Distinct strains of the re‐emergent Cassava common mosaic virus (genus: Potexvirus) infecting cassava in Argentina

Abstract

Cassava common mosaic disease (CCMD) has been reported in all regions where cassava is grown in the Americas and the causal agent, Cassava common mosaic virus (CsCMV), has been identified as a mechanically transmitted potexvirus (Alphaflexiviridae). In Argentina, cassava is grown mainly in the northeast (NEA) region that shares borders with Brazil and Paraguay. Increasing incidences of CCMD were observed during the years 2014 to 2016 associated with severe leaf mosaic symptoms and yield reductions where the occurrence of CsCMV was confirmed by RT‐PCR and sequencing. In this work, the virus has been successfully purified and a double‐antibody sandwich (DAS‐) ELISA test has been developed from an Argentinean isolate of CsCMV to extend the diagnostics of the disease. A collection of 726 samples was screened and CsCMV was detected with 100% prevalence in the NEA region. Additional co‐infecting viruses were detected in some plants (64.4%); in these, CCMD symptoms correlated with CsCMV only, although more severe symptoms could be observed in mixed infected plants. Sequence analysis of the conserved RdRp domain showed a wider diversity of CsCMV isolates. Interestingly, a separate phylogenetic cluster was formed by isolates from the NEA region that only shared 77.1% to 80.3% nucleotide identity with the other clusters. These results indicate the presence of mixed strains occurring in the NEA region and suggest the presence of geographically distinct strains of CsCMV in South America.

Cassava common mosaic viruscauses photosynthetic alterations associated with changes in chloroplast ultrastructure and carbohydrate metabolism of cassava plants

“…CsCMV was detected by double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) performed in polystyrene microtitre plates with anti-CsCMV-IgG as described Zanini et al (2018). All plants were tested.…”

“…Sections were cut with a diamond knife using an ultra-microtome and collected onto nickel grids. For immuno-electron microscopy, sections mounted on nickel grids were preincubated with 1% bovine serum albumin (BSA) in 1% phosphate buffered saline (PBS) overnight, and then treated with specific antiserum anti-CsCMV (Zanini et al 2018) for six hours. The sections were then exposed to gold conjugated protein A of 5 nm in diameter (Zymed, now part of the Invitrogen).…”

“…Among all reported cassava-infecting potexviruses (Lozano et al 2017), Cassava common mosaic virus (CsCMV) has been identified as the only one able to cause disease in single infection and to produce significant yield losses (Costa and Kitajima 1972; Venturini et al 2016; Zanini et al 2020). This pathogen has been detected infecting cassava crops in South America (Calvert et al 2012; Chaparro-Martinez and Trujillo-Pinto 2003; Silva et al 2011; Fernandez et al 2017; Zanini et al 2018) and recently in China (Tuo et al 2020).…”

“…The typical symptoms of CsCMV infection, known as cassava common mosaic disease (CCMD), vary in severity and include a wide range of foliar chlorotic mosaic (light green chlorotic areas, interspersed with dark green areas), sparsely distributed in the leaf blade of cassava plants (Zanini et al 2018). This kind of symptoms might be the consequence of chloroplast deformation and shut-off induced by the virus infection (Li et al 2016a).…”

Global Cropland Connectivity: A Risk Factor for Invasion and Saturation by Emerging Pathogens and Pests

“…Originally reported to cause significant yield losses in southern Brazil since the 1940s (reviewed in Lozano et al (2017)), recent outbreaks of CCMD have been reported in Peru and Argentina Xing, Hernandez Nopsa et al -17 (Di Feo et al 2015, Zanini et al 2018. Because of the likely spread of these pathogens through asymptomatic planting material, it is probable that patterns of spread throughout Latin America are related to high intensity areas of production.…”