Characterization of an Australian isolate of taro bacilliform virus and development of an infectious clone

Abstract

The badnavirus taro bacilliform virus (TaBV) has been reported to infect taro (Colocasia esculenta L.) and other edible aroids in several South Pacific island countries, but there are no published reports from Australia. Using PCR and RCA, we identified and characterized an Australian TaBV isolate. A terminally redundant cloned copy of the TaBV genome was generated and shown to be infectious in taro following agro-inoculation. This is the first report of TaBV from Australia and also the first report of an infectious clone for this virus.

A Review on Viruses Infecting Taro (Colocasia esculenta (L.) Schott)

“…The first complete nucleotide sequence of TaBV was recorded in Papua New Guinea (PNG), with four isolates that were found later in Australia and East Africa (Table 1) [5,27,45]. The PNG isolate has been found to contain 7458 bp consisting of four ORFs (Figure 1); ORF 1–3 are comparable to other badnaviruses, while ORF 4 is only comparable to ORFs of the atypical badnaviruses Citrus yellow mosaic virus (CYMV) and Cacao swollen shoot virus (CSSV) [5].…”

“…The function of the ORF 1 protein is unknown, whereas ORF 2 contains sequences that may be involved in virion assembly [5]. The ORF 3 of TaBV is a putative sequence that includes motifs, such as the movement protein (MP), CP, aspartic protease, reverse transcriptase (RT), and ribonuclease H (RNase H) [5,45]. ORF 4 contains a sequence of a putative protein with minimal homology to any published sequences [45].…”

“…The ORF 3 of TaBV is a putative sequence that includes motifs, such as the movement protein (MP), CP, aspartic protease, reverse transcriptase (RT), and ribonuclease H (RNase H) [5,45]. ORF 4 contains a sequence of a putative protein with minimal homology to any published sequences [45]. Additionally, the sequence of TaBV includes the highly conserved tRNA met -binding site and TATA sequence [5,27].…”

“…The symptoms of TaBV in taro include vein chlorosis, stunting, and leaves curling downwards (Figure 2) [4]. The virus is transmissible through three methods—the mealybug vector, vegetative propagation, and via seeds or pollen—while no mechanical transmission has so far been reported [41,45,46]. However, a study has shown that TaBV-infected plants may or may not exhibit symptoms, where the majority of the symptoms are observed on the youngest leaves [46].…”

Identification and molecular characterization of Taro bacilliform virus and Taro bacilliform CH virus from East Africa

“…TaBV is transmitted mainly by vegetative propagation, mealybugs in a semipersistent manner, and in some cases through seed or pollen, but it is not mechanically transmissible (Gollifer et al ., ; Macanawai et al ., ). Although no consistent symptoms have been associated with TaBV infection, there have been some reports of mild symptoms such as vein clearing, stunting and downward curling of the leaf blades in some cultivars (Yang et al ., ; Revill et al ., ; Kidanemariam et al ., ).…”