Mixed Infections ofPepino Mosaic VirusStrains Modulate the Evolutionary Dynamics of this Emergent Virus

Abstract

Pepino mosaic virus (PepMV) is an emerging pathogen that causes severe economic losses in tomato crops (Solanum lycopersicum L.) in the Northern hemisphere, despite persistent attempts of control. In fact, it is considered one of the most significant viral diseases for tomato production worldwide, and it may constitute a good model for the analysis of virus emergence in crops. We have combined a population genetics approach with an analysis of in planta properties of virus strains to explain an observed epidemiological pattern. Hybridization analysis showed that PepMV populations are composed of isolates of two types (PepMV-CH2 and PepMV-EU) that cocirculate. The CH2 type isolates are predominant; however, EU isolates have not been displaced but persist mainly in mixed infections. Two molecularly cloned isolates belonging to each type have been used to examine the dynamics of in planta single infections and coinfection, revealing that the CH2 type has a higher fitness than the EU type. Coinfections expand the range of susceptible hosts, and coinfected plants remain symptomless several weeks after infection, so a potentially important problem for disease prevention and management. These results provide an explanation of the observed epidemiological pattern in terms of genetic and ecological interactions among the different viral strains. Thus, mixed infections appear to be contributing to shaping the genetic structure and dynamics of PepMV populations.

Differential Tomato Transcriptomic Responses Induced by Pepino Mosaic Virus Isolates with Differential Aggressiveness

“…Currently, four PepMV genotypes are distinguished: the Peruvian genotype (LP), which was first isolated from Solanum peruvianum and is similar to the original pepino (S. muricatum) isolate (Ló pez et al, 2005;Pagán et al, 2006); the European tomato genotype (EU), which was first reported in greenhouse tomato production in Europe (Mumford and Metcalfe, 2001;Aguilar et al, 2002;Cotillon et al, 2002;Verhoeven et al, 2003;Pagán et al, 2006); the CH2 genotype, which was first isolated from tomato seeds from Chile (Ling, 2007); and the US1 genotype, which was first described in the United States (Maroon-Lango et al, 2005). In recent years, the CH2 genotype has largely replaced the EU genotype in commercial tomato production in several European countries (Hanssen et al, 2008;Gó mez et al, 2009). Two Belgian CH2 PepMV isolates have recently been characterized in detail and were designated mild (isolate 1906, further referred to as the mild CH2 isolate) and aggressive (isolate PCH 06/104, further referred to as the aggressive CH2 isolate) based on symptom expression in naturally infected commercial greenhouse tomatoes and in subsequent greenhouse trials (Hanssen et al, 2009(Hanssen et al, , 2010a.…”

El virus del mosaico del pepino dulce (Pepino mosaic virus) afectando al cultivo del tomate (Solanum lycopersicum): Caracterización y Epidemiología

“…Desde la detección del PepMV en España se han realizado diferentes estudios detallados para la caracterización genética de las poblaciones españolas del virus Pagán et al, 2006;Gómez et al, 2009) que han demostrado que el virus ha entrado en varias ocasiones en el país. Hasta el año 2004 la mayoría de las infecciones, más del 80%, estaban ocasionadas por infecciones simples de aislados de la cepa "EU".…”

“…Desde el año 2006, el porcentaje de infecciones mixtas "EU+CH2" y simples de aislados tipo "CH2" ha ido variando en la población de PepMV de la Península. En el año 2008 ambos tipos de infecciones llegaron a igualarse y a representar el 96% de la población mientras que el restante 4% lo constituían infecciones simples de aislados del tipo "EU" (Gómez et al, 2009).…”

“…Muy recientemente, se ha publicado el trabajo que vendría a ser la continuación del nuestro al realizar el estudio poblacional del virus desde el año 2005, aunque restringido a la región de Murcia (Gómez et al, 2009).…”

“…En estos momentos la incidencia de la cepa EU en infecciones simples ha disminuido desde el año 2004 al verse desplazada por la cepa CH2 que parece presentar una mayor capacidad de adaptación al cultivo como ya se ha sido citado Gómez et al, 2009) y que en estos momentos seria la cepa mayoritaria tanto en infecciones simples como en mixtas con la cepa EU. Aunque nuestro trabajo se encuentra en cierta forma sesgado al estudiar únicamente muestras con sintomatologías necróticas, los últimos datos que se conocen acerca de la composición genética de la población del virus en España, son coincidentes con nuestros resultados (Gómez et al, 2009).…”