Plant Breeding and Diseases Resistant Plants
Plant Breeding
Plant breeding is an art and science of changing the genetics of plants for the benefit
of humankind. Plant breeding can be accomplished through many different
techniques ranging from simply selecting plants with desirable characteristics for
propagation, to more complex molecular techniques. Plant breeding has been
practiced for thousands of years, since near the beginning of human civilization. It
is now practiced worldwide by individuals such as gardeners and farmers, or by
professional plant breeders
Objectives of Plant Breeding
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 consideration.
1. Higher yield: The ultimate aim of plant breeding is to improve the yield of
economic produce. It may be grain yield, fodder yield, fibre yield, tuber yield,
cane yield or oil yield depending upon the crop species. Improvement in yield
can be achieved either by evolving high yielding varieties or hybrids.
2. Improved quality: Quality of produce is another important objective in plant
breeding. The quality characters vary from crop to crop. E.g. grain size, color,
milling and baking quality in wheat. Cooking quality in rice, malting quality
in barley, size, color and size of fruits, nutritive and keeping quality in
vegetables and protein content in pulses, oil content in oilseeds, fiber length,
strength and fineness in cotton.
3. Abiotic resistance: Crop plants also suffer from abiotic factors such as
drought, soil salinity, extreme temperatures, heat, wind, cold and frost,
breeder has to develop resistant varieties for such environmental conditions.
4. Biotic resistance: Crop plants are attacked by various diseases and insects,
resulting in considerable yield losses. Genetic resistance is the cheapest and
, the best method of minimizing such losses. Resistant varieties are developed
through the use of resistant donor parents available in the gene pool.
5. Change in maturity Duration / Earliness: Earliness is the most desirable
character which has several advantages. It requires less crop management
period, less insecticidal sprays, permits new crop rotations and often extends
the crop area.
6. Desirable Agronomic Characteristics: It includes plant height, branching,
tillering capacity, growth habit, erect or trailing habit etc., is often desirable.
For example, dwarf ness in cereals is generally associated with lodging
resistance and better fertilizer response. Tallness, high tillering and profuse
branching are desirable characters in fodder crops.
7. Elimination of Toxic Substances: It is essential to develop varieties free
from toxic compounds in some crops to make them safe for human
consumption. For example, removal of neurotoxin in Khesari (Lathyruys
sativus) which leads to paralysis of lower limbs, erucic acid from Brassica
which is harmful for human health. Removal of such toxic substances would
increase the nutritional value of these crops.
8. Wider adaptability: Adaptability refers to suitability of a variety for general
cultivation over a wide range of environmental conditions. Adaptability is an
important objective in plant breeding because it helps in stabilizing the crop
production over regions and seasons.
Methods of plant breeding
Plant breeding involves the improvement of economically important plants by
scientific methods. The following are the methods of plant breeding:
1. Plant introduction: The process of introducing high yielding varieties of
plant from their growing locality into a new locality is called plant
introduction. This is simply transfer of plants from one place to another.
, 2. Selection: The oldest method of plant improvement is by the selection of the
best plants and by growing only the seed from them. This is useful only so
long as the population of plants is a mixture of pure lines. There are three
methods of selection:
a) Mass selection: It is the most ancient and popular methods of crop
improvement that is practiced by farmers. It is a method of selection of
better seeds from a number of plants at the time of harvesting based on
phenotype or external appearance of fruit set, size of fruits, the time of
harvesting based on phenotype or external appearance of fruit set.
b) Pure line selection: Pure line is the progeny of single self- fertilized
homozygous plant. In pure line selection, large numbers of plants are
selected from a self-pollinated crop and is harvested individually,
individual plant progenies from them are evaluated separately and the
best one is released as pure line variety. Therefore it is also known as
individual plant selection.
c) Clonal selection: Progeny of a single plant obtained by asexual
reproduction is known as clone. A procedure of selecting superior
clones from the mixed population of asexually propagating crops is
referred to as clonal selection.
3. Hybridization: Hybridization is defined as the breeding of two different
organisms from genetically diverse groups or species. Hybridization is a very
old technique that has been used to increase the genetic variability among the
population.
There are generally eight steps to hybridization, they are as follows:
1. Selection of Plant: It is referred to as choosing both the parental plants for
the process, the plant must be healthy and can grow in the given condition are
the two main prerequisites of the process.
2. Homozygosity: Inducing homozygosity in the parental plants is important to
establish the purity of lines, which is eliminating the unwanted traits. It is
Plant Breeding
Plant breeding is an art and science of changing the genetics of plants for the benefit
of humankind. Plant breeding can be accomplished through many different
techniques ranging from simply selecting plants with desirable characteristics for
propagation, to more complex molecular techniques. Plant breeding has been
practiced for thousands of years, since near the beginning of human civilization. It
is now practiced worldwide by individuals such as gardeners and farmers, or by
professional plant breeders
Objectives of Plant Breeding
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 consideration.
1. Higher yield: The ultimate aim of plant breeding is to improve the yield of
economic produce. It may be grain yield, fodder yield, fibre yield, tuber yield,
cane yield or oil yield depending upon the crop species. Improvement in yield
can be achieved either by evolving high yielding varieties or hybrids.
2. Improved quality: Quality of produce is another important objective in plant
breeding. The quality characters vary from crop to crop. E.g. grain size, color,
milling and baking quality in wheat. Cooking quality in rice, malting quality
in barley, size, color and size of fruits, nutritive and keeping quality in
vegetables and protein content in pulses, oil content in oilseeds, fiber length,
strength and fineness in cotton.
3. Abiotic resistance: Crop plants also suffer from abiotic factors such as
drought, soil salinity, extreme temperatures, heat, wind, cold and frost,
breeder has to develop resistant varieties for such environmental conditions.
4. Biotic resistance: Crop plants are attacked by various diseases and insects,
resulting in considerable yield losses. Genetic resistance is the cheapest and
, the best method of minimizing such losses. Resistant varieties are developed
through the use of resistant donor parents available in the gene pool.
5. Change in maturity Duration / Earliness: Earliness is the most desirable
character which has several advantages. It requires less crop management
period, less insecticidal sprays, permits new crop rotations and often extends
the crop area.
6. Desirable Agronomic Characteristics: It includes plant height, branching,
tillering capacity, growth habit, erect or trailing habit etc., is often desirable.
For example, dwarf ness in cereals is generally associated with lodging
resistance and better fertilizer response. Tallness, high tillering and profuse
branching are desirable characters in fodder crops.
7. Elimination of Toxic Substances: It is essential to develop varieties free
from toxic compounds in some crops to make them safe for human
consumption. For example, removal of neurotoxin in Khesari (Lathyruys
sativus) which leads to paralysis of lower limbs, erucic acid from Brassica
which is harmful for human health. Removal of such toxic substances would
increase the nutritional value of these crops.
8. Wider adaptability: Adaptability refers to suitability of a variety for general
cultivation over a wide range of environmental conditions. Adaptability is an
important objective in plant breeding because it helps in stabilizing the crop
production over regions and seasons.
Methods of plant breeding
Plant breeding involves the improvement of economically important plants by
scientific methods. The following are the methods of plant breeding:
1. Plant introduction: The process of introducing high yielding varieties of
plant from their growing locality into a new locality is called plant
introduction. This is simply transfer of plants from one place to another.
, 2. Selection: The oldest method of plant improvement is by the selection of the
best plants and by growing only the seed from them. This is useful only so
long as the population of plants is a mixture of pure lines. There are three
methods of selection:
a) Mass selection: It is the most ancient and popular methods of crop
improvement that is practiced by farmers. It is a method of selection of
better seeds from a number of plants at the time of harvesting based on
phenotype or external appearance of fruit set, size of fruits, the time of
harvesting based on phenotype or external appearance of fruit set.
b) Pure line selection: Pure line is the progeny of single self- fertilized
homozygous plant. In pure line selection, large numbers of plants are
selected from a self-pollinated crop and is harvested individually,
individual plant progenies from them are evaluated separately and the
best one is released as pure line variety. Therefore it is also known as
individual plant selection.
c) Clonal selection: Progeny of a single plant obtained by asexual
reproduction is known as clone. A procedure of selecting superior
clones from the mixed population of asexually propagating crops is
referred to as clonal selection.
3. Hybridization: Hybridization is defined as the breeding of two different
organisms from genetically diverse groups or species. Hybridization is a very
old technique that has been used to increase the genetic variability among the
population.
There are generally eight steps to hybridization, they are as follows:
1. Selection of Plant: It is referred to as choosing both the parental plants for
the process, the plant must be healthy and can grow in the given condition are
the two main prerequisites of the process.
2. Homozygosity: Inducing homozygosity in the parental plants is important to
establish the purity of lines, which is eliminating the unwanted traits. It is
