1Indian Institute of Spices Research, Calicut-673012, India
2National Research Centre for Banana, Trichy, Tamil Nadu
3Cardamom Research Centre, Indian Institute of Spices Research, Appangala, Madikeri, India.
Abstracts of the papers presented at the International Conference of Indian Virological Society on “Emerging and Re-emerging viral Diseases of the Tropics and Subtropics” at Indian Agricultural Research Institute, New Delhi, India, December 11–14, 2007.
Sequences belonging to ssDNA geminiviruses, dsDNA pararetroviruses and a non-retro ssRNA virus were reported to exist in plant genomes in integrated forms. Geminiviridae and Nanoviridae are two families of plant viruses with ssDNA genome infecting wide range of plant families. Though geminiviral sequences were reportedly found integrated in plants there are no reports regarding integration of nanovirus sequences in plant genomes. In the present study, we discovered the existence of full length ORF sequence (513 bp) coding for coat protein gene of Banana bunchy top virus (BBTV) in at least four varieties of cardamom (Elettaria cardamomum Maton). Healthy and BBTV infected banana samples were used as negative and positive controls in all the tests. When total DNA from cardamom and banana were subjected to PCR using BBTV CP specific primers, an expected amplified product of ∼510bp specific to CP gene was observed in cardamom and infected banana while no such band was seen in healthy banana.
The product obtained from infected banana and cardamom were cloned, sequenced and sequence analysis showed 99.5% identity between them. Identity with available BBTV CP gene sequences, varied from 90.3 to 99.5%. Internal primers were designed based on the 513bp sequence for efficient detection through nested PCR in different cardamom plants. Nested PCR could detect a ∼420bp region of CP specific to BBTV in all the plants tested. DAC-ELISA and IC-PCR results clearly ruled out the presence of BBTV particles in the cardamom samples. Further confirmation of the integrated BBTV sequence in cardamom was done through Southern blotting of total DNA from cardamom probed with BBTV CP specific probe. Interestingly the samples were negative in RT-PCR indicating that integrated sequences were possibly not transcribed. This is the first report of the integration of nanovirus sequence in plant kingdom.
