Corosolic acid content and SSR markers in Lagerstroemia speciosa (L.) Pers.: a comparative analysis among populations across the Southern Western Ghats of India.

Lagerstroemia speciosa commonly known as 'Banaba' is native of south-east Asia which exhibits both horticultural and therapeutic value. The anti-diabetic and anti-obese property of the tree is attributed to corosolic acid (CRA)-a pentacyclic triterpene seen predominantly in the mature leaves. Although there are studies on either chemical or genetic variation in L. speciosa from different regions, none have dealt with their association to discuss the formation of chemical diversity. For the first time, we have analyzed CRA content in 12 natural populations corresponding to 42 samples seen in the Southern Western Ghats (SWG) using chromatography techniques and genetic variation estimated using SSR markers. Significant variation in percentage distribution of CRA ranging from 0.005% to 0.868% dr.wt. was recorded wherein populations from the north SWG contain relatively more active principle (mean=0.321%) than their counterparts in the south (mean=0.064%). Similarly, SSR data showing relatively high rate of gene flow (Nm=2.72) and low genetic differentiation (FST=0.14) is indicative that populations from north are genetically more diverse than those in the south (Nm=0.48; FST=0.38). The scatter plot derived by Principle Component Analysis (PCA) of chemical and genetic data shows similar pattern of clustering that reveals strong association between the two sets of data. It is concluded that the observed variation in CRA content in natural populations of the species depends more on the genetic background and less on edaphic factors.