Evaluation of somaclonal variation for genetic improvement of patchouli (Pogostemon patchouli), an exclusively vegetatively propagated aromatic plant

Patchouli (Pogostemon patchouli) is an important, exclusively vegetatively propagated aromatic plant, whose essential oil is widely used in perfumery and cosmetic products. Forty SC1 generation (first generation following in vitro phase) somaclones selected randomly from about 400 somaclones developed from the variety Johore, were multiplied through stem cuttings and evaluated in SC₂ and SC₃ generations to study the extent of somaclonal variation generated for plant height, herb yield, essential oil content, essential oil yield, and seven constituents of the essential oil. Significant or highly significant somaclonal variation was observed for plant height, herb yield, essential oil content, essential oil yield, and contents of patchouli alcohol, α-guaiene, α,δ-patchoulene, and α-bulnesene in the essential oil. The number of somaclones significantly superior to the parental variety for plant height, herb yield, essential oil content, and patchouli alcohol content in the essential oil ranged from 8–16 and the maximum superiority over the parental variety for these traits ranged from 21–79%. Broad-sense heritability estimates of plant height, herb yield, and essential oil content were 0.60–0.70 while those of essential oil yield and patchouli alcohol content were 0.44 and 0.47, respectively. Heritability estimates of other studied essential oil constituents were generally low (0.12–0.38). A high positive correlation was observed between essential oil yield and herb yield suggesting that selection for herb yield would be effective in improving essential oil yield. Patchouli alcohol content in the essential oil was negatively correlated with all the studied traits. Somaclonal variation, heritabilities of traits, and inter-trait correlations are reported for the first time in patchouli.