VIEW ARTICLE

Ecology and Epidemiology

The Role of Sporangia in the Epidemiology of Pearl Millet Downy Mildew. S. D. Singh, Plant pathologist, Millet Improvement Program, International Crops Research Institute for the Semi-Arid Tropics, ICRISAT P.O., Patancheru, 502 324, Andhra Pradesh, India; R. J. Williams, principal pathologist, Millet Improvement Program, International Crops Research Institute for the Semi-Arid Tropics, ICRISAT P.O., Patancheru, 502 324, Andhra Pradesh, India. Phytopathology 70:1187-1190. Accepted for publication 3 June 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-1187.

Several experiments were conducted at ICRISAT Center on the role of sporangia in the epidemiology of pearl millet downy mildew (DM). Exposure of field-grown plants to sporangial inoculum provided by earlier planted "infector rows" resulted in considerably more DM on all cultivars tested than was obtained by exposure of these cultivars to oospores by several other methods. In large isolated field plots of DM-susceptible hybrids, DM incidence and severity were considerably greater in plots with a central source of sporangia (potted plants with sporulating DM-infected leaves) present from crop emergence than in plots with no such initial sporangial source. Sporangia remained infective for up to 340 m downwind from a sporangial source during the rainy season, but during the dry post-rainy season no infection occurred at distances more than 80 m from a sporangial source. The significance of these results in the epidemiology of pearl millet DM and their application for large scale field screening for DM resistance are discussed.