Chloroplast DNA Sequences in Species Characterisation in the Genus Citrus from North-East India

The north-eastern region of India is reported to be a centre of origin and rich in diversity of Citrus (L.) species, where some wild and endangered species namely C. indica, C. macroptera, C. latipes, C. ichagensis and C. assamensis exist in their natural and undisturbed habitat. The taxonomy of Citrus L. and its allies has been a challenging task for the botanists around the world. Most of its complexity is derived both from the biology of the species and also its cultivation history In addition to morphological studies, phylogenetic inference using molecular data has also led to classification changes in the genus Rutaceae. Thus far, only chloroplast data and ITS have been used, at times combined with morphology to infer the phylogeny. In order to have comprehensive information about the extent of genetic relation between and also to investigate the occurrence of cryptic genomic hybridity among various Citrus species of North-east India, an assessment of the species inter-relationship of Citrus both wild and cultivated forms from the region was analyzed using chloroplast target DNA sequences. In the present investigation the recognition of C. maxima, C. medica and C. reticulata in three distinct clusters or sub-clusters which supports their distinctiveness as true basal species of edible Citrus. C. indica a true wild species endemic to Garo Hills of Meghalaya also has clustered independently and this observation has supported its uniqueness as one of the progenitor species of Citrus. From our study it is amply clear that C.reticulata also has close relation to C.ichagensis, as these species have clustered together in the phylogenetic trees, denoting their close relationship. Our studies on partial sequences of Chlorplast DNA did not demonstrated a clear differentiation between subgenera Citrus and Papeda at the cpDNA level.