Pathogenicity to potato tubers of Fusarium spp. isolated from potato, cereal and forage crops

Potatoes are commonly grown in rotation with cereal and forage crops. Storage trials were conducted in Prince Edward Island, Canada from 2002 to 2004 to determine whether isolates of Fusarium spp. obtained from cereals or forages were able to cause disease (dry rot) in stored potato tubers. In each year of study, tubers of the cultivars 'Red Norland', 'Yukon Gold' and 'Russet Burbank' were wounded and then inoculated with an agar plug containing active mycelium of one of the 30 isolates tested. Following incubation for 5 weeks in a storage facility, tubers were cut longitudinally at the point of inoculation and the depth of necrosis measured. Isolates of F. sambucinum, F. coeruleum and F. avenaceum originating from potato tubers were strongly pathogenic to inoculated potato tubers. Isolates of F. oxysporum f.sp. medicaginis sourced from alfalfa were nonpathogenic to potato tubers, however, isolates of F. avenaceum from alfalfa and clover and F. oxysporum from clover were pathogenic to potatoes. Isolates of F. poae and F. sporotrichioides sourced from cereals were nonpathogenic and weakly pathogenic, respectively, to inoculated tubers. All isolates of F. graminearum (obtained from cereal crops) that were tested were pathogenic to potato tubers. Thus, crops grown in rotation with potatoes may harbour Fusarium spp. that can act as pathogens in subsequent potato crops.