Alves, A.A.C.

Duque, L.

Ferguson, Morag E.

Fregene, Martin A.

Mkamilo, G.S.

Mutegi, R.

Setter, Tim L.

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050010001500200025000.20 0.30 0.40 0.50 0.60HI in WSstem starch Correlation ofHI vs stem starchWS WWHI 0.53 0.36Parameter Stem starchTRAITS RELATED TO DROUGHT TOLERANCE MECHANISMS INCASSAVA*Alfredo Alves1; Tim Setter2; Martin Fregene3; Morag Ferguson4; Luis Duque2; Rosemary Mutegi4; Geoffrey Mkamilo51Embrapa Cassava & Tropical Fruits (CNPMF), Cruz das Almas, Brazil (aalves@cnpmf.embrapa.br); 2Cornell University (CU), Ithaca, USA; 3International Center for TropicalAgriculture (CIAT), Cali, Colombia; 4International Institute of Tropical Agriculture (IITA), Nairobi, Kenya; 5Agricultural Research Institute (ARI), Mtwara, Tanzania. * GCP SP3 Project G3005.03: Identifying the physiological and genetic traits that make cassava one of the most drought tolerant cropsCassava (Manihot esculenta Crantz) is:Ministry ofAgriculture, Livestockand Food Supply• one of the most important staple food in the human diet in thetropics;• manly cultivated in areas considered marginal for other crops;• a great contributor to food-security against famine for droughtprone areas of Africa, Asia and Latin America.Drought tolerance contrasting cassava varieties have beenscreened and evaluated in four representative semi-aridenvironments in Brazil, Colombia, Tanzania and Ghana toidentify traits related to drought tolerance mechanisms incassavaObjective:INTRODUCTIONRESULTS  AND  IMPACTS1. Effect of water deficit on root yield indifferent harvest timesAverage of 22 varieties, 2 water treatment (WW, WS), 3 reps.02464.5 MAP 6 MAP 10 MAPTimeWWWSStorage Root FW (kg/plant)Source ANOVA 4.5 MAP 6 MAP 10 MAPMS 1.614 3.524 26.025Variety F 16.93 19.01 8.89P < 0.001 < 0.001 < 0.001Water MS 0.844 18.732 222.703treatment F 8.86 101.04 76.10P 0.004 < 0.001 < 0.001MS 0.229 2.351 14.998Interaction F 2.41 12.68 5.12P 0.002 < 0.001 < 0.001Error MS 0.095 0.185 2.927Significant variety andinteraction effects on tuberroots yield under stressed andcontrol conditions2. Traits behind the mechansms that make cassava a famousdrought tolerant crops2.1. Stomatal conductance01002003004005004.5 MAP 6 MAPTimeLeaf Cond.(mmol.m-2.s-1)WWWSCorrelationsWS WW4.5 MAP 0.41 0.306.0 MAP 0.41 0.28Storage Root FW (10 MAP)Stomatalconductancewater deficitclose stomata↓ water loss2.2. Plant and leaf growth5 MAPSTRESS CONTROLRESULTS  AND  IMPACTS (Cont.)040801201602004.5 MAP 6 MAP 8 MAP 9 MAP 11 MAPTimeStem Length (cm)WWWS050100150200Leaf Area (cm2 ) WSWW4.5 MAP 6 MAP 8 MAP 9 MAP 10 MAPTime2.2. Plant and leaf growth (Cont.)CorrelationsWS WWStem length (6 MAP) 0.45 0.54Stem length (8 MAP) 0.67 0.53Stem length (9 MAP) 0.69 0.51Leaf area (4.5 MAP) 0.58 0.59Leaf area (6 MAP) 0.43 0.44Leaf area (8 MAP) 0.47 0.45Storage Root FW (10 MAP)Parameter2.3. Leaf retention4.5 MAP 6 MAP 8 MAP 9 MAP 11 MAPTime0204060801004.5 MAP 6 MAP 8 MAP 9 MAP 10 MAPTimeLeaf Retention (%) WWWSWS WW4.5 MAP 0.51 0.406.0 MAP 0.60 0.438.0 MAP 0.47 -0.149.0 MAP 0.61 -0.0911.0 MAP 0.40 -0.12LeafretentionStorage Root FW (10 MAP)2.4. Carbohydrate accumulation in the stemStarch (iodine stain)Cassava stem05101520253035TNC, g / plantstorage rootsstemleaf petioleleaf bladeWS atDay-30Plants atDay-0WW atDay-30Storage carbohydrate in the stemuse to sustain tissue metabolism under stress2.5. Harvest index (HI)1) Better yielding genotypes have more open stomata,indicating they have deeper roots and access soil water.2) Genotypes that accumulate substantial stem starchreserves may be more able to sustain meristems andother respiring organs during a prolonged stress.3) Genotypes that maintain partitioning to storage rootsand have high harvest index yield better in drought.CONCLUSIONSHarvest index0501001502002503000.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50Yield (g FW) R2 = 0.6873R2 = 0.8718WWWS

Traits related to drought tolerance mechanisms in cassava

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Traits related to drought tolerance mechanisms in cassava

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