Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: August 1, 1997
Publication Date: N/A
Technical Abstract: The incidence of dwarf bunt as a function of inoculum density was studied in a susceptible and a partially resistant cultivar at three disease-conducive locations for three seasons. Plots were fumigated with methyl bromide prior to seeding. Each cultivar was seeded into two four-foot rows at a rate of 1 g/foot in four replicates. The soil surface was inoculated with 0, 16 X 10(^2), 16 X 10(^3), 16 X 10(^4), 16 X 10(^5), and 16 X 10(^6) teliospores per row, or seed was inoculated with 0, 2 X 10(^2), 2 X 10(^3), 2 X 10(^4), 2 X 10(^5), and 2 X 10(^6) teliospores per gram. To indicate maximum possible infection, two twenty-foot rows of each cultivar were soil-surface inoculated at 10X the highest treatment rate. Mean percent diseased spikes per treatment at each location and year was calculated. In the soil inoculated plots, a minimum of 16 X 10(^3) teliospores per row was needed to cause trace amounts (0.6%) of disease, even when the positive indicator had up to 88% incidence. Only trace amounts or no disease occurred below the 16 X 10(^5) rate. In the seed inoculated plots, infection was rare and occurred only at inoculation rates of 2 X 10(^5) or higher; the highest incidence was 0.4%.