WHAT IS ARTIFICIAL HYBRIDISATION?

Artificial hybridization is one of the major approaches to crop improvement programs. This process involves using only desired pollen grains and protecting stigma from contamination [here, contamination refers to unwanted pollens].

Artificial hybridisation

Pollen-stigma compatibility is essential for successful pollination and fertilization. Once a compatible pollen grain lands on stigma and gets accepted by pistil, the process of fertilization starts. The dialogue between the pollen and stigma is mediated by chemicals & ions, especially Boron, etc.

Pollen-pistil interaction taking place in hybridization is essential in crop improvement programs as only desired pollens are introduced on stigma through pollination in artificial hybridization. This process helps avoid unwanted pollens to get over stigma, thereby saving time, and helps in growing plants with desired traits or characters.

Steps in Artificial hybridization:

The hybridization process involves two steps:

1.EMASCULATION

2.BAGGING

--EMASCULATION

Since we know that this process is a method of selective breeding thus, before the anthers mature, these are to be thrown out before these could release pollens. So, the step of removal of anthers from a flower [especially bisexual ] before it could release pollens is called Emasculation.

This process has no importance in Unisexual flowers [ pistillate flowers- having pistils only] and is done by forceps.

The above figure clearly depicts how emasculation is done by using forceps.

Types of emasculation:

1.Hand emasculation: In plants with large flowers, emasculation can be achieved by removing anthers by forceps.

2.Suction method: Used in case of small flowers. When flowers open in the morning, anthers are sucked out using a suction tube.

3.Hot water treatment

4.Alcohol treatment: This method is not used commonly. In this method, the whole inflorescence is dipped into an alcohol solution.

5.Cold treatment

6.Genetic emasculation.

7.Use of gametocide: like Zinc methyl arsenate in rice.

2. BAGGING

After the removal of anthers, now the stigma has to be protected from foreign pollens[ undesirable pollen grains ].

For this process, the flower has to cover with a pollination bag.

Pollination bags are designed to fit well over the inflorescence or individual flowers of a plant type. The bag's size, shape, and strength should ensure that there is no contact with flowers to avoid the development of diseases and physical hindrances in seed development. The size of the bag will vary with the size of the inflorescence to be covered. Pollination bags may be 2D or 3D. The 3D bags have a gusset for expansion to avoid contact between the plant and the bag. Sometimes pollination bags may have a window to allow examination of inflorescence without removing the bag. Bags with a flap over the window, when provided, protect from strong sunlight. [ source: Wikipedia ].

POLLINATION:

The pollen grains from the desired male parent should be transferred to the emasculated flower. This is normally done in the morning hours during anthesis [ opening of flower bud]. The flowers are then again bagged after artificial crossing.

TAGGING:

The flowers are tagged just after bagging. They are attached to the inflorescence or the flower with the help of a thread.

The tag contains the following information,

Date of emasculation

Date of pollination

Parentage

No. of flowers emasculate.

SUMMARY OF ARTIFICIAL HYBRIDISATION:

Thus, artificial hybridization involves is the technique for crop enhancement by producing desired characters in the plant by various techniques like emasculation, bagging, pollination, and tagging.