Methods of measuring the prevalence of Phoma exigua on potatoes and in soil

Abstract

S U M M A R YMethods are described for assessing inoculum of Phoma exigua by directly wounding potato test tubers and by inoculating soil into Arran Banner test tubers or slices.Large samples of tubers were wounded by dropping onto perforated metal sheet or grading on farm riddles, but standardization was achieved by inflicting four uniform wounds with shaped brass teeth. Tubers were then incubated for 12 wk at 5 "C.Soil samples to be tested were inoculated into crush wounds on surfacesterilized test tubers or tuber slices which were incubated for 8 wk at 5 "C. Assessments were speeded by immersing wounded slices in a mixture of Agrimycin and isopropylphenyl carbamate (IPC) solutions before inoculating, and then incubating for 2-3 wk at 10 "C. Although the sensitivity of test tubers is limited by their latent infection, comparisons of the tests in 3-5 years showed that the test tuber methods were frequently more sensitive than direct wounding, especially when amounts of inoculum were small.

Cross-pathogenicity of Verticillium dahliae between potato and sunflower

“…Certain plant parasites show increased virulence (Foldyca and Green, 1963 (Schnathorst, 1981). Infected seed tubers are also a major source of contamination of soils and potato storage areas (Adams et al, 1980;Bang, 1986;Hide et al, 1977).…”

The role of stem inoculum in the transmission ofFusarium sulphureum to potato tubers

“…In 1999, 40 tubers from each plot were wounded with the nail method and 40 tubers with four severe cut and crush wounds using shaped brass teeth held in a modified drill stand (Hide et al, 1977).…”

Variation in pathogenicity on potato tubers and sensitivity to thiabendazole of the dry rot fungusFusarium avenaceum

“…Tubers of potato cvs Romano, Cara or Maris Piper were washed in water and surface-sterilised by washing in 95% ethanol and flaming. Each tuber was crush-wounded in four equidistant places (Hide et al, 1977). A disc (5 mm) cut from the edge of a colony of the fungus on low nutrient agar, SNA (Nirenberg, 1976), was placed into each wound.…”