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Systemic Induction of Peroxidases, 1,3-β-Glucanases, Chitinases, and Resistance in Bean Plants by Binucleate Rhizoctonia Species

First and third authors: Department of Plant Science, Macdonald Campus of McGill University, 21,111 Lakeshore, Ste-Anne-de-Bellevue, Québec, Canada H9X 3V9; and second author: Département de Phytologie, Pavillon de Recherche en Sciences de la Vie et de la Santé, Université Laval, Quebec, Canada G1K 7P4

Inoculation of bean hypocotyls with a nonpathogenic binucleate Rhizoctonia (BNR) species induced systemic resistance and protection of the roots and cotyledons to later challenge with the root rot pathogen Rhizoctonia solani or the anthracnose pathogen Colletotrichum lindemuthianum. Bean seedlings that were treated with BNR 48 h prior to their challenge with R. solani or C. lindemuthianum had few necrotic lesions and reduced disease severity as compared with seedlings not treated with BNR. Treatment with BNR 48 h prior to their challenge also elicited a significant and systemic increase in all cellular fractions of peroxidases, 1,3-β-glucanases, and chitinases compared with the diseased and control plants. Compared with control plants, total peroxidases and glucanases increased twofold and eightfold, respectively, in all protected bean tissues. BNR 232-CG could not be recovered from the challenged hypocotyls or cotyledons, indicating that there was no contact between the inducer and the pathogen. Both the 1,3-β-glucanases and the peroxidases were positively correlated with induced resistance.

Additional keywords: hydrolases , induced systemic resistance , oxidases .