Intraspecies variability in virus interactions with switchgrass

Background/Question/Methods

Viruses are integral elements of natural ecosystems, including prairie grasslands, but little is known about virus effects on plant performance and how within-species variability influences virus-plant interactions. Switchgrass (Panicum virgatum), is an important native prairie grass from which selected cultivars have been developed for forage production and possible bioenergy production.  Here we investigate how plant-virus interactions are influenced by trait variation within both host and virus species. We focus on aphid-vectored Barley yellow dwarf viruses (BYDVs), which naturally infect switchgrass in the Midwestern US.

We conducted a series of field and growth chamber experiments to assess the impact of intraspecies variability in both switchgrass and BYDV-PAV on infection rates and first year growth of hosts. We quantified a suite of traits in 29 cultivars of switchgrass and examined their relationship with susceptibility. We further compared the effects of two different isolates of BYDV-PAV on host performance. Lastly, we assessed the performance of infected and uninfected individuals of two cultivars in the field.

Results/Conclusions

We found that among switchgrass cultivars, increased rates of growth and leaf production were predictive of elevated virus susceptibility. This finding extends results seen in comparisons among species to variation within species and suggests the broad generality of these trait relationships. We further found that BYDV-infection significantly reduced host growth parameters in growth chamber and field conditions, with the effect size varying by virus isolate and switchgrass cultivar.  These findings demonstrate the importance of considering virus influence in plant community ecology and in developing better understanding of variation within virus communities as well.