Variation in plant morphology and leaf essential oil composition of a representative Cinnamomum verum collection from Sri Lanka

Abstract

Sri Lankan cinnamon germplasm is an underexploited genetic resource of high breeding potential. A representative collection of a cultivated cinnamon germplasm with 48 accessions, is established at the University of Ruhuna, Sri Lanka. From that collection, 40 three-year-old vegetative-propagated accessions, were used in this study to study the variations in plant morphology and leaf oil composition. Flush colour was determined as four main categories of pink, red, brown, and green in all 48 accessions. Leaf length, leaf width, leaf length to width ratio and petiole length varied from 7.9 to 14.5 cm, 3.8 to 7.3 cm, 1.8 to 3.07 cm, and 1 to 2.2 cm, respectively, in the selected 40 accessions. Both the good fragrant aroma category of bark fragrance and the sweet pungent category of bark taste were recorded in 21 of the 40 accessions. Twenty (20) accessions from above collection were selected for leaf oil analysis. Gas chromatography-mass spectrometry (GC-MS) of leaf oil revealed the presence of 146 chemical compounds. Eugenol was the major compound of 17 accessions (52.2% to 79.5%). Two accessions with zero eugenol contained 86.8% and 91.9% of benzyl benzoate (BB), in contrast to that of 0%-0.65% from other accessions. One accession produced 16.6% eugenol and 22.3% BB. A green flush colour associated with a higher BB percentage suggested a potential morphological marker for BB. The PCA for 20 accessions explained 88.11% of total variance. The cinnamon accessions with high BB, KA11 and GB17, were clustered together, and HB12 was isolated on a different cluster. Positive correlations were detected between linalool and β-caryophyllene (0.649), linalool and BB (0.770) (p < 0.01), and negative correlations between eugenol and linalool (-0.630) and eugenol and BB (-0.886) (p <0.01).