Effect of Striga Species on Sorghum (Sorghum Bicolor L Moench) Production and its Integrated Management Approaches

Abstract

Sorghum is the most widely cultivated cereal crop in the world, particularly in the semi-arid tropical region of the countries and is staple food crop for millions of the food-insecure people. However, number of biotic and abiotic factors are limiting sorghum grain yield. These constraints are: diseases, drought, soil fertility, and pests, notably parasitic weed striga species. Among biotic stress, striga weed species are one of the most biological constraints which cause yield losses and perturb food security and human welfares in the world. Striga is an important parasitic weed causing substantial economic losses in cereal and legume crop production in subSaharan Africa. Striga spps are obligate root-parasitic plants of the major agricultural cereal crops including sorghum, maize and millets in tropical and semi-arid regions of Africa, Middle East, Asia and Australia. Striga can cause severe to complete losses in crop grain yield. Production of cereal crops such as sorghum, maize, rice and millet is threatened by striga species in different parts of the world particularly in semi-arid tropics of Africa. The percentage of crop yield loss due to striga infestations depends on amount of striga seeds in the soil, distribution of rainfall, soil fertility and variety of cereal species grown. Striga species spend most of their life cycle underground and develop above ground for stem formation and flowering. Striga stands for the principal biological constraints of crop production than any other biological pests such as insects, birds, or plant diseases in Sub-Saharan Africa. Sorghum production in world is seriously constrained by both biotic and abiotic stresses. Among the biotic stresses is witchweed (Striga spp.), a noxious parasitic weed causing major damage in cereal crops. However, resistance through reduced germination stimulant production or altered germination stimulant composition provides a sustainable and most effective way for managing the parasitic weeds. Integrated striga management approaches such as a combined use of Striga resistant varieties and Fusarium oxysporum fsp. Strigae (FOS), a biocontrol agent of striga, is an option to control the parasite and to boost sorghum productivity. Understanding host gene action influencing striga resistance, with or without FOS treatment, is key to develop improved sorghum varieties with durable resistance and high yield. Varying levels of resistance have been identified and exploited in the breeding programs of several crops. Considerable efforts have been invested in breeding for striga resistance in cereals and significant progress has been made in the development of improved selection methods.