油茶栽培历史与长江流域油茶遗传资源

普通油茶(Camellia oleifera)是我国第一大木本油料作物。普通油茶作为油料作物的栽培历史, 现存确切记载不到1,000年, 长江流域可能是最早栽培油茶的地区之一。普通油茶的野生近缘种是油茶育种宝贵的遗传资源。普通油茶属于山茶科山茶属(Camellia)油茶组(Sect. Oleifera), 其野生近缘种应包括山茶属油茶组和短柱茶组(Sect. Paracamellia)的物种, 但油茶组和短柱茶组的划分仍有争议, 物种间的系统发育关系仍不清楚。油茶组和短柱茶组是山茶属中多倍体出现频率最高的类群, 而且存在突出的种内多倍性现象, 人工选择和种间杂交可能在其中起到促进作用。长江流域是普通油茶的主产区, 也是最主要的野生普通油茶分布区, 拥有丰富的野生普通油茶遗传资源。本研究统计了山茶属油茶组和短柱茶组物种的分布地, 并与野生普通油茶的潜在分布区进行了比较。分析结果显示, 长江流域与珠江流域的分水岭——南岭、苗岭及附近地区是油茶组和短柱茶组物种多样性最高的地区, 同时也是野生普通油茶潜在的高适生区, 可能是普通油茶及其野生近缘种潜在的种间杂交带。物种多样性从南向北呈下降趋势, 可能反映了从南向北的扩散方向。普通油茶及其野生近缘种间的潜在杂交带可能蕴含着丰富的遗传多样性, 为选择育种提供了天然的育种场, 应对这些地区优先开展研究和保护, 挖掘与利用有重要经济价值的遗传资源。

Cultivation history of Camellia oleifera and genetic resources in the Yangtze River Basin

Camellia oleifera is the dominant woody oil crop in China. According to current records, the cultivation history of C. oleifera as an oil crop may be less than 1,000 years, and the Yangtze River Basin may be one of the earliest cultivation areas. Wild relatives of C. oleifera are valuable genetic resources for breeding. Camellia oleifera belongs to Sect. Oleifera of the genus Camellia in the family Theaceae. Wild relatives of C. oleifera may include species in Sect. Oleifera and Sect. Paracamellia. However, the division of Sect. Oleifera and Sect. Paracamellia is still under debate, and the phylogenetic relationships among species remain unresolved. Sect. Oleifera and Sect. Paracamellia have the highest frequency of polyploids in the genus Camellia, and the same species may have various ploidies, which may be promoted by artificial selection and interspecies hybridization. The Yangtze River Basin is the main production area of C. oleifera, and the main distribution area of wild C. oleifera, thus containing rich genetic resources of wild C. oleifera. This study analyzed the distribution of species in Sect. Oleifera and Sect. Paracamellia of the genus Camellia and compared the results with the potential distribution areas of wild C. oleifera. Results show that drainage divides between the Yangtze River Basin and Pearl River Basin (Nanling Mountain, Miaoling Mountain, and adjacent regions) have the highest diversity of species in Sect. Oleifera and Sect. Paracamellia. Meanwhile, these regions are also potential highly suitable growing regions for wild C. oleifera, where there may be potential interspecies hybrid zones between C. oleifera and its wild relative species. Species diversity decreases from the south to the north, likely representing the dispersal direction from south to north. The potential interspecies hybrid zones between C. oleifera and its wild relative species may contain rich genetic diversity and provide natural breeding stations for selective breeding. These regions should be priority areas for research and conservation in order to explore and utilize genetic resources with important economic values.