Race-specific elicitors from the Peronospora parasitica / Arabidopsis thaliana pathosystem

Abstract

Intercellular washing fluids (IWFs) were isolated from compatible interactions ofPeronospora parasitica with Arabidopsis. IWFs were filter-sterilized then infiltrated into leaves of resistant and susceptible Arabidopsis genotypes. P. parasitica isolates WELA (virulent on Landsberg erecta (La-er) and Weiningen (Wei-0) but avirulent on Columbia (Col-0) and RLD) and NOCO (virulent on Col-0 and RLD but avirulent on La-er) were used. A “reciprocal check” pattern of necrosis-induction was observed in which IWFs from a compatible interaction caused necrosis in leaves of the Arabidopsis genotypes resistant to the “parent” fungal isolate but not in those genotypes susceptible to it. Analysis of variance showed that the interaction between fungal isolate and necrosis in host genotypes was highly significant. The necrosis-inducing activity was significantly correlated with a high degree of asexual sporulation in the compatible interaction from which the IWF was isolated. However, the necrosis-inducing activity was not correlated with the protein content of the IWF.