Root and Tuber Crops in the Tropics Cassava Cocoyam Potato Sweet Potato Taro Yam

Root and Tuber Crops in the Tropics

CassavaCocoyamPotatoSweet PotatoTaroYam

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Definitions

Root (cassava, sweet potato)

No leaves or reproductive organsTuber (potato, yams)

Fleshy underground stem Minute scale leaves with buds (eyes)

Corm (aroids, cocoyam and taro)

Short, bulblike underground upright stem With scale leaves

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World Production of Root and Tuber Crops (106 mt)

0

100

200

300

Mil

lio

n m

t

Po

tato

Ca

ssa

va

Sw

Po

tato

Ya

ms

Ta

ro

Co

co

ya

m

FAOSTAT, 2003

About half of the potato production is in the temperate zone

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Food Utilization of Root and Tuber Crops (1996 data)

Crop Production(1,000 mt)

% inDevelopingCountries

Cassava 92,500 > 99.9%

Potato 161,200 40%

Sweet potato 70,100 98%

Yam 16,000 99%

Total 350,900

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Feed Utilization of Root and Tuber Crops (1996 data)

Crop Production(1,000 mt)

% inDevelopingCountries

Cassava 31,000 71%

Potato 54,900 72%

Sweet potato 58,100 >99%

Yam 400 100%

Total 144,800

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Origins of Major Root and Tuber Crops

Cassava

Cocoyam

Potato

Sweet Potato

Taro

Yam

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Cassava - Manihot esculentaYuca, Mandioca, Tapioca

Plant Slender shrub, 5 m Enlarged roots

Sweet to bitterWhite to yellow

Palmate leaves

Propagation Stem cuttings

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Cassava - Manihot esculenta

Origin South America

Distribution Tropics and

subtropics

Staple food in many tropical regions Excellent

carbohydrate source

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Cocoyam - Xanthosoma sagittifoliumMalanga, Tannia, Elephant’s Ear

Plant Perennial herb Corms and cormels

Propagation Harvest same plant

multiple times Portions of central

corm

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Cocoyam - Xanthosoma sagittifolium Malanga, Tannia, Elephant’s Ear

Origin West Indies and

northern S. America

Distribution Tropical regions Common in

Indonesia

Adaptation Lowland tropics

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Potato - Solanum tuberosum

Plant Herbaceous Subterannean stems Leaves

Propagation Eyes from tubers

Important staple crop

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Potato - Solanum tuberosum

Origin Highlands of South

America

Distribution Widely cultivated

from highland tropics to temperate zones

Adaptation Cool climate

adaptation

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Sweet potato - Ipomoea batatas

Plant Creeping herb Enlarged roots vary in

shape and color Leaves variable in size,

shape, color

Propagation Young stem cuttings

Important carbohydrate source

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Sweet potato - Ipomoea batatas

Origin Central America

Distribution Widely cultivated

both in tropics and subtropics

Adaptation Tropics to subtropics Below 2200 m

altitude

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Taro - Colocasia esculenta

Plant Perennial herb Subterraneous stem

Calcium oxalate crystals

Heart shaped leaves

Propagation Suckers Corm apices with leaf

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Taro - Colocasia esculenta

Origin Southeast Asia

Distribution West Africa Caribbean Pacific islands

Staple food

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Yam Dioscorea alata, cayenensis and rotundata

(Sixty species cultivated for food and pharmaceuticals)

Plant Climbing vine, 10 m Tubers vary in

shape Leaves ovate with

cordate base

Propagation Tubers

Staple food in arid regions of Africa

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Yam

Dioscorea alata, cayenensis and rotundata (Sixty species cultivated for food and pharmaceuticals)

Origin Asia and West Africa

Production Mainly Africa

Adaptation Lowland tropics Drought tolerant

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Plant Characteristics

Crop Growthperiod (mo)

Annual orperennial

Plantingmaterial

Cassava 9-24 Perennial Stem cuttings

Cocoyam 9-12 Perennial Corms

Potato 3-7 Annual Tubers

Sweet potato 3-8 Perennial Vine cuttings

Taro 6-18 Perennial Corms

Yam 8-11 Annual Tubers

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Plant Adaptation

Crop Rain(mm)

Temperature(ºC)

Drought

Cassava 1,000-1,500 25-29 Yes

Cocoyam 1,400-2,000 13-29 No

Potato 500-750 15-18 No

Sweet potato 750-1,000 >24 Yes

Taro 2,500 21-27 No

Yam 1,150 25-30 Yes

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Plant Soil Adaptation

Crop Fertilityneeds

OMrequirement

Tolerant ofswampy land

Cassava Low Low No

Cocoyam High High No

Potato High High No

Sweet potato Low Low No

Taro High High Yes

Yam High High No

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Plant Storage Duration

Crop Storage time inground

Post harveststorage life

Cassava Long Short

Cocoyam Long Long

Potato Short Long

Sweet potato Long Short

Taro Moderate Variable

Yam Long Long

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Crops compared for Edible Energy Production

Crop Edible energy productionMJ/ ha/ day

Potato 216

Yam 182

Maize 159

Sweet potato 152

Rice 151

Wheat 135

Cassava 121

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Crops compared for Edible Protein Production

Crop Edible protein productionkg/ ha/ day

Cabbages 2.0

Potato 1.4

Dry peas 1.4

Wheat 1.3

Lentils 1.3

Tomatoes 1.2

Chickpeas 1.1

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Nutritional aspects of root and tuber crops

Crop Starch% FW

Protein% FW

Vitamin Amg/ 100g FW

Vitamin Cmg/ 100g FW

Cassava 27-36 0.5-2.0 17 50

Potato 13-16 2.0 Trace 31

Sweet potato 18-28 1.0-2.5 900 35

Yam 18-25 2.5 117 24

Aroids 19-21 2.0 0-42 9

FW = fresh weight

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Nutritional Composition of 100 g of Food

Crop Percentwater

Protein (g) Food energykcal

Fats(g)

Cassava 68 0.9 124 0.1Beans 69 7.8 118 0.6Sweet potato 71 1.7 114 0.4Rice 73 2.0 109 0.1Yam (raw) 74 2.1 101 0.2Potato 80 2.1 76 0.1Plantains 80 1.3 77 0.1Maize (grits) 87 1.2 51 0.1

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Importance of Root and Tuber Crops

Important source food and income for the most food insecure households

Why? High energy production per ha/day Yield better under adverse conditions

than other crops

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Future Trends for Root and Tuber Crops

Increased regional production concentration

Sub Saharan Africa, 60% cassava productionWest Africa, 90% yam productionChina, 82% of sweet potato production

Increased specialization of End UseIncrease of processed forms of foodIncreased use of root/tubers for feed and

starch derived products

Relative importance remain same 10.5% of agricultural value

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International Research Centers involved with Root and Tuber Crops

CIAT (Colombia)

Cassava for Americas and AsiaCIP (Peru)

Potato Sweet potato Andean roots and tubers

IITA (Nigeria)

Cassava for Africa Yam for Africa

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International Research Centers involved with Root and Tuber Crops

CIAT

CIP

IITA

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Any Questions?