Striga research in sorghum and millets in southern Africa: status and host plant resistance.
The distribution of 13 species of Striga in the 10 countries of southern Africa is discussed. Earlier reports on some of these species are reviewed and a few of the observations are updated. Screening and evaluation of sorghum germplasm from Angola, Botswana, Lesotho, Swaziland and Zimbabwe, and exotic lines and varieties from outside the region, indicate that resistance is shown by some cultivars in the 2 groups of materials. From accessions in the region, between 2 and 20% were found to be resistant. Among the introduced lines, some cultivars previously identified as resistant to white Striga asiatica in India (SAR lines) were also found to be resistant to red S. asiatica, S. forbesii and S. hermonthica, the 3 most economically significant species in the region. The cultivar SAR 19 was shown to have multiple resistance to Striga, being resistant to red S. asiatica and S. forbesii and tolerant to S. hermonthica. Cultivars SAR 16, SAR 26, SAR 29 and SAR 35 were also resistant to red S. asiatica and S. forbesii, while SAR 29 and its hybrid SPL 38A × SAR 29 showed potential for resistance to S. hermonthica. Host specificity of red S. asiatica and S. hermonthica to sorghum and maize was demonstrated in Tanzania. Pearl millet was not attacked by either of the 2 species. Some evidence of intracrop-specific and intercrop-specific strains of these 2 species were obtained in Botswana and Tanzania.