HOST-SPECIFIC SV-TOXIN OF THE FUNGAL PATHOGEN CAUSING BROWN SPOT OF EUROPEAN PEAR

Stemphylium vesicarium causing brown spot of European pear produced multiple host-specific phytotoxins (S-toxin I and II) in culture.
SV-toxins selectively induced vein necrosis only on leaves of susceptible cultivars at a concentration of 0.01 to 0.1 μg/m1. SV-toxin had the infection-inducing activity.
Toxin induced an increase in electrolyte leakage from susceptible leaf tissues but not resistant ones.
An ultrastructural study showed that plasma membrane modification specifically occurred at the plasmodesmata of susceptible leaf cells treated with toxin.
The plasmalemmal invagination appeared at both ends of the plasmodesmata 3 hours after toxin treatment.
Many Golgi vesicles were in the cytoplasm close to or fused to the invaginated plasma membranes.
Polysaccaride-like materials were released from the fused vesicles to extracellular spaces between cell walls and invaginated plasma membranes.
No ultrastructural changes were detected in other organelles in the cells.
These results suggest that the target site for SV-toxin action may be on the plasma membranes of susceptible pear cells.

VIII International Symposium on Pear

P. Singh, H. Nakajima, H. Otani, M. Kodama, K. Kohmoto, P. Park, R. Bugiani, P. Cavanni

host-specific toxin, plasma membrane, Stemphylium vesicarium

https://doi.org/10.17660/ActaHortic.2002.596.85