Host‐range and survival studies ofPeronosclerospora sorghiat two locations in Nigeria

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Abstract
Several native grasses, sorghum lines and maize genotypes were tested for susceptibility to Peronosclerospora sorghi (Weston and Uppal) C. G. Shaw at two locations in Nigeria. In the southwestern location, neither the native grasses nor the sorghum varieties were infected, but most maize varieties were susceptible to downy mildew. In the north‐central location, differential sorghum lines T x 412, T x 430, FFBL, L1499, T x 415 and most maize varieties were systemically infected. Among the native grasses, only Dactylactenium aegyptium (L.) P. Beauv. and Roettboelia cochinchinensis (Louv.) Clayton were partially susceptible to downy mildew. Oospores from diseased sorghum and conidia from both infected sorghum and maize genotypes were found to be involved in the downy mildew disease cycle in the north‐central location, while only conidia from infected maize were detected and caused disease on maize in the southwestern location. This suggests the presence of a sorghum pathotype of downy mildew which infects both maize and sorghum in the north‐central zone and a maize pathotype which infects only maize in the southwestern zone. Oospores could not be detected in infected maize plants or in soils in the southwestern zone; however, infected maize plants with abundant sporulation were found in some hydromorphic areas during the dry season.