Contribution à la mise au point d'une méthode de lutte biologique contre la maladie des pourritures de la couronne de la banane

摘要

The antagonist activity of two yeast strains (Pichia anomala K strain and Candidaoleophila O strain) against the parasitic complex responsible for crowns rot of banana has beenevaluated. Their efficiency has been tested on three separated fungi : Colletotrichum musae,Fusarium moiliforme, Cephalosporium sp. and on a parasitic complex formed by theassociation of these three fungi.Antagonist effects have been observed both on the two first fungi and on the complex.Strain O added at 108 ufc/ml on crowns which were previously inoculated with the complexshowed the highest protection (56,0 %). This protection was superior to those observed againstthe fungi inoculated separately.The influence of the time between the addition of the O strain (108 ufc/ml) and theinoculation of the pathogens on the level of protection has also been measured. It appeared thatprotection by the O strain was remarkably reinforced when the strain was added 24 hoursbefore the complex (57,0 %). This, in comparison with the additions performed 15 minutes or3 hours after the pathogens inoculation.The utilisation of the O strain at 108 ufc/ml has been combined with the utilisation of50μm polybags. These latter allow the formation of a modified atmosphere during the length ofthe bunches transfer. The protection level was at 61,0% when both methods were combinedwhereas protection by the yeast alone was of 41,0%.A strict correlation between the severity of the symptoms and the protection by theyeast has been highlighted. When the severity of the disease increases, protection by the yeastdecreases.