Abstract:

Cinnamon leaves are the primary source of Cinnamomum cassia essential oil. However, the lack of specialized leaf-oriented cultivars currently hinders the high-quality development of the cinnamon industry. To explore the diversity of leaf phenotypic traits and volatile oil content among different germplasms, and to screen elite leaf-use cultivars with high oil yields, this study was conducted using 300 accessions of 3-year-old F₁ progeny seedlings from Guangxi. Twelve phenotypic traits (nine quantitative and three qualitative) were systematically measured, and multivariate statistical analysis was employed to decipher the phenotypic diversity and identify superior germplasm. The results are as follows. (1) The volatile oil content in the leaves of 300 cinnamon accessions ranged from 0.15% to 1.56%, with an average of 0.62%. Accession PN2 exhibited the highest content (1.56%). (2) The genetic diversity of quantitative traits was significantly higher than that of qualitative traits. For the nine quantitative traits, the coefficient of variation (CV) ranged from 9.54% to 48.11% (with branch height showing the highest CV), and the diversity index (H’) ranged from 1.968 to 2.729 (with leaf volatile oil content recording the highest H’). In contrast, the three qualitative traits exhibited a CV of 12.61% to 30.88% and an H’ of 0.085 to 0.678. The genetic diversity index of nine quantitative traits was much higher than that of three qualitative traits. (3) Correlation analysis revealed that the leaf volatile oil content was significantly and positively correlated with plant height, branch height, leaf length, leaf width, and leaf drying rate (P<0.01), and significantly positively correlated with crown width (P<0.05). In contrast, a highly significant negative correlation was observed with leaf thickness (P<0.01). (4) Principal component analysis (PCA) yielded eight principal components, which collectively accounted for 86.706% of the total variance, thereby capturing the majority of the genetic information in the cinnamon germplasm. Plant height, crown width, and leaf length were identified as the key contributing factors. (5) Cluster analysis categorized the 300 germplasm accessions into 3 distinct groups. Group I (53 accessions) demonstrated the best overall performance, with a mean volatile oil content of 0.70% and a comprehensive score of 0.53. Based on a combined evaluation of these scores and oil content, 9 excellent accessions (PN5, PN11, PN18, PN20, etc.) were selected from this group, with volatile oil contents ranging from 0.885% to 1.305% and comprehensive scores between 0.563 and 0.691. This study provides high-quality germplasm resources and a theoretical foundation for breeding leaf-use cinnamon varieties.

Key words: cinnamon, leaf-use varieties, phenotypic traits, volatile oil content, excellent germplasm, correlation analysis, principal component analysis, cluster analysis