155 views | Akanimo Sampson | November 14, 2020
International Institute of Tropical Agriculture (IITA) scientists have made significant advances in the longstanding efforts of the IITA Maize Improvement Programme (MIP) to develop genotypes with durable resistance to Striga parasitism using molecular markers.
The team of IITA scientists, molecular breeders, and geneticists, is coordinated by the Institute’s early and extra-early Maize Programme Lead, Baffour Badu-Apraku.
Badu-Apraku is a maize breeder with a PhD in Genetics and Plant Breeding from Cornell University, Ithaca, USA. He was the Coordinator of IITA’s West and Central Africa Collaborative Maize Research Network (WECAMAN) from 1992 to 2006.
Before joining IITA, he was the leader of the Ghana National Maize Program and also the Joint Coordinator of the Ghana-CIDA Grains Development Project (GGDP) from 1987 to 1992. Under his leadership, a QPM laboratory was established for the screening of maize genotypes for high lysine content in Ghana.
The QPM variety, Obatanpa GH, was developed and released and has been widely adopted in Ghana and in Benin, Togo, Mali, Senegal, Cameroon, Côte d’Ivoire, Burkina Faso, Nigeria, Chad, Guinea, Uganda, Malawi, Swaziland, Zimbabwe, Mozambique, South Africa, and Ethiopia.
In addition, appropriate recommendations for maize and legume-based cropping systems and several maize, cowpea, and soybean varieties were released and widely adopted in Ghana. Through his maize breeding program at IITA since 1992, several Striga-resistant and drought-tolerant early and extra-early populations have been developed and are serving as valuable sources of varieties and inbred lines for breeders of the subregion.
Over the years, many early and extra-early Striga, drought and low soil nitrogen-tolerant varieties and more recently hybrids have been developed in his program, formally released, and widely adopted by farmers in the subregion.
He has also conducted research to improve maize selection and evaluation procedures including breeding for resistance to multiple stresses, identification of indirect selection criteria, and grouping of evaluation sites into mega-environments using the GGE biplot analysis of genotype × trait interaction and factor analysis of repeatability estimates.
Badu-Apraku’s most recent achievement includes the development of Striga-resistant and low soil nitrogen-tolerant extra-early varieties and hybrids with genes for tolerance to drought at the flowering and grain-filling periods.
However, the major advances are:
Identification of genomic regions significantly associated with indicator traits for Striga resistance under infestation in early maturing tropical maize inbred lines in a genome-wide association study (GWAS)
Identification of quantitative trait locus (QTL) controlling resistance to Striga in two extra-early maturing maize mapping populations Identification of QTL controlling resistance to Striga in an early maturing mapping population containing genes derived from a cross between normal endosperm maize and wild maize (Zea diploperennis)
Parasitism by Striga hermonthica in sub-Saharan Africa is a major cause of dramatic maize yield losses and threatens over 300 million people’s livelihoods. Farmers in the sub-region often experience complete crop failure under severe infestation and have been forced to abandon their farmlands.
About two decades ago, IITA initiated a project, funded by the Rockefeller Foundation to develop high–yielding and Striga–resistant inbred lines and hybrids as well as identify QTL for marker–assisted selection (MAS) to facilitate and speed up the transfer of resistance genes into susceptible genotypes.
Through this project, IITA scientists have made considerable advances in developing several maize genotypes with durable Striga resistance genes using conventional breeding approaches. They have developed several populations, varieties, inbred lines, and hybrids with durable resistance and distributed these to the national maize programs in SSA. However, progress in developing molecular markers for use in MAS has been very slow.
Nevertheless, in 2017, with funding support from the Bill & Melinda Gates Foundation , the IITA-MIP has made remarkable progress under the DTMA/STMA Project through gene stacking in efforts to develop early and extra-early inbred lines using novel resistance genes from the wild maize that support little or no emergence of S. hermonthica into susceptible but outstanding genotypes.
The scientists’ breeding efforts have resulted in developing several multiple stress–resistant early and extra-early inbred lines and hybrids with combined resistance/tolerance to Striga, drought, and low soil nitrogen.