Inoculation Techniques for Assessing Pathogenicity of Rhizoctonia solani, Macrophomina phaseolina, Fusarium oxysporum and Fusarium solani on Pepper Seedlings

Abstract

In this study, surveys were carried out during 2015 and 2016 for wilt and root rot diseases caused by Rhizoctonia solani, Macrophomina phaseolina, Fusarium oxysporum, and Fusarium solani in pepper fields in Adıyaman, Diyarbakır, Mardin and Şanlıurfa provinces of Turkey. The purpose of this study was to evaluate the effects of different inoculation methods (root dip, soil infestation with wheat bran and soil infestation with rice grain) on pathogenicities of R. solani, M. phaseolina, F. oxysporum and F. solani on pepper seedlings. Inoculated pepper seedlings (cv. İnan-3363) were left to grow for three months after transplanting under growth chamber conditions. Inoculation of infective rice-grain was used to test pathogenicity of all four fungi. Root dip inoculation method was used for F. solani and F. oxysporum when the soil was infested with wheat bran method for R. solani and M. phaseolina inoculation. All tested isolates resulted in the stem and root rot, leaf chlorosis and bruising. To test the pathogenicity of fungi, soil infestation with rice grain inoculation was the most suitable method. All tested fungi induced similar foliar symptoms, root rot severity and caused a similar reduction in dry root weights when rice-grain inoculum was used. With other inoculation methods, all pathogens similarly affected root rot severity. Whereas, F. oxysporum was the least virulent pathogen among tested fungi affecting foliar symptom severity; for fresh root and plant weights, and dry root and plant weights; R. solani, M. phaseolina and F. solani were similarly virulent when these parameters were used. The results of the present study may have a useful connotation to monitor pepper seedlings against these pathogens. In conclusion, we recommend rice-grain inoculation to test pathogenicities of R. solani, M. phaseolina, F. oxysporum and F. solanion various pepper cultivars.