Abstract only

Approximately one-third of the developing world's wheat area is located in environments that are regarded as marginal for wheat production because of drought, heat, and soil problems. Nearly one-third of the area planted to bread wheat and about three-fourths of the area planted to durum wheat suffer from severe drought stress during the growing season. Despite these limitations, the world's dry and difficult cropping environments are increasingly crucial to food security in the developing world. Worldwide, investment in irrigation infrastructure continues to fall, while population growth and demand for wheat are increasing. Gains in wheat productivity in marginal environments are important because it is unlikely that increased productivity in the favorable environments will be sufficient to meet the projected growth in demand for wheat from the present to 2020. The demand for wheat is projected to be 40% greater than its current level of 552 million tons by 2020. Improved productivity in marginal areas would improve food security for the poorer populations that live there. It is widely believed that the Green Revolution had very little effect in marginal environments, where the harsh agricultural conditions and slow spread of Green Revolution technology resulted in very modest yield gains. For some time, the development community has been concerned about progress in marginal areas and the level of research resources allocated to those areas. This paper provides new information to address these issues by answering the question: Is growth in wheat yield potential in marginal environments approaching the levels attained in favorable environments? More specifically, we: *describe breeding research that improved productivity in marginal environments (with an emphasis on CIMMYT's wheat breeding strategies); *estimate rates of growth in wheat yield potential in marginal and favorable environments; *examine the crossover and spillover of wheat varieties from favorable to marginal environments; *identify implications for wheat productivity growth in marginal environments; and *discuss future challenges for marginal environments. Data for this study were obtained from CIMMYT's Elite Spring Wheat Yield Trial (ESWYT), grown in 246 locations in 65 countries between 1979 and 1999, and from CIMMYT's International Spring Wheat Yield Nursery (ISWYN), grown in 411 locations in 82 countries between 1964 and 1995. Nurseries such as the ISWYN and ESWYT are one way in which breeders in developing countries regularly gain access to and exchange a large number of new wheat varieties bred by CIMMYT and partners in national research programs. This system of breeding, germplasm and information exchange is often referred to as "the international wheat research system." Its impact on wheat yield trends in marginal environments will be discussed later. Data on spring wheat varieties planted in 1990 and 1997, including their pedigrees, year of release, area planted to each variety, and target mega-environment, were obtained from the CIMMYT Wheat Impacts database. A mega-environment (ME) is a broad, frequently transcontinental but not necessarily contiguous area with similar biotic and abiotic stresses, cropping system requirements, consumer preferences, and potential volume of production. Mega- environments usually encompass more than one country and are useful for defining breeding objectives, because each ME comprises millions of hectares that are relatively homogenous for wheat production. The ISWYN data were grouped into two periods: the Green Revolution period (1964-78) and the post-Green Revolution period (1979-95). The ESWYT data (1979- 99) was taken from the latter period. The average of the top three wheat yields for each location per year was used in the analysis. Locations were grouped by ME.

Socioeconomics Program

English

0309|R01CIMPU|AGRIS 0301|AL-Economics Program

Juan Carlos Mendieta

CIMMYT Staff Publications Collection