the Symposium on Wheats for More Tropical Environments - cimmyt

34Wheat Breeding in Nor<strong>the</strong>ast ArgentinaI.R. Cettour. Chaco. aDd J.E. Nissi. Cordoba. Instltuto NacloDal deTecDologia Agropecaaria. ArgeDtiDaThe wheat-growing region of nor<strong>the</strong>astArgentina is located in <strong>the</strong> provinces ofChaco and Fonnosa between 25° and28°5 latitudes and 58° and 62°Wlongitudes (Figure 1). The climate issubtropical and has an average annualrainfall of800 mm in <strong>the</strong> west and1,100 mm in <strong>the</strong> east. with <strong>the</strong> greaterproportion falling in <strong>the</strong> spring,summer and early fall. The averagetemperature for January is 27.4°C. andfor July, 15.5°C. Frost causes damageto wheat if it occurs late in <strong>the</strong> year,during <strong>the</strong> heading stage. In <strong>the</strong> spring.<strong>the</strong>re are high temperatures: if <strong>the</strong>seare accompanied by north winds.shriveling of <strong>the</strong> grain can occur.In nor<strong>the</strong>astern Argentina. wheat isgrown under dryland conditions.Without fertilization. Crop growth is aresult of moisture accumulated in <strong>the</strong>soU before sowing, ra<strong>the</strong>r than ofrainfall. Wheat cultivation began toexpand in <strong>the</strong> region after 1962. when<strong>the</strong>re were approximately 5,000hectares: this area had increased to82,000 hectares by 1968. This was duein part to a severe drop in <strong>the</strong> price ofcotton, <strong>the</strong> principal crop of <strong>the</strong> area.This caused a divers1ftcation ofagriculture, and wheat was one of <strong>the</strong>crops that replaced cotton.Mter 1969. <strong>the</strong> area dedicated to wheatfluctuated greatly, as did productionand yield: this was caused by wea<strong>the</strong>rconditions. low prices and competitionAtlanticOcean"Jaure 1. The wheat-P'OwlDg reatoD of Dor<strong>the</strong>a.terD ArgeDtlna