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Home , Dioscorea, Dioscoreaceae, Taro

and Yams Yams

Dioscoreaceae (600 species)

Yam - Dioscorea species Sixty species cultivated for food and pharmaceuticals Production Field

• Monocot • - herbaceous perennial – Climbing vine, 10 m – ovate with cordate base – vary in shape – Growth cycle Vines die at end of rains or when cold • Tubers dormant and resume growth when favorable • Dioecious (mostly)

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Cultivated Dioscorea species Major Food Species Domesticated about 3,000 BC • Food species • Pharmacuetical Common name Species Origin – species • alata – composita Water yam alata – Cultivated spp – deltoides Winged yam – – elephantipe Yellow Guinea cayenensis West African • cayenensis yam forest • rodundata – floribunda – Cultivated species – speculiflora White Guinea rotundata West African – – sylvatica yam savanna • trifida Cush-cush yam trifida Tropical America Yampi

Tropical Horticulture - Texas A&M University Tropical Horticulture - Texas A&M University Origins of Important Yam Dioscorea species Domesticated separately in each continent

D. trifida D. rotundata D. cayenensis D. alata

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Origin of Species Origin of Species • White Guinea Yam - D. rotundata • Water Yam, D. – Hybrid origin alata • Savanna-zone Dioscorea spp • Forest spp, D. cayenensis in W. Africa – Cultivated species – D. rotundata is most important – Hybrid origin species in Africa • Species in North Central part of • Yellow Guinea Yam - D. cayenensis southeast Asian – Second most important species peninsula – Also hybrids between White and – Reached Yellow Guinea Yams in 1,500 BC

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Adaptation Adaptation • Lowland wet-dry tropics • Soil – Transition between forest and – Friable and deep soils savanna • Allows proper expansion • Temperatures • Penetrate soils as expand – 25 to 30°C – Excellent drainage • Does not tolerant waterlogging • Rain – High fertility and organic matter – 2-4 month dry season • First in crop rotation – 1150 mm (46”) • Same nutrient removal as – Drought tolerant • Myccorrhizal infection • Sensitive to low pH if aluminum is high

Tropical Horticulture - Texas A&M University Tropical Horticulture - Texas A&M University Dissemination of Dioscorea species Domesticated separately in each continent Continental Movement

• Exploration period • Asiatic and African yams used on ships for C - world 1550 transfer

C • D. alata, D. cayenensis and D. 00 B 1,5 rotundata taken to by slave trade 1500

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Yam Production in the World 90% in , Benin, , and Ivory Coast World Yam Yield and Production

Region Yield Production Mt/ha 1000s mt World 9.2 38,643 Africa 9.2 37,314 Nigeria (26,475), Ghana (3,603), Ivory Coast (2,963), Benin (1,772) Americas 8.9 1,019 (231), Colombia (256) Asia 15.6 225 Japan (200) 16.0 286 Papua (231)

FAOSTAT, 2003

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Propagation Yield increases with larger sett size • Asexual – Most common 35 Villanueva, 1986 • Setts - division of tubers (250 g) 30 • 20% of previous crop saved 25 – Other propagules 20 • Seed yams - small tubers 15 10 • Stem cuttings (mt/ha) Yield 5 • Yield affected by 0 – Sett size 125 250 375 500 1000 Size of sett (g) – Sett type

Tropical Horticulture - Texas A&M University Tropical Horticulture - Texas A&M University Planting Yield increases with type of sett At least half grown in mixed cropping systems Crown or proximal end has preformed shoot initials and 25 begins growth quicker Villanueva, 1986 • Density 20 35 Villanueva, 1986 – 10-15 cm deep 15 30 10

– Mounds or ridges Yield (mt/ha) 25 5 • 0.6 to 1.3 m tall 0 20 • 0.75 to 1.0 m apart Furrow Flat Ridge Mound Seed bed type 15 • 1 - 1.5 m between rows 10 Yield (mt/ha) Yield – Pre-sprouting common 5 in early planting in W 0 Africa (Nov - Jan) Tail Middle Crown Sett type

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Trellising increases yield Growth Cycle • Support systems • Grown as an annual – Stakes 2 - 4.5 m long (6-15’) • Initial growth slow – May substitute old maize stalks, tree stumps – Weed control is critical • Tuber formation 25 Villanueva, 1986 – Begins in 10 weeks 20 – Continues to shoot 15 dieback 10 • Maturity in 6 - 11 Yield (mt/ha) Yield 5 months

0 – Varies with spp and Unstaked Bamboo stake Tropical Horticulture - Texas A&M University variety Tropical Horticulture - Texas A&M University

Harvesting Harvesting • Harvest time – End of rainy season or early dry season • Manual process – Plant has growth stopped • Dug with • Leaves begin to yellow – Time is flexible wooden spades • Once plant senescent, roots deteriorate or digging sticks • Early harvest called “milking” • Injury to tuber – Remove lower part of tuber (2-4” below – Infection due to crown) rot – Upper part grows to end of season – Second growth produces small tubers – Shorter post • Often used as seed yams harvest life

Tropical Horticulture - Texas A&M University Tropical Horticulture - Texas A&M University Storage Pests • Tolerant to most pathogens • Stored for several months – Yam rust, yam – Harvested tubers dried a few hours spot, yam mosaic • Stored in well-ventilated water proof • Yam beetles serious in building parts of Nigeria • Under shade in open – Temperature • Rodents • Optimal is 15oC • Chilling injury <10oC • Sprouting can be problem - rub off

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Uses Pharmaceuticals • Traditionally used for medicinal • Food purposes – High in • sapogenin – 99% of production for food – – Baked, fried, boiled () – Extracted from Central American spp • Some species are toxic • D. composita and D. floribunda

– Alkaloid dioscorine C13H19O2N • Perennial climbing vines – D. hispida poisonous • 4% sapogenins in tubers • Boil to leach out alkaloid – Base for drugs such as • Cortisone • Sex hormones (Birth control pills) Tropical Horticulture - Texas A&M University Tropical Horticulture - Texas A&M University

Disadvantages Advantages of Yams • Labor intensive • Efficient producer of starch – Harvest • Drought tolerant – Need to trellis • Stored for several months without • Need high fertility refrigeration. • Sensitive to waterlogging

Tropical Horticulture - Texas A&M University Tropical Horticulture - Texas A&M University Plant Taro • Perennial herb • Leaves – Large • 25-85 cm long • 20-60 cm wide – Long petioles – Edible esculenta

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Plant Origin of Taro

• • Indo-Malayan region – Rings of leaf scars and scales – Eastern and – Cormels from lateral – Domesticated 4,000 to 7,000 years ago buds • About 2,500 years ago – Thick brown outer – East to , Japan, SE Asia, Oceania covering • about 1,500 years ago • Acridity – West to Arabia, eastern Mediterranean, and – Calcium oxalate crystals – Cooking or fermentation eliminates

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Origin of Taro Hawaiian Legend • About 2,000 years ago – Along coast to East Africa • Wakea (Sky Father) and his daughter – Across continent to Ho’ohokulani conceived a child • Beginning 1600s – Child was deformed & lifeless – Used as provisions on ships during • Small plant arose from child’s grave slave trade – It was a taro plant – Moved to Americas – Became everlasting breath of Hawaii • Hawaiian’s direct descendants

Tropical Horticulture - Texas A&M University Tropical Horticulture - Texas A&M University Origin and Dispersal of Taro Domesticated 4,000 to 7,000 years ago World Taro Yield and Production

Region Yield Production Mt/ha 1000s mt World 6.0 9,040

2,500 years ago Africa 5.1 6,813 Nigeria (3,908), Ghana (1,724) 1600s Hawaii Americas 10.7 25 1,500 years Asia 15.0 1,926 China (1,545) ago 2,000 years ago Oceania 6.4 274 (173)

FAOSTAT, 2003

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Planting Propagation Planted throughout the year • Vegetative • Density – Hulis – 2-3’ square (50-75 cm) • Higher density better for lowland (wet) culture • Top cm of and 20-25 cm – Can be intercropped as well • Larger sett size leads to greater yield

20 Villanueva, 1986 18 16 Villanueva, 1986 16.2 14 15 12.4 9.7 10.7 12 Yield Yield 10 10 8.6 (mt/ha) (mt/ha) 8 7.8 6 5 4 17,778 Plant 2 26,667 0 density 0 40,000 /ha 15-20 50-60 100-120 Lowland Upland Sett size (g) 50x50 cm = 40,000 pl/ha; 50x75 cm = 26,667 pl/ha; 75x75 cm = 17,778 pl/ha Tropical Horticulture - Texas A&M University Tropical Horticulture - Texas A&M University

Harvest and Uses Nutrition • Harvest • Cooked corms – By hand – Source of starch – Throughout year • More digestible than other root crops • Uses • Baby formula and other foods – Boiled, baked, toasted, or fried • Good for those with digestive problems – , a pounded, paste like food made – Can be significant source of from boiled taro (now rare) • Cooked leaves – - biscuits, , bread – Same as spinach – Chip industry developing

Tropical Horticulture - Texas A&M University Tropical Horticulture - Texas A&M University Traditional Medicinal Use Any Questions? • Taro stems – Slows bleeding, helps clotting of platelets – Relieves stinging from insect bites. • Poi – Settles stomachs - aids digestion – Reduces diarrhea symptoms

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World Sweet Yield and Production Trellising increases yield Region Yield Production Mt/ha 1000s mt World 14.6 136,899 25 Africa 4.5 10,833 Burundi (750), Nigeria (2,481), Rwanda (1,161), (899), 20 (2,476) Americas 8.2 1,808 Argentina (307), Brazil (484), 15 (252), Peru (241) Asia 18.5 122,966 China (115,417), India (1,135), (1,774), Japan (1,055), 10 Vietnam (1,664) Yield (mt/ha) Yield Oceania 5.4 608 Papua New Guinea (487) 5

N. America 16.8 619 USA (619) 0 Unstaked Bamboo stake FAOSTAT, 2003

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Plant Density and Yield in Lowland Seed bed preparation affects yield and Upland Taro

25 20 Villanueva, 1986

20 16.2 15 12.4 15 9.7 10.7 Yield 10 8.6 10 (mt/ha) 7.8 Yield (mt/ha) Yield 5 5 17,778 Plant 0 26,667 0 density Furrow Flat Ridge Mound 40,000 plants/ha Lowland Seed bed type Upland

50x50 cm = 40,000 pl/ha; 50x75 cm = 26,667 pl/ha; 75x75 cm = 17,778 pl/ha

Tropical Horticulture - Texas A&M University Tropical Horticulture - Texas A&M University Larger sett size gives greater yield (upland taro)

18 16 Villanueva, 1986 14 12 Yield 10 (mt/ha) 8 6 4 2 0 15-Oct 50-60 100-120 Sett size (g)

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