EMBU, KENYA
Regional Research Centre

NAIROBI, KENYA
CIMMYT

Development and dissemination of improved maize cultivars in Kenya: quality protein maize (QPM)

— Mutinda, CJ; Gethi, MM; Diallo, AO

Maize (Zea mays L.) is the most important staple food crop in Kenya. It is grown over a wide range of agro-ecological zones ranging from sea level to over 2180m above sea level (asl), with average rainfall varying from 250mm to over 2000mm per year. The total land area under maize production in Kenya is about 1.6 million hectares. 70–90% of this production is from small-scale farms. According to Food and Agriculture Organisation (FAO) statistics, the area under maize production (1972–1992) remained stagnant while maize production increased by 1.6% per year. Consumption, by contrast, increased at a rate of 2.1% a year.

Although maize is primarily a provider of calories, supplying almost 20% of the world’s food calories, it also provides about 15% of all food crop protein (National Research Council, 1988). From a nutritional perspective, however, the protein of maize and most cereals is deficient in the essential amino acids lysine and tryptophan (Olson and Hey, 1987). Opaque-2 mutant has been selected by most researchers as the most amenable for uses in applied maize breeding programmes (Bjarnason and Vasal, 1992). Opaque-2 maize, however, has several agronomic problems, such as low yield, ear rot and weevil damage, that make it unviable as a crop.

Breeding efforts at CIMMYT used the opaque-2 gene to convert normal maize, using modifier genes that gave the endosperm a normal or translucent appearance without loss of the increased protein quality contributed by the opaque-2 gene.

Although nobody would recommend the use of maize as a sole source of dietary protein, maize is a primary weaning food for babies and a staple food of the population in several African countries. Replacement of normal maize with QPM can be used for monogastrics (pigs and poultry) whose dietary source of the essential amino acids is mainly from feed.

The purpose of the project was specifically to identify superior QPM cultivars, adapted in the mid-altitude environment for dissemination and QPM maize germplasm, to infuse into our breeding programs in Kenya.

A trial of the QPM hybrids in 37 sites across eastern and southern Africa indicated superiority of two hybrids compared to the local checks (Table 1). These two hybrids were consequently nominated for the Year 2002 National Maize Performance Trial (NPT). Once their high grain yield performance and stability across sites in the mid-altitude environment is proven, they will be released to farmers.

Possible approaches to development of QPM have been summarised by Kevin Pixley (Kevin V. Pixley, 2002). According to Pixley, the most prudent approach for success in a breeding programme is to pursue several strategies simultaneously. Two ways of doing this include:

• Introducing QPM, recombining it with local (normal) materials, developing new QPM germplasm, and forming new hybrids or open pollinated varieties (OPVS), OR
• Introducing QPM, utilising the QPM to convert local (normal) materials to QPM, and releasing QPM versions of the normal varieties.

The option of conversion of local germplasm has the obvious disadvantage of the end product, which, after several years of research effort, will resemble the normal variety that was already available at the beginning of the project (except for enhanced nutritional value). And it may not be easy to convert germplasm to QPM. So there is no guarantee of rapid success with any given conversion project.

Our centre’s research thrust involves S1 selections in F2 QPM crosses between normal streak tolerant and QPM lines developed at CIMMYT-Zimbambwe. S1 selection for host plant resistance in maize has been found to be feasible (Mutinda et al., 1998).

Table 1. QPM hybrids evaluated across 37 sites in eastern and southern Africa, 1999/2002

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