Breeder technicians grain legumes Morphology, Physiology

www.iita.orgA member of CGIAR consortium
Research Technicians’ Training
Grain Legumes
Morphology, Physiology etc.

Legumes are classified into three groups
- Caesalpinacea
- Mimosacea
- Papilionacea

Important food leguminous crops:
• Soybean
• Cowpea
• Groundnut
• Common bean
• Pigeon pea
• African yam bean
• Bambara groundnut

• All of these economically important grain
legume crops belong to the family Papilionacea
• As legumes they fix atmospheric nitrogen in
their root nodules
• Many benefit from inoculation with the
bacterium – Rhizobium
• Usually they do not need nitrogen fertilizers

Uses of legumes
 Pulses i.e. dry grains – cowpea, green gram,
common bean, pigeon pea, mung bean, Lima
bean etc.
 Oil seeds – groundnut, soybean
 Cover crops & manures – pueraria, lablab,
centrosema
 Dyes – Indigofera, Pterocarpus

Uses contd.
 Livestock feed – cowpea haulm
 Shade trees - Gliricidia
 Ornamentals - Jacaranda, Cassia

• Grains of legume crops are rich in
protein, minerals, starch/carbohydrates,
dietary fibre
• They complement amino acids in cereals
• Some grains have anti-nutritional
components

 Leaves are alternate and usually compound
 Flowers are showy, irregular and mostly
hermaphrodites
 Flowers have the standard petal, wings and
keel
 Each anther has two locules dehiscing
lengthwise

 Usually 10 stamens
 Anthers dehisce lengthwise to discharge pollen
 Ovary with one locule is surrounded by the
stamens
 Fruit/pod split along ventral suture or could be
non dehiscent

As with other crops selection from primitive to
modern forms have resulted in:
 Plants allocating more carbon and nitrogen
to fruits than to vegetative parts
 Increased fruit and seed sizes
 Fruit less prone to shattering
 Reduced or lost seed dormancy

Cowpea – Vigna unguiculata L. Walpers

 Cowpea is the most important grain legume crop
grown in the dry savannah regions of Africa
 The highest production comes from West Africa
 Nigeria produces and consumes the highest
amount of cowpea grains
 Yield is generally low due to abiotic and biotic
stresses

Originated in Africa –
Highest level of genetic
diversity in sub-
Saharan Africa

 Cowpea grows in areas with rainfall of 400
mm to >1,200 mm
 It is therefore adapted to drought prone
areas of the savannah
 Most cowpea come from the sahel and sudan
savannah.

• It has 11 pairs of chromosomes; 2N = 22
• Leaves are alternately arranged on stem
• Leaves are trifoliate
• Leaves are glabrous in cultivated lines,
hairy in some wild relatives

Hastate
Globose

• Petioles have swollen bases
• Stems are cylindrical, mostly green with
purple pigment at nodes or entire stem
surface.
• Plant habit could be erect, semi-erect or
prostrate.
• Stems climb when plant is shaded.

Cowpea is typically day length sensitive
 Plants flower early during short days
 Long day length delays flowering but does not
prevent flowering
 Most modern varieties are day length
insensitive

Cowpea and soybean plants develop from seeds
• Plants go through seedling, vegetative and
reproductive stages of development
• Plants could be determinate or indeterminate
• Modern varieties are mostly determinate
• Indeterminate types produce more fodder

 Dry matter accumulation in cowpea
and soybean during vegetative and
early reproductive stages are
comparable
 Higher leaf area duration (LAD)
resulted in more grain yield in
soybean than cowpea

Leaf area index (LAI) = dimensionless
quantity that characterizes plant
canopies.
It is the one-sided green leaf area per
unit ground surface area (LAI = leaf
area / ground area, m2 / m2)

 Cowpea has strong tap root system
 Roots can grow up to a depth of >1 meter
 Roots are important in water and mineral
absorption and possibly drought tolerance
 Roots have nodules in which live symbiotic
bacteria

 Cowpea symbiose with nodule bacteria
found across Africa
 The bacteria – Rhizobium converts
atmospheric nitrogen to compounds that
host plant can assimilate
 Cowpea can fix up to 150 kg N/ha
 Supplies 80-90% of the host plant’s N needs

 Nitrogen fixed before flowering contributes
about 60% of the fruits total requirement for N
 Leaves and nodulated roots in particular
contribute their mobilised N to the fruit
 Petioles, stems and peduncles also contribute but
to a lesser extent
 Remaining 40% required N in fruit come from
fixation after flowering

 Usually, indeterminate varieties fix more N
than determinate varieties
 Late maturing varieties fix more N and leave
more in the soil after harvest – dropped leaves,
stems and underground roots release N
contained in them to the soil

• Flowers are showy
• Could be white, yellow, light or deep
purple coloured

• Flowers are borne on very short pedicels
attached to peduncles which vary in length
depending on the variety
• Inflorescence is axillary and crowded to the tip
of peduncles
• Cushion-like nectary is located between pairs of
flowers
• Peduncles develop from the nodes

 Flower buds light
coloured when
ready to open
 Anthers dehisce
on day flower
opens

 Dissected flower
bud with intact
anthers

Emasculated flower bud

 Like all legumes most of the flower buds
drop in cowpea and soybean. Between 20
and 80 %
 Only a few develop into pods
 Number of pods per peduncle varies with
varieties but usually not more than
four/peduncle. There could be five or more
pods on some peduncles.

 Pods contain variable number of seeds each
 Seeds/pod could range between 1 and up to 20
in very rare cases.
 Length of pods depends on seed number
present
 Yardlong bean (V. sesquipedalis) can reach up
to 1 meter and more in length

 Grain is the most economically important
part of cowpea
 Grain yield depends on:
 Number of seeds that mature
 Cultivar performance
 Environment
 Plant population density
 Stress caused by biotic factors
 Nitrogen source

Seeds are variable
in size, shape and
colour

 Grain yield adversely affected by
drought and high night temperature
 Insect pests
 Aphid at seedling
 Flower thrips at flowering
 Maruca at podding
 Pod sucking bugs at pod filling
 Bruchid on stored seed/grain

Bread dough with 10% cowpea flour

Thanks for your attention

Breeder technicians grain legumes Morphology, Physiology

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