Genetic Conservation and New Questions in English

(C) Nikolai Vavilov identified several centres of origin for cultivated plants.
Subsequent research and the concept of megadiversity centres have expanded this list.
The $Andamans$ (Andaman and Nicobar Islands) are recognized as a significant biodiversity hotspot and a post-Vavilov megadiversity centre due to their unique flora and fauna and high degree of endemism.

(B) Nikolai Vavilov,a prominent Russian botanist and geneticist,conducted extensive studies on the geographical distribution of cultivated plants.
In $1926$,he proposed $11$ major centers of origin for crop plants worldwide,based on the diversity of wild relatives and landraces found in those regions.
Therefore,the correct number of centers recognized by Vavilov is $11$.

(D) The Irish Potato Famine, which occurred between $1845$ and $1852$, was caused by the oomycete (fungus-like protist) $Phytophthora$ $infestans$.
This pathogen causes the disease known as late blight of potato.
The rapid spread of this fungus destroyed the potato crops, which were the primary food source for the Irish population, leading to widespread starvation and mass migration.

(C) The late blight of potato is a devastating disease caused by the oomycete pathogen $Phytophthora\, infestans$.
Natural resistance to this disease was identified in the wild species $Solanum\, demissum$.
This wild species has been used in breeding programs to introduce resistance genes into the cultivated potato variety $Solanum\, tuberosum$.

(D) $In \text{ situ}$ conservation refers to the maintenance of biological diversity within natural habitats. This approach involves protecting the entire ecosystem, including all species and their interactions, in their original environment. Examples of $In \text{ situ}$ conservation strategies include the establishment of National Parks, Wildlife Sanctuaries, and Biosphere Reserves. Therefore, all the listed options are correct.

(D) $Ex situ$ conservation refers to the conservation of components of biological diversity outside their natural habitats.
This method involves keeping threatened species in human-controlled environments.
Examples include botanical gardens, zoological parks, wildlife safari parks, and gene banks (such as seed banks, cryopreservation, and tissue culture).
Therefore, both offsite collections (like zoos and botanical gardens) and gene banks are methods of $ex situ$ conservation.
Since options $B$ and $C$ are correct, the most appropriate answer is $D$.

(A) Gene banks are specialized institutions that maintain stocks of genetic material to preserve biodiversity.
They include various methods such as $seed\,banks$ for storing seeds,$orchards$ for maintaining live growing plants,$tissue\,culture$ for vegetative propagation,and $cryopreservation$ for storing germplasm in liquid nitrogen at $-196^{\circ}C$.
These methods collectively ensure the preservation of the entire range of genetic variability.

(B) Orthodox seeds are those that can be dried to low moisture content (typically around $5\%$) without losing their viability.
These seeds can be stored for long periods under low-temperature conditions,specifically between $-10^oC$ and $-20^oC$.
Examples of such seeds include most cereals and legumes,which are commonly stored in seed banks using these conditions to maintain genetic diversity.

(C) The dwarfing gene $Norin-10$ was discovered in a Japanese wheat variety. This gene was later used by Dr. Norman Borlaug in the development of semi-dwarf,high-yielding wheat varieties during the Green Revolution,which significantly increased wheat production globally.

(D) The maximum genetic diversity of crop plants is found in regions where agriculture is practiced in a $Primitive$ manner. In such areas,farmers continue to cultivate traditional landraces and local varieties that have evolved over centuries to adapt to specific local environments. These varieties possess a wide range of genetic traits,unlike modern commercial agriculture,which relies on a limited number of high-yielding,genetically uniform varieties.

(C) Genetic diversity refers to the variety of genes within a species.
Wild relatives of cultivated crops possess a vast pool of genetic variation,including genes for resistance to diseases,pests,and environmental stress.
These traits are often lost during the process of domestication and selective breeding in modern varieties.
Therefore,wild relatives are the primary source for obtaining maximum genetic diversity for crop improvement programs.

(C) Cryopreservation is a technique used to store living cells,tissues,or embryos at extremely low temperatures.
This process is carried out using liquid nitrogen at $-196^oC$.
At this temperature,all metabolic activities of the biological material are suspended,allowing for long-term preservation without damage.

(B) The resistance to red rot disease was introduced into commercial sugarcane varieties at the Sugarcane Breeding Institute, Coimbatore, by crossing them with the wild species $Saccharum spontaneum$. This wild species serves as a valuable genetic resource for incorporating disease resistance traits into cultivated crops.

(D) The term 'New World' refers to the Americas, while the 'Old World' refers to Europe, Asia, and Africa.
Maize $(Zea \, mays)$ originated in the Americas (New World) and was introduced to the rest of the world (Old World) following the voyages of Christopher Columbus.
Barley, Rice, and Wheat are crops that originated in the Old World (specifically the Fertile Crescent and Asia).

(B) The 'Old World' refers to Africa, Asia, and Europe, while the 'New World' refers to the Americas. Rice $(Oryza \, sativa)$ originated in Asia (Old World) and was introduced to the Americas (New World) during the Columbian Exchange. In contrast, Potato, Corn, and Sweet Potato are crops that originated in the Americas (New World) and were introduced to the Old World.

(D) In the mid-$1960$s,the Indian agricultural sector underwent a significant transformation known as the Green Revolution.
As part of this initiative,semi-dwarf wheat varieties were introduced from Mexico,specifically developed by Dr. Norman Borlaug.
The two primary varieties introduced were Sonora-$64$ and Lerma Rojo-$64$.
These varieties were high-yielding and disease-resistant,which helped India achieve food self-sufficiency.

(A) Nikolai Vavilov,a renowned Russian botanist and geneticist,conducted extensive expeditions worldwide to collect plant germplasm. During his research on the centers of origin of cultivated plants,he collected a vast number of crop varieties. Specifically,his collection of wheat varieties is documented to be approximately $26000$ samples,which served as a foundational resource for global plant breeding programs.

(C) Germplasm refers to the total genetic material (hereditary information) present in an organism. In sexually reproducing organisms,this genetic information is primarily stored and transmitted through the reproductive cells (gametes),which are also known as germ cells. Therefore,germplasm is contained in reproductive cells.

(D) The potato $(Solanum \ tuberosum)$ originated in the Andes region of South America.
Peru is considered the center of origin and diversity for potatoes.
Therefore,Peru is the best location for germplasm collection because it contains the highest genetic variability of wild and cultivated potato species.

(D) The correct answer is $D$.
In $1963$,Norman Borlaug developed semi-dwarf varieties of wheat by introducing the dwarfing genes ($Rht$ genes) from the Japanese variety $Norin-10$.
These high-yielding,disease-resistant varieties played a crucial role in the Green Revolution.
For his contributions to global food security,he was awarded the Nobel Peace Prize in $1970$.

(D) gene bank is a type of biorepository that preserves genetic material.
In plant conservation,genetic material is stored in the form of seeds (seed banks) or through vegetative material and tissue culture techniques (for plants that do not produce seeds or have recalcitrant seeds).
Therefore,both $(b)$ and $(c)$ are correct methods used in gene banks.

(D) Genetic erosion refers to the loss of genetic diversity within a species or population.
$1$. Deforestation leads to the destruction of natural habitats,causing the loss of wild relatives of crops and diverse plant species.
$2$. Shifting cultivation often involves clearing large areas of land,which can lead to the loss of local landraces and genetic variability.
$3$. The adoption of genetically uniform high-yielding varieties (HYVs) in modern agriculture replaces traditional,diverse landraces,leading to a significant reduction in the genetic pool of crops.
Therefore,all the mentioned factors contribute to genetic erosion.

(D) The correct answer is $D$.
Shoot tip culture is widely used in plant tissue culture to obtain virus-free plants.
Even if a plant is infected with a virus,the apical meristem (shoot tip) usually remains free of the virus because the virus cannot keep pace with the rapid rate of cell division in the meristematic tissue.
This technique is extensively used for the international exchange of germplasm in vegetatively propagated crops such as banana,potato,and sugarcane.

(A) $Ex-situ$ conservation involves the conservation of selected rare plants or animals in locations outside their natural habitats.
$Ginkgo$ $biloba$,which was once listed as an endangered species,is now flourishing in botanical gardens and urban landscapes worldwide due to successful $ex-situ$ conservation efforts.

(A) Orthodox seeds are seeds that can be dried to low moisture content (dehydration) and stored at low temperatures for long periods without losing their viability. This property makes them suitable for long-term storage in seed banks. In contrast,recalcitrant seeds cannot tolerate such dehydration or low-temperature storage.

(C) The term $New \text{ World}$ refers to the Americas, while the $Old \text{ World}$ refers to Africa, Asia, and Europe.
$Potato$ $(Solanum \text{ tuberosum})$ originated in the Andes region of South America $(New \text{ World})$ and was introduced to Europe $(Old \text{ World})$ during the $16^{th}$ century.
Rice, Sugarcane, and Wheat are crops that originated in the $Old \text{ World}$ (Asia and the Middle East).

(A) Cryopreservation is a technique used for the long-term storage of germplasm, such as seeds, embryos, or tissues, in a frozen state.
This process involves storing biological material in liquid nitrogen at a temperature of $-196^{\circ}C$.
At this extremely low temperature, all metabolic activities of the cells are suspended, allowing the material to be preserved for long periods without degradation.

(D) The Central National Herbarium,which is the largest herbarium in India,is located at the Indian Botanical Garden in Howrah,near Calcutta (Kolkata). It houses a vast collection of dried plant specimens.

(C) The centre of origin of rice $(Oryza \text{ } sativa)$ is widely recognized as the Indo-Malayan region, which includes parts of India, China, and Southeast Asia. Vavilov identified this region as a primary centre of diversity for many cultivated crops, including rice.

(B) $RR-21$ is a well-known high-yielding variety of wheat $(Triticum \text{ } aestivum)$.
It was developed through plant breeding programs to increase agricultural productivity.
Therefore, the correct option is $B$.

(D) plant species threatened with extinction can be preserved in a $Gene \ Bank$.
$Gene \ Banks$ are a type of $ex-situ$ conservation where genetic material (seeds,pollen,or tissues) is stored under controlled conditions to maintain biodiversity.
While $Botanical \ Gardens$ and $National \ Parks$ are also used for conservation,$Gene \ Banks$ are specifically designed for the long-term preservation of genetic diversity of threatened species.

(A) $Gene \text{ } Bank$ is a type of biorepository that preserves genetic material. For plants, this could be in the form of seeds, tissue cultures, or $DNA$. For animals, it involves the storage of semen, ova, or embryos in cryopreservation. Since an extinct species no longer exists in the wild, its genetic information can only be maintained through these specialized storage facilities, making $Gene \text{ } Bank$ the correct answer.

(B) living fossil is an organism that has remained unchanged over a long period of geological time and has no close living relatives.
$Ginkgo$ $biloba$ is a classic example of a living fossil because it is the only surviving species of the division $Ginkgophyta$,with fossils dating back over $200$ million years.
$Gnetum$,$Riccia$,and $Pinus$ do not fit the definition of a living fossil in the same context as $Ginkgo$.

(A) Tissue culture is a technique in plant biotechnology where small pieces of plant tissue (explants) are grown in a sterile nutrient medium to produce whole plants. This method allows for the vegetative propagation of plants without the use of seeds,ensuring that the offspring are genetically identical to the parent plant.

(B) $Gene \text{ } bank$ is a type of biorepository that preserves genetic material. For plants, this could be by freezing cuttings from the plant, or stocking the seeds (e.g., in a seed bank). These facilities are crucial for the conservation of endangered plant species and the maintenance of genetic diversity.

(D) Wild varieties of plants are essential reservoirs of genetic diversity. They often contain genes for resistance to diseases,pests,and environmental stresses (like drought or salinity) that may have been lost in domesticated crop varieties during selective breeding. By conserving these wild relatives,scientists can use them in plant breeding programs to incorporate these beneficial traits into future crop varieties,thereby improving yield and resilience.

(C) The concept of "Centres of Origin of Cultivated Plants" was proposed by the Russian botanist and geneticist Nikolai Vavilov.
He identified specific geographical regions where the greatest diversity of crop plants and their wild relatives is found, which he termed as the centres of origin.

(A) The top four crops of the world by annual production are maize,wheat,rice,and potatoes.
Maize,wheat,and rice belong to the family $Poaceae$ (also known as $Gramineae$).
Potatoes belong to the family $Solanaceae$.
Therefore,the top four crops belong to the families $Poaceae$ and $Solanaceae$.

(A) $Simmondsia \ chinensis$ $(Jojoba)$ seeds contain approximately $50\%$ liquid wax.
This liquid wax serves as a high-performance lubricant for machinery that operates under high pressure,provided there are no significant temperature fluctuations.

(C) $Azadirachta indica$ (Neem/Margosa) is considered an underutilized oil crop.
Its oil is extracted from the seeds,which contains various bioactive compounds used in medicine and agriculture.

(B) Triticale is a man-made cereal crop developed by crossing wheat and rye.
There are two main types of Triticale:
$(i)$ Hexaploid Triticale: Developed by crossing tetraploid wheat $(Triticum \text{ turgidum})$ with diploid rye $(Secale \text{ cereale})$.
$(ii)$ Octaploid Triticale: Developed by crossing hexaploid wheat $(Triticum \text{ aestivum})$ with diploid rye $(Secale \text{ cereale})$.

(B) The plant commonly known as 'jojoba' is $Simmondsia$ $chinensis$.
It is a shrub native to the Sonoran Desert in Mexico and the southwestern United States.
It is well-known for the liquid wax (jojoba oil) extracted from its seeds,which is widely used in the cosmetic and pharmaceutical industries.
Therefore,the correct option is $B$.

(B) $Triticale$ is a man-made cereal crop produced by crossing wheat $(Triticum)$ and rye $(Secale)$.
It is primarily used as a forage crop because its flour lacks the gluten quality required to make bread or chapatis.

(C) Non-traditional oil crops are plants that are not typically cultivated for oil but possess seeds with high oil content. Both $Cucurbita\ foetidissima$ (wild gourd) and $Citrullus\ colocynthis$ (colocynth) are recognized as potential non-traditional sources of vegetable oils. These plants are adapted to arid environments and their seeds contain significant amounts of oil that can be extracted for industrial or nutritional purposes.

(A) $Parthenium \ argentatum$ (Guayule) is a plant primarily known as a source of natural rubber,not furniture wood. Therefore,this pair is incorrectly matched.
$Leucaena \ leucocephala$ is a leguminous plant that fixes atmospheric nitrogen.
$Simmondsia \ chinensis$ (Jojoba) is well-known for producing liquid wax from its seeds.
$Psophocarpus \ tetragonolobus$ (Winged bean) is a highly nutritious plant where seeds are consumed for their protein content.

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

(B) The scientific name of Jojoba is $Simmondsia\ chinensis$.
It is a shrub that is native to the deserts of Mexico and the southwestern United States.
It is economically important because its seeds produce a liquid wax,commonly known as jojoba oil,which is widely used in the cosmetic and pharmaceutical industries.

(D) The genus $Triticum$ includes species with different ploidy levels.
$Triticum$ $monococcum$ is a diploid $(2n = 14)$ species.
$Triticum$ $durum$ and $Triticum$ $turgidum$ are tetraploid $(4n = 28)$ species.
$Triticum$ $aestivum$,commonly known as bread wheat,is a hexaploid $(6n = 42)$ species.
Therefore,the correct answer is $T. aestivum$.

(D) $Azadirachta indica$ (Neem),$Shorea robusta$ (Sal),and $Madhuca indica$ (Mahua) are all examples of plants that produce oil-bearing seeds but are traditionally classified as underutilized or non-conventional oil crops in industrial agriculture.
These species are often harvested from the wild or agroforestry systems and have significant potential for the production of non-edible oils used in soaps,lubricants,and biofuels.

(C) $Triticale$ is a man-made hybrid cereal produced by crossing wheat ($Triticum$ $aestivum$) and rye ($Secale$ $cereale$).
Initially,the first $Triticale$ produced was a hexaploid $(6n)$ hybrid.
Later,octaploid $(8n)$ varieties were also developed through further breeding programs.
Therefore,$Triticale$ can be both hexaploid and octaploid depending on the specific variety.