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Root and Tuber Crops in the Tropics
CassavaCocoyamPotatoSweet PotatoTaroYam
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
Origins of Major Root and Tuber Crops
Cassava
Cocoyam
Potato
Sweet Potato
Taro
Yam
Tropical Horticulture - Texas A&M University
Cassava - Manihot esculentaYuca, Mandioca, Tapioca
Plant Slender shrub, 5 m Enlarged roots
Sweet to bitterWhite to yellow
Palmate leaves
Propagation Stem cuttings
Tropical Horticulture - Texas A&M University
Cassava - Manihot esculenta
Origin South America
Distribution Tropics and
subtropics
Staple food in many tropical regions Excellent
carbohydrate source
Tropical Horticulture - Texas A&M University
Cocoyam - Xanthosoma sagittifoliumMalanga, Tannia, Elephant’s Ear
Plant Perennial herb Corms and cormels
Propagation Harvest same plant
multiple times Portions of central
corm
Tropical Horticulture - Texas A&M University
Cocoyam - Xanthosoma sagittifolium Malanga, Tannia, Elephant’s Ear
Origin West Indies and
northern S. America
Distribution Tropical regions Common in
Indonesia
Adaptation Lowland tropics
Tropical Horticulture - Texas A&M University
Potato - Solanum tuberosum
Plant Herbaceous Subterannean stems Leaves
Propagation Eyes from tubers
Important staple crop
Tropical Horticulture - Texas A&M University
Potato - Solanum tuberosum
Origin Highlands of South
America
Distribution Widely cultivated
from highland tropics to temperate zones
Adaptation Cool climate
adaptation
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
Sweet potato - Ipomoea batatas
Origin Central America
Distribution Widely cultivated
both in tropics and subtropics
Adaptation Tropics to subtropics Below 2200 m
altitude
Tropical Horticulture - Texas A&M University
Taro - Colocasia esculenta
Plant Perennial herb Subterraneous stem
Calcium oxalate crystals
Heart shaped leaves
Propagation Suckers Corm apices with leaf
Tropical Horticulture - Texas A&M University
Taro - Colocasia esculenta
Origin Southeast Asia
Distribution West Africa Caribbean Pacific islands
Staple food
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
International Research Centers involved with Root and Tuber Crops
CIAT
CIP
IITA
Tropical Horticulture - Texas A&M University
Any Questions?