This document discusses root and tuber crops, including cassava, cocoyam, potato, sweet potato, taro, and yam. It provides definitions of roots, tubers, and corms, and details the origins, production levels, uses, nutritional profiles, and research centers for the major root and tuber crops. Root and tuber crops provide important sources of food and income, especially in developing countries, as they have high energy production per hectare and tolerate adverse growing conditions better than other crops.

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

2. Tropical Horticulture - Texas A&M University
Definitions
Root (cassava, sweet potato)
No leaves or reproductive organs
Tuber (potato, yams)
Fleshy underground stem
Minute scale leaves with buds (eyes)
Corm (aroids, cocoyam and taro)
Short, bulblike underground upright stem
With scale leaves

3. Tropical Horticulture - Texas A&M University
World Production of Root and Tuber
Crops (106 mt)
0
100
200
300
Million
mt
Potato
Cassava
SwPotato
Yams
Taro
Cocoyam
FAOSTAT, 2003
About half of the potato production
is in the temperate zone

4. Tropical Horticulture - Texas A&M University
Food Utilization of Root and Tuber
Crops (1996 data)
Crop Production
(1,000 mt)
% in
Developing
Countries
Cassava 92,500 > 99.9%
Potato 161,200 40%
Sweet potato 70,100 98%
Yam 16,000 99%
Total 350,900

5. Tropical Horticulture - Texas A&M University
Feed Utilization of Root and Tuber
Crops (1996 data)
Crop Production
(1,000 mt)
% in
Developing
Countries
Cassava 31,000 71%
Potato 54,900 72%
Sweet potato 58,100 >99%
Yam 400 100%
Total 144,800

6. Tropical Horticulture - Texas A&M University
Origins of Major Root and Tuber Crops
Cassava
Cocoyam
Potato
Sweet
Potato
Taro
Yam

7. Tropical Horticulture - Texas A&M University
Cassava - Manihot esculenta
Yuca, Mandioca, Tapioca
Plant
Slender shrub, 5 m
Enlarged roots
Sweet to bitter
White to yellow
Palmate leaves
Propagation
Stem cuttings

8. 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

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Cocoyam - Xanthosoma sagittifolium
Malanga, Tannia, Elephant’s Ear
Plant
Perennial herb
Corms and cormels
Propagation
Harvest same plant
multiple times
Portions of central
corm

10. 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

11. Tropical Horticulture - Texas A&M University
Potato - Solanum tuberosum
Plant
Herbaceous
Subterannean stems
Leaves
Propagation
Eyes from tubers
Important staple crop

12. 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

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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

14. 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

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Taro - Colocasia esculenta
Plant
Perennial herb
Subterraneous stem
Calcium oxalate crystals
Heart shaped leaves
Propagation
Suckers
Corm apices with leaf

16. Tropical Horticulture - Texas A&M University
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

18. 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

19. Tropical Horticulture - Texas A&M University
Plant Characteristics
Crop Growth
period (mo)
Annual or
perennial
Planting
material
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

20. 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

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Plant Soil Adaptation
Crop Fertility
needs
OM
requirement
Tolerant of
swampy 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

22. Tropical Horticulture - Texas A&M University
Plant Storage Duration
Crop Storage time in
ground
Post harvest
storage life
Cassava Long Short
Cocoyam Long Long
Potato Short Long
Sweet potato Long Short
Taro Moderate Variable
Yam Long Long

23. Tropical Horticulture - Texas A&M University
Crops compared for Edible Energy
Production
Crop Edible energy production
MJ/ha/day
Potato 216
Yam 182
Maize 159
Sweet potato 152
Rice 151
Wheat 135
Cassava 121

24. Tropical Horticulture - Texas A&M University
Crops compared for Edible Protein Production
Crop Edible protein production
kg/ha/day
Cabbages 2.0
Potato 1.4
Dry peas 1.4
Wheat 1.3
Lentils 1.3
Tomatoes 1.2
Chickpeas 1.1

25. Tropical Horticulture - Texas A&M University
Nutritional aspects of root and tuber crops
Crop Starch
% FW
Protein
% FW
Vitamin A
mg/100g FW
Vitamin C
mg/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

26. Tropical Horticulture - Texas A&M University
Nutritional Composition of 100 g of Food
Crop Percent
water
Protein (g) Food energy
kcal
Fats
(g)
Cassava 68 0.9 124 0.1
Beans 69 7.8 118 0.6
Sweet potato 71 1.7 114 0.4
Rice 73 2.0 109 0.1
Yam (raw) 74 2.1 101 0.2
Potato 80 2.1 76 0.1
Plantains 80 1.3 77 0.1
Maize (grits) 87 1.2 51 0.1

27. 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

28. Tropical Horticulture - Texas A&M University
Future Trends for Root and Tuber
Crops
Increased regional production
concentration
Sub Saharan Africa, 60% cassava production
West Africa, 90% yam production
China, 82% of sweet potato production
Increased specialization of End Use
Increase of processed forms of food
Increased use of root/tubers for feed and
starch derived products
Relative importance remain same
10.5% of agricultural value

29. Tropical Horticulture - Texas A&M University
International Research Centers
involved with Root and Tuber Crops
CIAT (Colombia)
Cassava for Americas and Asia
CIP (Peru)
Potato
Sweet potato
Andean roots and tubers
IITA (Nigeria)
Cassava for Africa
Yam for Africa

30. Tropical Horticulture - Texas A&M University
International Research Centers
involved with Root and Tuber Crops
CIAT
CIP
IITA

31. Tropical Horticulture - Texas A&M University
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