andmatKshowed the most variability and the highest divergence at all genetic distances. This ITS2+matKcombination, screened for with TaxonDNA analysis, showed the highest success rate in species identification of the Qi-Nan germplasm. Clustering in the phylogenetic trees constructed with Bayesian inference and maximum likelihood indicated that the Qi-Nan germplasm was most closely related toA.sinensisand more distantly related toA.yunnanensis,A.crassna,A.malaccensisandA.hirta. Therefore, this study determined that the source species of the Qi-Nan germplasm isA.sinensis.