Motility is an important attribute for Ralstonia solanacearum to colonized potato (Solanum tuberosum) roots in soil. Quantitative and qualitative chemotaxis assays revealed that this bacterium is specifically attracted to diverse concentration of phenolics, organic and amino acids, sugars and other nutrients induced by microbes and especially to root exudates from the host plant around its root surface. Therefore, potato may secrete some compounds considered as chemotactic signals between potato roots and the pathogen in soil. The application of effective concentrations of different soil amendments resulted in significant changes in the chemical composition of root exudates in sterilized and non-sterilized sandy soil. These changes demonstrate an important role in the induced defense mechanism of systemic acquired resistance. The chemical change in root exudates may be responsible for breaking or cutting the chemical signals between potato roots and bacterial pathogenicity so that both the percentage of infection and disease severity decreased. In control group, the root exudates collected after 40 days from potato cultivation was higher than collected after 20 days showing significant differences in its composition. |
