Challenges to the exploitation of host plant resistance for Striga management in cereals and legumes by farmers in sub-Saharan Africa: a review

Abstract

ABSTRACTStriga hermonthica, Striga asiatica and Striga gesneroides are obligate root parasites that cause severe yield losses in cereals and legumes in sub-Saharan Africa. Genetic control of Striga through resistance is widely considered to be the most practical and economically feasible method for long term control. The paper presents a comprehensive account of the Striga resistance mechanisms and environmental limitations to their usage in sub-Saharan Africa. Components of Striga resistance in cereals and legumes include low germination stimulant production, low haustorial initiation factor, mechanical barriers, incompatibility, antibiosis and Striga avoidance due to root growth habits. The successful exploitation of resistance has been limited by existence of specificity towards hosts, parasites that have evolved races specific host cultivars, Striga genetic variance which enables parasite to adapt to new resistance alleles and diverse hosts which support the parasite even in the absence of cereals together with low fertility due to nutrient mining in the smallholder sector. The results imply that different resistance mechanism may need to be present in genetically heterogeneous varieties or cereals with different resistance mechanisms may be rotated in the same field. Comprehensive Striga management systems should also address soil fertility in the small holder farmers of sub-Saharan Africa.