Preliminary study of seed transmission of downy mildew in some vegetable brassica cultivars in Australia

Peronospora parasitica causes large losses in the brassica vegetable seedling industry. Commercial brassica vegetable seed in Australia was tested under aseptic conditions to determine whether P. parasitica is seedborne. There was no evidence of seed infection by P. parasitica. This was attributed to one or more of the following possibilities - no infection in the seeds tested, a low frequency of seed transmission that was undetectable in the tests used, absence of oospores due to heterothallism, or failure of infected seeds to produce symptoms in seedlings.