Molecular characterisation of coat protein and nuclear shuttle protein genes of Banana bunchy top virus from Western Ghats in India

Abstract

Among the various factors responsible for low yield in banana (Musa spp.), bunchy top disease caused by Banana bunchy top virus (BBTV) is the most important and devastating disease in most of the tropical countries including India. Several approaches were advocated to control or combat the bunchy top virus in banana transmitted by banana aphid. However, no tactics are able to completely protect these plants against virus infections. The selection of BBTV-free banana plants is the prerequisite for the production of disease free plants and hence early detection of this disease in these plantlets is considered necessary. So, PCR-based detection of BBTV in the current study will be useful in eliminating the infected plants in the early stage. An extensive survey was conducted in Tamil Nadu, India to collect Banana bunchy top virus (BBTV) isolates from hill banana cv. Virupakshi (AAB) which was found to be severely affected by bunchy top virus. Cloning and sequencing of the coat protein (CP) and nuclear shuttle protein (NSP) gene sequences of BBTV were carried out to elucidate the phylogenetic relationship of the hill banana virus isolates with other existing BBTV isolates. Two species-specific primers viz. CP and NSP were used for the amplification of CP and NSP genes of BBTV, respectively. Polymerase chain reaction (PCR) amplified 510 bp CP and 250 bp NSP gene sequences of BBTV. Complete and partial sequences of CP and NSP genes of BBTV were obtained. The analysis revealed that CP gene shared 90% nucleotide sequence identity with other Indian isolates and one Burundi isolate and 89% identity with an Egyptian isolate of BBTV. The comparison of the NSP with the other isolates revealed a 98% identity with three Indian isolates, 97% with an Australian isolate and 95% with a Pakistan isolate of BBTV, whereas only 88% identity was shared with China and Taiwan isolates. The present study suggests that the hill banana isolate falls within the South Pacific group of BBTV isolates.