Molecular analysis of genetic diversity in elite Indian cultivars of essential oil trade types of aromatic grasses (Cymbopogon species)

Eleven elite and popular Indian cultivars of Cymbopogon aromatic grasses of essential oil trade types - citronella, palmarosa and lemongrass - were characterized by means of RAPDs to discern the extent of diversity at the DNA level between and within the oil biotypes. Primary allelic variability and the genetic bases of the cultivated germplasm were computed through parameters of gene diversity, expected heterozygosity, allele number per locus, SENA and Shannon's information indices. The allelic diversity was found to be in the order: lemongrass > palmarosa > citronella. Lemongrasses displayed higher (1.89) allelic variability per locus than palmarosa (1.63) and citronella (1.40). Also, RAPDs of diagnostic and curatorial importance were discerned as 'stand along' molecular descriptors. Principal component analysis (PCA) resolved the cultivars into four clusters: one each of citronella and palmarosa, and two of lemon-grasses (one of C. flexuosus and another of C. pendulus and its hybrid with C. khasianus). Proximity of the two species-groups of lemongrasses was also revealed as they shared the same dimension in the three-dimensional PCA. The molecular distinctions are discussed in relation to oil-chemotypic variations.