A rapid and simple screening method for pathogenicity of Rhizoctonia solani and Macrophomina phaseolina on cotton seedlings

摘要

Cell-free15-day-old culture filtrates of 19 isolates of Rhizoctonia solani and 19 isolates of Macrophomina phaseolina differed significantly in their capacity to inhibit germination of cottonseeds after 4 days of incubation and to inhibit elongation of radicle after 12 days of incubation. Data for pathogenicity of R. solani and M. phaseolina isolates and each of seed germination and radicle length were entered into a computerized linear regressions analysis, which constructed six predictive models by using seed germination or radicle length, singly or in combination, as physiological predictors. It was found that the radicle length model (r =-0.936, p=0.000) and the seed germination model (r=-0.851, p=0.000) were the best models for predicting pathogenicity of R. solani and M. phaseolina isolates, respectively. The results of the present study suggest that cell-free culture filtrate assay reflects the relative pathogenicity of the various isolates of R. solani and M. phaseolina and may provide a practical complimentary method to greenhouse tests.