Demand-Driven Technologies for Sustainable Maize ... - IITA

Despite the high potential of maize in the savanna ecology, maizeproduction and productivity in this zone are constrained by severalmajor biotic and abiotic factors prominent among which are theparasitic weed, Striga hermonthica (Del.) Benth, drought, and decliningfertility of the soils.Striga hermonthica constitutes a major constraint to the rapid spreadand hence to increased maize production and productivity in thesavannas of WCA. The levels of infestation are often so high that maizecan suffer 100% yield loss and farmers may be compelled to abandontheir fi elds. Annual yield losses due to Striga species in the savannaecology are estimated to be US $7 billion and threaten the livelihoodsof over 100 million African people (M’Boob 1986).Host plant resistance is considered the most practical and effectivemeans for the control of damage caused by Striga (Parkinson et al.1989; Kim, 1991; 1994). A Striga breeding program was thereforeinitiated in Côte d’Ivoire in 1994 through funding support of theInternational Institute of Tropical Agriculture (IITA) and West andCentral Africa Collaborative Maize Research Network (WECAMAN)to combat the threat posed by S. hermonthica to the rapid spread ofmaize into the savannas. The objective of the program is to developmaize populations, varieties and inbred lines that combine earlinesswith resistance to S. hermonthica. Using inbreeding, backcrossing,hybridization and recurrent selection methods, two extra-early sourcepopulations and several extra-early varieties and inbred lines withresistance/tolerance to Striga and the major important diseases in WCAhave been developed in the IITA-WECAMAN program. Badu-Aprakuet al. (1999) reported earlier advances in the breeding program.However, information is lacking on the performance of the recentlydeveloped Striga resistant/tolerant varieties, synthetics and inbredlines, and on the advances made in the recurrent selection programinvolving the two extra-early source populations. Furthermore, thereis a need to classify the extra-early Striga resistant/tolerant inbred linesin the breeding program into appropriate heterotic groups in order tomaximize their use. The objectives of this paper were to (1) presentan overview of the strategy and recent progress in developing Strigaresistant extra-early maturing maize populations, varieties and inbredlines, (2) report on the performance of extra-early maturing maizevarieties and inbred lines evaluated for Striga resistance, and (3) assessgenetic diversity in the Striga resistant extra-early maturing inbred linesusing UPGMA cluster analysis in an effort to select parental inbredsfor the development of heterotic populations and for introgression ofdesirable genes from the inbred lines into elite populations.27