the Symposium on Wheats for More Tropical Environments - cimmyt

101very late, high temperatures at <strong>the</strong> endof February or in early March. while <strong>the</strong>crop is in an<strong>the</strong>sis. can cause sterility of<strong>the</strong> florets. resulting in very low yields.The massive irrigation schemes inNigeria's wheat-growing regions. <strong>the</strong>Chad, <strong>the</strong> Hadehia-Jama'are and <strong>the</strong>Sokoto-Rima river basins in Barno,Kano-Bauchi and Sokoto states.respectively (Figure 1). are <strong>the</strong> mainvehicles to <strong>the</strong> possible attainment ofNigeria's green revolution (16).However, <strong>the</strong>se rivers are fed by scantyrainfall, 300 to 500 mm in Barno state,600 to 900 mm in Kano/Bauchi and400 to 600 mm in Sokoto. It is spreadover a short period. mainly from July toSeptember; thus. water is expensiveand may be limiting, especially in yearsof low rainfall.The effect of drought is usually verysevere on wheat. as it not only cuts offwater needed for normal metabolism.but also decreases <strong>the</strong> supply ofnutrients from <strong>the</strong> soil. Under suchstress situations. farmers face aconsiderable amount of risk. There is,<strong>the</strong>refore, a need to develop wheatgermplasm with a reasonable amountof heat and drought tolerance, in orderto stabilize yield under presentconditions and to effect a moresuccessful extension of wheatproduction into sou<strong>the</strong>rn Nigeria.Germplasm Improvementin NigeriaIn <strong>the</strong> last two decades. over 15,000wheat varieties and lines have beenintroduced and screened in Nigeria by<strong>the</strong> Institute for Agricultural Research,Ahmadu Bello University. Zaria. Theobjective has been to identify cultivarswhich are high yielding under Nigerianconditions and possess acceptablebread-making qualities (14). Wheatintroductions have come mostly fromCIMMYT. <strong>the</strong> International Center forAgriculture Research in <strong>the</strong> Dry Areas(ICARDA) in Syria, <strong>the</strong> Food andAgricultural Organization (FAO) ando<strong>the</strong>r parts of <strong>the</strong> world (14.15).Although INIA 66. Indus 66 andMexipak are grown in some areas of <strong>the</strong>South Chad Scheme. only five varietieshave been recommended by <strong>the</strong>Figure 1. Wheat-growing regions in Nigeria