Concept of Breeding Techniques

Introduction

Breeding is the branch of biology which deals with the production of improved and new crop varieties, which are superior to exisiting varieties with several charactceristics. It helps for the production of several superior qualities originally found in verious plants crops into a single plant.

Plant breeding is the branch of biology that deals with improvement of heredity characters of crops and production of new crops with better and varieties of characters.

Objectives of plant breeding

Some of the objectives of plant breeding is mentioned below :

1. Increase in the yield : The most challenging part of present world is to provide enough food supply for the increasing population. Though a great improvement in the method of agriculture and irrigation different kinds of fertilizers are used and increases in the area of land for agriculture have been done, still the food production is not enough. So, to overcome this problems plant breeding can be the best solution. Since, with the help of plant breeding, plant with a better production both in quality and quantity can be obtained.
2. Improved quality: The quality of different plants is different. For example, grain size, colour milling, baking quality in wheat. If we are able to introduce a plant with the different quality characters by breeding technique. We can have the best quality.
3. Agronomic characters: Improvement in characters like plant height, tillering, branching, erect habit etc, are desirable. Generally the drawfness in cereal plant used due to lodging resistance and responsiveness for fertilizers.
4. Change in the duration of maturity: It permits new plants rotations. The maturity period of plant can be with this technique.
5. Resistance to disease insect pests: Normally crops are destroyed by different insects pests as well as by different diseases. Scientists have done a lot of effort to made varieties which can defense to different disease as well as insect pests.

Method of plant breeding

The method involved in plant breeding are :

1. Introduction

2. Selection

3. Hybridization

4. Mutation

1. Plant introduction

It is the process which involve in the introduction of high yielding varieties of plants from their growing locality to the new locality. It is also known as the easiest and improvement. This is simply the planting of plant growing in one place to another place. The introduce plant will adjust the new environment on its own. This adjustment is known as acclimatization.

2. Selection

It is the traditional method of breeding and it was only practice by man in ancient time. It is simply the technique of breeding which deals with the selection of better one from the entire crop plants. There are three method of selection –

1. Mass selection
2. Puree line selection
3. Clonal selection

1. Mass selection-It is the traditional and easiest method of development practiced by the farmer in ancient time.The best looking and healthy plants areselected from the entire plant in the filed and harvested for better result.This technique only depend on the external characters phenotype which involve in the improvement of local or wild varieties.

2. Pure line selection or single plant selection – In 1903, W.L. Johannes of Denmark individual obtained by selfing”.In other word pure line can be defined as a group of plants which are obtained from a single self-fertilized homozygous plant. Pure line selection is the process of selection of homozygous plant from the mixed population and multiplying them without any contamination to produce healthy offspring.

3. Clonal selection- In some plant, due to the low viability, seeds may not found. In such condition, plants use some other extra vegetative organs for their propagation. Fruits likes mango, apple, orange, they have a wide heterozygosity and have high degree of polypoidy. If such plants are propogated by seeds, they may show variation in characters which may affect the purity of race and cause low amount of production. The plant obtained by vegetative is called clone. The clone of plants are genetically identical in nature. After many years of vegetative propagation, it again shows its original characters.

Hybridization

It is the process which deals with the artificial crossing of to genetically different plant for producing new varieties. Hybridization mostly deal with creation of a variable population for the selection of type and with desired combination characters artificially. Many valuable characters scattered in different species, varieties can be found in a single variety containing all good characters.

Kind of hybridization:

The crossing over can be done within some or different species. Hybridization have following types on the basis of taxonomic relationship between parental plants involve in the group:

1. Intra- specific hybridization
2. Inter-specific hybridization
3. Intra-genic hybridization
4. Inter-genic hybridization

1.Intra-specific hybridization- This is the type of hybridization which involve in the crossing over between the same species. Usually these crosses are useful for the development of self pollination crops. Hence, it can be useful for only to maintain and improve the individual varieties.

2. Inter-specific hybridization- This is the type of hybridization which involve in the crossing over made between the plants of two different varieties of the same species. In this hybridization the desirable characters of both the parental plants can be combined. This cross can be made in both the self pollination and certain cross pollination crops. A desirable varieties of plant can be produced in this hybridization.

3. Intra- genic hybridization- This is the type of hybridization in which the crosses are made between the plants of different species of the same genus. This method is able to produce diseases and pest resistance plants.

4. Inter-genic hybridization- This is the type of hybridization which deals with the crosses that are made between two different genera of the same family. The parental plants are taxonomically distant related. Some of the example of this type of hybridization are; Triticale, Rabble, Raphanobressica, etc. This technique also produces the plants that can resist the diseases as well as pests.

Brinjal + Tomato = Bromato

Sugarcane + Sorghum = Sugarcane-sorghum

Usefulness of hybridization

Hybridization is the one of the most useful technique that works for the welfare of human beings. Plant breeding technique also even help in the Nepal to create many new plants. It is most important for the agricultural countries such as Nepal. It helps to form new and advance plant which enhance the agriculture as well their economic status. It helps to obtain diseases and pests resistance plant which can uplift the agriculture.

Hybridization procedure

The steps of hybridization procedure are as follows:

1. Selection of parents- The first step of hybridization included the selection of parental plant for the cross. The selected parental plant must have the desirable characters that want in the resulting plant. Plants are selected on the following basis:

i). The parental plant must have maximum number of desirable characters.

ii). It should be healthy and vigour.

iii). It should be tested for their homozygosity.

2. Emasculation- It is the second step of hybridization in which the stamens are removed carefully before maturity of anther. The process of removing the stamen before anthesis is known as emasculation. Only the flowers of female parent are emasculated to prevent the self pollination.
3. Bagging, tagging and labeling- This is the third step of hybridization which involve in the bagging, tagging and labeling of the emasculated flower of female parents.
4. Crossing- It is the fourth step of hybridization in which cross pollination is done artificially between genetically unlike plants. In this process pollen of the selected male flower is brought in contact to the female emasculated flower and artificial pollination is done.
5. Harvesting seeds and raising plants- It is the fifth step of hybridization in which crossed seeds are collected and harvested and the result is observed.
6. Trial, multiplication and distribution- It is the sixth step of hybridization which is also known as trial period. Here, the seed are distributed among the farmer and multiplied.

Refrence:

Arvind K. Keshari,Kamak K. adhikari. A Text Book of Higher Secondary Biology. Kathmandu: Vidyarthi Pustak Bhandar, 2014.

Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069

Mehta, Krishna Ram. Principle of biology. 2nd edition. kathmandu: Asmita, 2068,2069.

Jorden, S.L. principle of biology. 2nd edition . Kathmandu: Asmita book Publication, 2068.2069.