Taxonomy morphology

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A. Lopez-Montes, Edemodu Alex
Training on increasing capacity of research technicians in breeding
IITA, Ibadan July 27th to August 14th, 2015
Yam Biology and Botany

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OUTLINE
Taxonomy
Morphology

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 Monocotyledons
TAXONOMY
 Ord.Dioscoreales
 Fam.Dioscoreaceae
 Genus:Dioscorea
 Sections:
Enantiophyllum
Lasiophyton
Combilium
Opsophyton
Macrogynodium

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TAXONOMY
 Sections: Enantiophyllum D. rotundata
D. alata
D. cayenensis
D. opposita
D. japonica
Vines twine
to the right
Lasiophyton
D. dumetorum
D. hispida
Combilium
Opsophyton
Macrogynodium
Vines twine
to the left
D. bulbifera
D. trifida
D. esculenta

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 Diverse yam species
D. alata
D. dumetorum
D. bulbifera
D. rotundata
 Variability
within species
D. alata
Heterogeneous varieties
Food security Resilience Sustainability Income generation Interspp. hybrids
Advantages of Diversity and Variability of the Genus
TAXONOMY
D. esculenta
D. trifida
D. dumetorum

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ABOVE GROUND
From expose lower nodes
From the tuber’ bark
From the corm-like structure
Adventitious roots
0-30 cm
Very few more than 1 m
MORPHOLOGY
UNDER GROUND : Two Structures
Fibrous root system
Storage organs or tubers
Vine – like stems
Leaves
Inflorescence
ROOTS
TUBERS
Originated from hypocotyl
Bulbils in leaf axils
Shape, number and form: Vary
depending of specie

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From the corm-like structure
Adventitious roots

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From the tuber’ bark
Adventitious roots

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Stem
MORPHOLOGY
Twining vines: Circummutation
Branches
Shape: depend on the specie,
Cross section:
alata: stellate, rectangular or polygonal
Other spp: circular or cilindrical
Stem structure:Typical Angiospermae
Epidermis: stomata and glands
Stem cortex: 3 to 7 layers of cells
Contain chlorophyll : Green
Dwarf only reported in D. rotundata
Leaf
Borne in long petiole
Usually simple, cordate or accuminate
Leaf arrangement: opposite or alternate
Typically not pubescent
Anatomy: typical of a monocotyledon leaf
Stomata present only in the lower epidermis
Except D. bulbifera with some few on the
upper leaf epidermis

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MORPHOLOGY
Bulbils
D. alata
D. bulbifera
Occasionally D. rotundata
Produced in the leaf axils at the same time that underground tuber
Leaf axil: three primordia; one for bulbil and two for buds
Inflorescene
D. alata, D. bulbifera, D. rotundata, D. cayenensis: are dioecious,
Ocassionally monoecious in D. rotundata
Simple or compound: Spikes (racemes) are verticillated: congested in leaf axil
Flower Size: 2-5 mm in diameter
Male spikes: short (5-6 cm); Female spikes are larger

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Inflorescence
MORPHOLOGY

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Staminate flowers: Small, incospicuous, born axilary or terminally
Sesile, glabrous and spherical
Calyx of three sepals, greenish yellow in color
Corolla of three petals, greenish yellow in color
3-6 staments
Anher: two sacs, dehise releasing highly vacuolated, small, sticky pollen
grains.
Pistilate flowers: Up to 60 flowers per spike in D. rotundata
Size: about 5 mm long
Calyx of three sepals, greenish yellow in color
Corolla of three petals, greenish yellow in color
Simple pistil has a trifurcate central stigma, 2-3 staminoides around the
style
MORPHOLOGY
Flower

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Source: Asiedu et al 1998
MORPHOLOGY

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Dehiscent, tri-locular capsules, two seed per capsule
Seeds are winged: wind dispersal
Wing can encircle all or part of the seed
Embryo is small
FRUITS and SEED
MORPHOLOGY

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FRUITS
MORPHOLOGY

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MORPHOLOGY
Senescence and
mature fruit

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THANKS
Future Vision