Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi-110012, 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.
Large cardamom (Amomum subulatum) is affected by foorkey disease in India that causes excessive stunting of the lateral shoots. Isometric virus particles of 17–20 nm were observed to be associated with the diseased plants, which showed week ELISA reading to the polyclonal antibodies to Banana bunchy top virus (BBTV). The primers specific to the replicase (Rep) gene of BBTV resulted in amplification of about 850 bp with the diseased samples. Molecular cloning and sequencing of this product showed close similarity with the Rep gene of BBTV. The specific primers were designed from this sequence and the complete sequence of 1100 nucleotides of the DNA component (Foor-1) was achieved. Foor-1 DNA shared 74.9–77.5% similarity with the Rep encoding DNA of BBTV isolates and only 28.2–49.5% with that of nanoviruses infecting legumes. Foor-1 DNA contained stem and loop structure with nonanucleotides (TATTATTAC) similar to BBTV genome. The ORF analysis of Foor-1, however, showed presence of truncated ORFs encoding proteins not more than15.7 kDa. A primer pairs were designed from the stem and loop region of Foor-1 DNA and a full-length clone (Foor-2) was sequenced, which contained 1102 nucleotides. The Foor-2 DNA had 95.8% similarity with the Foor-1 DNA and contained two major ORFs encoding 33.61 kDa protein in +3 reading frame and 14.08 kDa protein in the -1 reading frame. Foor-2 DNA has the genome organization similar to nanoviruses and shared 74.1–78.9% sequence identity with BBTV Rep and master Rep encoding DNA components, whereas it showed only 29.9–50.2% identity with that of legume-infecting nanoviruses. The 33.61-kDa proteins (286 amino acids) contained NTP-binding motif and shared 87–88.8% sequence identity with the Rep protein of BBTV and only 28.0–56.9% with that of legume-infecting nanoviruses. The Foor-2 DNA encoding a putative nanovirus-replicase is a distinct genomic component of a nanovirus associated the foorkey disease of large cardamom.
