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

Abstract

Taro (Colocasia esculenta) and tannia (Xanthosoma sp.) are important root crops cultivated mainly by small‐scale farmers in sub‐Saharan Africa and the South Pacific. Viruses are known to be one of the most important constraints to production, with infections resulting in severe yield reduction. In 2014 and 2015, surveys were conducted in Ethiopia, Kenya, Tanzania and Uganda to determine the identity of viruses infecting taro in East Africa. Screening of 392 samples collected from the region using degenerate badnavirus primers revealed an incidence of 58–74% among the four countries surveyed, with sequence analysis identifying both Taro bacilliform virus (TaBV) and Taro bacilliform CH virus (TaBCHV). TaBCHV was identified from all four countries while TaBV was identified in all except Ethiopia. Full‐length sequences from representative TaBV and TaBCHV isolates showed that the genome organization of TaBV isolates from East Africa was consistent with previous reports while TaBCHV isolates from East Africa were found to encode only four ORFs, distinct from a previous report from China. Phylogenetic analysis showed that all East African TaBV isolates form a single subgroup within known TaBV isolates, while TaBCHV isolates form at least two distinct subgroups. To the authors' knowledge, this is the first report describing the occurrence and genome organization of TaBV and TaBCHV isolates from East Africa and the first full‐length sequence of the two viruses from tannia.

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].…”

“…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].…”

“…Besides TaBV, there is another badnavirus infecting taro, Taro bacilliform CH Virus (TaBCHV). The first complete nucleotide sequence was recorded in China, before others in the United States in America (USA) and East Africa (Table 1) [17,19,27]. TaBCHV contains six ORFs, with ORF1-4 being comparable to the ORFs of TaBV (Figure 1) [19].…”

“…Multiple viruses have been found to infect taro, including the four main viruses; Dasheen mosaic virus (DsMV) , Taro bacilliform virus (TaBV) , Colocasia bobone disease virus (CBDV) , and Taro vein chlorosis virus (TaVCV) [5,6,8,9,17,18,19,20,21,22,23,24,25,26] that this review will centre on. This review will also mention a relatively new virus Taro bacilliform CH virus (TaBCHV) [17,19,27].…”

Complete Genome sequence of a new variant of jujube mosaic-associated virus isolated from jujube (Ziziphus jujuba Mill.) grown at Aksu in Xinjiang of China

“…The genus Badnavirus is the largest of the eight known Genera of the Caulimoviridae, with nearly twice as many species as all other genera [1]. The genome consists of one circular double-stranded DNA of 6.9 to 9.2 kb [2], which typically encodes three open reading frames (ORFs), all of which are located on the on the plus strand [3,4]. Badnavirus ORF1 encodes a small protein of unknown function.…”