Method of Plant Breeding Questions in English

(C) Germplasm refers to the total genetic material (the sum total of all the alleles of the genes) present in a population or a species.
It is contained within the reproductive cells (gametes) as well as the somatic cells of an organism.
Therefore,the germplasm collection includes all the diverse alleles of all the genes in a given crop and its wild relatives,which can be found in both reproductive and somatic tissues.

(C) Hybrid vigour,also known as $heterosis$,refers to the phenomenon where the progeny of a cross between two genetically different parents exhibits superior traits compared to the parents.
This phenomenon is primarily attributed to $heterozygosity$,which occurs due to the union of genetically distinct gametes.
$Heterozygosity$ helps in masking deleterious recessive alleles and promotes the expression of beneficial dominant alleles,leading to increased vigor,growth,and productivity in the hybrid offspring.

(B) The pureline selection method involves the selection of a single plant from a genetically variable population,followed by repeated self-fertilization of its progeny.
Since the progeny is derived from a single self-fertilized plant,all individuals in the population possess identical genotypes.
Therefore,the resulting varieties are homozygous (having identical alleles for a trait) and uniform (phenotypically identical).

(B) Hybrid vigour or heterosis is the phenomenon where the progeny of a cross between two genetically distinct parents shows superior traits compared to the parents.
This vigour is expressed in the $F_1$ generation.
If the seeds from the $F_1$ generation are sown again,the traits segregate in the $F_2$ generation,leading to a loss of hybrid vigour and a decrease in yield due to inbreeding depression.
Therefore,to maintain the high yield and desired traits,farmers must purchase fresh $F_1$ hybrid seeds every year.

(D) Green manure consists of young leguminous plants that are grown and then ploughed back into the soil to improve its fertility.
Examples of green manure crops include $Sesbania \text{ } aculeata$, $Crotalaria \text{ } juncea$, and $Sesbania \text{ } rostrata$.
Among the given options, $Sesbania$ is a well-known green manure crop.

(C) Crop rotation is an agricultural practice of growing a series of different types of crops in the same area across a sequence of growing seasons.
It helps in maintaining soil health by preventing the depletion of specific nutrients,as different crops have different nutrient requirements.
It also helps in breaking the life cycles of pests and diseases,thereby improving the overall fertility and productivity of the soil.

(A) $Norman$ $Borlaug$ is widely known as the 'Father of the Green Revolution' globally. He developed high-yielding varieties of wheat,which significantly increased food production in countries like Mexico and India,thereby preventing famine and ensuring food security. The Green Revolution refers to the period of significant increase in agricultural productivity due to the introduction of high-yielding varieties of seeds,modern irrigation methods,and the use of fertilizers and pesticides.

(A) The phenomenon where the offspring of a cross between two genetically distinct individuals or lineages exhibit superior traits (such as increased growth, yield, or fertility) compared to their parents is known as $Hybrid \text{ } vigor$ or $Heterosis$. This occurs due to the masking of deleterious recessive alleles by dominant alleles and the accumulation of favorable dominant alleles in the $F_1$ hybrid.

(A) Triticale is the first man-made cereal crop. It was developed by crossing wheat ($Triticum$ $aestivum$) and rye ($Secale$ $cereale$). The purpose of this cross was to combine the high yield and grain quality of wheat with the hardiness and disease resistance of rye.

(D) Polyploid wheat, such as hexaploid wheat $(Triticum \text{ } aestivum)$, is developed through a combination of interspecific hybridization followed by chromosome doubling.
First, hybridization occurs between different species to create a hybrid.
Since these hybrids are often sterile due to the inability of chromosomes to pair during meiosis, chromosome doubling (often induced by chemicals like colchicine) is performed to restore fertility and create a stable polyploid organism.

(D) Triticale is the first man-made cereal crop.
It was produced by crossing wheat ($Triticum$ $aestivum$) and rye ($Secale$ $cereale$).
This intergeneric hybridization was performed to combine the high yield and grain quality of wheat with the hardiness and disease resistance of rye.

(D) $Triticum$ $aestivum$ is the common bread wheat. It is a hexaploid organism,meaning it contains six sets of chromosomes $(6n = 42)$. It originated from the hybridization of three different wild grass species.

(A) Induced mutagenesis is a technique used in plant breeding to create genetic variation.
Gamma rays,emitted from radioactive isotopes like $Co_{60}$,are the most commonly used physical mutagens for inducing mutations in crop plants.
They have high penetrating power and are effective in causing chromosomal breaks and point mutations,which can lead to desirable traits in crops.

(C) The "Pusa Komal" variety of cowpea $(Vigna \text{ } unguiculata)$ is a disease-resistant variety developed through conventional breeding methods like hybridization and selection. This specific variety is known for its resistance to the disease caused by the bacterium $Xanthomonas \text{ } axonopodis \text{ } pv. \text{ } vignicola$, commonly known as bacterial blight.

(C) The correct sequence is as follows:
$(A)$ The capacity to generate a whole plant from any cell/explant is called Totipotency $(i)$.
$(B)$ The transfer of resistance genes occurs through Sexual hybridization $(ii)$. Subsequently,Selection $(iii)$ occurs between the target and the plant source.
$(C)$ The rice variety $IR8$ was developed in the country Philippines $(iv)$.
Therefore,the correct associations are: $(i)$ Totipotency,$(ii)$ Sexual hybridization,$(iii)$ Selection,$(iv)$ Philippines.

(B) The variety of rice known as $IR-8$ was developed at the International Rice Research Institute $(IRRI)$ in Manila,Philippines.
This variety is often referred to as the 'Miracle Rice' because it played a crucial role in the Green Revolution in Asia,significantly increasing rice yields and helping to address the food crisis in the region.

(A) Mutation breeding is a technique used to induce genetic variation in crops to develop new varieties with desirable traits. In the case of the mung bean ($Vigna$ $radiata$),mutation breeding was successfully used to develop a variety that is resistant to the yellow mosaic virus. This is a classic example of crop improvement mentioned in the $NCERT$ biology curriculum.

(A) Mass selection is a breeding method used primarily for cross-pollinated crops. In this method,a large number of plants with similar desirable phenotypes are selected from a population,and their seeds are harvested in bulk to form the next generation. This process is repeated over several generations to improve the population. Since self-pollinated crops are already homozygous,mass selection is less effective for them compared to cross-pollinated crops.

(D) Haploid plants are highly significant in plant breeding because they allow for the rapid production of homozygous lines. By doubling the chromosome number of haploid plants (using agents like colchicine),researchers can produce completely homozygous diploid plants in a single generation. This eliminates the need for multiple generations of self-pollination to achieve homozygosity,thereby accelerating the selection process for desirable traits.

(C) Heterosis or hybrid vigor refers to the phenomenon where the progeny of a cross between two genetically diverse parents exhibits superior traits compared to the parents.
In sexually reproducing plants,this vigor is lost in subsequent generations due to segregation and recombination during meiosis.
However,in vegetatively propagated plants,the hybrid genotype is maintained indefinitely through asexual reproduction (cloning).
Therefore,once a superior hybrid is developed,it can be propagated vegetatively to preserve its heterosis without the risk of losing it through sexual recombination.

(C) Triticale is the first man-made cereal crop. It is produced by crossing wheat ($Triticum$ $aestivum$) and rye ($Secale$ $cereale$). The goal of this hybridization was to combine the high yield and grain quality of wheat with the hardiness and disease resistance of rye.

(B) Kufri Pukhraj is a well-known high-yielding variety of potato $(Solanum \ tuberosum)$.
It was developed by the Central Potato Research Institute $(CPRI)$,Shimla.
This variety is known for its early maturity and resistance to certain diseases,making it a significant cultivar in Indian agriculture.

(B) Hybrid vigor or $Heterosis$ is the phenomenon where the progeny of a cross between two genetically distinct parents exhibits superior traits compared to both parents. This is primarily achieved through $Hybridization$ in plants,where two different varieties or species are crossed to produce offspring with improved yield,growth rate,or disease resistance.

(B) In plant breeding,$Cross-hybridization$ is considered a very tedious and time-consuming process. This step involves the emasculation (removal of anthers) of the female parent and the dusting of pollen grains from the male parent onto the stigma of the female parent. Since this requires manual handling of individual flowers and ensuring protection from unwanted pollen contamination,it is highly labor-intensive and time-consuming.

(B) Heterosis,also known as hybrid vigor,is the phenomenon where the progeny of two genetically diverse parents exhibit superior traits compared to both parents. This process is a fundamental outcome and objective of $Hybridization$ in plant and animal breeding programs to improve yield,growth rate,and disease resistance.

(B) Selection is a fundamental process in $Plant \ Breeding$. It involves choosing plants with desirable traits from a population to serve as parents for the next generation. This process helps in improving the quality and yield of crops.

(B) The process of plant breeding involves several steps to develop a new variety.
$1$. The first and most crucial step is the 'Collection of variability' or 'Selection of parents'.
$2$. Breeders select parents that possess the desired traits,such as disease resistance or high yield.
$3$. Without selecting appropriate parents,the subsequent steps like hybridization and selection of superior recombinants cannot be performed effectively.
$4$. Therefore,the selection of parents is the foundational step in any breeding program.

(D) The rice variety $GEB-24$ (also known as Gottu Nellu) is a well-known example of a naturally occurring mutation in rice. It was discovered in the $1920s$ in the Godavari delta region of India. It is highly valued for its fine grain quality and resistance to certain pests and diseases,making it a popular parent variety in rice breeding programs.

(D) In plant breeding,wild species are often used as a source of desirable genes. These wild relatives possess natural resistance to various biotic and abiotic stresses. Specifically,they contain genes for $A$ (disease resistance),$B$ (insect resistance),and $C$ (drought resistance). By hybridizing cultivated crops with these wild species,breeders can introduce these beneficial traits into the high-yielding varieties,thereby improving the overall quality and resilience of the crop.

(A) Sugarcane ($Saccharum$ $barberi$) was originally grown in north India,but it had poor sugar content and yield. Tropical canes grown in south India ($Saccharum$ $officinarum$) had thicker stems and higher sugar content but did not grow well in north India. By crossing these two species,a new variety was developed that combined the desirable qualities of high yield,thick stems,high sugar content,and the ability to grow in north India. This process of crossing two different species is known as interspecific hybridization.

(A) Resistance against the late blight disease caused by the fungus $Phytophthora$ $infestans$ in potato was successfully introduced through breeding programs.
This resistance was sourced from the wild species $Solanum$ $demissum$.
$Solanum$ $demissum$ is a wild relative of the cultivated potato that possesses natural resistance genes against various strains of $Phytophthora$ $infestans$.

(A) As a plant breeder,the primary objective is to ensure food security and economic viability.
$1$. Increasing crop yield and improving quality is the fundamental goal of any plant breeding program.
$2$. While resistance to pathogens,pests,and environmental stress are crucial,they are secondary to the primary requirement of producing sufficient quantity and high-quality food to meet human needs.
$3$. Therefore,the first and most essential trait to introduce or improve is the yield and quality of the crop.

(D) Triticale is the first man-made cereal crop. It was developed by crossing wheat ($Triticum$ $aestivum$) and rye ($Secale$ $cereale$). This is an example of intergeneric hybridization,where two different genera are crossed to combine desirable traits like the high yield of wheat and the hardiness/nutritional quality of rye.

(C) The Mexican dwarf variety of wheat was developed by $Dr. Norman E. Borlaug$ at the $International$ $Center$ $for$ $the$ $Improvement$ $of$ $Maize$ $and$ $Wheat$ $(CIMMYT)$ in Mexico. $Dr. Borlaug$ is known as the father of the Green Revolution. He introduced high-yielding,semi-dwarf wheat varieties that significantly increased food production.

(B) Hybrid vigor or heterosis is the phenomenon where the progeny of a cross between two genetically different parents exhibits superior traits (such as increased yield,growth rate,or fertility) compared to both parents. This is primarily achieved through $Hybridization$ in plants,where two distinct varieties or species are crossed to combine desirable traits.

(A) Vegetative propagation involves the production of new plants from vegetative parts like roots,stems,or leaves. Since these plants are genetically identical to the parent,the process is known as cloning. Therefore,$Clonal$ $selection$ is the method used to select superior clones from a population of plants that reproduce vegetatively.

(A) Triticale is the first man-made cereal crop.
It is an intergeneric hybrid produced by crossing wheat ($Triticum$ $aestivum$) and rye ($Secale$ $cereale$).
It combines the high yield and grain quality of wheat with the hardiness and disease resistance of rye.
Therefore,it is considered a man-made hybrid crop.

(D) Haploid plants are produced through techniques like anther or pollen culture.
These plants contain only one set of chromosomes.
When these haploid plants are treated with colchicine,they undergo chromosome doubling to produce homozygous diploid plants.
These homozygous lines are highly valuable in plant breeding programs because they allow for the rapid fixation of desirable traits and the elimination of deleterious recessive alleles,thereby accelerating the development of pure lines.

(A) In plant breeding,the primary objective is to ensure food security and economic stability.
$1$. The most critical factor for any crop is its yield and quality,as these directly impact food availability and market value.
$2$. While resistance to pathogens,pests,and environmental stress are essential for protecting the crop,these traits are secondary to the fundamental goal of achieving high yield and quality.
$3$. Therefore,a plant breeder first focuses on improving the yield and quality of the crop before addressing specific stress-related resistances.

(A) The cultivated varieties of sugarcane, such as $Saccharum \text{ } officinarum$ (originally from tropical India) and $Saccharum \text{ } barberi$ (originally from North India), were crossed to combine desirable traits like high sugar content, thick stems, and the ability to grow in North India. This process of crossing two different species is known as $Interspecific \text{ } hybridization$.

(A) The resistance to late blight disease caused by the fungus $Phytophthora \text{ infestans}$ in potatoes was successfully introduced through plant breeding techniques.
This resistance gene was sourced from the wild species $Solanum \text{ demissum}$.
By crossing cultivated potato varieties with $Solanum \text{ demissum}$, breeders were able to incorporate the necessary resistance traits into the commercial crop.

(B) Selection is considered the oldest method of crop improvement.
It involves choosing plants with desirable traits from a population and using their seeds for the next generation.
This practice has been used by humans since the beginning of agriculture to improve crop quality and yield.
Hybridization,mutation breeding,and other modern techniques were developed much later.

(D) Wild species of crop plants are often rich in genes that provide resistance to various biotic and abiotic stresses.
These genes are transferred to cultivated varieties through hybridization to improve crop performance.
Specifically,wild relatives are known to carry genes for $1$. Disease resistance,$2$. Insect resistance,and $3$. Drought tolerance (or other abiotic stress tolerances).
Therefore,transferring these genes is highly beneficial for crop improvement programs.
Thus,the correct option is $D$.

(A) The variety of rice known as $IR-8$ was developed at the International Rice Research Institute $(IRRI)$ located in Manila,Philippines. This variety,often referred to as the 'miracle rice',played a crucial role in the Green Revolution in Asia by significantly increasing yields,thereby helping to address the food crisis in the region. $IR-36$ was also a successful variety developed later,but $IR-8$ is historically recognized for its initial impact on solving the food crisis.

(C) In plant breeding for disease and pest resistance,specific morphological traits are introduced to reduce pest infestation.
Cotton varieties with smooth leaves and nectarless flowers are developed to resist $Bollworms$.
$Bollworms$ are attracted to nectar and hairy surfaces for egg-laying and feeding,so these traits effectively reduce their population.

(B) The $Norin-10$ gene is a famous semi-dwarf gene found in wheat ($Triticum$ $aestivum$).
It was introduced into wheat varieties by Dr. Norman Borlaug during the Green Revolution.
This gene reduces the height of the wheat plant,which prevents lodging (falling over) and allows the plant to support more grain,thereby significantly increasing the yield.

(C) The foundation of any plant breeding program is genetic variation.
Genetic variation refers to the diversity in gene frequencies among individuals of a population.
Plant breeders rely on this variation to select individuals with desirable traits,such as high yield,disease resistance,or better quality.
Without genetic variation,there would be no raw material for the breeder to work with,making selection and improvement impossible.

(B) Hybrid plants are generally more robust and productive than their parents. This phenomenon is known as $Hybrid \text{ } Vigor$ or $Heterosis$. In plant breeding, hybridization is used to combine the desirable traits of two different parents to produce offspring that exhibit superior characteristics, such as increased yield, better disease resistance, and improved growth.

(C) The correct terms for the blanks are:
$(i)$ Totipotency: It is the ability of a single cell to divide and produce all the differentiated cells in an organism.
$(ii)$ Sexual hybridization: It is a common method used in plant breeding to transfer resistance genes from wild relatives to cultivated varieties.
$(iii)$ Selection: After hybridization,the progeny is screened and selected for the desired traits.
$(iv)$ Philippines: The rice variety $IR8$ (the 'miracle rice') was developed at the International Rice Research Institute $(IRRI)$ located in the Philippines.
Therefore,the correct sequence is $(i)$ Totipotency,$(ii)$ Sexual hybridization,$(iii)$ Selection,$(iv)$ Philippines.

(B) In plant breeding, the step of $Cross-hybridization$ among the selected parents is considered very tedious and time-consuming.
This process involves the manual emasculation (removal of anthers) and pollination of flowers to ensure that the desired pollen grains are transferred to the stigma of the selected female parent.
Since this requires handling thousands of plants individually to achieve the desired cross, it is labor-intensive and requires significant time.