Prevalence of pearl millet downy mildew in Eritrea
Abstract
A systematic survey of the prevalence and severity of downy mildew (Sclerospora graminicola) on pearl millet (Pennisetum glaucum) was conducted in 32 fields sown with pearl millet landraces and 7 fields sown with an improved ICRISAT variety (ICMV 221) in 8 subzones of Eritrea in 2000. Downy mildew incidence (%) was calculated from the ratio of diseased to total plants in 1 m2 subplots and 27 diseased leaf samples collected to assess variations in pathogenicity. Data on total rainfall and number of rainy days from sowing to soft dough were also collected. Downy mildew was present in most fields, but its incidence varied with location (40-78% incidence in the Keren subzone, but less than 1% in Mogolo and Dghe), and even the improved, resistant cultivar ICMV 221 had between <1-28% disease incidence. The variation in downy mildew incidence did not directly relate to variation in total rainfall or to the number of rainy days, but was probably related instead to variation in pathogen virulence within the region. There was also no consistent effect of rotational cropping sequence on disease incidence