the Symposium on Wheats for More Tropical Environments - cimmyt

5 _Country ReportsSelecting and Introducing Wheatsfor <strong>the</strong> Environments of <strong>the</strong> TropicsC.E. Mann, Wheat Program, CIMMYT, Bangkok, ThailandAbstractThe estimated wheat area in <strong>the</strong> tropics, i.e., between 23ON and 23°5 latitudes,is 3 to 4 million hectares. The potential existsfor <strong>the</strong> expansion ofthis area as aresult ofresearch. A survey ofclimatic conditions and wheat yield levels from 28experiment stations in 15 countries between 1 and 39° Nand S latitudes showsonly a moderate association between climate and yield. Average minimumtemperaturefor <strong>the</strong> month afterflowering has <strong>the</strong> highest correlation with yield(r= -.51), indicating that o<strong>the</strong>r more controllablefactors, such as cropmanagement and germplasm, have considerable influence on yield. Importantresearch objectivesfor tropical wheat are presented in this paper, and <strong>the</strong>importance ofstrong national programs is stressed.The purpose of this overview of tropicalwheat is to establish a frame ofreference for <strong>the</strong> country reports. Afterdiscussing <strong>the</strong> present wheatproduction situation in <strong>the</strong> tropics and<strong>the</strong> interests of national programs inpursuing wheat research, a tentativelist of production constraints which arecommon to many places in <strong>the</strong> tropicswill be presented. This is done mainlyfrom <strong>the</strong> author's experience; <strong>the</strong>country reports may ei<strong>the</strong>r substantiatethis list or emphasize o<strong>the</strong>r factors,some of which may be generalproblems applicable to <strong>the</strong> tropics, ando<strong>the</strong>rs, problems specific to certaintropical environments.The Wheat Situationin Tropical CountriesThe word "tropics" as used here refersto <strong>the</strong> area between <strong>the</strong> tropiCS ofCancer and Capricorn, that is, between23°N and 23°5 latitude. There are 85countries that have 20,000 or moresquare kilometers of territory within <strong>the</strong>tropics. Of <strong>the</strong>se, some have no interestin wheat production, and some have noarable land in <strong>the</strong>ir tropical zones.Eliminating <strong>the</strong>se. <strong>the</strong>re are still 57countries which have grown wheat in<strong>the</strong> tropics at some time during <strong>the</strong> lastthree years, ei<strong>the</strong>r experimentally orcommercially (Table 1).Among those countries that lie entirelywithin <strong>the</strong> tropics, or which grow <strong>the</strong>majority of <strong>the</strong>ir wheat in <strong>the</strong> tropics,566,000 hectares of wheat were grown;nearly half of this amount was in <strong>the</strong>Sudan. A more meaningful figure isreached by also including thosecountries that, although <strong>the</strong> majority of<strong>the</strong>ir wheat is grown outside <strong>the</strong>tropics, have substantial wheat areaswithin <strong>the</strong>ir tropical zones as well. Thisallows <strong>the</strong> inclusion of <strong>the</strong> vast areas ofpeninsular India and sou<strong>the</strong>rn China,<strong>the</strong> wheat-growing area in nor<strong>the</strong>rnBrazil, and smaller portions of o<strong>the</strong>rcountries, such as <strong>the</strong> lowlands ofBolivia and sou<strong>the</strong>rn Bangladesh. Thisfigure is estimated at between 3 and 4million hectares, with more than half of<strong>the</strong> total in India. Clearly, wheat is nota completely new crop in <strong>the</strong> tropics.Table 1 indicates <strong>the</strong> growing interestin expandJng wheat production intotropical areas; a number of countrieswhich grow no wheat commercially are,never<strong>the</strong>less, beginning to do someresearch on wheat.