In vitro quantification of the reaction of barley to common root rot

An in vitro technique was used to quantify the infection level of common root rot. This disease produces a brown to black discoloration of the subcrown internodes of barley. Quantification was based on the percentage of germinated infected pieces (1.5 mm) of subcrown internodes cultured on potato dextrose agar media. The disease severity was apparent among four different visually classified categories and numerical values for each category were applied. The results were highly correlated (r = 0.97, P < 0.01) among the different in vitro experiments, indicating that this testing procedure is repeatable. Highly significant differences (P < 0.001) were found for the length of first leaf and fresh weight between plants inoculated and uninoculated with common root rot. However, the effect of inoculation on fresh weight only differed significantly (P < 0.02) among the genotypes.