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(Dioscorea spp.)

• Yams are starchy staples in the form of large tubers produced by herbaceous annual and perennial trailing vines grown in Africa, the Americas, the Caribbean, South Pacific and Asia.

It’s vines can be smooth or pricky, reaching 10 m (32.8 ft) or more in length depending on the variety.

It’s leaves are simple and usually oval to heart-shaped with petioles which are the same length, or slightly longer, than the leaf blade itself.

YAM

• This plant can produce one singular tuber or several tubers which extend from stolons from a central corm (up to 20)

• The tubers can be cylindrical, curved or lobed, with brown, grey, black or pink skin and white, orange or purplish flesh.

Did you know that….

…the tubers of yam have organoleptic qualities that can be make them the pre-ferred carbohydrates staple and can contribute up to 350 calories per person each day? (Asiedu et al., 2001)

…yams are produced over 5 million hectares in 47 countries in tropical and subtropical regions of the world?

Origin, History and Domestication

• Lebut (2009) stated that the genus dispersed worldwide at the end of Cretaceous period, evolved in the different directions throughout the New and Old World, and resulted in distinct species.

• The main dispersal regions included:AmericasMadagascarSouth and Southeast AsiaMelanesiaAustralia

Origin, History and Domestication

• According to Coursey (1967), the separation of the Asian and African species occurred later, during the Miocene period. Furthermore, D. alata and D. esculenta, originated from Burma and Assam, localities of Southeast Asia.

D. esculentaD. alata

Origin, History and Domestication

• Degres (1993) noted that D. cayenesis is of African origin, given that wild species can be found on the continent.

• The origins of other yam cultivated species are African and Asian, except for D. trifida, whose origin is South America (Lebut, 2009)

Yellow Yam

Classification & VarietyKindom PlantaeSubkingdom

Tracheobionta

Division Liliopsida

Subclass LiliidaeOrder Liliales

Superdivision Spermatophyta

Genus Dioscorea

Family Dioscoreacreae

Yam

Flowering Plants

Yam Family

Vascular Plants

Plants

Seed Plants

Class Liliopsida Monocotyledons

Dioscorea alata L. (Water yam)

Yellow Guinea Yam

Hottentot Bread

Dunguey

Air yam

Importance/Uses to Man and Animals

• Yams are:valuable source of carbohydrates, fibers, and low level of fatsprocessed into various staple intermediate and end product forms (Jaleel et

al., 2007)

• Dioscorea species are:important source of secondary metabolites used in pharmaceutical industry

and medicine.(wild species) sources of compounds used in synthesis of sex hormones and

corticosteroids (Coursey, 1967).(cultivated species) sources of food in some other countries (Coursey, 1967).

Importance/Uses to Man and Animals

• The plant has many aerial tubers that also aid in reproduction.• Powdered tubers are used as a remedy for piles, gonorrhea and are

applied externally to sores.• Some tubers of Dioscorea are important sources of diosgenin (Satour

et al., 2007)• Yams are used for consumptions for both humans and animals.

Nigerian Yam Porridge Chips

Importance/Uses to Man and Animals

• Wu et al. (2005) analyzed the consumption of D. alata and concluded that although the mechanisms are not yet fully understood, it’s consumption can reduced risk of breast cancer and cardiovascular disease.

• Traditional medicines used yams to cleanse skin impurities.• Yams can treat anemia giving wealth nutrients (Okwu &Ndu,

2006).• Tubers are responsible for increased fertility in women who

habitually consume it (Balbach & Boarim, 1993).• Dioscorea are used for the treatment of Addison’s disease,

some allergies, bursitis, contact dermatitis, psoriasis, rheumatoid arthritis, sciatic, Brown Recluse Spider Bites, insect stings, and other diseases and ailments (Foster and Duke, 1990).

Approximate Yam Nutrition per 100g9mg Salt

17 mg calcium 17 mg Vit. C

32 mg Vit. B2 55 mg Phosphorus

112 mg Vit. B1 816 mg Potassium

1 g Protein 4 g Fiber

23 g Sugar 103 Calories

It does not have any Vitamin A, iron, fat, and no vitamin B3.

Major Constraints/Problems in the Philippines

• Limited supply of planting materials.

• Lack of information about yam production, processing,

product development, preservation and market-linkaging.

Production Practice and Management

Growing Conditions• Soil PH Acidic, Neutral, Alkaline• Soil Drainage Average• Soil Type Clay, Loam• Growth Rate Very Fast• Water Requirements Average Water• Habit Vining/Climbing• Seasonal Interest Summer, Fall

Production Practice and Management

Growing Conditions• Land Preparation Loose soils with organic matter more

suitable for the Dioscorea spp. Large size pits must be prepared with the rigid soil. Normal size of the pit is about 1X1X1 feet. Straw, coconuthusk, paddy husk as well as grass debris can be used as organic matter. Pits are filled with these matter and tubers with active bud can

be planted on it.

Production Practice and Management

Growing Conditions• Recommended Spacing Greater yam: 1X1

Lesser yam: 1X0.5• Fertilizer Recommendation Fertilizer application must be done

before 4.5 months to obtain optimum growth rate. Not necessary to apply fertilizer after that.

Time of application Amount (kg/ha)

TSP Urea MOP

Basal Dressing 65 150 60

1 Top dressing (1.5-2 months after planting) 65 - 60

2 Top dressing (3.5-4 months after planting) 65 - 60

Production Practice and Management

Growing Conditions• Weed management Weed control must ne done prior to top

dressing. Mulching is important to weed control as well as soil and water conservation.

Yam is considered as a high value crop.

Stony and highly compacted soils are not good for yam production.

Salinity and acidity dominate the problems related to agricultural land use.

Major Pests and Diseases Attacking Yam and their control

• Main diseases and account for the highest field and storage losses in susceptible cultivars (Abang et al., 2003):

Virus (Yam Mosaic Virus or YMV)Anthracnose and Scutellonema bradys

- anthracnose stands out as the principal phytosanitary problem in several areas of yam cultivation and production.Nematodes

- which interact with fungi and bacteria, attack the tubers in the field and continue to cause damage in the post harvest.

Dry rot disease-a limiting factor in yam cultivation and negatively influences the

market value of the product, especially when found in conjunction with the nematode Scutellonema bradys, which acts as its etiologic agent.

Yam meloidogynoses are diseases that cause heavy losses in yam production and marketing (Abang et al., 2002; Royeroet al., 2007)

Major Pests and Diseases Attacking Yam and their control

Yam infected by Rot and Anthracnose

Yam infected by Anthracnose

Yam (left) infected by Nematodes

Yam infected by Dry Rot

Yam (Leaf) infected by Yam Mosaic Virus

Major Pests and Diseases Attacking Yam and their control

• Micropropagation and and Organogenesis are two of many

biotechnological techniques that could be adopted to obtain healthy

seedlings, increasing the potential of cultivation (Alizadeh et al., 1998;

Chen et al., 2003; Royeroet al., 2007) especially in commercially D. alata

(Bagolun et al., 2006).

Economic and Marketing in the Global Market

• Yam is the currently the 4th most important tuber-root crop in the world, after potato, cassava, and sweet potato; second most important tropical root or tuber crop.

• In 2008, the estimated world production of yams was 51.7 M tons, with Africa leading the production.

• West Africa accounts for 90%-95% of world yam production with Nigeria the largest single producer.

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