Field application of plant resistance inducers (PRIs) to control important root rot diseases and improvement growth and yield of green bean (Phaseolus vulgaris L.)

Abstract

The efficiency of plant resistance inducers (PRIs) i.e. chitosan (CH), salicylic acid (SA) and humic acid (HA) in controlling Fusarium solani and Rhizoctonia solani the causal agents of root rot diseases under in vitro and on growth and yield of green bean cv. Giza 3 were evaluated. In vitro treatments of CH 1.0 g/l, CH 1.0 g/l + HA 5.0% and CH 0.5 g/l + SA 2.5%, as sterilized PDA medium addition, caused the highest reduction in mycelia growth and spore germination of F. solani and R. solani on incubated plates compared to control plates (medium free of inducers). Under greenhouse conditions, combined treatments of PRIs were superior than single treatments, while, CH 1.0 g/l + SA 5% or HA 5.0% treatments were more effective than single treatments in controlling of Rhizoctonia root rot. These treatments caused disease reduction reached to 70.4 and 67.4% of pre-emergence stage after 10 days of seed sowing, and 62.8 and 60.4% of post-emergence stage after 40 days of seed sowing. Meanwhile, the highest values of survival plants 79.4 and 77.8% were recorded with the same treatments. Under field conditions, the obtained results indicated that soaking bean seeds in CH 1.0 g/l + SA 5% followed by foliar application with half of this concentrations CH 0.5 g/l + SA 2.5%, (for 3 times in 7 days interval starting from the second true leaf stage), resulted in the higher percentages of reduction of damping-off and root rot incidence 68.2, 63.8, 70.0% and 67.4, 63.3, 69.6% after 10, 40 and 60 days during both seasons, respectively, compared with other treatments. Furthermore, such treatment was superior than commercial fungicide seed treatment in controlling of green bean root rot, where, fungicide treatment reduced damping-off and root rot incidence after 10, 40 and 60 days up to 64.6, 60.4, 64.0% and 64.0, 59.6, 63.4% during both seasons. Combined treatments of PRIs and commercial fungicide treatment resulted in increasing of vegetative growth characters, yield and quality of green bean pods compared to other treatments during two successive seasons. It could be suggested that using plant resistance inducers in comparison with fungicides, might be considered as an eco-friendly, safe, cheap and easily applied method for controlling such soil-borne plant pathogens considering the avoidance of environmental pollution and the side effects of fungicides application.