In the developing world, approximately 60 percent of the total maize area is planted to improved materials (hybrids or improved open-pollinated varieties), and the rest to local materials. If Argentina, Brazil and China are excluded, however, the proportions are reversed: only 40 percent of the total maize area is planted to improved germplasm. Since most of the required increases in maize production in the foreseeable future is likely to come from yield growth rather than area expansion, this means that further deployment of improved maize hybrids and varieties is crucial.
Genetically, there is no relation between grain colour and yield potential. However, over the years, cumulative investment in maize improvement research has been far greater for yellow maize because it is the dominant germplasm adapted to temperate environments in the developed world. In 1990, expenditures on maize breeding research in the private sector of the United States alone totalled about US$ 110 million (Byerlee and Lopez-Pereira, 1994). By contrast, annual costs of total maize research by the public sector in all developing countries, including both breeding and crop management research, may have been in the range of US$ 80-100 million in the early nineties, and all international public sector and multinational private sector research for developing countries (much of which was directed at maize breeding) would have been about US$ 20 million annually9
9 These crude estimates are based on information in Pardey, Roseboom, and Anderson (1991), and in CIMMYT data files.
As noted earlier, however, much of the maize in the developing world is produced in non-temperate environments, and a far greater proportion of that maize is white. There are at least two implications of this for varietal development. First, near-direct transfer of maize varietal technology from the developed world, with its long history of research on yellow maize for temperate environments, is unlikely to provide many benefits in the developing world outside of Argentina and China, or a few other countries, such as Chile, Turkey, or parts of Mexico. Second, the relative importance of white maize in the developing world, as suggested by production and area figures, implies that maize varietal improvement in developing countries would tend to concentrate somewhat more on white germplasm.
Outside of Asia, the majority of maize varieties and hybrids released by the public sector in the developing world have indeed been white (Table 8). The figures for Latin America, however, are heavily influenced by Mexico and other Central American countries, and are also biased towards white releases because private sector hybrids, which are mostly yellow-grained, are not included 10. In the sub-tropical/mid-altitude and highland environments, where white maize has traditionally been more important, there has been a tendency for public sector releases to be more yellow than white in recent years, and there may be some shift towards increased release of yellow materials regardless of the type of seed.11 These trends suggest that the increased preference in the developing world for the use of maize as livestock feed may be shifting emphases somewhat in breeding towards yellow maize (Lopez-Pereira and Morris, 1994).
10 In general, white maize production is associated with smaller, semi-subsistence farmers and yellow maize with larger, more commercially oriented farmers. In Mexico, nearly all private sector hybrids are white, including releases by multinationals.
11 Improved open-pollinated varieties have sometimes been considered more appropriate for subsistence or semi-subsistence farmers, while hybrids have been used more by commercial producers.
TABLE 8 - Maize: improved varieties and hybrids released in developing countries by grain colour, 1966-90
|
Geographic Area |
Total Releases |
Colour |
|
|
White |
Yellow |
||
|
Number |
(............percent............) |
||
|
Sub-Saharan Africa |
199 |
72 |
28 |
|
West Asia and North Africa |
26 |
65 |
35 |
|
South, East and Southeast Asia1 |
169 |
21 |
79 |
|
Latin America and the Caribbean |
318 |
66 |
34 |
|
TOTAL |
712 |
57 |
43 |
1 Excludes temperate China.
Source: M.A. López-Pereira and M.L. Morris, Impacts of International Maize Breeding Research in the Developing World, 1966-1990, Mexico, D.F., CIMMYT, 1994.
The International Maize and Wheat Improvement Center (CIMMYT) includes both white and yellow materials in its breeding programmes, which are aimed at developing countries. The number of white pools (pre-breeding materials of broader genetic composition) roughly equals the number of yellow pools. However, more populations of somewhat narrower genetic make-up, or materials directed at inbred development, are white rather than yellow. CIMMYT's Asian Regional Maize Program tends to concentrate more in the development of yellow maize populations. On the other hand, the Mid-Altitude Research Station in Zimbabwe, which focuses on Eastern and southern Africa, handles almost completely white materials, with the exception of a few lowland tropical inbred lines. These figures should be treated with caution since the number of pools, populations and hybrid-oriented materials does not indicate the relative emphasis given to their improvement; but the colour patterns above are consistent with the production patterns world-wide and in given regions. The production projections presented below assume the share of white maize in total output will not change significantly over the years to come. However, as maize research and development systems are increasingly privatized and oriented towards commercialized production and livestock, the needs of consumers who prefer white maize may become a greater challenge, as suggested by some of the trends in public sector releases observed above. In general, however, an even larger constraint to the development and diffusion of improved white maize hybrids and varieties to farmers is the concomitant development of efficient seed industries that supply adequate quantities of quality seed at prices that encourage optimal levels of seed use. A well-functioning seed industry is also characterized by a sufficient variety of products, and seed which is available to farmers when and where it is needed (Morris, 1997). However, in many developing countries these functions are not adequately met at present.
In many instances in developing countries, yield gains from crop management changes in maize, both white and yellow, could be greater than those from varietal change alone. This consideration must be qualified by the generally more location-specific nature of crop management research and the extension efforts required to disseminate crop management information to farmers, especially small farmers. In other words, the research and diffusion costs, for equivalent yield increases from varietal development and crop management research, may in some cases be lower for varietal improvement than for crop management. Nonetheless, in most countries varietal improvement and crop management research should be viewed as complementary, not competitive activities.
In developing countries, including those where most of the world's white maize is produced, soil fertility management is probably the most important crop management problem. Within this area, overcoming nitrogen deficiencies through inorganic or organic means, or through improving nitrogen use efficiency in maize varieties or hybrids, is by far the most widespread concern. Also important are questions related to phosphorous or zinc uptake by the maize plant (G. Edmeades, personal communication). Use of inorganic fertilizers on maize is considerably lower in much of the developing world than it is in developed countries, with fertilizer use on maize being particularly low in sub-Saharan Africa.
A close second crop management problem in developing country maize production is moisture stress. Unlike soil fertility, moisture stress is less easily addressed by input management, in this case water control, since most maize in the developing world is non-irrigated and large-scale expansion of irrigated maize area is unlikely. Also, unlike soil fertility, moisture availability over the season is subject to considerable uncertainty when the growing period begins.
In general, the third most important management problem in developing country maize production is weed control, perhaps followed by plant density management. Complicating the development of management options is the possibility that all four general factors mentioned here, soil fertility, moisture availability, weeds and plant density, are likely to interact with one another.
Because of the greater location specificity of crop management research, it is more difficult to characterize the worldwide effort in crop management research for maize than the resources employed on maize research in general or germplasm development in particular. Nonetheless, data on numbers of scientific staff doing public sector research in developing countries suggest that considerable resources, world-wide, are expended on crop management research on maize. Furthermore, new developments in data base collection and management, crop modelling and geographic information systems may loosen the constraints of location specificity.
