the Symposium on Wheats for More Tropical Environments - cimmyt

118The soil in <strong>the</strong> Passo Fundo region isclassified as dark red dystrophic latosol(oxisol). Data relating to somecharacteristics of a soil profile which isbeing used in a trial on lime dosage aregiven in Table 3. As can be seen. <strong>the</strong>pH is very low. and is slightly increasedby lime applications. Aluminum and/ormanganese levels are sufficiently highto cause ei<strong>the</strong>r <strong>the</strong> death or greatreduction in plant growth in cultivarswhich are susceptible to crestamento(toxicity caused by aluminum and/ormanganese). Before creating cultivarsresistant to this physiological disease.<strong>the</strong> area was considered inadequate foragriculture. Lime applicationsneutralize acidity. as well as aluminumand manganese. in <strong>the</strong> top layers. but<strong>the</strong> problem remains in <strong>the</strong> deeperlayers. below 20 cm (Table 3). Cultivarssusceptible to crestamento. whengrown in <strong>the</strong>se soils amended withlime. no longer show very evidentcrestamento symptoms. but are usuallyunable to compete in yield withresistant cultivars.The genetic breeding of wheat in RioGrande do SuI was initiated in 1914.The present breeding objectives are <strong>the</strong>development of germplasm with:• Agronomic characteristics for highyield potential• Short straw and/or high resistance tolodging• Tolerance to crestamento• Resistance to leaf rust (Pucciniarecondtta trttici)• Resistance to stem rust (Pucciniagraminis triticO• Resistance to septoria leaf blotch(Septoria tritici)• Tolerance to glume blotch (Septorianodorum)• Tolerance to helminthosporium(Cochliobolus sattvus)• Resistance to mildew (Erystphegraminis trtttct)• Resistance to scab (Gibberella zeae)• Resistance to wheat mosaic virus• Tolerance to barley yellow dwarfvirus• Resistance to sprouting• Resistance to loose smut (Ustilagotrittci)Table 3. Soil acidity and location in <strong>the</strong> soil profile of aluminum, calcium and magnesium,11 years after <strong>the</strong> application of lime, Passo Fundo, Rio Grande do Sui, Brazil, 1984Amount of lime applieda 12.4 tlha!J 24.8 tlhat:1JSoil depth pH AI Ca+ Me pH AI Ca+ Me pH AI Ca+ Me(em) (me/lOa e) (me/100 e) (me/100 e;0- 1.25 4.5 2.5 3.5 4.8 1.0 6.4 5.2 0.4 7.71.25 - 2.5 4.3 3.2 2.9 4.7 1.4 5.6 5.2 0.6 7.02.50· 5.0 4.2 3.6 2.6 5.0 1.2 7.0 5.0 0.8 6.95.00 - 10.0 4.3 3.6 2.4 4.7 1.6 5.6 5.3 0.5 8.110.00·20.0 4.3 3.9 2.3 4.6 2.2 4.4 5.0 1.1 6.320.00 - 30.0 4.4 4.2 1.9 4.4 3.3 2.9 4.9 2.7 3.630.00 - 40.0 4.4 4.0 2.2 4.5 3.2 2.8 4.6 3.0 3.4!l The amount required to raise soil pH to 6.0 when experiment began in 1973~/ Double <strong>the</strong> amount of !.ISource: Soils group, CNPT, EMBRAPA, Brazil