Breeder technicians grain legumes Morphology, Physiology

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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

Government & Nonprofit