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.
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