Microbiological Features Associated with the Suppression of Fusarium Wilt of Lettuce Studied by Applying a Single Selected Compost

The effect of compost suppressiveness towards Fusarium oxysporum f. sp. lactucae has been studied using a combined approach. Bioassays have been carried out in controlled conditions to obtain standardization of the environment in order to minimize the disturbances and variability of the soil microbial communities. Compost addition has demonstrated significant efficacy in controlling the disease. The microbial activities and the bacterial and fungal concentrations have been quantified and correlated in a principal component analysis in order to clarify the correlation between the original variables. The samples were clearly distinguished between the substrates in which the plants were grown and the rhizosphere samples. Denaturing Gradient Gel Electrophoresis (DGGE) has been used to track the microbial communities throughout the bioassays. The approach has shown to be useful in detecting both bacterial and fungal species that preferentially associate with the roots of seedlings. Detected microorganisms assumed to be involved in compost-mediated suppression had a high probability of being vital because they were not detected in the substrate where the plants were grown at the start of the experiment.