Abstract
BackgroundCotton blue disease (CBD), an important global cotton crop pathology responsible for major economic losses, is prevalent in the major cotton-producing states of Brazil. Typical CBD symptoms include stunting due to internodal shortening, leaf rolling, intense green foliage, and yellowing veins. Atypical CBD symptoms, including reddish and withered leaves, were also observed in Brazilian cotton fields in 2007. Recently, a Polerovirus named Cotton leafroll dwarf virus (CLRDV) was shown to be associated with CBD.ResultsTo understand the distribution and genetic diversity of CLRDV in Brazil, we analyzed 23 CBD-symptomatic plants from susceptible cotton varieties originating from five of the six most important cotton-growing states, from 2004–2007. Here, we report on CLRDV diversity in plants with typical or atypical CBD symptoms by comparing viral coat protein, RNA polymerase (RdRp), and intergenic region genomic sequences.ConclusionThe virus had a widespread distribution with a low genetic diversity; however, three divergent isolates were associated with atypical CBD symptoms. These divergent isolates had a CLRDV-related coat protein but a distinct RdRp sequence, and probably arose from recombination events. Based on the taxonomic rules for the family Luteoviridae, we propose that these three isolates represent isolates of a new species in the genus Polerovirus.
Highlights
Cotton blue disease (CBD), an important global cotton crop pathology responsible for major economic losses, is prevalent in the major cotton-producing states of Brazil
We report on Cotton leafroll dwarf virus (CLRDV) diversity in plants with typical or atypical CBD symptoms by comparing viral coat protein, RNA polymerase (RdRp), and intergenic region genomic sequences
The virus had a widespread distribution with a low genetic diversity; three divergent isolates were associated with atypical CBD symptoms
Summary
Cotton blue disease (CBD), an important global cotton crop pathology responsible for major economic losses, is prevalent in the major cotton-producing states of Brazil. Typical CBD symptoms include stunting due to internodal shortening, leaf rolling, intense green foliage, and yellowing veins. Atypical CBD symptoms, including reddish and withered leaves, were observed in Brazilian cotton fields in 2007. Cotton blue disease (CBD) plays an important role due to its worldwide distribution and the high-magnitude of its associated productivity losses. Cotton blue disease was first described in the Central African Republic in 1949. It is transmitted by the aphid Aphis gossypii and its symptoms include leaf rolling, intense green foliage, vein yellowing, and a severe to moderate stunting caused by internodal shortening. In Brazil, CBD is a serious crop problem capable of reducing the productivity of susceptible varieties by up to 80%, if intensive insecticidal control is not properly performed during the growing season
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