Influence du substrat sur l\'isolement et la croissance radiale de Trachysphaera fructigena , agent de la maladie du bout de cigare des Musacées

La maladie du bout de cigare est une affection parasitaire des fruits des Musacees principalement causee par Trachysphaera fructigena au Cameroun. Cette maladie saisonniere sevit dans les regions de moyenne a hautes altitudes (400-2000 m). Bien qu\'elle ait ete depuis longtemps signalee au Cameroun, tres peu de travaux lui ont ete consacres. Cette etude a pour objectifs de determiner les conditions d\'isolement du pathogene et d\'identifier les milieux de culture permettant une production abondante et rapide du mycelium. Les fruits infectes ont ete recoltes dans differentes zones de culture de bananiers. La croissance radiale de 3 souches obtenues a ete evaluee sur 14 milieux de culture a 20°C. L\'isolement de T. fructigena ne semble etre possible que sur les jeunes fruits n\'ayant pas encore atteint leur maturite physiologique, et sur les fruits contamines dans les sites de stockage. Le milieu V8 et ceux faits a base de pomme de terre, de pulpe de banane, plantain, et papaye sont respectivement les meilleurs pour la croissance radiale apres 4 a 7 jours d\'incubation. Ces resultats permettront de faciliter l\'isolement et une production abondante et rapide du mycelium de T. fructigena en vue des etudes sur sa biologie et ses interactions avec l\'hote. Cigar-end disease is an affection of Musaceae fruits mainly caused by the fungus Trachysphaera fructigena in Cameroon. The disease occurs in areas of average to high altitudes (400-2000 m above the sea level). Although the disease has been identified in Cameroon long time ago, few research works have been done on this fungus. The purpose of this study is to determine the conditions of isolation of the pathogen and to identify culture media which allow the fungus to rapidly grow and produce large quantity of mycelium. The infected fruits from which the fungus was isolated were harvested in different banana culture areas. Radial growth of 3 single isolates obtained was evaluated on 14 culture media at 20°C. The isolation of T. fructigena seems to be possible only from young infected fruits at their early stage of development, and from fruits contaminated in storage rooms. V8 medium and media prepared with potato juice, banana, plantain and papaw pulps were the best for radial growth after 4 to 7 days of incubation. These results will make it easy to isolate T. fructigena and rapidly produce large amount of its mycelium for studies related to its biology and interactions with the host. Keywords : Maladie du bout de cigare, Musacees, Milieux de culture, Trachysphaera fructigena ; Croissance radiale. Cigar-end disease; Musaceae; Culture media, Trachysphaera fructigena; Radial growth. CaJEB Vol. 3 (2) 2007: pp. 103-114