SYSTEMIC INDUCTION OF PEROXIDASES, 1,3-BETA-GLUCANASES, CHITINASES, AND RESISTANCE IN BEAN-PLANTS BY BINUCLEATE RHIZOCTONIA SPECIES

Inoculation of bean hypocotyls with a nonpathogenic binucleate Rhizoct onia (BNR) species induced systemic resistance and protection of the r oots and cotyledons to later challenge with the root rot pathogen Rhiz octonia solani or the anthracnose pathogen Colletotrichum lindemuthian um. Bean seedlings that were treated with BNR 48 h prior to their chal lenge 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 peroxid ases, 1,3-beta-glucanases, and chitinases compared with the diseased a nd control plants. Compared with control plants, total peroxidases and glucanases increased twofold and eightfold, respectively, in all prot ected bean tissues. BNR 232-CG could not be recovered from the challen ged hypocotyls or cotyledons, indicating that there was no contact bet ween the inducer and the pathogen. Both the 1,3-beta-glucanases and th e peroxidases were positively correlated with induced resistance.