SUMMARY
This study was carried out to evaluate the efficiency of some plant growth regulators (PGRs) to protect common bean plants against damping-off and root rot which caused by Rhizoctonia solani (Kuhn). Fourteen isolates of R. solani were isolated from common bean plants. Pathogenicity tests of these isolates were carried out on common bean (Giza 6 cv.) in greenhouse experiments during growing season in 2014. Results showed that all the tested isolates of R. solani were pathogenic to common bean plants with different degrees of infection. PGRs (indole 3-butric acid, gibberellic acid and N6-benzyladenine) have been evaluated as soaking seeds treatments before sowing at concentrations 50 and 100 ppm under greenhouse conditions. Treatments with the tested PGRs were effective in reducing disease severity (DS) percent at the tested parameters, i.e. damping-off and root rot. Also, data indicate that the highest significant reduction of diseases severity was observed in the case of N6-benzyladenine treatment (100 ppm), followed by indole 3-butyric acid (100 ppm). The concentration 50 ppm of PGRs was the most effective in reducing both diseases (damping-off and root rot). Application of the tested PGRs has significantly enhanced the height and the fresh weight of common bean plants compared to the control and fungicides (Moncut 25%). Gibberellic acid (100 ppm) was the most effective in increasing the height and the fresh weight of plants than the other treatments at seasons 2015 and 2016. Laboratory estimates, showed that treated plants with the tested PGRs content more phenolic compounds compared to untreated plants. The treatment with N6-benzyladenine was more content of phenolic compounds than the other treatments. There is an inverse relationship between the level of phenolic compounds in treated plants and the disease severity.