“…Such plating methods were used to differentiate among cultivars and breeding lines in the selection for and study of resistance to PED (10,14,17,25-28, 45,62). Those assays were also employed to describe the epidemiology of the disease and colonization by the pathogen under various agricultural and environmental conditions (2)(3)(4)15,16,18,19,24,40,43,48,52,61). Expression of PED symptoms is greatly affected by environmental and agricultural conditions (e.g., weather during the growing season, irrigation frequency, and nitrogen fertilization), and selection of breeding lines based solely on symptoms is generally discouraged.…”