COLLETOTRICHUM-GLOEOSPORIOIDES AS THE CAUSE OF STEM TIP DIEBACK OF CASSAVA

A fungus with morphological features corresponding to the group specie s Colletotrichum gloeosporioides was consistently isolated from cassav a with shoots showing dieback symptoms in Ghana. When four locally-gro wn cultivars were inoculated with isolates of the fungus, they develop ed disease symptoms, which consisted of discrete dark brown lesions on the stems followed by defoliation. Koch's postulates were completed b y re-isolating the fungus from the inoculated plants. The relatedness of the isolates to other members of the genus Colletotrichum, whose id entities were well established, was investigated by comparison of the nucleotide sequence of domain 2 of their ribosomal DNA. The cassava is olates differed from authentic isolates of C. gloeosporioides by only one nucleotide among the 193 analysed. The causal agent of cassava ste m tip dieback (STDB) is thus identified as a form of C. gloeosporioide s.