Cotton blue disease in central-west Brazil: Occurrence, vector (Aphis gossypii) control levels and cultivar reaction

Abstract

Cotton blue disease (CBD) is the viral disease which poses the greatest threat to cotton in Brazil. One efficient way of controlling this disease is by using resistant cultivars. However, the recent emergence of an atypical form of CBD (ACBD), caused by a new virus genotype capable of overcoming these resistant cultivars, is causing concern. Thus, the aims of this study were to evaluate the distribution of ACBD in the states of Mato Grosso (MT) and Goiás (GO), to determine the relationship between vector infestation level, disease incidence and yield, and to check the reaction of cotton cultivars to two viral isolates. In both cotton production areas, 1128 plots were surveyed and 6.5% showed plants with the virus, 97.3% and 2.7% with ACBD and CBD, respectively. In cultivars susceptible to ACBD, a positive linear relationship between changes in the levels of aphid infestation and incidence of viral infection was indentified, and a negative linear relationship between infestation level and yield. The maximum acceptable level of aphids up to 80 days after sowing for susceptible cultivars was approximately 15%. Although 83% of the cultivars were shown to be resistant to CBD, only 19.2% were resistant to ACBD. There was also a number of cultivars with considerable resistance to both isolates.

Genome analysis of cotton leafroll dwarf virus reveals variability in the silencing suppressor protein, genotypes and genomic recombinants in the USA

“…Yield losses associated with the typical CDB in susceptible cultivars have been reported up to 80% if cotton aphids were not adequately controlled during the early crop season in South America [ 6 ]. In Brazil, the atypical CDB is less aggressive, causing fiber yield loss in susceptible cultivars from 14.6 to 21.5% in fields with a vector threshold level of 80% [ 45 ]. Despite the detection of CLRDV in most of the growing areas of the USA, the economic importance and epidemiology of this virus is poorly understood.…”

Infectious clones of cotton leafroll dwarf virus strains used for genotype evaluation in cotton

“…The RT-qPCR protocol applied for differential detection of CLRDV strains was effective for identification of CLRDV-at single infection in 50% of the plants, whereas CLRDV was found as single infection in only 5.8% of 68 plants (Table 2), indicating that CLRDV-at might occupy the ecological niche of CLRDV in Brazilian cotton fields, as suggested by Galbieri et al (2017). However, an unexpected result was obtained, as in 13 of the 68 plants positive via RT-PCR using primers for the CP gene of poleroviruses, the strain typing of these plants via RT-qPCR resulted negative.…”

The Viral Threat in Cotton: How New and Emerging Technologies Accelerate Virus Identification and Virus Resistance Breeding

“…CLRDV susceptible cotton cultivars may lose all their yield in the presence of the virus. At the end 1990s, the Brazilian cotton industry nearly collapsed due to CDB ( Galbieri et al, 2017 ). The null or reduced yield imposed by CLRDV obligates Brazilian producers to seek resistant varieties ( Hoffmann et al, 2019 ).…”