the Symposium on Wheats for More Tropical Environments - cimmyt

23grain-filling stages are required.Screening efforts are underway toidentify germplasm of this type. Itsdevelopment would benefit tropicalwheat areas, as well as manytraditional wheat-producing areas, suchas Bangladesh, nor<strong>the</strong>ast India,sou<strong>the</strong>rn Pakistan, South China. <strong>the</strong>Cerrados of Brazil and o<strong>the</strong>r subtropicalareas.Better ellsease resistanceAs mentioned earlier, diseases will be aproblem primarily in <strong>the</strong> more humidregions. Leaf rust. stem rust.helminthosporium, fusarium, root rotsand possibly barley yellow dwarf are<strong>the</strong> diseases that will most likely beimportant. Good resistance to leaf rustand stem rust are available in existinggermplasm. Intensive efforts, frequentlyin cooperation with national programsaround <strong>the</strong> world, are now underway toidentify sources of resistance toHelmtnthosportum and Fusariumspecies. A cooperative program hasbeen initiated with China to identifywheats with better resistance tofusarium head scab. and a similarcooperative effort is being pursued withBrazil to identify better resistance toHelmtnthosporium species. Theseefforts, in combination with o<strong>the</strong>rs,should give us wheats with muchimproved levels of resistance within <strong>the</strong>next five years.It is probable that root rots will causesevere losses in certain environmentswithin <strong>the</strong> tropiCS. We know very littleabout <strong>the</strong> array of organisms that causeroot rots; this topic will be fur<strong>the</strong>rdiscussed during <strong>the</strong> symposium.Barley yellow dwarf is a problem inmany environments of <strong>the</strong> world, notjust in <strong>the</strong> tropics. CIMMYT, incooperation with many nationalprograms, has undertaken aninternational effort to developgermplasm with better barley yellowdwarf resistance. Once resistance isidentified, it will only be necessary totransfer it into adapted wheats.Agronomic practicesIn many tropical countries. littleresearch has as yet been conducted on<strong>the</strong> agronomic practices reqUired tosuccessfully grow wheat. In <strong>the</strong> nearfuture, we must elucidate <strong>the</strong> variousagronomic practices that will berequired to successfuly cultivate wheatin <strong>the</strong> diverse environmental conditionsof <strong>the</strong> tropics. Paramount among <strong>the</strong>sepractices will be proper dates ofseeding, weed control, fertilization and.of course, proper soil management.The majority of <strong>the</strong> soils in <strong>the</strong> tropicsare paddy soils with a high clay contentand, generally. a hard pan which helpsto retain moisture during <strong>the</strong> grOWingof <strong>the</strong> rice crop. We know little aboutgrOWing wheat on <strong>the</strong>se soils, but <strong>the</strong>problems associated with <strong>the</strong>cultivation of wheat under <strong>the</strong>secircumstances are many. It is quitelikely that wheat will be first grownunder upland conditions in <strong>the</strong> tropics.since more research information isavailable for <strong>the</strong>se conditions. Thevarious problems related to agronomywill be covered in much more detaildUring <strong>the</strong> symposium.ConclusionsIn closing, let me repeat that <strong>the</strong>purpose of this symposium is not toresolve <strong>the</strong> various constraints tointroducing wheat into <strong>the</strong> tropics.Ra<strong>the</strong>r. our main objective is to bringtoge<strong>the</strong>r wheat researchers from around<strong>the</strong> world in an effort to facilitate <strong>the</strong>exchange of ideas and information. Weare striving for a collective awarenessand common understanding of <strong>the</strong>major problems before us. In strivingfor this common ground. <strong>the</strong> stage willbe set for <strong>the</strong> kind of cooperative globaleffort needed to successfuly developwheats for more tropical environments.