Warming can enhance the detrimental effect of pathogens on a host plant, Miscanthus sinensis, in a cool-temperate montane grassland in Nagano, Japan

This study investigated the effects of two fungal pathogens, the smut fungus Sporisorium kusanoi and the discomycete Naemacyclus culmigenus, on the Japanese pampas grass Miscanthus sinensis, under experimental warming. In a cool-temperate grassland in a montane region, a field experiment was conducted with two treatments: 1) warming plots in open-top chambers (OTC); and 2) control plots with ambient temperature. Mean air temperature was 1.1 degrees C higher in OTC than control. The fate, length, number of leaves, and aboveground biomass of uninfected and infected shoots of M. sinensis naturally established within the plots were recorded during the 2014 growing season. Disease symptoms emerged earlier in OTC. Infected shoots were shorter and had fewer leaves in OTC, whereas uninfected shoots were similar between OTC and control. Shoot biomass tended to be higher for uninfected shoots than infected shoots, but similar between OTC and control. Finally, shoot survival tended to be lower in OTC than control, as well as in infected than uninfected shoots. These results indicated that survival and growth of M. sinensis shoots were reduced following pathogen infection and that the detrimental effects of pathogens were more apparent under the warming condition.