Delineation of Ocimum gratissimum L. complex combining morphological, molecular and essential oils analysis

Abstract Presence of differences in the essential oil content, chromosome count and the morphology, led to consider Ocimum gratissimum as a polymorphic complex species often subcategorized into subspecies, varieties, and forms. Characterization of O. gratissimum complex is carried out using morphological, molecular markers combined with chemical analysis of essential oils in an attempt to resolve the complexity present. At the morphological level, the applied analysis of variance and Tukey’s honestly significant difference test reveals that all the studied morpho-metric characters were effective in discriminating the O. gratissimum morphotypes. Molecular marker (ISSR) used in this study generated a total of 341 loci, of which 290 loci were polymorphic depicting 84.28% polymorphism. The efficiency of ISSR’s markers was revealed through principal component analysis plot that grouped all the accessions according to the morphotypes irrespective of their geographical locations. Chemo profiling of essential oils revealed eugenol (38.6–79.2%) and thymol (47.6–50.7%), as the major essential oil constituents distributed in O. gratissimum accessions studied. Pearson correlation coefficient ( r  = 0.482) suggested a moderate correlation between the genetic markers and essential oils content, thus depicting genetic markers may be linked to the essential oils constituents. The results of the present study suggest the possibility of using morphological, molecular, and chemical analysis to differentiate between O. gratissimum complexes.