Ecological Factors Affecting Infection Risk and Population Genetic Diversity of a Novel Potyvirus in Its Native Wild Ecosystem.

Cristina Rodríguez-Nevado,Nuria Montes,Israel Pagán

doi:10.3389/fpls.2017.01958

Abstract

Increasing evidence indicates that there is ample diversity of plant virus species in wild ecosystems. The vast majority of this diversity, however, remains uncharacterized. Moreover, in these ecosystems the factors affecting plant virus infection risk and population genetic diversity, two traits intrinsically linked to virus emergence, are largely unknown. Along 3 years, we have analyzed the prevalence and diversity of plant virus species from the genus Potyvirus in evergreen oak forests of the Iberian Peninsula, the main wild ecosystem in this geographic region and in the entire Mediterranean basin. During this period, we have also measured plant species diversity, host density, plant biomass, temperature, relative humidity, and rainfall. Results indicated that potyviruses were always present in evergreen oak forests, with a novel virus species explaining the largest fraction of potyvirus-infected plants. We determined the genomic sequence of this novel virus and we explored its host range in natural and greenhouse conditions. Natural host range was limited to the perennial plant mountain rue (Ruta montana), commonly found in evergreen oak forests of the Iberian Peninsula. In this host, the virus was highly prevalent and was therefore provisionally named mediterranean ruda virus (MeRV). Focusing in this natural host–virus interaction, we analyzed the ecological factors affecting MeRV infection risk and population genetic diversity in its native wild ecosystem. The main predictor of virus infection risk was the host density. MeRV prevalence was the major factor determining genetic diversity and selection pressures in the virus populations. This observation supports theoretical predictions assigning these two traits a key role in parasite epidemiology and evolution. Thus, our analyses contribute both to characterize viral diversity and to understand the ecological determinants of virus population dynamics in wild ecosystems.

Highlights

Viruses are the most frequent causal agents of emerging infectious diseases in crops (Anderson et al, 2004; Woolhouse et al, 2005), and are responsible of yield losses that may have great economic and social impact (Oerke, 2006; Vurro et al, 2010)
Human management of the host population has a great impact on plant virus populations (Pagán et al, 2012; Alexander et al, 2014; Rodelo-Urrego et al, 2015), so that plant viruses native from wild ecosystems may have different population dynamics than those typical in agroecosystems
Identification of the potyviruses present in the 171 infected plants indicated the presence of five virus species: Zucchini yellow fleck virus (ZYFV) (34/171), which was detected in six host plant species with a prevalence ranging between 4.76 and 61.54%; Clover yellow vein virus (ClYVV) (10/171), which was detected in two plant species with prevalence of 2.86–13.33%; and Endive necrotic mosaic virus (ENMV) and Turnip mosaic virus (TuMV) (2/171 each), which were found infecting individuals of a single plant species each, with prevalence of 3.51% and 4.65%, respectively

Summary

Introduction

Viruses are the most frequent causal agents of emerging infectious diseases in crops (Anderson et al, 2004; Woolhouse et al, 2005), and are responsible of yield losses that may have great economic and social impact (Oerke, 2006; Vurro et al, 2010). Viral infection can drastically reduce the number of individuals in the host populations by decreasing the competitive and reproductive abilities of infected plants (Anderson et al, 2004; Malmstrom et al, 2005; Vijayan et al, 2017) These studies show evidence that in wild host populations plant viruses may have great impact, little is known on their epidemiology and evolution and on the associated determinants (Pagán et al, 2016). Human management of the host population has a great impact on plant virus populations (Pagán et al, 2012; Alexander et al, 2014; Rodelo-Urrego et al, 2015), so that plant viruses native from wild ecosystems may have different population dynamics than those typical in agroecosystems. The factors driving the infection risk and population genetic diversity might be different than those identified for crop viruses (Fraile et al, 2017)

Methods

Results

Conclusion