The Ethylene Biosynthesis Genes and Modulate Disease Severity of .

is one of the most destructive soilborne plant pathogens since it has a broad host range and there is no chemical disease management. Therefore, there is a need to unravel the molecular interaction between the pathogen and the host plant. For this purpose, we examined the role of 1-aminocyclopropane-1-carboxylic acid synthases (ACSs) of upon infection. We observed that the , , and plants are partially resistant to , since the disease severity of the mutants was lower than the wild type (wt) Col-0 plants. Quantitative polymerase chain reaction analysis revealed that , , and plants had lower endophytic levels of than the wt. Therefore, the observed reduction of the disease severity in the mutants is rather associated with resistance than tolerance. It was also shown that and were upregulated upon infection in the root and the above ground tissues of the wt plants. Furthermore, the addition of 1-aminocyclopropane-1-carboxylic acid (ACC) and aminooxyacetic acid (AOA), the competitive inhibitor of ACS, in wt , before or after inoculation, revealed that both substances decreased wilt symptoms compared to controls irrespectively of the application time. Therefore, our results suggest that the mechanism underpinning the partial resistance of and seem to be ethylene depended rather than ACC related, since the application of ACC in the wt led to decreased disease severity compared to control.