First report of cassava torrado-like virus, cassava polero-like virus and cassava new alphaflexivirus associated with cassava frogskin disease in Brazil

Cassava Frogskin Disease: Current Knowledge on a Re-Emerging Disease in the Americas

“…Observations such as these prompted the use of Secundina as an indicator plant for CFSD, as described in the previous section. Nevertheless, extensive field inspections in Colombia, Paraguay, and Brazil consistently show that the symptoms developed in Secundina are an exception, and that most genotypes that show root symptoms of CFSD do not develop leaf or stem symptoms [ 18 , 19 , 27 ]. In Venezuela, most genotypes with root symptoms of CFSD did not show symptoms in the aerial part of the plant, unless they were grafted to Secundina [ 13 ].…”

“…Reoviridae ) [ 14 , 31 ]. Although the exact role of reovirids in the formation of root symptoms remains uncertain, the results from surveys by different groups have consistently found them in all fields were CFSD is reported [ 17 , 19 , 31 , 48 ]. Neither CFSD nor cassava-infecting reovirids have been reported in Africa or Asia.…”

“…Other pathogens: Since the first diagnostic works aiming to identify the causal agent of CFSD, different viral particles and bacteria-like agents have been observed in samples collected in Colombia and elsewhere ( Figure 2 ). By applying a technology known as high-throughput sequencing of small interfering RNA to cassava samples with CFSD, and then using RT-PCR to confirm the presence of the virus contigs assembled, mixed virus infections were readily confirmed in Colombia [ 15 , 20 , 31 ] and then in Brazil [ 19 ]. These works confirmed the occurrence of at least three new viruses infecting cassava in the Americas, a polerovirus, a potexvirus, and a torradovirus, in different mixed infections with CsFSaV and phytoplasma.…”

“…Except for susceptible plants used as indicators, which can show symptoms of the disease during the first 8–12 months under strong inoculum pressure, for most cassava genotypes it can take 2 or 3 crop cycles for CFSD root symptoms to develop ( Table 1 ; Supplementary Figure S1 ). This characteristic may be related to the nature of the inoculum, which to date includes several pathogens occurring in mixed infections [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ] ( Figure 2 ).…”

Complete genome sequence of a novel secovirid infecting cassava in the Americas

“…Cassava torrado-like virus (CsTLV) is a partially characterized member of the family Secoviridae [ 1 , 2 ] that was originally detected in cassava plants ( Manihot esculenta Crantz) displaying root symptoms of cassava frogskin disease (CFSD) [ 3 ], an endemic disease of cassava in the Americas that can severely affect the root yield of the crop [ 4 ]. The virus is found in mixed infections [ 3 , 5 ] and can induce leaf chlorotic spots symptoms in single infections in cassava [ 2 ]. Maf/HAM1 proteins are nucleoside triphosphate (NTP) pyrophosphatases that reduce mutagenesis by intercepting non-canonical NTPs and preventing their incorporation into DNA or RNA.…”