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2Department of Biology, Higher Training College, University of Yaoundé 1, Cameroon
3Department of Microbiology, University of Yaoundé 1, Cameroon
Cassava anthracnose disease (CAD) is one of important fungal disease of cassava which attacks stem and leaves, consequently leading to low yield and even plant death. This study was carried out to determine the relation between cyanogenic (HCN) concentration in leaves from four cassava cultivars and their tolerance to CAD. One local cultivar (CV1) and three improved (CV2, CV3, CV4) were used in a randomized block design. Disease severity, incidence, concentration of HCN in leaves, inhibitory effects of HCN extract (in vitro) were evaluated. The cyanide concentration was determined by titration using a solution of 0.02 N AgNO3. Low cyanide cultivars CV1 and CV3 with mean values of HCN, 0.5 and 0.6 mg/g respectively were more susceptible to CAD (average severity 12.9 and 10.2%). While, high acid cultivars CV2 (1.1 mg/g), CV4 (1.2 mg/g) showed the highest tolerance to CAD (4.0% severity on both cultivars). HCN extracts had inhibited 87.5 and 51.2% of Colletotrichum gloeosporioides growth at day 1 and day 7 respectively after incubation. A direct relationship existed between HCN in cassava leaves and tolerance to CAD. The capacity of cassava to synthesize HCN can be used in selection programs to obtain cassava cultivars resistant to CAD.