Analysis of water soluble polysaccharides as a potential chemotaxonomic marker for landraces in Bixa orellana.

Annatto tree (Bixa orellana L.) is native to Brazil and is now under cultivation in many parts of world for its reddish orange 'annatto' dye. There are three types of landraces in annatto and they are distinguished based on fruit shape i.e., ovate, conical and hemispherical, whose pigment yield differs. Since annatto pigment yield varies with landrace, it is necessary to characterize markers towards the identification of landraces. In this study, we characterized water soluble polysaccharides (WSP) of twigs from three landraces using size-exclusion chromatography (SEC), Fourier-transform Infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR) and gas liquid chromatography (GLC) for their potential use as chemotaxonomic markers to distinguish the landraces. GLC analysis on WSP showed hemispherical type contained 38% rhamnose, while conical and ovate types contained 17% and 34% glucose, respectively. Thus, glucose and rhamnose content of WSP could be used to distinguish the three landraces. Further, differences in calculated molecular weight as revealed by SEC (281.8, 151.3 and 79.4 kDa for conical, hemispherical and ovate types, respectively) could also be used to distinguish the three landraces.