AUTHOR=Qi Huasha , Sun Xiuxiu , Yan Wuping , Ye Hang , Chen Jiali , Yu Jing , Jun Dai , Wang Chunmei , Xia Tengfei , Chen Xuan , Li Dongliang , Zheng Daojun 

TITLE=Genetic relationships and low diversity among the tea-oil Camellia species in Sect. Oleifera, a bulk woody oil crop in China

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.996731

DOI=10.3389/fpls.2022.996731

ISSN=1664-462X

ABSTRACT=<p>Tea-oil <italic>Camellia</italic> is one of the four woody oil crops in the world and has high ecological, economic and medicinal values. However, there are great differences in the classification and merging of tea-oil <italic>Camellia</italic> Sect. <italic>Oleifera</italic> species, which brings difficulties to the innovative utilization and production of tea-oil <italic>Camellia</italic> resources. Here, ISSR, SRAP and chloroplast sequence markers were analyzed in 18 populations of tea-oil <italic>Camellia</italic> Sect. <italic>Oleifera</italic> species to explore their phylogenetic relationships and genetic diversity. The results showed that their genetic diversity were low, with mean <italic>H</italic> and <italic>π</italic> values of 0.16 and 0.00140, respectively. There was high among-population genetic differentiation, with ISSR and SRAP markers showing an Fst of 0.38 and a high Nm of 1.77 and cpDNA markers showing an Fst of 0.65 and a low Nm of 0.27. The <italic>C. gauchowensis</italic>, <italic>C. vietnamensis</italic> and Hainan Island populations formed a single group, showing the closest relationships, and supported being the same species for them with the unifying name <italic>C. drupifera</italic> and classifying the resources on Hainan Island as <italic>C. drupifera.</italic> The tea-oil <italic>Camellia</italic> resources of Hainan Island should be classified as a special ecological type or variety of <italic>C. drupifera</italic>. However, cpDNA marker-based STRUCTURE analysis showed that the genetic components of the <italic>C. osmantha</italic> population formed an independent, homozygous cluster; hence, <italic>C. osmantha</italic> should be a new species in Sect<italic>. Oleifera.</italic> The <italic>C. oleifera</italic> var. <italic>monosperma</italic> and <italic>C. oleifera</italic> populations clustered into two distinct clades, and the <italic>C. oleifera</italic> var. <italic>monosperma</italic> populations formed an independent cluster, accounting for more than 99.00% of its genetic composition; however, the <italic>C. oleifera</italic> populations contained multiple different cluster components, indicating that <italic>C. oleifera</italic> var. <italic>monosperma</italic> significantly differs from <italic>C. oleifera</italic> and should be considered the independent species <italic>C. meiocarpa.</italic> Haplotype analysis revealed no rapid expansion in the tested populations, and the haplotypes of <italic>C. oleifera</italic>, <italic>C. meiocarpa</italic> and <italic>C. osmantha</italic> evolved from those of <italic>C. drupifera</italic>. Our results support the phylogenetic classification of <italic>Camellia</italic> subgenera, which is highly significant for breeding and production in tea-oil <italic>Camellia</italic>.</p>