Vital staining of plant cell suspension cultures: evaluation of the phytotoxic activity of the phytotoxins phomalide and destruxin B

A cell suspension culture assay to determine the phytotoxicity of the funga l toxins phomalide, a host-selective toxin produced by the fungus Phoma lin gam (Tode ex Fr.) Desm., perfect stage Leptosphaeria maculans (Desm.) Ces, et de Not., and destruxin B, the major host-selective toxin produced by the fungus Alternaria brassicae (Berk.) Sacc., was carried out with three Bras sica spp. It was established that phomalide was significantly less phytotox ic to Cutlass (Brassica juncea), the cultivar resistant to L. maculans, tha n to Westar (B, napus), the cultivar susceptible to L. maculans, at concent rations less than or equal to 2x10(-5)M. Similar to phomalide, destruxin B, at concentrations less than or equal to 5x10(-5) M, decreased the viabilit y of cells of the cultivar resistant to A. brassicae (Ochre, Sinapis alba) less than the viability of cells of the susceptible cultivar (Westar, B, na pus). Considering the high selectivity of phomalide and its direct correlat ion with plant disease resistance, phomalide may have great potential appli cation in breeding programs screening/selecting for blackleg resistance in brassicas.