2. Introduction
• Yam is a tropical tuber crop that is cultivated in Africa, Asia
and South America.
• After cassava, yam is the second most important tuber crop
in Africa.
• In West Africa,50 million tons are cultivated on about 4
million hectares annually, accounting for more than 90% of
the world’s production.
3. Origin and distribution
• Dioscorea rotundata was first domesticated in West Africa in
about 5000 BC.
• Three main centers of origin of yams have been identified:
West Africa
Southeast Asia
Tropical America.
Different species of the genus Dioscorea may have different
regions of origin.
4. Types of yam
White yam (D. rotundata) and yellow yam (Dioscorea
cayennensis)
• These are native to Africa and are the most widely cultivated
types of yams in this region.
• They can grow large with vines reaching lengths of up to 12m.
• The tubers usually weigh between 2.5 and 5 kg each, but can
attain weights of as much as 25 kg.
5. Water yam (Dioscorea alata)
• Also called as ‘winged yam’ or ‘purple yam’
• It is perennial, vigorously twining vine with winged stems.
• The vines grow to 10m and are freely branching.
• The tubers are large with purple flesh.
• The plants normally grow for 8–10 months, and then go
dormant for 2–4 months.
• During dormancy the aerial stems die back.
6. Lesser yam (Dioscorea esculenta)
• It was one among the first yam species cultivated.
• It is native to Southeast Asia and is among the most
commonly cultivated species there.
• Its vines seldom grow longer than 3 m and the tubers are
rather small.
• It is easily prepared and have good flavor.
• The small size of the tubers allows for mechanical
cultivation.
7. Air potato (Dioscorea bulbifera)
• It forms bulbils at the base of the leaves.
• The bulbils are more important food product compared with
the tubers.
• The name ‘air potato’ is derived from the size of the bulbils
equaling those of potatoes (0.5–2 kg).
• Air potato is hardly grown commercially.
• But, it is popular in home gardens as it starts yielding after 4
months and continues producing for the entire life of the vine
8. Chinese yam (Dioscorea opposita)
• As the name suggests, it is native to China
• The plant is smaller than the African yams.
• Its tolerance to frost enables cultivation in much cooler
climates.
• It is mostly being grown in China, Korea, and Japan.
• The tubers are harvested about 6 months after planting
9. Bitter yam (Dioscorea dumetorum)
• The cultivation of this species requires less labor
than other yams.
• Its wild forms may be highly toxic.
• They are used as bait and subsequently used to
poison animals.
11. sree keerthi
• A high Yielding variety of Greater yam( Dioscorea alata ) with
large sized tubers, good cooking quality and excellent taste.
• It is a clonal selection from germplasm.
• They Climb to a height of 4-5 m.
• Starch content is 20-22 % on fresh weight basis and maturity
duration is 9-10 months.
• Average Yield is 25-30 T / Ha.
• They are suitable for intercropping with banana and can be
grown in mature coconut gardens.
12. Sree Shilpa
• It is the first hybrid released in Dioscorea alata.
• Inter varietal hybrid between Da-140 & Sree Keerthi
• Tubers are medium sized, oval and has good cooking quality.
• It has cordate leaves with overlapping lobes, lamina slightly
cupping, and petiole purple at both ends.
• Swollen oval tubers with white flesh.
• Yield potential is 40 t/ ha. and average yield is 28 t/ ha.
• They are easily harvestable.
13. Sree Roopa
• It is a variety of Greater yam
( Dioscorea alata )
• Tubers are medium sized and
excellent cooking quality.
• It is also a clonal selection from
germplasm.
• Starch content 16-18 % and
protein 1-2 % on fresh weight
basis.
• Duration is 9-10 months and
average yield is 25-30 T / Ha.
Sree Karthika
• High yielding greater yam
variety
• Tubers long, oval with
excellent cooking quality.
• Maturity period is 9 months
• Average yield is 30 T/Ha.
14. Sree Latha
• A high yielding and widely adaptable variety of Lesser yam
(Dioscorea esculenta ).
• It is a selection from indigenous germplasm.
• They climb to a height of 2.5-3 m.
• Duration is 7.5- 8 months and average yield is 25 T/ Ha.
• Cooking quality fair, non bitter with good flavor and
acceptable taste.
• Starch content is 24.4 % and shelf life of tuber is 2-3
months.
15. Sree Kala
• Early maturing variety of lesser yam.
• It is a selection from exotic germplasm named Kombi.
• It matures in 7 months.
• oval tuber shape and has excellent culinary quality.
• Average yield is 20 T/Ha.
16. Sree Priya
• A high Yielding variety of white yam ( Dioscorea rotundata)
• It is a seedling selection from the African variety Umidika
• Cylindrical tubers and excellent cooking quality.
• They are drought tolerant with novel flavored
• Suitable for intercropping in mature coconut gardens as well
as with banana.
• Starch content is 20 - 21 % and protein content is 2- 3 % on
fresh weight basis.
• Maturity duration is 9 - 10 months and average yield is 35 -
40 T / Ha.
17. Sree Dhanya
• A high yielding variety of white yam (Dioscorea rotundata )
with cylindrical tubers.
• It is the first dwarf bushy variety and it does not require
staking
• It is accommodated in closer spacing.
• Duration is 9 months. Average yield is 20 T / Ha.
18. Sree Subhra
• It is a selection from the African variety lwo.
• Tubers are brown skinned and partially hairy with cylindrical
shape.
• They are drought tolerant.
• Starch content is 21-23 % on fresh weight basis and average
yield 35-40 T / Ha.
• Duration is 9 - 10 months.
19. Sree Neelima
• It is a high yielder (35 / ha)
• Has good culinary and
nutritive quality
• Tuber light purple flesh
color
Sree Swathy
• It is a greater yam variety
released for its high
yield(30 t /ha)
• Moderate tolerance to
anthracnose disease.
20. Orissa Elite
• It is a clonal selection of
greater yam with long
cylindrical tubers.
• They have excellent
cooking quality.
• They are field tolerant to
leaf spot, scales and mealy
bugs.
• Avarage yield is 25 T/Ha.
Indu
• Released from KAU
• It is grown as pure crop as
well as intercrop.
• Suitable for the alluvial soil
of Kuttanad.
21. USES:
Consumption:
• A popular product made from white and yellow yam named
‘Fufu,’‘Foutou,’ or ‘Iyan’ or ‘Pounded yam’ which is usually
eaten with different sauces and a source of animal protein.
• ‘Ube,’‘Ubi,’ or ‘Uhi is a product prepared from water yam
which is popular in west Africa.
Medicinal:
• It contains abundant amounts of thiocyanate, which is an
agent counteracting sickle cell anemia in humans.
• Dioscorea batatas, a species cultivated in China (locally
called ‘Shanyao’) only for medicinal purposes are used in
anthroposophist medicine.
• Dioscorea villosa, a species rich in diosgenin(steroid)which
is used in estrogen replacement therapy
22. botany
• Yam tuber has its origin in a hypocotyl structure.
• Tuber grows from a small corm structure located at base of
stem.
• 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)
23. CLIMATE:
• The climate of is of two wet seasons: the main wet
season begins in March and ends in July, and a shorter
one occurs in September and October.
• It is characterized by a mean air temperature of around
27⁰C.
• a relative humidity of about 70%, and an annual rainfall
of 1000–1200 mm.
SOIL:
• Yam is grown in fertile forest soils and also cultivated
in sandier savannah types of soils.
24. Propagation
Tubers
• This is the most important method of propagation in the
field.
• The planting material is called a ‘set’ and the size of each set
should be between 400 and 500 g.
• The sets are pregerminated in moist sawdust or coconut coir.
• There are three types of sets that can be obtained from whole
tuber– head sets ,middle sets, and tail sets.
• Head sets are the best to plant because of the presence of
eyes, which give rise to the new plants.
• Whole small tubers can also be planted.
25. Minisets
• Minisets are small pieces of tubers of 25–50 g size that are
dipped into a fungicide/insecticide.
• The cut surfaces are then allowed to dry before planting to
produce seed yams (planting material)
• The miniset technique produces both healthy and high-
yielding planting material while reducing costs of seed yam
production and improving availability of planting material.
26. Vine cuttings
• Vine cuttings are another way to produce plants that form
healthy mini tubers to be used as seed material.
• 6- to 8-cm-long basal vine cuttings are dipped into a rooting
hormone and placed into a propagating bin.
• If successful, vine cuttings give a high multiplication rate
without the use of tubers,which can limit the costs for
planting material.
• This method is still poorly adopted by farmers.
• However, with the expected simplification of this
technology, farmers could apply it in order to produce
healthy seed tubers.
27.
28. Planting method
• When cultivating as monocrop, yam is planted with
a spacing of 50-100 cm X 100cm.
• In intercropping the distance between yam plants is
determined by the number and types of associated
crops.
• Yams are planted using four main methods, namely
(1) ridges
(2) mounds
(3) holes
(4) flats.
29. manures
• Apply cattle manure 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 .
• 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.
30. Irrigation
• At weekly intervals in the initial stage and later at about 10
days interval.
• During rainy season no irrigation is needed.
Intercropping.
• Intercropping with legumes like cowpea, horsegram, cluster
bean and French bean has been found to smother weeds.
• Provide an extra income without adversely affecting the
tuber yield and diosgenin content.
31. Staking of yam
• It is necessary to optimally expose the leaves to the sunlight
throughout its growth, especially in the climbing yam.
• The larger the surface area of the plant exposed to sunlight,
the higher are the yields that are obtained.
• Nonstaked cultivation is also practiced.
• It suppresses weeds better, but gives lower yields.
• Yam plants are usually staked soon after emergence.
32. • Different methods of staking include
(1) individual staking (one stake per plant)
(2) pyramidal staking (tops of several stakes
are slanted to form a peak),
(3) trellising (string wire between two strong
posts).
Unstaked plants
34. Weed management
• Weed control is most important during the first 12– 16
weeks after planting for seed yam i.e. until the yam foliage
will start covering the soil.
• The critical period for table yam is 4–16 weeks after
planting.
• Weeding is done 3–4 times during the season.
• Yield reduction of upto 90% due to heavy weed infestations
have been reported.
35. Harvesting
• Yams mature 7–9 months after planting, indicated by the
yellowing of the leaves and natural dieback of the vines.
• In order to maximize yield, harvesting must be done when
the yam reaches full maturity and before the soil becomes
too dry.
• Yields about 20-25t/ha.
Curing
• yams with bruises must be cured, and dipped in wood ash, in
order to avoid fungal rot.
36. Storage
• Good storage is best achieved in shaded, cool conditions
(29–32⁰C) with relative humidity of 90–95%.
• Traditionally, yam is stored in barns of vertically arranged
wooden poles and palm leaf midribs.
37. Pest of yam
NEMATODES (Scutellonema bradys and Meloidogyne spp.)
• Early nematode attack endangers seedling emergence due to
rotting of the sets in the soil.
• Important preventive measures include proper clearance and
land preparation.
• Nematodes can be controlled by crop rotation.
• Staggered planting is also effective.
• Intercropping of Crotalaria spp. alone, or in combination
with pigeon pea(Cajanus cajan)has also shown to be an
effective control measure.
38. YAM BEETLE
• Attack occurs just before harvest when the beetles feed
voraciously.
• The holes the beetles drill into the tubers reduce their market
value.
• Incidences of yam beetle can be controlled by growing the
crop far away from water bodies.
• Spraying with botanicals such as neem preparations
• Mulching with Cymbopogon citrates and Ocimum viride
reported as effective control strategies.
39. MEALY BUGS (Planococcus dioscorea) and SCALE
INSECTS (Aspidiella hartii)
• Mealy bugs and scale insects form whitish colonies, which
may cover the entire tuber.
• The sucking insects cause a certain weight loss of the tuber.
• Infested tubers are not suitable for sale.
40. Diseases of yam
TUBER ROTS (Botryodiplodia theobromae, Rhizopus
nodosus, Fusarium oxysporum, Fusarium solani)
• Tuber rots mainly affect tubers of white yam, especially in
storage.
• Tubers having suffered damage to their epidermis must not
be stored in the same lot as unaffected tubers.
• yam sets may be dipped in ash solution and air-dried before
planting.
• Fungal incidences can also be controlled by a proper crop
rotation.
41. YAM MOSAIC VIRUS
• Transmitted by aphids.
• Typical symptoms on yams include mosaic, shoestring,
green vein banding on leaves, and stunting.
• Effective preventive measures involve planting of resistant
varieties and the use of healthy planting material
42. ANTHRACNOSE
• Anthracnose is a serious disease, which can have devastating
impacts in early stages.
• Attacks results in blackening between leaf veins and dieback
of leaves.
• The disease is favored by wet, humid, and warm weather
conditions.
• It is most severe on white yam than on other edible yams.
• Anthracnose spreads by infected seed, rain splash, and moist
wind
• Use of resistant variety is the best way to control.
