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

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

doi:10.3389/fpls.2022.996731

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

Front Plant Sci. 2020 Sep 30:13:996731. doi: 10.3389/fpls.2022.996731. eCollection 2022.

Authors

Huasha Qi^{1

2}, Xiuxiu Sun^{1

2}, Wuping Yan^{1

3}, Hang Ye⁴, Jiali Chen^{1

2}, Jing Yu⁵, Dai Jun⁶, Chunmei Wang^{1

2}, Tengfei Xia^{1

2}, Xuan Chen^{1

2}, Dongliang Li^{1

2}, Daojun Zheng^{1

2}

Affiliations

¹ Hainan, Academy of Agricultural Sciences, Sanya Institute, Sanya, China.
² Key Laboratory of Tropic Special Economic Plant Innovation and Utilization, National Germplasm Resource Chengmai Observation and Experiment Station, Institute of Tropical Horticulture Research, Hainan Academy of Agricultural Sciences, Haikou, China.
³ School of Agricultural Sciences, Jiangxi Agricultural University, Nanchang, China.
⁴ Guangxi Key Laboratory of Special Non-Wood Forest Cultivation and Utilization, Improved Variety and Cultivation Engineering Research Center of Oil-Tea Camellia in Guangxi, Guangxi Forestry Research Institute, Nanning, China.
⁵ College of Horticulture, Hainan University, Haikou, China.
⁶ Qionghai Tropical Crop Service Center, Qionghai, China.

Abstract

Tea-oil Camellia 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 Camellia Sect. Oleifera species, which brings difficulties to the innovative utilization and production of tea-oil Camellia resources. Here, ISSR, SRAP and chloroplast sequence markers were analyzed in 18 populations of tea-oil Camellia Sect. Oleifera species to explore their phylogenetic relationships and genetic diversity. The results showed that their genetic diversity were low, with mean H and π 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 C. gauchowensis, C. vietnamensis and Hainan Island populations formed a single group, showing the closest relationships, and supported being the same species for them with the unifying name C. drupifera and classifying the resources on Hainan Island as C. drupifera. The tea-oil Camellia resources of Hainan Island should be classified as a special ecological type or variety of C. drupifera. However, cpDNA marker-based STRUCTURE analysis showed that the genetic components of the C. osmantha population formed an independent, homozygous cluster; hence, C. osmantha should be a new species in Sect. Oleifera. The C. oleifera var. monosperma and C. oleifera populations clustered into two distinct clades, and the C. oleifera var. monosperma populations formed an independent cluster, accounting for more than 99.00% of its genetic composition; however, the C. oleifera populations contained multiple different cluster components, indicating that C. oleifera var. monosperma significantly differs from C. oleifera and should be considered the independent species C. meiocarpa. Haplotype analysis revealed no rapid expansion in the tested populations, and the haplotypes of C. oleifera, C. meiocarpa and C. osmantha evolved from those of C. drupifera. Our results support the phylogenetic classification of Camellia subgenera, which is highly significant for breeding and production in tea-oil Camellia.

Keywords: Camellia Sect. Oleifera; classification; genetic relationships and diversity; germplasm resources; tea-oil Camellia.