| Summary: | Red-flowered oil-tea camellia (<i>ROC</i>) is an important woody oil species growing in the south, and its oil has high nutritional value. There are four main species of <i>ROC</i> in China, namely, <i>Camellia chekiangoleosa</i> (<i>CCH</i>), <i>Camellia polyodonta</i> (<i>CPO</i>), <i>Camellia semiserrata</i> (<i>CSE</i>) and <i>Camellia reticulata</i> (<i>CRE</i>). Reports on the comprehensive comparative analysis of <i>ROC</i> are limited. This study investigated the fruit characteristics and nutritional components of four <i>ROC</i> fruits, and the results showed that <i>ROC</i> had high oil content with levels of 39.13%–58.84%, especially the <i>CCH</i> fruit, which reached 53.6–58.84%. The contents of lipid concomitants of <i>ROC</i> oil were also substantial, including β-amyrin (0.87 mg/g–1.41 mg/g), squalene (0.43 mg/g–0.69 mg/g), β-sitosterin (0.47 mg/g–0.63 mg/g) and α-tocopherol (177.52 μg/g–352.27 μg/g). Moreover, the transverse diameter(TD)/longitudinal diameter (LD) of fruits showed a significant positive correlation with the oil content, and <i>ROC</i> fruits with thinner peels seemed to have better oil quality, which is similar to the result of the oil quality evaluation obtained by the gray correlation coefficient evaluation method. Four <i>ROC</i> oils were evaluated using the gray correlation coefficient method based on 11 indicators related to the nutritional value of <i>ROC</i>. <i>CCH</i> oil had the highest score of 0.8365, and YS-2 (a clone of <i>CCH</i>) was further evaluated as the best <i>CCH</i> oil. Finally, the results of heatmap analysis showed that triglycerides could be used as a characteristic substance to distinguish <i>CCH</i> oil from the other three <i>ROC</i> oils. The PLSDA (Partial least squares regression analysis) model and VIP (Variable important in projection) values further showed that P/S/O, P/O/O, P/L/L, P/L/Ln, S/S/O, S/O/O and P/S/S (these all represent abbreviations for fatty acids) could be used as characteristic differential triglycerides among the four <i>ROC</i> oils. This study provides a convenient way for planters to assess the nutritional quality of seed oil depending on fruit morphology and a potential way to distinguish between various <i>ROC</i> oils.
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