In-Vivo Propagation Protocols for Kapparawalliya (Plectranthus amboinicus Lour)

Plectranthus amboinicus, a member of the family Lamiaceae, is an herb that is commonly employed in traditional medicinal systems owing to its distinct therapeutic qualities. The demand for this rare herb is rising rapidly, suggesting that wild harvesting may be insufficient and could even result in the extinction of this precious herb. Thus, initiating commercial cultivation of the species is imperative to meet the growing demand for the herb while preserving its genetic foundation. The current study comprised three independent experiments that evaluated the most suitable cutting type, potting media, and irrigation schedule for in-vivo propagation of P. amboinicus under protected house conditions.
Four distinct cutting types (tip/softwood cutting, single nodal semi-hardwood cuttings, double nodal semi-hardwood cuttings and triple nodal semi-hardwood cuttings), five different potting mixtures (topsoil: sand: compost-1:1:1, topsoil: sand: compost-1:2:1, topsoil: sand: compost-1:1:2, topsoil: compost-1:1 and topsoil: compost-1:2) and four different irrigation schedules (daily watering to field capacity, daily watering to 50% of field capacity, watering at one-day intervals to field capacity and watering at one-day intervals to 50% of field capacity ) were tested in Completely Randomized Design with 20 replicates per treatment. Data on plant height (cm), number of new buds and number of newly emerged leaves were collected at weekly intervals. Data on chlorophyll content (SPAD) and leaf area (mm2) were recorded six weeks after cutting establishment. Data were analyzed using analysis of variance (ANOVA), and treatment means were compared at the 5% level of significance. The results showed that softwood cuttings of P. amboinicus exhibited significantly higher growth and yield (P≤0.05), while the potting medium was composed of topsoil: sand: compost (1:2:1). The optimum irrigation schedule, out of the four examined, was daily watering to field capacity. In conclusion, softwood cuttings, topsoil: sand: compost (1:2:1) with daily watering to field capacity could be used as the most promising agronomic practice for the successful in-vivo propagation of P. amboinicus.