First report of Banana bunchy top virus infecting banana in Iran

Banana bunchy top disease is one of the most serious diseases of bananas (Musa spp.) worldwide. The disease is caused by Banana bunchy top virus (BBTV), the type species of the Babuvirus genus; Family Nanoviridae. The genome of BBTV is comprised of at least six circular single-stranded DNA (ssDNA) components, each approximately 1 Kb in size. Symptoms of BBTV infection include plant stunting, foliar yellowing and most characteristically, dark green streaks on the pseudostem, petioles and leaves (Harding et al. 1993; Vetten et al., 2005).

From 2004 to 2006, a series of field surveys were conducted in the major banana-growing areas in Iran: Mazandaran province (Sari, Babol, Behshahr, and Ghaemshahr) in the north and Hormozgan province (Jask and Varz-Abad) in the south. A total of 164 banana plant samples with bunchy top, stunting and leaf samples with green streak symptoms were collected. Samples were tested for the presence of BBTV with a double-antibody sandwich enzyme-linked imunosorbent assay (DAS-ELISA) using positive control and polyclonal antibodies against BBTV, according to the supplier’s instructions (Bio-Rad, CA 94547, USA). Of the samples tested, 27 were positive for BBTV using DAS-ELISA. To confirm BBTV identification, polymerase chain reaction (PCR) was carried out using samples that previously tested positive by ELISA. Forward [F3: 5'-GGAAGAAGCCTCTCATCTGCTTCAGAGAR C-3'; nts 287 to 258] and reverse [FPCR4: 5'-TTCCCAGGCGCACACCTTGAGAAACGA AAG-3'; nts 284 to 313] primers were used to amplify complete BBTV DNA-1 (Furuya et al., 2005). PCR analysis showed fragments of approximately 1 Kb in 19 samples. Furthermore, using primer pairs designed to differentiate BBTV strains (Su et al., 2003), Iranian BBTV isolates were divided into two distinct strains. To our knowledge, this is the first report of the occurrence of BBTV in Iran.