MOLECULAR IDENTIFICATION AND PHYLOGENY OF MUSA SPECIES FROM NORTH-EASTERN INDIA BY INTERNAL TRANSCRIBED SPACER 2 OF NUCLEAR DNA

The internal transcribed spacer region of the ribosomal RNA gene cluster in the nuclear DNA has been used as one of the most informative molecular markers for identification and phylogenetic analysis of fungi and plants in the last three decades. The aim of the present study was to evaluate the application of ITS2 locus of rRNA region in nuclear DNA as molecular marker in the identification and molecular phylogeny of 15 Musa specimens (Musaceae) in North-Eastern India. The sequence characteristic of the ITS2 locus revealed a length variation from a minimum of 210 bp in Musa mannii to a maximum of 223 bp in M. balbisianawith an average of 214 bp. The GC contents of the ITS2 locus also varied from a minimum of 64.95% in M. markkui to 70.97% in M. balbisiana with an average of 69.01%. Sequence homology analysis of the ITS2 regions revealed sequence similarity from a minimum of 90% for M. markkui followed by 97% for M. acuminata and 98% for M. nagensium while the remaining species showed 99% to 100% similar sequence identities in public database. The phylogenetic analysis based on ITS2 sequence revealed a monophyletic origin of all taxa under different genera of the family Musaceae. The clade I comprising of 4 representative taxa of the section Callimusa (Australimusa, Callimusa and Ingentimusa) found only in few Southeast Asian countries and Australia were clearly separated from clade II which consists of 21 taxa of the section Musa(Eumusa and Rhodochlamys) including the 15 taxa from North-Eastern India. The clade II was further separated into two sub-clades, M. balbisiana group in clade IIa and M. acuminata and Rhodochlamys group in clade IIb. A new taxon with poorly described genetic and molecular characteristics, M. puspanjaliae was found to show an independent lineage of evolution within the sub-clade IIb suggesting closer genetic similarity with M. acuminata as compared to the M. balbisiana. Low bootstrap values (<50%) were observed in several branches of the phylogenetic tree of Musaceae reconstructed based on ITS2 sequences except in case of clade I (96%) and few sub-clades (51% to 98%). Therefore, it is concluded that ITS2 locus can be employed as one of the potential molecular marker for the identification of Musa specimens but inferences of phylogenetic tree based on ITS2 sequence are poorly supported as revealed by low bootstrap values.