Downy mildew (Sclerospora sorghi (kulk) weston & uppal of sorghum (Sorghum vulgaris, pers in Uganda

Earlier observations on introduced varieties showed that sorghum downy mildew (SDM) could be a destructive disease of sorghum in Uganda. Hence a study was undertaken to screen number of locally grown sorghums, and these introduced varieties for resistance to this disease in particular and to local races of all possible diseases of the crop in general. Investigations in the field and in the greenhouse have shown that in about three hundred lines screened, three of them exhibited a high degree of resistance or immunity ro SDM and about twenty of them expressed some filed resistance which varied in expressivity when tested under a wider range of environmental conditions. These varieties ranked between the consistency of resistance expressed by the hybrids and the inconsistency expressed by the local sorghums. The rest of the lines were mostly susceptible. The reaction of these lines to the other foliar and head diseases of sorghum was variable though in general, those sorghum which sowned resistance to SDM were also moderately resistant to most of these diseases. Basic experiments on the study of the fungus were also carried out. Two effective techniques for artificially inoculating sorghum with S.sorghi were established. One of the methods utilizes the sexual spores of the fungus as source of inculum and the other one uses the sexual spores. In host range investigation experiments mainze (Zea mays) is the only important commercial crop infected by the fungus. The mode of germination and infection of Sclerospora sorghi was determined and described. Evaluation of some of the common fungicides as foliar sprays to control SDM revealed that none of them reduced the incidence of infection. However, some of the fungicides selectively controlled some of the others diseases of the crop.