Abstract:
Ceylon cinnamon (Cinnamomun verum) is a globally demanded spice and
positioning as a world’s largest exporter. However, Sri Lanka currently has only two
improved cultivars, Sri Gemunu and Sri Wijaya which yield up to 1500 kg ha⁻¹ under
optimal conditions and vegetatively propagated for genetic uniformity. These cultivars
exhibit phenotypic plasticity that complicates reliable identification. This study
evaluated the environmental stability and phenotypic plasticity of qualitative leaf
morphological traits in twenty cinnamon accessions across two agroecological regions
of WM3a (Mid country Research Station [MRS]) and WL2a (Thalgampola, Galle) in Sri
Lanka. The experiment was conducted using a Randomized Complete Block Design
with three replications. Mother plants at MRS were compared with their vegetatively
propagated clones established in Thalgampola for two years. Standardized leaf
sampling from the 5th and 6th nodes below apical shoot tips were assessed for six
qualitative traits of leaf arrangement (opposite, subopposite, opposite or subopposite
in different branches and opposite to subopposite within the same branch), shape
(elliptic, broadly elliptic, narrowly elliptic, ovate, broadly ovate, oval, lanceolate, ovatelanceolate,
and oblong-lanceolate), apex (acute, obtuse, acuminate, long acuminate,
narrowly acuminate, and acuminate with broad acumen), base (acute, subacute,
cuneate, rounded, sub-cordate, and obtuse contracted into petiole then shortly
cuneate), venation, and margin. Chi-square and Cramér’s V analyses revealed that leaf
arrangement, apex, base, and venation were environmentally stable (p > 0.05, V < 0.5).
Leaf shape showed moderate plasticity (p = 0.033), while leaf margin exhibited strong
environmental responsiveness (p < 0.001), varying between entire and slightly
undulate forms across regions. These findings indicate that environmentally stable
traits serve as reliable taxonomic markers for cultivar identification across diverse
sites, while phenotypically plastic traits may indicate adaptive responses, supporting
breeding and propagation strategies.
