Fungal growth and in planta distribution of host-specific AAL-toxin in tomato plants infected with the tomato pathotype of Alternaria alternata

Abstract

The tomato pathotype of Alternaria alternata causes Alternaria stem canker of tomato (Solanum lycopersicum L.) by producing a host-specific AAL-toxin. The chemical structure and biological activities of AAL-toxin are analogous to those of the mycotoxin fumonisin. Determination of pathogen development and toxin production in infected tomato plants is of prime importance for pathological evaluation and risk assessment of AAL-toxin. On a resistant cultivar, AAL-toxin and the pathogen were restricted to a small region surrounding only the initial inoculation site. On the other hand, widespread distribution of the toxin and the pathogen were detected in a susceptible cultivar. The pathological signifi cance and contamination risk from the toxin were supported by the results of in planta production of the toxin in diseased tomato plants.

Phytotoxic dioxolanones are potential virulence factors in the infection process of Guignardia bidwellii

“…Thus, the production of one of the toxins of the fungus during active growth in planta was proven. The detection of phytotoxins in planta needs highly sensitive methods of measurement, because most toxins are highly potent, therefore, only small quantities are required to cause symptoms of infection 9 . A concentration of 45 µg/g leaf material (wet) of guignardic acid was determined experimentally in the infected sample.…”