Maize is grown in diverse climatic conditions across tropical environments. Currently more than 80 million hectares of maize are planted in non-temperate maize environments in the developing world. Of this total, approximately 51.5 million hectares are sown to lowland tropical maize, thus constituting roughly 65% of the developing world's non-temperate maize area. In more recent years, a serious effort has been made to characterize maize mega-environment and to use this information as a basis of priority setting for various classes of maize germplasm that are needed. In the CIMMYT Maize Program we have used maturity as an important criteria within a particular ecological adaptation to classify environments. Considering maturity alone, there are at least four major groups designated as extra-early, early, intermediate, and late (extra-late materials are also grown in restricted areas but their importance is relatively negligible). According to maturity the distribution of area planted to different classes is as follows: 3.5, 12, 19 and 17 million hectares for extra early, early, intermediate and late maize tropical germplasm. Annually more than 25 million hectares are sowed in the developing world with CIMMYT related cultivars. Several constraints affect maize production in the lowland tropical maize ecology. Among the abiotic factors, the most important ones are drought, water logging, low fertility, and acid soils. Among the biotic stresses, the most important are B. maydis leaf blights, tropical rusts, stalk rusts and ear rots. Other diseases are important in only certain regions, such as corn stunt disease in Central America, downy mildew in Asia, and maize streak virus in Africa. Insects such as fall armyworm, stem borers, com earworms, and stored grain pests also cause serious losses to maize production in different regions. Over the past decade or so, the Maize Program has established several research activities aimed at particular problems in the regions where the problems are endemic and the work can thus be handled most efficiently. This is particularly true for downy mildew, maize streak virus and the acid-tolerant maize work. For corn stunt disease, we still provide assistance to breeding work from headquarters. The lowland tropical maize subprogram at headquarters is involved in the following activities: .Germplasm development .Population improvement .Hybrid development and testing .Training activities Some 10% of subprogram resources are devoted to germp1asm development, 35% to population improvement, and roughly 55% to hybrid related activities, including the intermediate steps or synthetic formations based on several combining abilities. Important highlights of the activities conducted in the year 2000 and 2001 are described below.

English

0408|AGRIS 0401|AL-Maize Program

Juan Carlos Mendieta

CIMMYT Staff Publications Collection