The challenge
- Maize is the major staple food in in eastern and southern Africa and is therefore important for agriculture and livelihoods.
- Currently, demand outstrips supply and the region is a net importer of maize, annually.
- However, maize yields in Africa are very low, only 1.3 tons per hectare (t/ha), compared to 4.9 t/ha worldwide, 8.4 t/ha in industrialized countries and 3.3 t/ha in developing countries in other parts of the world.
- Insect pests in the field and in storage are among the factors that reduce yields and food availability in eastern and southern Africa. Various species of stem borers typically cause maize losses of up to 15% in susceptible germplasm in the infested ecologies, while the storage pests, maize weevil (Sitophilus zeamais) and larger grain borer (LGB) (Prostephanus trancutus), cause more widespread losses estimated at between 20-30%.
- It is estimated that more than 100 million people live in high risk areas where poverty levels are highest, due to other factors including drought, low soil fertility, and Mosaic Streak Virus (MSV).
- Host plant resistance (HPR) to storage pests using conventional breeding is a seed-embedded technology and, therefore, the easiest control method for farmers, as well as being the most environmentally safe.
Breeding for resistance: germplasm and other technologies
Despite the heavy losses caused by stem borers and storage pests in Africa, few maize improvement programs include breeding for resistance. This is likely due to the genetic and logistical challenges posed by screening and selection for insect resistance. CIMMYT and partners have developed germplasm and other technologies to combat stem borers and storage pests. Through IRMA II and other efforts, germplasm resistant to stem borers has been developed and released in Kenya and Vietnam. Breeding efforts using resistance from a few Caribbean germplasm bank accessions have resulted in hybrids that demonstrate superiority in grain yield and increased resistance to maize weevils. Data show losses of just 6% for yield compared to 20% for the checks, and increased LGB resistance with 20% loss compared with 42% for the checks.