Abstract
Understanding the evolutionary history of a virus and the mechanisms influencing the direction of its evolution is essential for the development of more durable strategies to control the virus in crop fields. While the deployment of host resistance in crops is the most efficient means to control various viruses, host resistance itself can act as strong selective pressure and thus play a critical role in the evolution of virus virulence. Cucumber mosaic virus (CMV), a plant RNA virus with high evolutionary capacity, has caused endemic disease in various crops worldwide, including pepper (Capsicum annuum L.), because of frequent emergence of resistance-breaking variants. In this study, we examined the molecular and evolutionary characteristics of recently emerged, resistance-breaking CMV variants infecting pepper. Our population genetics analysis revealed that the high divergence capacity of CMV RNA1 might have played an essential role in the host-interactive evolution of CMV and in shaping the CMV population structure in pepper. We also demonstrated that nonsynonymous mutations in RNA1 encoding the 1a protein enabled CMV to overcome the deployed resistance in pepper. Our findings suggest that resistance-driven selective pressures on RNA1 might have contributed in shaping the unique evolutionary pattern of CMV in pepper. Therefore, deployment of a single resistance gene may reduce resistance durability against CMV and more integrated approaches are warranted for successful control of CMV in pepper.
Highlights
Analyzing the genetic diversity and population structure of a virus is an essential approach for understanding its evolutionary history and related mechanisms that drive its evolution and dispersion
Six additional isolates were collected from pepper cultivars resistant to Cucumber mosaic virus (CMV) pathotype P1 and their virulence was accessed on several pepper cultivars
All tested pepper cultivars, including Baerota and PR-Sagslee which are resistant to CMV pathotype P1, were susceptible to the six newly collected isolates (Table 1), indicating the new CMV variants were capable of overcoming resistance in pepper
Summary
Analyzing the genetic diversity and population structure of a virus is an essential approach for understanding its evolutionary history and related mechanisms that drive its evolution and dispersion. Group of plant viruses, are known to have a rapid evolutionary rate due to error-prone replication and short generation times, allowing for fast virulence changes to sustain infection (Cabanillas et al 2013; Lauring et al 2013). In this sense, the widespread use of resistant cultivars may apply significant selective pressures to direct the adaptive virulence evolution of viruses in crop fields (Garcia-Andres et al 2009). Mechanistic links between diversity, virulence, and in vivo selective pressures are little understood in the crop fields
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