Higher leaf positions associated with biotrophic pathogen infection

Abstract Understanding differences in disease position (i.e. the average height of infected leaves) among fungal pathogens is crucial for predicting and managing plant diseases. However, we know little about how disease position varies across disease and host plant types, and whether the local climate (i.e. temperature and precipitation) affects disease position. Here, we investigated disease position in herbaceous plants across key grassland ecosystems in China, including the Qinghai-Tibetan Plateau, Inner Mongolia Plateau, and North China Plain. We tested how fungal pathogen characteristics (e.g. disease types and pathogen lifestyles), host plant characteristics (e.g. biomass, natural height and plant growth type), and climatic conditions (e.g. mean annual temperature [MAT] and precipitation [MAP]) affected disease position. Disease position tended to be higher for biotrophic versus necrotrophic pathogens, and this pattern was strongest in forbs and legumes. Disease position was also environment-dependent; higher temperatures and precipitation significantly increased disease position, but these effects varied among disease types. For both biotrophic and necrotrophic pathogens, larger host plants had lower mean disease positions. In this study, we provide evidence for how disease types and climatic conditions impact disease position; our findings emphasize the importance of disease position for understanding patterns of infection and managing disease outbreaks in a changing world.