SINTOMATOLOGíA E IDENTIFICACIóN DEL AGENTE CAUSAL DEL TIZóN GOMOSO DEL TALLO EN SANDíA (Citrullus lanatus (Thunb.) Matsum y Nakai) EN LA ISLA DE LA JUVENTUD

the gummy stem blight is considered the most important fungal disease in watermelon for the isle of youth. the disease causes damages to leaves and stems; it reduces the yield of the infested crops. often, it is associated with other fungi in the infested plants causing confusion. the objective of this work was to identify the causal agent of the gummy stem blight and to describe its characteristic symptoms. the observations of the disease in the field showed that the spots appeared on leaves and stems, and they advanced from the center of the watermelon plants towards the tips of the main stems. in the advanced state of the disease, black colored fructifications were observed in the center of the spots. generally, in the old leaves, they were perithecia of blackish chestnut color with very well defined asci and spindle shaped ascospores with a septum, whereas in the young leaves, mainly spherical pycnidia appeared with end-rounded pycnidiospores with a truncated septum in the center. in the similarity observed between the lesions developed from the artificial inoculation and those described for natural infections, as well as the likeness of the pathogen colonies and reproductive structures obtained in both cases, corresponded to those informed for the causal agent of the gummy stem blight / teleomorphic phase didymella bryoniae (fuckel) rhem and in their anamorphic phase (phoma cucuritacearum (fr,:fr) sacc), these are the first descriptions of the causal agent of the gummy stem blight carried out in cuba.