Plant Breeding Questions in English

(C) The concept of 'centre of origin' for cultivated plants was first proposed by Alphonse de Candolle in his book 'Origin of Cultivated Plants' $(1883)$. However,the systematic study and the development of the 'centre of origin' theory as a scientific framework for crop evolution were extensively established by the Russian botanist Nikolai Ivanovitch Vavilov in $(1926)$. In the context of standard biological examinations,Vavilov is most commonly associated with this concept.

(D) Plant breeding is the purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation,give better yields,and are disease resistant.
It encompasses the improvement of various types of plants,including agricultural crops (like wheat,rice),fodder crops (used for livestock),and fruit varieties (horticultural crops).
Therefore,plant breeding is a technique used for the improvement of all the mentioned categories.
Thus,the correct option is $D$.

(C) Plant breeding is defined as the purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation,give better yields,and are disease-resistant. It involves the application of scientific principles (genetics,molecular biology,and physiology) to improve plant traits,as well as the art of selecting and crossing plants to achieve specific aesthetic or functional goals. Therefore,it is considered both an art and a science.

(C) Modern plant breeding is considered to have started with the rediscovery of Gregor Mendel's laws of inheritance in $1900$.
Although Mendel's original research paper was published in $1866$,it remained largely unnoticed until $1900$,when it was independently rediscovered by Hugo de Vries,Carl Correns,and Erich von Tschermak.
This event provided the scientific foundation for genetics,which subsequently revolutionized plant breeding practices.

(D) Plant breeding is the purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation,give better yields,and are disease resistant.
It relies heavily on the principles of $Genetics$ to understand the inheritance of traits and to select desirable parents for hybridization.
It also relies on $Cytology$ to understand the chromosomal basis of inheritance,ploidy levels,and to perform techniques like polyploidy breeding.
Therefore,plant breeding has a close relationship with both $Genetics$ and $Cytology$.

(B) In India,the earliest systematic work in the field of plant breeding,specifically regarding sugarcane breeding,was initiated by $C.A. Barber$ at the Sugarcane Breeding Institute in Coimbatore. He is often recognized for his pioneering efforts in the early $20^{th}$ century.

(B) The basis of the Green Revolution is $Plant \ breeding$.
It was achieved through the introduction of high-yielding varieties $(HYV)$, increased irrigation facilities, the use of fertilizers, effective weed, pest, and pathogen control, and improved agricultural management practices.
$Plant \ breeding$ played a crucial role in developing disease-resistant and high-yielding crop varieties that significantly increased food production.

(D) The primary aims of plant breeding include:
$1$. Increasing the yield of crops (High yielding varieties).
$2$. Developing resistance against biotic stresses such as diseases,insects,and pests.
$3$. Improving the quality of produce.
$4$. Modifying the maturity period (e.g.,early maturing varieties) to suit different agricultural conditions.
Therefore,all the given options are correct objectives of plant breeding.

(A) The main aims of plant breeding are:
$(i)$ Development of high-yielding varieties.
$(ii)$ Development of disease-resistant varieties.
$(iii)$ Development of drought-resistant varieties.
Therefore,the primary objective is to produce improved varieties of plants that have better yield and quality.

(A) The term 'heterosis' was coined by the American geneticist $G.H. Shull$ in $1914$.
It refers to the phenomenon where the progeny of diverse varieties of a species exhibit greater biomass,speed of development,and fertility than both parents.

(D) Pureline selection is a method of plant breeding where individual plants are selected from a mixed population and their progeny are evaluated.
Since this method involves selecting a single plant and developing a line from its descendants,it is also known as $Single \ line \ selection$ or $Progeny \ selection$.
Therefore,both $Progeny \ selection$ and $Single \ line \ selection$ are synonymous with pureline selection.
Since the options provided include these terms,the most appropriate answer is $All \ the \ above$.

(D) Plant breeding is the purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation,give better yields,and are disease resistant.
Classical plant breeding involves crossing or hybridization of pure lines,followed by artificial selection to produce plants with desirable traits of higher yield,nutrition,and resistance to diseases.
Therefore,selection and hybridization are the most fundamental and popular methods used in the production of new plant varieties.

(A) Mass selection is a plant breeding method where individual plants are selected based on their phenotype,and their seeds are bulked to form the next generation. This method is primarily applied to cross-pollinated crops because these crops exhibit high genetic variability,allowing for effective selection of superior genotypes. While it can sometimes be used in self-pollinated crops,its efficiency is significantly higher in cross-pollinated species.

(D) The tropical sugarcane variety $Saccharum$ $officinarum$ is primarily grown in South India.
It possesses desirable traits such as a thick stem and high sugar content.
However,it does not grow well in North India due to climatic limitations.
In contrast,$Saccharum$ $barberi$ was originally grown in North India but had poor sugar content and thinner stems.
Plant breeders crossed these two varieties to combine the desirable qualities of both.

(B) Selection is considered the oldest method of plant breeding. Humans have been practicing the selection of plants with desirable traits (such as higher yield,better quality,or disease resistance) since the beginning of agriculture. By choosing the best seeds from a harvest to plant for the next season,early farmers performed a form of artificial selection,which laid the foundation for modern plant breeding.

(B) Inbreeding depression refers to the reduction in biological fitness in a given population as a result of inbreeding,which is the mating of related individuals.
Inbreeding increases the frequency of homozygous genotypes,which often leads to the expression of harmful recessive alleles.
This phenomenon is most significant and primarily observed in cross-pollinated crops,as they naturally maintain high levels of heterozygosity.
When cross-pollinated crops are forced to self-pollinate (inbreed),the accumulation of deleterious recessive traits causes a marked decline in vigor and yield,known as inbreeding depression.

(D) Plant breeding is the purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation,give better yields,and are disease resistant.
Its primary objectives include:
$1$. Increasing crop yield: Developing high-yielding varieties to meet the food demand of the growing population.
$2$. Improving quality: Enhancing nutritional value,taste,or shelf life of the produce.
$3$. Biotic and Abiotic resistance: Developing varieties resistant to diseases,pests,drought,salinity,and extreme temperatures.
Since all the mentioned options are key goals of plant breeding,the correct answer is $D$.

(A) Nobel laureate Norman $E$. Borlaug,working at the International Centre for Wheat and Maize Improvement in Mexico,developed semi-dwarf wheat varieties. These varieties,such as $Sonalika$ and $Kalyan Sona$,were high-yielding and disease-resistant,which played a crucial role in the Green Revolution in India.

(B) The process of plant breeding for developing improved varieties involves the following steps in order:
$1$. Collection of variability: Genetic variability is the root of any breeding program.
$2$. Evaluation and selection of parents: The germplasm is evaluated to identify plants with desirable traits.
$3$. Cross-hybridization among the selected parents: Desired characters are combined by crossing two parents.
$4$. Selection and testing of superior recombinants: This step involves selecting the progeny that have the desired combination of characters.
$5$. Testing,release,and commercialization of new cultivars: The selected lines are evaluated for yield and other agronomic traits in research fields and then released for farmers.
Thus,the correct sequence is $(ii), (i), (iv), (iii), (v)$.

(B) Assertion $A$ is true because plant breeding is a purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation,give better yields,and are disease-resistant. This involves creating genetic variation.
Reason $R$ is also true because the fundamental goals of both plant and animal breeding are to improve the quality and quantity of products (yield) and to enhance resistance to diseases and environmental stresses.
However,Reason $R$ does not explain why genetic variation is obtained through plant breeding; it merely states that the goals are similar. Therefore,$R$ is not the correct explanation of $A$.

(B) The standard steps involved in plant breeding for crop improvement are as follows:
$1$. Collection of variability: Genetic variability is the root of any breeding program.
$2$. Evaluation and selection of parents: The germplasm is evaluated to identify plants with desirable traits,and these are selected as parents.
$3$. Cross hybridization among the selected parents: The selected parents are crossed to combine the desired characters into one plant.
$4$. Selection and testing of superior recombinants: This step involves selecting the progeny that have the desired combination of characters and testing them for agronomic traits.
$5$. Testing,release,and commercialization of new cultivars: The selected lines are evaluated in research fields and then in farmers' fields before being released as new varieties.

(D) The sugarcane species $Saccharum$ $officinarum$ was originally grown in South India. It is characterized by having a thicker stem and a higher sugar content compared to the species grown in North India ($Saccharum$ $barberi$). However,$Saccharum$ $barberi$ had poor sugar content and yield. By crossing these two varieties,breeders successfully combined the desirable qualities of high yield,thick stems,and high sugar content with the ability to grow in the sugarcane-growing areas of North India.

(D) Plant breeding is the purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation,give better yields,and are disease-resistant.
The main steps in breeding a new genetic variety of a crop are:
$1$. Collection of variability: Genetic variability is the root of any breeding program.
$2$. Evaluation and selection of parents: The germplasm is evaluated to identify plants with desirable traits.
$3$. Cross hybridization among the selected parents: This is the process of combining the desired characters from two different parents.
$4$. Selection and testing of superior recombinants: Selecting the progeny that have the desired combination of traits.
$5$. Testing,release,and commercialization of new cultivars: The selected lines are evaluated for yield and other agronomic traits.
Patenting a new plant is a legal or commercial process that occurs after the development and release of a variety,but it is not a biological step in the breeding process itself.

(D) The conventional method of breeding for disease resistance involves several steps:
$1$. Screening germplasm for resistance sources: This involves identifying plants that possess the desired resistance genes ($iii$ is correct).
$2$. Hybridization of selected parents: The resistant plants are crossed with high-yielding or other desirable varieties ($ii$ is correct).
$3$. Selection and evaluation of the hybrids: The progeny are tested for resistance and other traits.
$4$. Testing and release of new varieties: The selected lines are evaluated in multi-location trials for yield and other agronomic traits before being released to the market ($iv$ is incorrect).
$5$. Productivity is generally expected to increase or be maintained while adding resistance,so stating there is 'no change' is not a defining characteristic of the breeding method ($i$ is incorrect).
Therefore,statements $(ii)$ and $(iii)$ are correct.

(C) Wild varieties of plants are crucial for plant breeding programs.
They possess a diverse gene pool that includes genes for resistance to various biotic stresses such as diseases,pests,and insects,as well as abiotic stresses like drought or salinity.
By preserving these wild relatives,breeders can introduce these beneficial traits into cultivated crops to improve their yield and resilience.
Therefore,they serve as a vital reservoir of genetic diversity for crop improvement.

(C) The wheat production revolution in India during the $1960$s was primarily driven by the introduction of semi-dwarf wheat varieties. These varieties were developed by Dr. Norman $E$. Borlaug and brought to India by Dr. $M$.$S$. Swaminathan. The key feature of these varieties was a mutation that resulted in a significant reduction in plant height (semi-dwarf trait),which prevented lodging (falling over) and allowed the plants to support heavy,grain-filled ears of wheat,thereby drastically increasing yield.

(A) In plant breeding,the entire collection of plants or seeds having all the diverse alleles for all genes in a given crop is known as the $Germplasm$ collection. This collection serves as the fundamental resource for any breeding program,providing the necessary genetic variability required for crop improvement.

(N/A) Traditional farming can only yield a limited biomass as food for humans and animals.
- Better management practices and increases in acreage can increase yield,but only to a limited extent.
- Plant breeding as a technology has helped increase yields to a very large extent.
- The Green Revolution was dependent to a large extent on plant breeding techniques for the development of high-yielding and disease-resistant varieties in wheat,rice,maize,etc.
Plant breeding is the purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation,provide better yields,and are disease-resistant.
Conventional plant breeding has been practiced for thousands of years; since the beginning of human civilization,recorded evidence of plant breeding dates back to $9,000-11,000$ years ago.
Many present-day crops are the result of domestication in ancient times.
Today,all our major food crops are derived from domesticated varieties.
- Classical plant breeding involves crossing or hybridization of pure lines,followed by artificial selection to produce plants with desirable traits of higher yield,nutrition,and resistance to diseases.
Through plant breeding,increased crop yield and improved quality can be obtained. Increased tolerance to environmental stresses (salinity,extreme temperatures,drought),resistance to pathogens (viruses,fungi,and bacteria),and increased tolerance to insect pests are also key objectives.

(A) The main steps in breeding a new genetic variety of a crop are as follows:
$(i)$ Collection of variability: Genetic variability is the root of any breeding programme.
- In many crops,pre-existing genetic variability is available from wild relatives of the crop.
- Collection and preservation of all the different wild varieties,species,and relatives of the cultivated species is a pre-requisite.
The entire collection having all the diverse alleles for all genes in a given crop is called germplasm collection.
$(ii)$ Evaluation and selection of parents: The germplasm is evaluated to identify plants with desirable combinations of characters.
The selected plants are multiplied and used in the process of hybridisation. Purelines are created wherever desirable and possible.
$(iii)$ Cross hybridisation among the selected parents: The desired characters often have to be combined from two different plants (parents).
For example,high protein quality of one parent may need to be combined with disease resistance from another parent. This is possible by cross-hybridising the two parents to produce hybrids that genetically combine the desired characters in one plant.
This is a time-consuming and tedious process since the pollen grains from the desirable plant chosen as the male parent must be collected and placed on the stigma of the flowers selected as the female parent.
Also,it is not necessary that the hybrids combine the desirable characters; usually,only one in a few hundred to a thousand crosses shows the desirable combination.
$(iv)$ Selection and testing of superior recombinants: This step consists of selecting among the progeny of the hybrids those plants that have the desired character combination.
The selection process is crucial to the success of the breeding objective and requires careful scientific evaluation of the progeny.
This step yields plants that are superior to both parents.
- These are self-pollinated for several generations until they reach a state of uniformity so that the characters will not segregate in the progeny.
$(v)$ Testing,release,and commercialisation of new cultivars: The newly selected lines are evaluated for their yield and other agronomic traits of quality,disease resistance,etc.
This evaluation is done by growing these in research fields and recording their performance under ideal fertiliser application,irrigation,and other crop management practices.

(N/A) Insect and pest infestation is a major cause for the large-scale destruction of crop plants and produce.
Plant breeding for insect resistance is useful because it reduces the reliance on chemical insecticides,thereby minimizing environmental pollution and health hazards.
Resistance in host crop plants can be achieved through morphological,biochemical,or physiological characteristics:
$1$. Morphological: Hairy leaves in plants like cotton provide resistance to jassids,and in wheat,they provide resistance to cereal leaf beetles. Solid stems in wheat prevent infestation by the stem sawfly,while smooth-leaved and nectar-less cotton varieties do not attract bollworms.
$2$. Biochemical: High aspartic acid,low nitrogen,and low sugar content in maize lead to resistance against maize stem borers.
Breeding methods for insect resistance follow the same steps as those for other agronomic traits,utilizing germplasm collections or wild relatives as sources of resistance genes.

Crop	Variety	Insect Pests
Brassica (rapeseed mustard)	Pusa Gaurav	Aphids
Flat bean	Pusa Sem $2$,Pusa Sem $3$	Jassids,aphids and fruit borer
Okra (Bhindi)	Pusa Sawani,Pusa $A-4$	Shoot and Fruit borer

(N/A) In the area of plant breeding,it is important to preserve both the seeds of cultivated varieties and their wild relatives because wild relatives often possess valuable genes for resistance to diseases,pests,and environmental stress.
While cultivated varieties are selected for high yield,they may lack these protective traits.
By preserving wild relatives,breeders can introduce these beneficial resistant genes into high-yielding cultivated varieties through hybridization.
For example,wild species of wheat or rice often contain genes for resistance to specific pathogens that are absent in modern high-yielding varieties.

(B) The Green Revolution was a period of significant increase in agricultural production,particularly in developing countries,during the mid-$20^{th}$ century.
It was primarily driven by the development and introduction of high-yielding varieties $(HYVs)$ of cereals,such as wheat and rice.
These $HYVs$ were developed through scientific plant breeding techniques.
Therefore,plant breeding is the most appropriate option associated with the success of the Green Revolution.

(D) The correct answer is $D$.
In plant breeding for crop improvement,specifically for sugarcane,two species were crossed to combine desirable traits.
$Saccharum$ $officinarum$ (originally grown in South India) had thick stems and high sugar content but did not grow well in North India.
$Saccharum$ $barberi$ (originally grown in North India) had poor sugar content and thin stems.
By crossing $Saccharum$ $barberi$ and $Saccharum$ $officinarum$,scientists successfully developed varieties that combined the high yield and thick stems of $Saccharum$ $officinarum$ with the ability to grow in the North Indian climate (inherited from $Saccharum$ $barberi$).

(B) The most effective and fundamental method to increase crop yield is the use of improved varieties of seeds.
Genetic improvement of crops through plant breeding allows for the development of varieties that are high-yielding,disease-resistant,and better adapted to environmental stresses.
While tractors,weed eradication,and proper management are important agricultural practices,the genetic potential of the seed remains the primary determinant of yield potential.

(D) Plant breeding is the purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation,give better yields,and are disease resistant.
$1$. Higher yield: Breeding aims to increase the productivity of crops.
$2$. Better quality: It focuses on improving the nutritional or commercial value of the produce.
$3$. Disease resistance: It aims to develop varieties that can withstand biotic stresses like pathogens (viruses,fungi,and bacteria).
Therefore,all the mentioned characteristics are the goals of plant breeding.

(A) Plant breeding is the purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation,give better yields,and are disease resistant.
Human civilization has been practicing plant breeding for thousands of years.
According to the $NCERT$ textbook,written evidence of traditional plant breeding practices dates back to $9000-11000$ years ago.

(D) Plant breeding is the purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation,give better yields,and are disease-resistant.
Key goals of plant breeding include:
$1$. Increased crop yield.
$2$. Improved quality of the produce.
$3$. Increased tolerance to environmental stresses (salinity,extreme temperature,drought).
$4$. Resistance to pathogens (viruses,fungi,and bacteria).
$5$. Increased tolerance to insect pests.
Option $D$ states 'Decreased tolerance to insect pests',which is contrary to the objectives of plant breeding,as the goal is to increase,not decrease,resistance/tolerance to pests.

(D) Plant breeding involves several steps to develop improved varieties.
$1$. Collection of variability: This involves the collection and preservation of all the different wild varieties,species,and relatives of the cultivated species (germplasm collection).
$2$. Evaluation and selection of parents: The germplasm is evaluated to identify plants with desirable combinations of characters. The selected plants are then multiplied and used in the process of hybridization.
$3$. Cross-hybridization among the selected parents: This step involves crossing the selected parents to combine desirable traits.
$4$. Selection and testing of superior recombinants: This step consists of selecting the progeny that has the desired combination of characters.
Since all the given options describe essential steps or components related to the evaluation and selection process in plant breeding,the correct answer is $D$.

(B) Conventional plant breeding involves crossing two genetically different individuals to produce a hybrid.
While the goal is to combine desired traits,hybridization is a complex process.
It does not always result in the combination of only desired traits; it often leads to the combination of both desired and undesired traits in the progeny.
Therefore,the statement that hybridization always results in the combination of only desired traits is incorrect.

(C) $Saccharum$ $barberi$ is a species of sugarcane that was originally grown in North India but had poor sugar content and low yield.
$Saccharum$ $officinarum$ is a species of sugarcane that was originally grown in South India and had thicker stems and higher sugar content.
Therefore,the characteristics for $Saccharum$ $barberi$ are $I$ (low sugar),$III$ (low yield),and $V$ (grown in North India).
The characteristics for $Saccharum$ $officinarum$ are $II$ (high sugar),$IV$ (high yield),and $VI$ (grown in South India).
Thus,the correct matching is $I, III, V$ for $Saccharum$ $barberi$ and $II, IV, VI$ for $Saccharum$ $officinarum$.

(A) $Saccharum$ $barberi$ was originally grown in North India,but it had poor sugar content and yield. $Saccharum$ $officinarum$ (tropical canes) had thicker stems and higher sugar content but did not grow well in North India. Therefore,the correct sequence is $Saccharum$ $barberi$ and $Saccharum$ $officinarum$.

(C) Conventional breeding is often limited by the availability of natural disease-resistance genes within the crop species or its wild relatives. Because the pool of available resistance genes is limited,conventional breeding programs can become monotonous or reach a plateau where no further significant improvements in resistance can be achieved. Therefore,the correct answer is that conventional breeding often becomes monotonous due to the limited number of disease-resistance genes.

(C) The standard steps involved in a plant breeding program are as follows:
$1$. Collection of variability: Genetic variability is the root of any breeding program.
$2$. Evaluation and selection of parents: The germplasm is evaluated to identify plants with desirable traits,which are then selected as parents.
$3$. Hybridization: Cross-hybridization is performed between the selected parents to combine desired characters.
$4$. Selection and testing of superior recombinants: Progeny are evaluated to select those that show the desired combination of traits.
$5$. Testing,release,and commercialization of new cultivars: The selected lines are evaluated for yield and other traits in research fields and then released as new varieties.
Therefore,the correct sequence is $i, iii, ii, v, iv$.

(D) The semi-dwarf rice varieties were developed at the International Rice Research Institute $(IRRI)$ in the Philippines.
The first semi-dwarf rice variety,$IR-8$,was developed from $IR-8$ (also known as 'Miracle Rice') and was introduced in $1966$.
This variety significantly increased rice production globally.

(C) In plant breeding,when a hybrid with superior traits (hybrid vigour) is obtained,it is often heterozygous. To stabilize these desirable traits and make the line true-breeding,the hybrid is self-pollinated for several successive generations. This process increases homozygosity,allowing the breeder to select for the desired traits and eliminate undesirable ones,eventually resulting in a stable,pure-breeding line.