The development of anthracnose symptoms on sorghum genotypes in the Nigerian savanna

The development of sorghum anthracnose symptoms was monitored on 17 sorghum genotypes of diverse origins during two rainy seasons in the savanna of Nigeria. Four symptoms of the disease were clearly revealed by the sorghum differentials. The development of these symptoms was best studied in the local and exotic genotypes ‘Warwarabashi’ and ‘IS 18442’, respectively. The symptoms, which appeared in sequence and marked the different phases of the disease, include chlorotic flecks on leaves, necrotic spots on leaf lamina, leaf sheath lesion, midrib infection and panicle infection. Resistant genotypes produced only chlorotic flecks without acervuli, moderately resistant genotypes produced necrotic spots on the leaf lamina without noticeable acervuli while the susceptible genotypes had midrib and leaf lamina infections, which are the most severe symptoms accompanied by proliferous acervuli. The relationships of different phases are also discussed.