Plant life cycle
Plant life cycle (i.e., annual, biennial, and perennial) can influence susceptibility of plants to pathogens (Clay 1995). Certain pathogens are more likely to infect and persist in perennial than annual plant populations because annual plants do not have overlapping generations, so this advantage of annual plant species is specific to horizontally transmitted pathogens. Whereas, pathogens that depend on alternative mechanisms to persist such as vertical transmission (i.e., transmission from seeds to mature plants, instead of horizontal transmission between plants), free-living infective stages, and alternative hosts would persist among annual plant species (Thrall et al.1993; Borer et al. 2007). To our knowledge, no studies have determined the prevalence of pathogens in plant species with different life-cycles.