Impact evaluation of growth stage and species on morpho-physiological traits and bioactive constituent of essential oil in Ocimum through multi-year experiment

The genus Ocimum displays excellent variability among the species and sub-species due to the highly cross-pollinated nature and interspecific hybridization. The present investigation was carried out to identify the commercially promising growth stage(s) in different Ocimum for exatraction of oil and bioactive compounds at heighest. A set of three cultivated species were evaluated to study the variation in morpho-physiological traits and essential oil composition harvested at three stages namely vegetative, flowering and seed setting stage. The experiment was conducted for three consecutive years in factorial randomized complete block design with three replicates. The analysis of variance exhibited that the individual effect of Ocimum species and growth stage along with their interaction effect was significant in all the morpho-physiological parameters and bioactive constituent of oil in a pooled analysis. Highest plant height (103.95 cm) was observed in O. gratissimum L. harvested at seed setting stage while harvesting at flowering stage exhibited maximum leaf area (26.80 cm²), oil (0.52 %) and eugenol content (85.82 %). Sweet basil harvested at seed setting stage disclosed maximum branches per plant (21.53) and leaves per plant (4949) although linalool content (47.99 %) was found highest in harvested at flowering stage. O. basilicum L. was detected a great source of methyl chavicol (7.48 %) though this species was weaker source for methyl cinnamate. Among the studied species, O. gratissimum showed a negligible amount of methyl eugenol content in oil. A positive correlation between the morpho-physiological traits, oil content and its constituents with the various growth stages were recorded. None of bioactive compounds exhibited any correlation with oil content. Principle component analysis revealed that of the total variation, O. gratissimum contributed maximum (61.58 %) variation followed by O. basilicum (35.36 %). The results of current study suggested that the different Ocimum species can be harvest at various growth stages to get the maximum yield and target chemical compounds based on the needy industrial value.