Research Projects

The genus Pogostemon Desf., commonly known as the Patchouli group is one of the economically important genera in the wild aromatic family Lamiaceae. It can be easily recognized by its exserted stamens and dense, unilateral, moniliform hairs on filaments (Bhatti & Ingrouille, 1997). It consists of about 96 species (POWO 2023; WFO, 2023) majorly diversified in tropical and subtropical regions of Asia and Africa (Bhatti & Ingrouille, 1997; Yao et al 2015; POWO 2023). The highest species diversity (53 taxa) is found in the Indian subcontinent of which 29 taxa are endemic (Singh et al. 2015; Sampath Kumar et al. 2020). Until mid of the 90th century, the genus Pogostemon was recognized as three separate genera by various authors viz. Dysohylla Blume, Pogostemon Desf.(Bentham, 1830; Hooker, 1885; Briquet, 1897; Gamble, 1924; Kudo, 1929; Mukerjee, 1940; El-Gazzar & Watson, 1967; Cantino & Sanders, 1986) and Eusteralis Raf. (Rafinesque-Schmaltz, 1837). Nevertheless, the multivariate techniques to explicate the relationship of these split genera resulted in an amalgamation of the genus as Pogostemon s.l. Notably, Press (1982) combined Dysophylla, Eusteralis with Pogostemon and treated them as a single genus Pogostemon s.l. based on the cladistic approach. Brummit (1992) and Cantino et al. (1992) also considered all three genera are congeners, should be treated as a single genus. Later authors (Sampath Kumar, 1995; Bhatti & Ingrouille, 1997; Ingrouille & Bhatti, 1998; Yao et al., 2015; Mabberley, 2017) were also treated Pogostemon S.l as congeners. In 1997, Bhatti & Ingrouille reclassified the genus Pogostemon s.l. and split into three subgenera viz. Allopogostemon, Dysophyllus, and Pogostemon based on morphological evidence. Nevertheless, considerable infra-specific inconsistency in the morphological traits and possibly convergent evolution made species of this genus complex in the classification (Bhatti & Ingrouille, 1997; Ingrouille & Bhatti 1998). A recent phylogenetic study on the Chinese Pogostemon based on the molecular markers also was not supported the subgeneric classification by monophyletic (Yao et al. 2016). Though the major concentration of the species of this genus distributed in India, systematic studies on this group is few decades old and the recent works are regional specific. Besides, the works done on this group was based on herbarium specimens as well as classical approach. Nevertheless, there is no modern approach like molecular phylogenetic studies in India have been done so far on this economically important group. With this background, the present proposal aimed to resolve the systematic complexity, geographical diversification and reveal the phylogenetic relationship among wild Patchouli species based on the combination of classical and modern approaches.