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Yam
Dioscorea species, commonly known as yams, are an important food crop grown in tropical regions for their starchy tubers. The three major species cultivated are D. alata, D. rotundata, and D. esculenta. Africa is the largest producer, with Nigeria, Ghana, Cote d'Ivoire, and Benin being major producers. Yams are vegetatively propagated and grown in warm, humid climates with adequate rainfall. Pests and diseases that affect yams include anthracnose, dry rot caused by nematodes, and mosaic virus. Tubers are manually harvested after 9-10 months, dried, and stored in well-ventilated structures for several months
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Yam
- 1. Govind Ballabh PantUniversity of Agriculture and Technology Pantnagar Production technology of warm season vegetable crops (APV532) TITLE :Yam (Discorea) Submitted By: Yashpal Singh Bisht Submitted To: Dr. S.P Uniyal I.D : 50937 Dr. Durvesh singh Department :MSc Ag. Horticulture(veg sci.)
- 2. Dioscorea Cultivation Botanical Name: Dioscorea esculenta (Lesser Yam) Dioscorea alata (Greater Yam) Dioscorea rotundata (White/African Yam) Family : Dioscoreaceae
- 3. Cultivated Dioscorea species Foodspecies Asia D.alata– Cultivated spp Africa D.cayenensis D.rodundata– Cultivated species Americas D.trifida •Pharmacuetical species D.composita D.deltoides D.elephantipe D.floribunda D.speculiflora D.sylvatica
- 4. Major Food Species Domesticatedabout 3,000 BC Common name Species Origin Greater Yam D. alata South east Asia Yellow Guinea yam D. cayenensis West African forest White/African Y0am D. rotundata West African savanna Cush-cush Yam D. trifida Tropical America
- 5. World Yam Yieldand Production (FAOSTAT, 2003) Region Yield Mt/ha Production 1000s mt Africa 9.2 37,314 Nigeria (26,475), Ghana (3,603), Ivory Coast (2,963), Benin (1,772) America 8.9 1,019 Brazil (231), Colombia (256) Asia 15.6 225 Japan (200)
- 6. Botany Yam tuberis neither a root structure nor a stem, but may have its origin as a hypocotyl structure. Tuber grows from a small corm structure located at base of stem. In all yams, tubers are renewed annually. Tubers may be single or two or three. D. esculenta produces a large number of small and spindle shaped tubers. D. bulbfera and D. alata produces a large number of small and spindle shaped tubers. D. bulbifera and D.alata produce aerial bulbs called bulbils from axils of leaves. Whole tubers or pieces of tubers with stem are used for planting in yams. Bulbils can also used for propagation. Stem is weak and climbs on trees by twining. In Dioscorea rotundata stem remains erect upto one metre height. Leaves are simple. All species are dioecious. Fruits are dehiscent tri-locular capsules. Seeds are small and dispersed by wind. Even though all the species have seed dormancy for three months, Dioscorea alata does not exhibit seed dormancy. In Dioscorea alata, majority of male clones are tetraploids (2n = 40) and majority of females have higher ploidy level (2n=60 or 80).
- 9. USES •Food –High instarch –99% of production for food –Baked, fried, boiled (fufu) •Some species are toxic –Alkaloid Diosgenin (3.0 to 3.5 %) C13H19O2N –D. hispida and D.dumetorum are poisonous use for hunting fish, arrow poision. Boil to leach out alkaloid
- 10. Plants belongingto genus Dioscorea of family Discoreaceae under Monocotyledons are commonly known as yams. Dioscorea alata (greater yam) and D. esculenta (lesser yam) are main yams of India. Another species, D. routundata (white yam or African yam), which is under extensive cultivation in Western Africa, recently introduced to India is becoming popular. All species are typical tropical crops grown for carbohydrate rich underground tubers. They form staple food in many parts of Western Africa. In D. alata, tubers are peeled, cooked and ued as vegetable. D. esculenta is consumed after boiling and peeling. Subterranean tuber of a true yam (Dioscorea sp.), the third most important tropical root crop after cassava and sweet potatoes. The venation and shiny, heart-shaped leaves of true yams are unmistakable compared to those of sweet potatoes and other root crops.
- 11. Climate and Soil: It is a tropical species preferring a tropical climate without extremity to temperature. It is adopted to moderate to heavy rainfall areas. Dioscorea plants can be grown in a wide variety of. soils. Extremely heavy clay soils are, in general not recommended, as they restrict tuber growth and make harvesting difficult. Dioscorea tolerates fairly wide variation in soil pH, though very acid soils should be avoided, the ideal soil pH being 5.5 to 6.5.
- 12. Varieties Improved varietiesdeveloped at Central Tuber Crops Research Institute (CTCRI), Sreekaryam, Thiruvananthapuram in Kerala are given below : Greater yam (Dioscorea alata) (Hindi : Ratula) (2n = 20, 30, 40-80) Sree Keerthi : Tubers are conical with brown skin and white flesh having 20-22% starch. It yields 25-30 t/ha in 9-10 months. Sree Roopa : Tubers are digitate in shape with black skin and white flesh. Productivity is 25-30 t/ha in 9-10 months. Sree Shilpa : Tubers are swollen, oval and smooth with black skin and white flesh. Yield is 28 t/ha in 8 months. Indu: It is a high yielding (39.39 t/ha) variety developed by Kerala Agricultural University. Tubers are digitate with brownish black skin and white to pale flesh.
- 13. White yam(D. rotundata) Sree Subhra : Tubers are cylindrical with brown and partially hairy skin and white flesh. Yield is 35-40 t/ha in 9-10 months. Sree Priya : It produces 2-3 tubers having smooth surface and good cooking quality. Yield is 35-40 t/ha in 9-10 months. Sree Dhanya : This is a dwarf and bushy variety with spineless stem and tubers containing 23.3% starch.
- 14. Propagation and timeof planting In greater yam and white yam, tuber pieces of 250- 300 g size are used as planting material. For this, tubers are cut longitudinally with a portion of stem end and allowed to dry under partial shade after dipping in cow dung slurry. Planting is usually done during March-April. Plough / dig land to a depth of 15-20 cm. Take pits of 45 cm3 at a distance of 1 m. Apply 1½ kg compost or well rotten cattle manure in the pit and full up to ¾ with top soil. Plant tubers and mulch with dry leaves. Approximately 1800-2700 kg seed material is required to plant one hectare.
- 15. Manuring Apply cattlemanure or compost @ 10 t/ha as basal dressing before planting. A fertilizer dose of 80 kg N, 60 kg P2O5 and 80 kg K2O per hectare in two split doses is needed for yams. Half dose of N, full dose of phosphorus and half dose of potash are to be applied within a week after sprouting. Remaining nitrogen and potash may be applied one month after the first application. Top dressing of fertilizers should be followed by weeding and earthing up.
- 16. Irrigation: Irrigation maybe given at weekly intervals in the initial stage and afterwards at about 10 days interval. However, during rainy season no irrigation is needed. In anamalais, it is raised under pure rainfed conditions. Intercropping. Intercropping with legumes like cowpea, horse, gram, cluster bean and French bean has been found to smother weeds and also provide an extra income without adversely affecting the tuber yield and diosgenin content.
- 17. Inter-culture Vines areallowed to trail on shrubs or trees or props for high productivity. Tubers are harvested in 9-10 months when leaves turn yellow in colour. Harvesting is done by digging surrounding, area and exposing tubers.
- 18. Lesser Yam Botanical Name:Dioscorea esculenta Chromosome Number : 2n = 40,60,90,100 Common Name: Suthni Sree Latha : Tubers are oblong to fusiform in shape with creamy white flesh and greyish brown skin covered with thin hairs. It yields 20-25 t/ha in 8-9 months. Tubers have 18.4% starch content. Sree Kala : Tuber is sweet, round and smooth. Yield is 20-25 t/ha in 8-9 months. Cultivation of lesser yam is different from that of greater yam or white yam. Plough / dig the land thoroughly and make small mounds at a distance of 70 cm after incorporating compost or well rotten cow dung. Plant whole tubers of 100-150 g. Manuring and other cultivation practices are similar to that of greater yam. Trailing is necessary to expose leaves to sunlight. It is done within 15 days after sprouting by coir rope attached to artificial supports in open area. Lesser yam is harvested in 8-9 months after planting. Harvesting is done by digging out tubers carefully.
- 19. HARVESTING: harvesting inFeb. - March Manual process •Dug with wooden spades or digging sticks Injury to tuber –Infection due to rot –Shorter post harvest life Average 50-60 tones from 1 hac in 2 year duration
- 20. STORAGE: Stored for severalmonths –Harvested tubers dried a few hours •Stored in well-ventilated water proof building •Under shade in open Temperature-Optimal is 15oC •Chilling injury <10oC •Sprouting can be problem -rub off
- 21. DISEASES & INSECTSIN YAM Anthracnose : Colletotrichum gleosporoides Symptoms Small, dark brown spots or black lesions on leaves which may be surrounded by a chlorotic halo; leaf necrosis; dieback of stem; withered leaves and scorched appearance Disease overwinters in plant debris; occurs worldwide Management resistant to anthracnose TDA 291 or TDA 297
- 22. Dry rot disease(caused by yam nematode) Scutellonema bradys Symptoms The infected tubers show dry rot of 1 to 2 cm. Initially this dry rot is of cream and light yellow lesions appear just below the outer skin without any external symptom. With progress in disease lesion spreads deeper (maximum up to 2 cm). At later stage the rot become light and dark brown to black in color and tubers may show external cracks. Entry of fungus through this wounds causes further decay of tubers in storage. There is no above ground symptom with yam nematode infestation. Management Use disease free tubers/setts for planting. Treating tubers with hot water for 40 min at 50-55 C before sowing and after harvest to reduce disease both in field and storage. In Africa smearing tubers with wood ash or cow dung shows reduced nematode infection in field. Follow crop rotation with non host or antagonist crops like ground nut, sorghum, maize, chill pepper etc.
- 23. Yam mosaic diseaseYam mosaic potyvirus The common symptoms are infected leaves show yellow and green patterns (called mosaics) between the veins or may show a narrow green strips bordering the veins (called vein banding). If the disease is severe the leaves become long, thin and strap shape (called shoe-string symptom) and whole plant become stunted. Plant may produce few small tubers with less starch content. Some plants may recover from the virus infection soon after first symptom but virus may survive in plant and reduce the vigour. Management Use healthy and disease free tubers or setts for planting. Select healthy and large tubers for planting instead of small tubers. Keep fields free from weeds. Collect crop debris and destroy them.
- 24. White Scale insects Aspidiellahartii Symptoms The leaves and tubers are covered with small white scales from field to storage. Even though it won't effect yield sometimes foliage cause poor growth and tubers may show delay in germination or even stopped. Severe infestation may leads to tuber shrivel.