Presentation on Plant Breeding Objective and Its Importance
1. Presentation On Breeding
Objective and its
Submitted to- Submitted by-
Dr. Kaushik Kumar Panigrahi Chandan
Asst. Prof 01C/14
Department of Plant Breeding and Genetics
Plant breeding is a science based on principles of genetics and
cytogenetic. It aims at improving the genetic makeup of the
Improved varieties are developed through plant breeding. Its
objectives are to improve yield, quality, disease-resistance,
drought and frost-tolerance and important characteristics of the
Plant breeding has been crucial in increasing production of
crops to meet the ever increasing demand for food. Some well
known achievements are development of semi-dwarf wheat
and rice varieties, noblization of Indian canes (sugarcanes), and
production of hybrid and composite varieties of maize, jowar
3. As written above, crop improvement means combining desirable
characteristics in one plant and then multiplying it. The job of a
plant breeder is to select plants with desired characters, cross
them and then identify the offspring that combine the attributes
of both parents. He then multiplies the progeny to supply to
farmers, growers or planters.
The modern age of plant breeding began in the early part of the
twentieth century, after Mendel’s work was rediscovered. Today
plant breeding is a specialized technology based on genetics. It is
now clearly understood that within a given environment, crop
improvement has to be achieved through superior heredity.
Plant breeding aims to improve the
characteristics of plants so that they
become more desirable agronomically and
economically. The specific objectives may
vary greatly depending on the crop under
The prime aim of plant breeding is to improve the characteristics of plants that they become more useful
automatically and economically. Some of the objectives may be summarized as follows.
1. Higher Yield:
Higher yield of grain, fodder, fibre, sugar, oil etc. developing hybrid varieties of Jawar, Maize,
2. Improved Quality:
The quality characters may vary from one crop to another such as grain size, shape, colour,
milling and backing quality of wheat, cooks quality in rice, malting in barley. Size shape and
flavour in fruits and keeping quality of vegetables, protein contents in legumes, methionine
and tryptophan contents in pulses etc.
6. 3. Disease and Pest Resistance:
Resistant varieties offer the cheapest and most convenient method of disease and pest control. They not
only helps to increase the production but also stabilize the productivity e.g. Rust resistance in wheat.
4. Maturity Duration:
It permits new crop rotation and extends crop area. Thus breeding for early maturing varieties suitable for
different dates of planting. This enables the farmer to take two-three crops in a year.
5. Agronomic Characters:
Three includes the characters such as dwarf, profuse tillering, branching erect resistance and fertilizer
6. Photo and Thermo Insensitivity:
Development of photo and thermo insensitive varieties in rice and wheat will permit to extend their
cultivation to new areas. E.g Cultivation of wheat in Kerala and West Bengal, Cultivation of rice in Punjab
and Himachal Pradesh.
7. 7. Synchronous Maturity:
It is desirable in crops like mung ( Vigna radiate) where several pickings are necessary.
8. Non-Shattering Characteristics:
E.g. Mung, Black Gram, Horse Gram, etc.
9. Determinate Growth Habit:
It is desirable in mung, pigeon pea and cotton, etc.
In some crops, seeds germinate even before harvesting if there are rains at the time of
maturity. E.g Mung, barley, etc. A period of dormancy in such cases would check the loss
due to germination while in other cases it may be removed it.
11. Varieties for a New Season:
Breeding crops suitable for seasons. E.g Maize (Kharif) which is grown in Rabi and
8. 12. Moisture Stress and Salt Tolerance:
Development of varieties for a rainfed area and saline soils would help to increase
crop production in India.
13. Elimination of Toxic Substance:
It will help to make them safe for consumption E.g Khesari ( Lathyrus sativus) seeds
have a neurotoxin causing paralysis.
14. Wider Adaptability:
It helps in stabilizing the crop production over region and seasons.
15. Useful for Mechanical Cultivation:
The variety developed should give response to application of fertilizers, manures
and irrigation, suitable for mechanical cultivation etc.
9. Scope of plant breeding
From times immemorial, the plant breeding has been helping the mankind. With
knowledge of classical genetics, number of varieties have been evolved in different crop
plants. Since the population is increasing at an alarming rate, there is need to
strengthened the food production which is serious challenge to those scientists concerned
with agriculture. Advances in molecular biology have sharpened the tools of the breeders,
and brighten the prospects of confidence to serve the humanity. The application of
biotechnology to field crop has already led to the field testing of genetically modified crop
plants. Genetically engineered rice, maize, soybean, cotton, oilseeds rape, sugar beet and
alfalfa cultivars are expected to be commercialized before the close of 20th century. Genes
from varied organisms may be expected to boost the performance of crops especially with
regard to their resistance to biotic and abiotic stresses. In addition, crop plants are likely to
be cultivated for recovery of valuable compounds like pharmaceuticals produced by genes
introduced into them through genetic engineering. It may be pointed out that in Europe
hirudin, an anti-thrombin protein is already being produced from transgenic Brassica
10. Important :Concepts
General Concepts: Special Concepts:
1.Plant introduction 1. Mutation breeding
2. Pureline selection 2. Polyploidy breeding
3. Mass selection 3. Transgenic breeding
4. Pedigree method 4. Molecular breeding
5. Bulk method
6. Single Seed descent method
7. Back cross method
8. Hetrosis breeding
11. Symbols for basic crosses
F: The symbol F (for filial) denotes the progeny of
a cross between two parents.
: The symbol is the notation for selfing.
S: The S notation is also used with numeric
subscripts. In one usage S0 = F1; another system
indicates S0 = F2.
12. Pureline refers to the homogenous progeny of a self pollinated
Mass selection is a method of breeding in which individual plants are
selected on the basis of phenotype from a mixed population , their
seeds are bulked and used to grow the next generation.
The deliberate mixture of isolines, closely related lines or unrelated
lines are referred to as multilines, and the method of developing a
variety from any of these mixtures is known as multiline breeding.
14. Key features:
2. Nonheritable variation
3. Highly uniform
4. Selection is ineffective
5. Narrow adaptation
6. More prone to new diseases
7. Isolation of pure lines
8. Sources of variation
15. ApplicationsPure-line breeding is desirable for developing cultivars for certain uses:
1. Varieties for mechanized production that must meet a certain specification for uniform
operation by farm machines.
2. for a discriminating market for visual appeal (e.g., uniform shape, size).
3. for the processing market (e.g., demand for certain canning qualities).
4. Advancing that appear in a population (e.g., a mutant flower for ornamental use).
5. Improving newly domesticated crops that have some variability.
1. It is a rapid breeding method.
2. The method is inexpensive to conduct.
3. The variety developed by this method has great “eye
appeal” because of the high uniformity.
4. It is applicable to improving traits of low heritability,
because selection is based on progeny performance.
5. Only the best pure line is selected for maximum genetic
1. The purity of the variety may be altered through
admixture, natural crossing with other varieties and
2. Narrow genetic base and so poor adaptability.
3. A new genotype is not created.
4. The method promotes genetic erosion
5. Progeny rows take up more resources (time, space).
6. Only applicable to self pollinated species.
18. Important Concepts of Breeding of Cross
1. Populations of cross-pollinated crops arc highly
heterozygous as well as heterogeneous.
2. Their genetic makeup is such that they show
variable inbreeding depression.
3. which in some cases may be very severe.
Consequently, breeding methods for cross-
pollinated crops aim at preventing inbreeding.
19. BREEDING METHODS FOR CROSS POLLINATED CROP
A) Mass selection
B) Recurrent Selection
1. Simple Recurrent Selection
2. Recurrent Selection for General Combining Ability
3. Recurrent Selection for Specific Combining Ability
4. Reciprocal Recurrent Selection
20. Mass Selection
Mass selection is the oldest breeding scheme
available for cross-pollinated crops.
In mass selection, a number of plants are
selected on the basis of their phenotype, and
the open-pollinated seed from them is bulked
together to raise the next generation.
21. The selected plants are allowed to open-pollinate,
i.e., to mate at random, including some degree of
selling (usually about 10% in maize, Z. mays).
Thus mass selection is based on the maternal
parent only, and there is no control on the pollen
22. Mass selection, as applied to cross-pollinated
crops is essentially the same as that applied to
self-pollinated crops; a generalised scheme for
the method is outlined in Fig. 1.1.
The selection cycle may be repeated one or
more times to increase the frequency of
favourable alleles; in such a case, the selection
scheme is generally known as phenotypic
23. The efficiency of mass selection primarily
depends upon the number of genes controlling
the character, gene frequencies and, more
importantly, heritability of the concerned trait.
25. Mass selection is an extremely simple breeding
programme. Work of the breeder is kept to a minimum
since selections is based on the phenotype of plants.
The selection cycle is very short, i.e., of only one
generation. Thus in every generation, one cycle of
selection is completed.
It is highly efficient in improving characters that are
easily identified visually and have high heritability,
e.g., plant height, size of car, date of maturity, etc.
Merits of Mass Selection
26. If proper care is taken, mass selection is effective in
improving yields of cross-pollinated crops.
Most cross-pollinated crops have a high additive
component of genetic variance, which responds to
Since the improved strain is likely to be similar to the
original population in the range of adaptation,
extensive yield trials may not be required before its
release as a new variety.
27. Selection of plants is based on the phenotype
of individual plants.
Most of the quantitative characters are
considerably affected by the environment.
Therefore, superior phenotype is often a poor
basis for the identification of superior
High intensities of selection reduce
population size and, as a result, lead to some
Demerits of Mass Selection
28. The selected plants are pollinated by both
superior and inferior plants present in the
population as the selected plants are allowed
to open-pollinate. This reduces the
effectiveness of selection.
Inbreeding depression may nullify the advances
made under selection.
29. Main Features are as follows:
1. Application: Recurrent Selection was
originally developed as a method of breeding
cross pollinated species. Now it is also used in
self-pollinated species. However, it is more
commonly used in cross pollinated species
than in self-pollinated species.
2. Base Population: A heterozygous base
population (cross pollinated species) is
required to start recurrent selection.
30. 3. Important Steps: A simple recurrent selection
scheme consists of five main steps (i) selection of
superior plants from base population (ii)Selfing of
selected plants (iii) Growing progeny of selected plants
in the next season from self seed (iv) Inter-mating
among progeny, and (v) Bulking of crossed seeds in
equal quantity. This completes original cycle of
recurrent selection. The bulk seed is used for next
cycle of selection which also involves about five steps.
31. 4. Use of end Product: The population
developed by recurrent selection can be used
in three ways, (a) In producing homozygous
inbreds by selfing, (b) In the production of
hybrid varieties, and (c) in the production of
5. Basic Assumptions: Recurrent selection is
based on three basic assumptions (i) Absence
of epistasis, (ii) absence of multiple alleles,
and (iii) Absence of linkage disequilibrium.
However, none of these assumptions is
32. 6. Impact: Recurrent selection is used to
improve the frequency of desirable alleles for a
character in a population. In this method the
heterozygosity that is lost due to selfing is
recovered by inter-mating of selected progeny.
33. Breeding Methods in Asexually Propagated
Crops which are propagated asexually or by vegetative means are known as
asexually propagated or vegetatively propagated or clonal crops. There are some
agricultural (Sugarcane, Potato, Sweet Potato, etc) and horticultural (Banana,
mango, citrus, pears, peaches, litchi, etc) crops that propagates by asexual means.
The main reasons of asexual reproduction are
1) Reduced flowering and seed set,
2) Non flowering in many cases.
3) To avoid inbreeding depression in certain crops and
4) Apomixis in some species.
Asexual reproduction produces the progeny, which are exactly identical to their
parent in genotype, because the progeny is derived from the vegetative cells
through mitosis. Therefore, the main advantage of asexually reproduction is that it
preserves the genotype of an individual indefinitely.
34. Importance of Asexually Propagated
1. Most of these plants are perennial and annual. E.g Sugarcane, potato, sweet
2. Many of them shows reduced flowering and seed set and many varieties do
not flower at all.
3. They are invariably cross-pollinated.
4. They are nightly heterozygous and show severe inbreeding depression.
5. Many species are interspecific hybrid. E.g Banana, sugarcane.
6. Many species shows wider adaptation.
7. These crop consist of a large number of clones. i. e. progeny derived from
single plat through asexual reproduction.