Michael Abberton Head, GRC, IITA-Ibadan
In the early years, maize improvement focused on lowland rust and lowland blight, which had been seen for a long time as the major factors limiting yield in lowland West Africa. Together with rapid selection for key agronomic traits, this focus resulted in very successful varieties grown over large areas in West and Central Africa during the 1980s.
A recurring feature of plant breeding efforts at IITA throughout the 50 years has been the need to address new challenges particularly with respect to pests and diseases. In the 1970s for maize this was maize streak virus (MSV) with the basis for success being the development of a robust protocol to screen for resistance and the working together of IITA scientists from different disciplines. These successes were achieved through breeding open-pollinated varieties, but in the late 1970s and early 1980s a program of inbred line and hybrid development was initiated. These allowed the production of higher yielding varieties and supplied NARS in the region with inbred lines carrying good characteristics including disease resistance. The development of hybrid maize at IITA was an important factor in the emergence of a number of seed companies, particularly in Nigeria.
Great progress has been made in recent years in the development and release of maize varieties resistant to the parasitic weed Striga, a major threat to maize production in many parts of sub-Saharan Africa, and varieties with increased levels of micronutrients, especially provitamin A.
The release and adoption of early maturing varieties has allowed the expansion of the area where maize can be grown to include semi-arid parts of Burkina Faso, Mali, and Niger.
An early focus of cassava improvement, from 1971, was on resistance to cassava mosaic disease (CMD). This was achieved in a triumph of classical plant breeding that had a massive impact in sub-Saharan Africa. Combining resistance to CMD with that for cassava bacterial blight (CBB) and high root yields turned cassava from a crop used in times of famine to a major source of calories for people in both rural and urban areas. This was an achievement that demonstrated clearly the impact that wellfocused plant breeding could have on food security. In 2002, a new and successful battle was fought against a more virulent strain of CMD in Nigeria.
Through various iterations of its strategy, IITA has maintained a pan-African approach to cassava improvement and this continues with breeding programs in all four subregions of sub-Saharan Africa. In the 1990s, IITA and the National Agricultural Research Organisation (NARO), Uganda developed a strong partnership to fight CMD in that country. Partnership with NARS through the Southern Africa Root Crops Research Network and the Eastern Africa Root Crops Research Network in the 1990s were important in the introduction and collaborative development of new cassava varieties in the two subregions. A major current focus in Eastern Africa is understanding the genetic control of, and breeding for, resistance to cassava brown streak virus.
The adoption of released cassava varieties with increased levels of provitamin A under the HarvestPlus program since 2009 is important, particularly for the nutrition and health of mothers and young children.
IITA soybean breeding essentially developed this species as a viable crop in many parts of sub-Saharan Africa. The development and introduction of soybean lines with “promiscuous nodulation” and the bringing together of this trait with desirable production characteristics, greatly increased the yield of soybean, particularly in Nigeria. To these was added greater seed lifespan to overcome decline of viability before planting. Until their development starting in the early 1980s, high yielding varieties successful in other parts of the world, could not be grown in sub-Saharan Africa without rhizobial inoculation. The impact of greater soybean production from adoption of new varieties and the promotion of its utilization in various food forms were seen in the enhanced nutritional status of children. New varieties have been developed and released in Nigeria that combine high yields with resistance to soybean rust that threatens increase in, and stability of, production of the crop.
Yam is a key staple crop for West Africa and the focus has been on the breeding of the two most widely grown species: water yam (indigenous to Asia) and white yam (indigenous to West Africa). Improved varieties have been developed and released in Nigeria and other countries with higher yields, good quality and storability, and increased disease resistance. For clonal crops, improved propagation methods go hand-inhand with varietal development. IITA working together with the National Root Crops Research Institute, Nigeria, developed and promoted the minisett method of rapid propagation and later introduced other methods based on vine cuttings and aeroponics.
Cowpea is indigenous to sub-Saharan Africa and IITA’s GRC houses the global collection”of more than 17,000 accessions, many of which have been used extensively in variety development. The early collection of more than 8,000 accessions was screened for disease and pest resistance from the 1970s and varieties were developed and released for both the humid areas and savannas. In the late 1980s, the cowpea breeding program moved from Ibadan to Kano with a focus on breeding for savannas and dual grain and livestock fodder purposes. The impact from adoption of these varieties has been well demonstrated, especially enhanced food security during the “hungry season” of the savannas. Fast maturing (60 days) cowpea varieties with increased disease resistance were particularly important.
East African highland banana and plantain in West Africa are important sources of income and nutrition and IITA has breeding programs for both these categories of the crop. A major success was the development and distribution of black sigatoka resistant cooking banana. These were developed through a collaboration between IITA Onne station and partners including the Agricultural Development Program at Owerri. This had a major effect on the acceptability and cultivation of cooking banana in Southeastern Nigeria. Work continued to develop black sigatoka resistant hybrids in plantain. Improved hybrids have now been distributed in many countries inside and outside Africa.
Collaboration and Capacity Development
A continuing preoccupation of IITA and its breeding programs, from the outset, has been to work closely with NARS. This involves transfer of breeding lines, joint varietal testing, and training. In general varieties developed by IITA and partners are released through the NARS.
IITA’s breeding programs continue to develop new varieties for adaptation to changing environmental conditions and market preferences in selected target regions. The programs increasingly use new tools and approaches to raise the efficiency and effectiveness of breeding and selection and they collaborate with colleagues in ancillary disciplines and the private sector to improve seed systems. Among other things, these improvements will reduce the periods required for coming up with new varieties that are superior to those currently in use and speed up the delivery of their seeds and planting materials to end-users.