Search

Abstract Host nutrient supply can mediate host–pathogen and pathogen–pathogen interactions. In terrestrial systems, plant nutrient supply is mediated by soil microbes, suggesting a potential role of soil microbes in plant diseases beyond soil‐borne pathogens and induced plant defenses. Long‐term nitrogen (N) enrichment can shift pathogenic and nonpathogenic soil microbial community composition and function, but it is unclear if these shifts affect plant–pathogen and pathogen–pathogen interactions. In a growth chamber experiment, we tested the effect of long‐term N enrichment on infection by Barley Yellow Dwarf Virus (BYDV‐PAV) and Cereal Yellow Dwarf Virus (CYDV‐RPV), aphid‐vectored RNA viruses, in a grass host. We inoculated sterilized growing medium with soil collected from a long‐term N enrichment experiment (ambient, low, and high N soil treatments) to isolate effects mediated by the soil microbial community. We crossed soil treatments with a N supply treatment (low, high) and virus inoculation treatment (mock‐, singly‐, and co‐inoculated) to evaluate the effects of long‐term N enrichment on plant–pathogen and pathogen–pathogen interactions, as mediated by N availability. We measured the proportion of plants infected (i.e., incidence), plant biomass, and leaf chlorophyll content. BYDV‐PAV incidence (0.96) declined with low N soil (to 0.46), high N supply (to 0.61), and co‐inoculation (to 0.32). Low N soil mediated the effect of N supply on BYDV‐PAV: instead of N supply reducing BYDV‐PAV incidence, the incidence increased. Additionally, ambient and low N soil ameliorated the negative effect of co‐inoculation on BYDV‐PAV incidence. BYDV‐PAV infection only reduced chlorophyll when plants were grown with low N supply and ambient N soil. There were no significant effects of long‐term N soil on CYDV‐RPV incidence. Soil inoculant with different levels of long‐term N enrichment had different effects on host–pathogen and pathogen–pathogen interactions, suggesting that shifts in soil microbial communities with long‐term N enrichment may mediate disease dynamics.

Host nutrient supply can mediate host–pathogen and pathogen–pathogen interactions. In terrestrial systems, plant nutrient supply is mediated by soil microbes, suggesting a potential role of soil microbes in plant diseases beyond soil‐borne pathogens and induced plant defenses. Long‐term nitrogen (N) enrichment can shift pathogenic and nonpathogenic soil microbial community composition and function, but it is unclear if these shifts affect plant–pathogen and pathogen–pathogen interactions. In a growth chamber experiment, we tested the effect of long‐term N enrichment on infection by Barley Yellow Dwarf Virus (BYDV‐PAV) and Cereal Yellow Dwarf Virus (CYDV‐RPV), aphid‐vectored RNA viruses, in a grass host. We inoculated sterilized growing medium with soil collected from a long‐term N enrichment experiment (ambient, low, and high N soil treatments) to isolate effects mediated by the soil microbial community. We crossed soil treatments with a N supply treatment (low, high) and virus inoculation treatment (mock‐, singly‐, and co‐inoculated) to evaluate the effects of long‐term N enrichment on plant–pathogen and pathogen–pathogen interactions, as mediated by N availability. We measured the proportion of plants infected (i.e., incidence), plant biomass, and leaf chlorophyll content. BYDV‐PAV incidence (0.96) declined with low N soil (to 0.46), high N supply (to 0.61), and co‐inoculation (to 0.32). Low N soil mediated the effect of N supply on BYDV‐PAV: instead of N supply reducing BYDV‐PAV incidence, the incidence increased. Additionally, ambient and low N soil ameliorated the negative effect of co‐inoculation on BYDV‐PAV incidence. BYDV‐PAV infection only reduced chlorophyll when plants were grown with low N supply and ambient N soil. There were no significant effects of long‐term N soil on CYDV‐RPV incidence. Soil inoculant with different levels of long‐term N enrichment had different effects on host–pathogen and pathogen–pathogen interactions, suggesting that shifts in soil microbial communities with long‐term N enrichment may mediate disease dynamics. [ABSTRACT FROM AUTHOR]

The rates and ratios of environmental nutrient supplies can determine plant community composition. However, the effect of nutrient supplies on within-host microbial interactions is poorly understood. Resource competition is a promising theory for understanding microbial interactions, because microparasites require nitrogen (N) and phosphorus (P) for synthesis of macromolecules such as nucleic acids and proteins., To better understand the effects of nutrient supplies to hosts on pathogen interactions, we singly inoculated and coinoculated Avena sativa with two virus species, barley yellow dwarf virus-PAV ( BYDV- PAV) and cereal yellow dwarf virus-RPV ( CYDV- RPV). Host plants were grown across a factorial combination of N and P supply rates that created a gradient of N : P supply ratios, one being replicated at low and high nutrient supply., Nutrient supply affected prevalence and the interaction strength among viruses. P addition lowered CYDV- RPV prevalence. The two viruses had a distinct competitive hierarchy: the coinoculation of BYDV- PAV lowered CYDV- RPV infection rate, but the reverse was not true. This antagonistic interaction occurred at low nutrient supply rates and disappeared at high N supply rate., Given the global scale of human alterations of N and P cycles, these results suggest that elevated nutrient supply will increase risks of virus coinfection with likely effects on virus epidemiology, virulence and evolution. [ABSTRACT FROM AUTHOR]