Striga on rice in West Africa; crop host range and the potential of host resistance.
Striga aspera and S. hermonthica can cause serious losses in upland rice in the guinea savanna areas of West Africa. In pot experiments, seed from Striga spp., collected from maize and rice crops in northern Cote d'Ivoire, were sown with maize, rice, millet and sorghum. S. aspera, collected from rice and maize, grew on maize, sorghum and rice, but not on millet. S. hermonthica from maize, sorghum or rice showed no specificity and parasitized all four test crops. S. asiatica collected from maize and Andropogon sp. grew on maize and rice, but not on millet. In field experiments, five cultivars of Oryza glaberrima and two cultivars of O. sativa, IR47255-B-B-5-4 and IR49255-B-B-5-2, offered partial resistance to S. aspera. These rice cultivars also showed lower levels of parasitization by S. hermonthica. Parasitization of rice by 17 Striga stems/m2 reduced rice grain yield by about 50%. Growth of O. glaberrima appeared to be less affected by Striga parasitization than that of a susceptible O. sativa cultivar.