Distribution, molecular characterization and diversity of banana bunchy top virus in Tripura, India

Banana bunchy top virus (BBTV) is a serious threat to banana (Musa spp.) production in India. Generally, BBTV isolates within the country share very low genetic diversity. However, in India, relatively greater diversity has been observed between isolates from north-eastern (NE) region (Meghalaya) and rest of India. Tripura is situated in the south-west corner of NE India and shares international border with Bangladesh. During 2014-2015, diagnostic surveys were conducted in seven districts of Tripura and polymerase chain reaction based detection established that BBTD is widely prevalent in all parts of Tripura showing an average incidence of 22.02%. Among the cultivars, maximum BBTV infection (27.03%) was recorded in 'Chini Champa', followed by plantain (24.29%). A representative population (31 isolates) of BBTV from Tripura was characterized based on DNA R and DNA S. Phylogenetic analysis based on BBTV DNA R and DNA S generated two broad clusters of Pacific-Indian Oceans (PIO) and south-east Asian groups including all Tripura isolates within PIO cluster. The clustering pattern and genetic diversity of BBTV population from Tripura suggested monophyletic origin of majority of representative isolates from a common ancestor of PIO group. The exchange of vegetative propagules within and in between countries could have contributed to the geographical expansion of PIO isolates in Tripura. However, four variant BBTV isolates has been identified from North Tripura and Khowai districts possessing somewhat unique variability than that of distinct isolate (BBTV-Umiam) reported from NE India (Meghalaya).