Evaluation of the effectiveness of Ocimum gratissimum essential oil in managing black mold, the major storage disease of onion in Burkina Faso

Onion production in Burkina Faso is predominantly off-season and remains insufficient to meet the annual consumption needs of the population. This deficit is partly due to postharvest losses caused by bulb rot during storage, primarily induced by Aspergillus niger. The objective of this study was to evaluate in vivo the effectiveness of O. gratissimum essential oil in inoculated onion bulbs. This study first evaluated the pathogenicity of A. niger on onion bulbs of the Violet Galmi, Safari, and Damani varieties after mycelial and conidial inoculations. The in vivo antifungal efficacy of O. gratissimum essential oil was then investigated on inoculated bulbs at concentrations of 0.15%, 1.50%, and 15%. The results obtained evidenced that mycelial inoculation caused a significantly higher mean rot intensity (40.28%) than conidial inoculation (4.39%). In addition, treatment with O. gratissimum essential oils at concentrations of 1.5% and 15% reduced the rot intensity by 37.19% and 47.67%, respectively. These findings demonstrate the promising antifungal potential of O. gratissimum essential oil as a biopesticide for protecting postharvest onion bulbs and reducing storage losses.