Complete genome sequences of two new virus isolates associated with cotton blue disease resistance breaking in Brazil

Abstract

Since 2006, Brazilian cotton (Gossypium hirsutum) crops planted with cultivars that are resistant to cotton blue disease have developed a new disease termed "atypical" cotton blue disease or atypical vein mosaic disease. Here, we describe the complete genomes of two virus isolates associated with this disease. The new virus isolates, called CLRDV-Acr3 and CLRDV-IMA2, were found to have a high degree of nucleotide and amino acid sequence similarity to previously described isolates of cotton leafroll dwarf virus, the causal agent of cotton blue disease. However, their P0 proteins were 86.1 % identical. These results show that this new disease is caused by a new CLRDV genotype that seems to have acquired the ability to overcome cotton blue disease resistance.

Function and diversity of P0 proteins among cotton leafroll dwarf virus isolates

“…When the genomic sequences of four previously identified CLRDV isolates were compared, significant differences were only observed in the P0 coding sequence [ 3 ]. In order to better characterize the sequence diversity of P0 proteins among CLRDV isolates, cotton plants from different varieties, displaying typical or atypical CBD symptoms were collected from different parts of Brazil.…”

“…In Brazil, CBD is present in almost all cotton growing fields and the disease was also partially controlled by the application of insecticides to decrease aphid populations and by the use of CBD-resistant cotton cultivars. Since 2006, several resistance breaking CLRDV isolates have been observed throughout the country, producing CBD-like symptoms in formerly resistance cotton lines [ 3 ]. Apart from typical CBD symptoms, resistant or susceptible cotton varieties infected with CLRDV resistance-breaking isolates may also display reddish and withered leaves.…”

“…Three open reading frames (ORF3, ORF4 and ORF5) are located in the 3’-end portion of the genome encoding for the structural proteins (capsid, movement and aphid-transmission proteins, respectively), while the 5’-end region of the genome encodes replication-related proteins (ORF1 and ORF2) and also a gene (ORF0) encoding the RNA silencing suppression protein P0. In general, the genome sequences of resistance breaking CLRDV isolates are very similar to CLRDV isolates from susceptible plants [ 3 ]. For example, the degree of sequence identity in all proteins encoded by ORFs 1 to 5 is greater than 93 % between two resistance breaking CLRDV isolates (Ima2 and Acr3) and two non-resistance breaking ones (PV1 and ARG) in cotton plants.…”

“…For example, the degree of sequence identity in all proteins encoded by ORFs 1 to 5 is greater than 93 % between two resistance breaking CLRDV isolates (Ima2 and Acr3) and two non-resistance breaking ones (PV1 and ARG) in cotton plants. However, when the identities among P0 proteins are compared, the diversity is consistently higher, with identity numbers ranging from 85.8 to 86.6 % among the four isolates [ 3 ].…”

BRS 430 B2RF and BRS 432 B2RF: Insect-resistant and glyphosate-tolerant high-yielding cotton cultivars

“…It is worth to highlight that the lint percentage was higher in FM 980 GLT; however, raw cotton yield in BRS 430 B2RF and BRS 432 B2RF was higher than FM 980 GLT, reflecting in higher fiber yield (Tables 1 and 2). High Volume Instrument (HVI) measurements reveal desirable physical attributes of a medium fiber length for both new cultivars: micronaire reading 4.4; fiber length (UHML) 30.5 mm (BRS 430 B2RF) ; c Symptoms of Atypical form of CLRDV, according to Silva et al 2015;d Disease severity (grades from 1 = resistant to 5 = highly susceptible) -data from two assays with no fungicide application. For bacterial blight, resistance was confirmed by using SNP marker ); e Relative disease index, where 1.0 is resistant and 0 is susceptible (Cia et al 2002) -data from plants inoculated artificially with Colletotrichum gossypii var.…”