Evaluation of wild and weedy sorghums for downy mildew resistance

Abstract

Downy mildew of sorghum [Peronosclerospora sorghi (Weston & Uppal) C.G. Shaw], is one of the widespread diseases of sorghum [Sorghum bicolor (L.) Moench] (Williams 1984). Systemically infected plants fail to produce panicles, resulting in complete loss of grain yield (Craig and Odvody 1985). Sources of resistance to this disease have been reported in wild sorghums (Mughogho et al. 1982). In an attempt to identify additional sources of resistance, we screened 308 wild and weedy sorghums belonging to 29 species and sub-species in greenhouse conditions at ICRISAT Asia Center (IAC) during 1990-91. Seeds of each accession, supplied by ICRISAT's Genetic Resource Division, were sown in two 12-cm square pots. Seedlings at the coleoptile-to-one-leaf stage were spray-inoculated with conidia (6xl05 conidia mL_1) as described by Reddy et al. (1992). The IAC isolate of the pathogen was used. Downy mildew incidence was recorded three weeks after the inoculation.