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🫘 Crossing Techniques in Red Gram

Emasculation and crossing techniques used in red gram breeding programmes.

This lesson covers core principles and exam-focused points from this topic in plant breeding.

Self pollination is the rule in Red gram and natural crossing extents up to 65 per cent.

Therefore it is also known as often cross pollinated crop.

Adaptations for self pollination

  1. Bisexual

  2. Close proximity of anthers and stigma

  3. Simultaneous maturity of anthers and stigma.

Selfing, emasculation and pollination techniques in Red gram

Selfing

Mature flower buds are to be covered with paper bags for one or two days.

Crossing

Hand emasculation followed by artifical cross pollination is essential. Emasculation

should be done in the previous day evening and the emasculated buds are protected by covers.

Early morning on the next day, pollination is done using pollen collected from the protected

flowers of the selected male parents.

Black Gram ( Vigna mungo ) (Diploid, 2n = 22 & 24) Family – Fabaceae

Self pollination is the rule. Here pollination occurs before floer opening (cleistogamous)

in night. Anthesis time 1 am – 4 am. The flower opens in the morning at 7 am. The interval

between pollination and opening of flower is 4 hours. This ensures self fertilization.

Selfing, emasculation and pollination techniques in Black gram

Selfing

As in red gram, bagging is done to avoid insect contact.

Crossing

Young unopened bud is kept between thumb and fore fingers of the left hand. The point

of dissecting needle is inserted just under the standard petal in an oblique position along the top

of the bud. The left side of the standard and wing petal are pushed outward and held with thumb

and left hand. The left side of the keel petal is removed with the forceps. The pistil and stigma

are then exposed and the anthers are removed with the forceps. Evening emasculation followed

by morning pollination gives best results. Pollination is done by gently rubbing anther of male,

inserting the staminal column and closing it with standard and wing petal. Since flower shedding

is common, putting better paper bag is avoided. The emasculated flowers are identified with

thread wound round. The crossed pod will be smaller in size with two or three seeds only.

Cowpea ( Vigna unguiculata ), Family – Fabaceae (Diploid 2n = 22 and 24)

Pollination

Highly self pollinated because of Cleistogamy, Close proximity of the anthers and

stigma and Simultaneous maturity of anthers and stigma

Selfing

Keeping the plants in insect proof cages will lead to selfing. Covering of individual

flower buds will lead to poor pod setting.

Crossing

Select young buds, in an inflorescence and remove all immature buds. Split open the keel

petals and remove the stamens one by one holding the filaments. Bring corolla back to position

and cover the bud with a folded leaflet. Protection is given by keeping the plants in insect proof

cages. Pollination is done on the next day morning by exposing the stigma from the keel petal

and brushing it with the pollen collected from the male parent.

Selfing and crossing are the essential procedures in crop improvement process. The exact

procedures used to ensure self or cross-pollination of specific plants will depend on the floral

structure and normal manner of pollination. Generally effecting cross-pollination in a strictly

self-pollinating species is more difficult than vice-versa because for instance preventing self

pollination occurring inside the unopened flowers is cumbersome.

Bengal Gram – Cicer arietinum (2n = 14, 16), (Channa, Chick Pea), Family –

Fabaceae

Chickpea is a self pollinated species with normal out crossing limited to 1.58%. self

pollination takes place one or two days before opening up of the flower. The flower open in the

morning and close in the afternoon and each flower opens on tow or three successive days. Time

of anthesis is 3 AM to 9 AM. For hybridization crossing work should be started when the first

pod on the selected plant is already formed. In Northern India, emasculation is done a day prior

to pollination. The pollination is done in the morning hours give better setting. In south India,

pollination immediately after emasculation give higher seed setting.

Soybean _ Glycine max _ (2n = 40) , Family – Fabaceae

Flower open early in the morning. The pollen is shed normally shortly before or after the

flower opens. But pollen shedding may occur sometimes with in the bud itself. Normally cross

pollination does not exceed 1 percent.

Emasculation and crossing

Hand emasculation is the method followed for crop breeding which is tedious since the

floral parts are so small and seed set is also less. Emasculation is done in the evening and

pollination is done in the morning hours.

Groundnut ( Arachis hypogaea ) (2n = 40), Family – Fabaceae

Self pollination is the rule in groundnut. Anthesis commences at 6 am and continues upto

8 am. Anther dehisces two hours prior to opening of the flower. Twenty four hours before

anthesis, the buds are very small. During the day, elongation of calyx, proceeds slowly but

process gets accelerated during night.

Selfing

Since cleistogamous condition prevails in groundnut, selfing is most easy in this crop.

Usually covering is unnecessary and difficult. Keeping the plants in insect proof cages will

ensure self pollination.

Crossing

Mature flower buds which are ready to open in the next day are selected and emasculated

in the evening. They can be easily identified by the size and length of calyx tube. The flower

bud of groundnut is of crescent shape, being bulged on one side and slightly depressed on the

other. The keel petal is located on the bulged side and the standard is present on the depressed

side. For emasculation, hold the bud between the thumb and the index finger of the left hand and

with the help of a razor blade in the right hand; make a cut on the depressed side at two-thirds the

length below the tip so as to cut the standard and a portion of the wing petals. Then gently pull

the calyx and corolla by holding at the tip of the flower bud. By doing this, the sepals and the

petals except the keel would be removed, with the help of the fine forceps gently liberate the

bundle of stamens and the pistil from the keel and nip off the anthers.

With a hand lens, examine the tips of filaments so as to ensure complete removal of the

anthers. Take a piece of straw tube (used for sipping cool drinks), 4 to 5 cm long and close one

side opening by bending the tip. Cover the emasculated flower bud with the straw tube by

slowly inserting calyx tube into it. This would ensure perfect protection to the stigma from any

natural cross pollination. The next morning take out the straw tube, dust the stigma with the

desired pollen and reinsert the tube. Pollination between 7 and 8 am was found to give more

success. If the stigma is found dry, pollinate after smearing it with 2 per cent sucrose solution.

Next day early morning between 7 am and 11 am pollen is collected from mature yellow

anthers of the selected male parent and dusted on the receptive stigma. For cross pollination, the

selected male flower is held between thumb and the middle finger after the standard and wing

petals are removed. The flower with keel protruding is taken to the stigma of the emasculated

flower. A gentle push on gently keel by the finger forces lumps of pollen grains of the cover the

entire stigmatic surface. Five to seven days after pollination successful crosses will produce

gynophores (pegs) with the dried flowers at their tips. These are then introduced into small wire

rings of 4 mm diameter which are marked for respective crosses.

Sesame ( Sesamum indicum ) (2n = 26), Family – Pedaliaceae

Gingelly is a self pollinated (Autogamous) crop. In some varieties cross pollination also

takes place to a limited extend of 5-6 per cent. Very high cross pollination between 14 and 65 per

cent has been recorded in a few varieties in India. Hence, the crop can be classified as often

cross pollinated . Cross pollination may occur due to wind and bee activities. On a bright clear

day, the flowers open between 5 and 7 am. In the mature flower bud, just before the flower

opens, the four unripe anthers are much below the stigma which at this stage is not receptive.

The anthers begin to burst longitudinally after 4am in the next day and commence to liberate

their pollen. At this time, the stigma becomes receptive. The plant comes to flowering 4 weeks

after sowing.

Selfing

  1. Tieing with thread: Selfing can be effected by tieing the corolla of the unopened flower

which is selected in the previous day evening itself.

  1. Smearing of semi-solid clay: Selfing can be done by smearing a speck of semi-solid

clay, on the upper portion of tubular petals of unopened flowers. The clay while on

drying does not allow the tubular petals to open and hence self pollination is the rule.

This method is cheap and less time consuming one. This method is noat effective during

rainy days. During rainy days, fevicol may be applied on young flower bud to ensure

selfing.

Crossing

Soda- straw method

The emasculation technique in sesame is easy for crossing due to epipetalous nature of

the stamens. The flower bud which is expected to open in the next day morning is selected in the

previous day evening between 3 P.M. and 6 P.M. and emasculated by just removing the corolla

tube in which the stamens are attached. Then, the emasculated flower buds are covered with a

piece of soda-straw tube, bent at the top in order to avoid contamination from foreign pollens.

During the next day morning, between 7 A.M. and 9.A.M., pollen from the desired male parents

were dusted gently on the surface of the stigmas of the emasculated flower buds after removing

the soda-straw and again covered. The unemasculated flowers are removed in the female parent.

Individual crossed flowers are tagged with coloured thread for the identification of crossed

capsules. Different coloured threads are used for different type of crosses.

Sunflower ( Helianthus annuus ) (2n = 20), Family - Astraceae

Sunflower in highly cross pollinated crop mainly through insects ( Entomophily ) and to a

limited extent by wind (Anemophily). The flower opening starts from outerside of the head and

proceeds towards centre. The head takes 5-10 days for complete blooming depend on size of

head and season. Anthesis occurs between 5 to 8 A.M. Pollen viable for 12 hours. Stigma is

receptive for 2-3 days. The staminal filaments elongate rapidly and the anthers appear above the

top of the corolla. Anthers dehisce early than maturity of stigma. ( Protoandry ). In this crop, the

cross pollination occurs due to protandry, limited area of stigmatic surfaces for receptivity, ray

floret colour attracts insects and abundance of sweet secretions in the disc florets.

Selfing

The flower head is protected with a suitable cover before the commencement of anthesis

in any of the florets and the cover is retained till fertilization is over in all the florets. Artificial

self pollination with pollen collected from the same flower or another flower of the same plant

using a soft brush will enhance seed settings.

Crossing

i. Hand Emasculation

Emasculation is done in the early morning by removing the anthers of the disc florets in 2

to 3 whorls with forceps and the other florets in the head are removed. About 9-10 am the

pollens from desired male parent are collected and dusted on the emasculated head. This process

is continued for 2 to 3 days.

ii. Without emasculation

In sunflower, head emasculation is difficult. Considering this difficulty, the heads are

pollinated without emasculation. On the basis of hybrid vigour, plants are distinguished from the

selfed plants. The presence of marker genes for identifying hybrids is also utilised effectively.

iii. Chemical induction of male sterility.

This is achieved by spraying of 100ppm GA (Gametocide) during bud-initiation stage

consecutively for three days in the morning.

Pollination is carried out by collecting pollen from heads which are already bagged prior to

flowering. Pollen may be collected from flowering heads into paper bags. Pollination is done in

the morning by applying the freshly collected pollen by a small piece of cotton, a hair brush or

through fine cloth bag. After each cross, care must be taken to avoid contamination by wiping

the hands with alcohol.

Castor ( Ricinus communis ) (2n = 20), Family – Euphorbiaceae

Cross pollination is the rule in this crop. It is mainly wind pollinated. But insect activity

is also seen to some extend since the young leaves just below the inflorescence exude copious

nectar at the time of flower opening cause insect pollination. Unisexual flowers, protogynous,

elevated position of female flower in the inflorescence, mechanisms to promote wind pollination

and nectar glands to attract insect promotes cross pollination. Here male flowers open first

( protoandry ). After one or two days of male flowers opening, female flowers open. However,

protogyny is also reported. The opening is between 4.30 and 5.00 A.M. Pollen grains are viable

for a 2 days and stigma is receptive for 3 days. Each candle takes 10-12 days to complete

flowering.

Selfing

The whole inflorescence is protected with not yet opened are selected. From the selected

inflorescence all the male flowers are removed and the female flowers protected with a suitable

cover. Artificial cross pollination is done when the stigmas of the retained female flowers

become receptive by rubbing the anthers of male flowers collected from the selected male parent.

During the rain day old bags are to be replaced with new bags to avoid fungal attack, and free air

movement.

Crossing

  1. Emasculation: It can be achieved by removing or rubbing off the staminate flowers by

finger and thumb.

  1. Crossing: Pollen grains are collected from the desired male parent and are dusted on the

stigma of the female parent. Again the inflorescence is covered.

Summary Cheat Sheet

Quick Recall Points

  • This lesson focuses on key plant breeding concepts, terminology, and exam-relevant applications.
  • Review major definitions, classifications, and method-wise distinctions from the sections above.
  • Revise tables and examples from this lesson for fast pre-exam recall.

Exam Traps

  • Do not confuse similarly named breeding methods without checking their core selection logic.
  • Pay attention to crop-specific examples because the same principle can behave differently by species.

References

1 source • [1]

[1]

Standard Plant Breeding Class Notes (GPBR211)

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