In Morocco, soils that are naturally suppressive to date palm Bayoud disease have long been discovered. Although suppressiveness was attributed to biological activities of indigenous microbes, our knowledge on the specific mechanisms underpinning this property remains limited. In this study, we investigated nutrient competition between Fusarium oxysporum f. sp. albedinis, the causal agent of Bayoud disease, and saprophytic Fusarium as a factor of disease suppressiveness/conduciveness in suppressive and conducive soils. Growth of pathogenic and saprophytic Fusarium isolates from one suppressive and one conducive soils on 95 carbon sources was assessed. Fusarium isolates exhibited distinct nutrient use profiles and varied significantly with soil in carbon utilization. Isolates from the suppressive soil had significantly the greatest resource use efficiency, followed by the pathogenic isolates that grew significantly faster than the isolates from the conducive soil. Data on nutrient niche overlap showed that the pathogen is outcompeted by saprophytic Fusarium populations in the suppressive soil and outcompetes those in the conducive soil. Taken together, our results provide insight into the role of competition for carbon resources among pathogenic and saprophytic Fusarium communities as a driving factor in soil suppressiveness/conduciveness. This finding may also open novel research paths and offer opportunities for the development of biocontrol techniques against Bayoud disease in Moroccan date palm groves.
Keywords: Date palm, Bayoud disease, nutrient competition, disease suppressio
