Genetic diversity of Ocimum gratissimum L. based on volatile oil constituents, flavonoids and RAPD markers

Morphological, chemical and genetic differences of 12 tree basil (Ocimum gr atissimum L.) accessions were studied to determine whether volatile oils an d flavonoids can be used as taxonomical markers and to examine the relation ship between RAPDs to these chemical markers. Eugenol, thymol, and geraniol were the major volatile oil constituents found in Ocimum gratissimum. Xant omicrol and cirsimaritin were the major external flavones. The accessions m orphologically described as O. gratissimum var. gratissimum contained eugen ol as the major volatile oil constituent, and cirsimaritin as the major fla vone. Ocimum gratissimum var. macrophyllum accessions contained thymol as t he major volatile oil constituent, and xantomicrol as the major flavone. A distinct essential oil and flavone chemotype (producing geraniol and a mixt ure of the flavones cirsimaritin, isothymusin, xanthomicrol, and luteolin) was found in an accession genetically more distant from the other two group s when analyzed by molecular markers, The accessions could be divided based on Volatile oil constituents into six groups: (1) thymol: alpha -copaene ( ot24, ot25, ot26, and ot28); (2) eugenol:spathulenol (ot17, ot63, and ot52) ; (3) thymol:p-cymene (ot65); (4) eugenol: gamma -muurolene (ot27 and ot29) ; (5) eugenol:thymol: spathulenol (ot85); and (6) geraniol (ot84). Cluster analysis of RAPD markers showed that there are three groups that are distin ct genetically and highly correlated (I = 0.814) to volatile oil constituen ts. (C) 2001 Elsevier Science Ltd. All rights reserved.