Use of rooted leaves for screening of Brassica germplasm response to clubroot (Plasmodiophora brassicae) and downy mildew (Hyaloperonospora parasitica)

Abstract

Rooted leaves and cotyledons of various cruciferous crops were used for the screening of Brassica germplasm response to two obligatory pathogens: clubroot (Plasmodiophora brassicae) and downy mildew (Hyalope-ronospora parasitica). The development of roots was induced after 20-hour dipping of leaf pedicels in the mixture of growth regulators: indolyl-butyric acid (10 mg/l) and nicotinic acid (5 mg/l). The detached rooted leaves and cotyledons were maintained in 250ml plastic containers with perlite under fluorescent tubes in a growth chamber. With additional foliar fertilizing they remain vital for four months, producing clubroot galls on roots when dip-inoculated with Plasmodiophora spores and sporulating mycelia of downy mildew on leaves after drop inoculation with Hyaloperonospora parasitica. The possibilities of enhancing the sensitivity of this alternative assay in combination with immunochemical methods are discussed.