Method of Plant Breeding Questions in English

(D) Grafting involves joining tissues from two different plants. If the scion or the stock is infected with systemic pathogens such as viruses,mycoplasmas,or viroids,these pathogens can easily spread through the vascular tissues (xylem and phloem) from the infected part to the healthy part of the grafted plant. Therefore,grafting is a known method for the transmission of viral,mycoplasmal,and viroid diseases.

(B) Hybrid vigour,also known as heterosis,is the phenomenon where the progeny of a cross between two genetically different parents exhibit superior traits compared to both parents. This is induced by crossing two genetically distinct plants,which leads to increased heterozygosity and the masking of deleterious recessive alleles.

(C) cross between individuals belonging to two different genera is known as an intergeneric cross. This type of hybridization is often used in plant breeding to combine desirable traits from different taxonomic groups.

(C) Hybridisation is the process of crossing two genetically different individuals (parents) to produce offspring that possess a combination of traits from both parents.
This process is widely used in plant and animal breeding to create new varieties with desirable characteristics,such as increased yield,disease resistance,or improved quality.
By combining different alleles,hybridisation increases genetic variation within a population.

(B) The greatest genetic diversity of plants is found in their centers of origin,also known as homelands.
These regions are where the wild ancestors of domesticated crops first evolved and diversified.
Because these areas have been the site of long-term evolutionary processes,they harbor the widest range of genetic variations,which are crucial for crop improvement and breeding programs.

(B) The high-yielding dwarf gene,$Dee-geo-woo-gen$,was identified in Taiwan.
It was used to develop semi-dwarf rice varieties such as $IR-8$ and $IR-24$ at the International Rice Research Institute $(IRRI)$ in the Philippines.
$Norin-10$ is a dwarfing gene associated with wheat,not rice.

(A) The Norin-$10$ gene is a well-known dwarfing gene discovered in Japanese wheat varieties.
It was used by American plant breeders,most notably Norman Borlaug,to develop high-yielding,semi-dwarf wheat varieties during the Green Revolution.
These varieties are characterized by shorter stalks,which prevent lodging (falling over) and allow the plant to support heavier grain heads.

(B) In $1963$,several varieties of wheat such as Sonora-$64$ and Lerma Rojo-$64$ were introduced into India from Mexico.
These varieties were high-yielding and disease-resistant,which led to the Green Revolution in India.
Later,these were further improved through mutation breeding to develop varieties like Sharbati Sonora.

(A) Germplasm refers to the total genetic material (genes) present in a population or species.
Centers of origin or diversity are the most suitable places for germplasm collection because they harbor the maximum genetic variability.
Peru is recognized as a primary center of origin for many important crops,such as the potato,making it a highly suitable location for germplasm collection compared to the other options listed.

(C) Sharbati Sonora is an improved variety of wheat developed in India. It was derived from the Mexican variety Sonora-$64$ through mutation breeding. This variety is known for its dwarf stature and significantly higher content of protein and the essential amino acid lysine compared to traditional wheat varieties.

(D) $G. hirsutum$ is an American (New World) crop which is tetraploid,having $26$ pairs of chromosomes.
It is believed to have originated through hybridization between an Asiatic diploid cotton species (having $13$ pairs of large chromosomes) and an American cotton species (having $13$ pairs of small chromosomes).

(A) Plant breeding is often described as both a science and an art.
While the scientific aspect involves the application of genetics,molecular biology,and statistics,the 'art' of plant breeding refers to the breeder's ability to select the best plants based on visual observation,experience,and intuition.
Among the given options,the 'Technique in hybridization' requires significant skill,manual dexterity,and the breeder's judgment to successfully perform emasculation and pollination,making it the most appropriate answer representing the 'art' aspect of plant breeding.

(B) Sonalika is a high-yielding,semi-dwarf,and disease-resistant variety of wheat developed in India during the Green Revolution.
It was introduced to increase wheat production significantly.
Chandramukhi is a variety of potato,while $A$-$77$ and Kuber are not standard improved wheat varieties.

(C) The improved variety of maize mentioned among the options is $Jawahar$.
$N.P. 710$ is a variety of wheat.
$Co. 4$ is a variety of sugarcane.
$S. 405$ is a variety of wheat.
Therefore,$Jawahar$ is the correct choice as it is a high-yielding variety of maize developed in India.

(A) $Sonora-64$ and $Lerma$ $Rojo$ are high-yielding,semi-dwarf varieties of wheat.
These varieties were introduced in India during the mid-$1960s$ as part of the Green Revolution.
They played a crucial role in significantly increasing wheat production in the country.

(B) $IR-36$ is a high-yielding, early-maturing, and disease-resistant variety of rice.
It was developed by crossing $13$ different rice varieties collected from six countries with $Oryza \text{ } nivara$, which is a wild species of rice found in central India.
This breeding program was conducted at the International Rice Research Institute $(IRRI)$.

(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.
One of the most effective methods to introduce disease resistance is by breeding cultivated crops with their wild relatives,which often possess natural resistance genes against various pathogens.
$Colchicine$ is used for polyploidy induction,while hormone and heat treatments are generally not used for developing disease resistance in plant breeding programs.

(A) The most effective method to increase crop yield,including wheat,is the use of high-yielding and disease-resistant improved varieties of seeds. This is a core principle of plant breeding,which has been instrumental in the Green Revolution in India to ensure food security.

(B) The correct answer is $B$.
Norman Borlaug,working at the International Centre for Wheat and Maize Improvement in Mexico,developed semi-dwarf wheat varieties in $1963$.
These varieties were high-yielding and disease-resistant,which led to the Green Revolution in India.

(A) The high-yielding varieties of Indian rice,such as $IR$-$8$ and its derivatives,were developed by crossing the semi-dwarf variety $O. sativa japonica$ (specifically the variety 'Dee-geo-woo-gen') with the tall,traditional Indian variety $O. sativa indica$. This cross combined the high yield and short stature of the japonica type with the adaptability and grain quality of the indica type.

(C) Hybridization is a process of crossing two genetically different individuals to produce an offspring that possesses traits from both parents.
The resulting offspring obtained from this cross is referred to as a $Hybrid$.
Therefore,the product of hybridization is known as a $Hybrid$.

(A) Crop improvement is achieved through various plant breeding techniques.
Introduction,hybridization,and mutation breeding are standard methods used to develop new and improved crop varieties.
Inbreeding is primarily a technique used in animal husbandry to increase homozygosity and is generally avoided in crop improvement because it leads to inbreeding depression,which reduces the vigor and productivity of the plants.

(B) The $indica$ varieties of rice are high-yielding but susceptible to many diseases. In contrast,$japonica$ varieties are known for their strong resistance to various diseases and pests. Therefore,plant breeders cross $indica$ varieties with $japonica$ varieties to combine the high-yield trait of $indica$ with the disease-resistance trait of $japonica$.

(C) The correct answer is $C$.
An allopolyploid is an organism that contains two or more sets of chromosomes derived from different species.
Triticale is the first man-made cereal crop,which was developed 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.

(C) In intravarietal hybridization,the crosses are performed between plants belonging to the same variety.
This method is used to maintain the purity of a variety or to improve specific traits within that variety.

(B) Selection is considered the oldest method of plant breeding.
It involves choosing plants with desirable traits from a population and using them for further propagation.
It serves as the fundamental basis for all crop improvement programs.

(B) Selection is a fundamental technique used in plant breeding to choose plants with desirable traits from a population. By selecting individuals with superior characteristics and breeding them,breeders can improve the quality and yield of crops over successive generations. Therefore,it is a core method within the field of plant breeding.

(B) The improved variety Indore $2$ is a well-known example of a crop variety developed through mutation breeding. It belongs to the cotton crop ($Gossypium$ $sp.$). Mutation breeding involves exposing seeds or plant parts to physical or chemical mutagens to induce genetic variation,which is then selected for desirable traits.

(C) In $Hybridization$, two or more plants of unlike genotypes are crossed together to produce offspring with new desirable combinations of characters as a result of genetic recombination.
This process allows breeders to combine the best traits from different parent plants into a single improved variety.

(B) Heterosis,also known as hybrid vigor,is the phenomenon where the progeny of a cross between two genetically distinct parents exhibits superior traits compared to both parents. This process fundamentally requires the crossing of two different inbred lines or varieties to combine desirable alleles and mask deleterious recessive traits.

(A) Hybridisation is a technique used in plant breeding to produce new varieties with desired traits.
In bisexual flowers,the process of emasculation is performed,which involves the removal of stamens (anthers) from the flower bud before they dehisce.
This prevents self-pollination and ensures that the female reproductive organs are pollinated by the pollen grains from a selected male parent.
Therefore,the removal of stamens is a critical step in the hybridisation process.

(A) The term "pureline" was coined by the Danish botanist $W. L. Johannsen$ in $1903$. He conducted experiments on beans ($Phaseolus vulgaris$) and demonstrated that pureline selection is effective in self-pollinated crops to isolate homozygous lines from a heterogeneous population. Therefore, the correct answer is $W. L. Johannsen$.

(D) Mass selection is one of the oldest methods of plant breeding,dating back to the beginning of agriculture.
It involves selecting individual plants with desirable traits from a heterogeneous population and harvesting their seeds in bulk to sow for the next generation.
This method is traditionally practiced by farmers who save the best seeds from their harvest for the next season.
It is particularly effective and commonly used in cross-pollinated crops to improve the overall performance of the population by increasing the frequency of desirable alleles.

(D) Pureline selection is a method of plant breeding primarily used for self-pollinated crops.
$1$. It is specifically practiced in self-pollinated crops to maintain genetic purity.
$2$. The process involves the selection of a large number of individual plants from a heterogeneous population.
$3$. The evaluation and testing of these selected lines typically take about $5$ to $6$ years to develop and release a new variety.
Therefore,all the given statements are correct.

(B) Clonal selection is a method used for the improvement of crops that are propagated vegetatively, such as $Sugarcane$, $Potato$, and $Onion$.
In these crops, the genetic makeup of the offspring remains identical to the parent plant.
$Wheat$, however, is a sexually reproducing crop that is typically propagated through seeds.
In sexually reproducing crops, clonal selection is not applicable because the offspring show genetic variation due to recombination and segregation during meiosis.
Therefore, clonal selection is not useful for $Wheat$.

(D) Clonal selection is a breeding method used for crops that are propagated vegetatively.
$1$. The varieties developed through this method are genetically identical to the parent,making them highly stable and easy to maintain over generations.
$2$. In vegetatively propagated crops,hybrid vigour (heterosis) can be easily fixed and maintained because there is no segregation or recombination in subsequent generations.
$3$. Since these crops do not reproduce sexually or have high levels of heterozygosity,clonal selection is often the most effective and sometimes the only practical method for their genetic improvement.
Therefore,all the given statements are correct advantages of clonal selection.

(B) $Top$ $cross$ is a specific type of breeding method in plant genetics where an inbred line is crossed with an open-pollinated variety. This technique is often used to evaluate the combining ability of the inbred line.

(B) The first step in any plant breeding program is the collection of variability.
After collecting the germplasm,the next crucial step is the evaluation and selection of parents with desired traits (such as disease resistance).
Therefore,selection is the primary and most essential step to identify the best individuals from the available genetic diversity before proceeding to hybridization or other techniques.

(A) Polyploidy is a condition in which an organism possesses more than two complete sets of chromosomes. In polyploid breeding,the primary objective is to induce or select plants with an increased number of chromosome sets (e.g.,triploid,tetraploid,etc.) compared to the normal diploid $(2n)$ state. Therefore,the number of chromosome sets increases.

(D) The cultivated potato, $Solanum$ $\text{tuberosum}$, is a tetraploid organism.
It contains four sets of chromosomes, which is denoted as $4n$.
This polyploid nature contributes to the vigor and yield of the crop.

(B) Mutation breeding is a technique used in plant breeding to create genetic variation.
Physical mutagens,such as ionizing radiations (e.g.,$X$-rays,$Gamma$ rays),are widely used to induce mutations in higher plants to develop new crop varieties with desirable traits.
$Gamma$ rays are high-energy electromagnetic radiations that can penetrate plant tissues and cause $DNA$ damage,leading to mutations.
Therefore,$Gamma$ rays are the correct agent among the given options.

(C) Haploids contain only one set of chromosomes $(n)$.
When these haploids are treated with agents like colchicine,they undergo chromosome doubling (diploidization) to become completely homozygous $(2n)$.
This process is highly significant in plant breeding as it allows for the rapid production of pure lines (homozygous lines) in a single generation,bypassing the need for multiple generations of self-pollination.

(B) In plant breeding,specifically in maize,a double cross involves crossing two single-cross hybrids.
$A$ single-cross hybrid is produced by crossing two inbred lines ($A \times B$ and $C \times D$).
When these two single-cross hybrids are crossed $([A \times B] \times [C \times D])$,it involves four distinct inbred lines.
This method is widely used to produce commercial hybrid maize seeds to exploit heterosis and improve yield.

(B) The phenomenon where the progeny (hybrid) shows superior traits compared to both parents is known as $Hybrid$ $vigour$ or $heterosis$.
This occurs due to the accumulation of dominant alleles and the masking of deleterious recessive alleles in the hybrid offspring,leading to increased growth,yield,and overall fitness compared to the parental lines.

(B) 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.
Hybridization is the most common and effective method used in plant breeding to combine the desirable traits of two different parent plants into a single progeny.
Through hybridization,breeders can cross-pollinate plants with different genetic makeups to produce offspring with improved economic characteristics such as higher yield,better quality,and resistance to biotic or abiotic stresses.

(C) Banana is a vegetatively propagated crop.
In vegetatively propagated crops,the most effective method of plant breeding is clonal selection.
Since Bombay green banana is a specific variety maintained through vegetative propagation,its cultivation is the result of clonal selection.

(A) Heterosis, also known as $Hybrid \text{ vigour}$, refers to the phenomenon where the progeny of a cross between two genetically distinct parents exhibits superior traits compared to both parents.
These superior traits include increased growth rate, higher yield, better adaptability, and improved fertility.
Therefore, the term $Heterosis$ is synonymous with $Hybrid \text{ vigour}$.

(A) Plants that are genetically identical and produced through asexual reproduction or vegetative propagation are known as clones. In plant breeding,when a single plant is propagated vegetatively,all the resulting progeny possess the same genotype as the parent plant. Therefore,the correct term for plants with similar genotypes produced in this manner is a clone.

(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.
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 fundamental methods used for the production of new plant varieties.

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