Archivio Journal of Plant Pathology

Abstract:

Clavibacter michiganensis subsp. michiganensis can cause severe losses to tomato crops and new types of alternative control must be identified. Induced resistance is a potential method. Among resistance inducers, the mushrooms Lentinula edodes (Le) and Agaricus subrufescens (Abl) exhibit the potential to be used in plant disease control. The objectives of this study were: (i) evaluate the potential of these mushrooms and of acibenzolar-S-methyl (aSm) to control bacterial canker; (ii) study the mode of action of these materials by measuring defense-relate enzyme activity; (iii) partially purify biologically active molecules. The aqueous extracts from mushroom isolates, as well as aSm, did not inhibit bacterial growth in vitro. However, 10% (v/v) solutions of extracts from the isolates Le-96/17 and Abl- 26, as well as aSm, reduced wilt in tomato plants under greenhouse conditions. Plants treated with aSm, Abl-26 and Le-96/17 showed an increase in peroxidase and chitinase. Pphenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO) activities increased with all treatments. Because isolate Le-96/17 induced the greatest wilt reduction, its aqueous extract was precipitated with ammonium sulfate. The fraction at 40-80% saturation was submitted to anion-exchange chromatography (AEC). The AEC fractions 3 and 4, the inducer aSm and the aqueous extract of Le-96/17 reduced the bacterial disease. The fractions 3 and 4, the 40-80% precipitate and the aqueous extract from Le-96/17 contained more than one protein band. In conclusion, the isolate Le-96/17 induced resistance to C. michiganensis in tomato and partial purification of the inducer molecules was obtained.