Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/1997
Publication Date: N/A
Technical Abstract: Wirestem of seedling Brassica oleracea crops is caused by Rhizoctonia solani AG-2-1 and AG-4. In four field tests, whole plots were fumigated with methyl bromide, then infested or not infested with 25-50 sclerotia/kg soil of AG-4 or AG-2-1. Twenty seedlings of three cultivars each of broccoli, cauliflower, cabbage and collard were transplanted into four replicate subplots. Numbers of healthy, diseases and dead plants were counted five times at 3- to 7-day intervals. After 3 weeks, plants were dug with intact roots and rated for wirestem severity on a 1-10 scale of increasing severity. Seedlings grown in soil infested with sclerotia of AG-4 developed severe wirestem, but seedlings inoculated with AG-2-1 did not. Overall, Snowcone (75% wirestem incidence) and Snow Crown (65%) cauliflower were the most susceptible cultivars, while Blue Max (42%) collard and a collard landrace (36%) were the least susceptible. The four crops did not differ significantly from one another because of differences among cultivars within crops. Percentage of diseased and dead plants 1 and 3 weeks after inoculation was correlated positively with severity (P less than or equal to 0.01) and AUDPC (P less than or equal to 0.04). Wirestem incidence 1 week after inoculation is a convenient, reliable measurement of host-plant resistance to infection by R. solani.