Method of plant breeding for crop improvement - class-IX

Horticulture has been defined as the agriculture of plants, mainly for food, materials, comfort and beauty. According to American horticulturist Liberty Hyde Bailey, "Horticulture is the growing of flowers, fruits and vegetables, and of plants for ornament and fancy." Hence, vegetable crop cultivation is known as Horticulture.

Wide hybridization can be used to transfer the desirable variability. It is used for producing haploids, diploids from tetraploids and trihaploids from hexaploids.

A. G.J Mendal is known for his discovery of fundamental laws of inheritance.

Totipotency - The ability of cells such as an embryonic stem cell to differentiate into any type of body cell. Plant cells are also totipotent, which helps to explain why a graft of a plant can generate a whole new individual out of just a small branch cutting.
Totipotent cells can form all the cell types in a body, plus the extraembryonic, or placental, cells. Embryonic cells within the first couple of cell divisions after fertilization are the only cells that are totipotent. Pluripotent cells can give rise to all of the cell types that make up the body; embryonic stem cells are considered pluripotent. Multipotent cells can develop into more than one cell type, but are more limited than pluripotent cells; adult stem cells and cord blood stem cells are considered multipotent.

The Rht-B1b and Rht-D1b dwarfing genes were derived from Norin-10, which was a semi-dwarf variety bred in Japan and released in 1935 (Gale and Youssefian, 1985). Norin-10 was used in US breeding programs in the 1950s in order to improve lodging resistance in winter wheat, in which lodging was a serious problem when high rates of nitrogen fertilizers were applied. A selection from a cross of Norin-10 with the US variety, Brevor was particularly promising and was used by Borlaug in the development of the green revolution wheat varieties. Wheat Norin-10 is a semi-dwarf wheat cultivar with very large ears that was bred at an experimental station in Iwate Prefecture, Japan. Norin-10 helped developing countries, such as India and Pakistan, to increase the productivity of their crops from approximately 60% during the green revolution. Thus, the correct answer is option B.

A crescograph is a device for measuring growth in plants. It was invented in the early 20th century by Sir Jagadish Chandra Bose. The Bose crescograph uses a series of clockwork gears and a smoked glass plate to record the movement of the tip of a plant (or its roots) at magnifications of up to 10,000. Marks are made on the plate at intervals of a few seconds, demonstrating how the rate of growth varies under varying stimuli. Bose experimented with temperature, chemicals, gases and electricity.

Plant breeding programs aim to improve crops in multiple ways. This includes developing varieties that are resistant to diseases, produce higher yields, and mature earlier to optimize farming cycles.

Hybrid plants can be developed by the breeding of the plants of different species. The parents are genetically different plants. The hybrid of maize plant was developed in order to obtain higher yield. The plants with the trait of producing higher yield were crossed with the other plant with superior character. The number of grains in the plant and the number of fruits is counted to obtain a higher yield. 

In intravarietal hybridization, the crosses are made between the plants of same variety. Thus, option C is correct.

The prime aim of plant breeding is to improve the characteristics of plants that they become more useful automatically and economically. Some of the objectives may be summarized as follows-
1. Higher yield: Higher yield of grain, fodder, fibre, sugar, oil etc.
2. Improved quality: The quality characters may vary from one crop to another, such as grain size, shape, colour, milling and backing quality of wheat, cooks quality in rice, malting in barley. Size shape and flavour in fruits and keeping quality of vegetables, protein contents in legumes, methionine and tryptophan contents in pulses etc.
3. Disease and pest resistance: Resistant varieties offer the cheapest and most convenient method of disease and pest control. They not only helps to increase the production but also stabilize the productivity.
4. Maturity duration: It permits new crop rotation and extends crop area. Thus breeding for early maturing varieties suitable for different dates of planting. This enables the farmer to take two-three crops in a year.
5. Agronomic characters: Three includes the characters, such as dwarf, profuse tillering, branching erect resistance and fertilizer responsiveness. Thus, option D is correct.

Emasculation involves the removal of stamens from bisexual flowers of the female parents in order to avoid self-pollination in these flowers. It is done before the anthers are mature. If in a condition the female parent bears bisexual flowers, then elimination of anthers from the flower bud before the anther matures. This step is known as emasculation.  

'Sugarcane Breeding Institute' is the sugarcane research and development institute located in Coimbatore, India. On the 1st day of April 1932, a sub-station of the 'Sugarcane Breeding Institute', Coimbatore (Tamil Nadu) was established at Karnal (Haryana) with funds provided by the then 'Imperial Council of Agricultural Research' (now the Indian Council of Agricultural Research abbreviated as ICAR). 

Central Food Technological Research Institute, is one of the laboratories of the Council of Scientific and Industrial Research located in Mysore, Karnataka. 

Modern hexaploid wheat (Triticum aestivum) arose through the combination of hybridization between different wild grass species followed by spontaneous chromosome doubling (polyploidy) to restore fertility.

Improved Indian rice varieties, such as those developed during the Green Revolution, were primarily derived from crosses between the indica subspecies (native to India) and the japonica subspecies (known for high yield).

The primary objective of plant breeding is to create new and improved plant varieties that possess desirable traits such as higher yield, better nutritional quality, or disease resistance.

A cross involving four inbred or pure lines of maize is known as a double cross, which is commonly produced by crossing two different single-cross hybrids to restore vigor and uniformity in commercial maize production.

A cybrid (cytoplasmic hybrid) is produced by the fusion of a protoplast containing a nucleus and cytoplasm with a cytoplast (a cell without a nucleus). Thus, it contains the cytoplasm of both parents but the nuclear genome of only one.

Plant breeding is the branch of agricultural science and biology that focuses on the genetic improvement of plants to produce desired characteristics.

Plant breeding typically involves hybridizing parents with desirable traits, followed by the selection of the best offspring from the resulting population to stabilize those traits.

Self-pollination of hybrid offspring over several generations leads to the segregation of alleles and an increase in homozygosity, which helps in stabilizing the desired traits.

Somatic hybridization involves the fusion of protoplasts. To achieve this, the cell walls must be removed using enzymes like cellulase and pectinase to allow the plasma membranes to fuse.

Emasculation is the process of removing the anthers from a bisexual flower to prevent self-pollination, ensuring that the flower can only be fertilized by the desired pollen during hybridization.

Hybrid plants can exhibit sterility due to meiotic irregularities, mosaicism from somatic mutations or chromosomal variation, and hybrid vigor (heterosis). Crossing over is a normal meiotic process occurring in all sexually reproducing plants, not uniquely a hybrid feature, and hybrids are typically heterozygous rather than homozygotic.

This is a dihybrid cross. The F1 generation is heterozygous for both traits (TtWw). In the F2 generation, the probability of a short (tt) blue (ww) plant is 1/4 * 1/4 = 1/16. For 2160 plants, 2160 / 16 = 135.

ADT-37 is an inter varietal cross between Oryza Japonica and Oryza Indices. 

Genetic variability is the cornerstone of breeding with the advent of molecular biology, traditional interspecific, intergenetic and plant type barriers to gene transfer have been removed. By isolating the gene for a particular trait and inserting it into a new host by a range of techniques the gene becomes a part of the host.DNA.

Bengal Desi is a well-known variety of cotton (Gossypium arboreum) grown in India.

Hybrid vigour will be lost due to inbreeding depression. The increase in the level of production traits due to crossing is called hybrid vigour or heterosis. The term hybrid vigour points at the vigour, which is a real factor that can bee seen by the naked eye, in comparison to pure breeding. The other word heterosis is derived from heterozygosity and points toward the direction form where the effect arises. The direction of the effect of crossing is opposite the effect of inbreeding. Inbreeding depression is the reduced biological fitness in a given population as a result of inbreeding - ie., breeding of related individuals. Population biological fitness refers to its ability to survive and reproduce itself.

The crossing between genetically different plants to produce a new variety is called as hybridization. Genetically modified crops can be produced by insertion of genes with desired traits by the process of hybridization. The first natural hybridization was recorded by Cotton Mather. This was observed and documented in corn in the year 1716. 

• The crossing between genetically different plants to produce a new variety is called hybridization.
• Genetically modified crops can be produced by the insertion of genes with desired traits by the process of hybridization.
• The plants of potato and tomato are the plants of the different genus. These plants are allowed to perform hybridization.
• The resulting plant variety is known as pomato. Cherry-type tomatoes are grown on the climber while the potatoes are developed below the soil. 
  
  

Carnauba wax is made from the leaves of the palm tree. It is also known as palm wax. It is obtained from the leaves of the carnauba palm by collecting and drying them, beating them to loosen the wax, then refining and bleaching the wax.

Black rust (or stem rust) of wheat is a fungal disease caused by the pathogen Puccinia graminis tritici.

Late blight of potato is caused by Phytophthora infestans a oomycetae (fungi). Cool climate and wet weather help infection and spread, responsible for the irish famines in the nineties.

• Mutation breeding is the process of exposing seeds to certain chemicals and radiation in order to generate mutants with desirable traits to bred with other cultivators. This will change the base sequence of genes of crop plants. In mung bean, resistance to yellow mosaic virus and powdery mildew were induced by mutations.
  
• Recombinant DNA technology is the process of joining DNA molecules together from 2 different species that are inserted into a host organism to produce new genetic recombinations.
• Transgenic mechanism is the mechanism of random integration of foreign DNA in transgenic animals.
• Gene therapy is a therapeutic process of delivery of nucleic acid into a patient's cell as a drug to treat a disease.

Heterosis is also called as hybrid vigour. It is the increase in such characteristics as size, growth rate, fertility and yield of a hybrid organism over those of its parents. Plant and animal breeders exploit heterosis by mating two different pure-bred lines that have certain desirable traits. Because of this, hybrids are generally found to be superior to their parents. Thus, the correct answer is option B.

 A mutation is a permanent change in the sequence of DNA. Mutations can be caused by external (exogenous) or endogenous (native) factors, or they may be caused by errors in the cellular machinery. Physical or chemical agents that induce mutations in DNA are called mutagens and are said to be mutagenic. Exogenous factors: environmental factors such as sunlight, radiation, and smoking can cause mutations. Endogenous factors: errors during DNA replication can lead to genetic changes as can toxic by-products of cellular metabolism.

Gurdev S. Khush crossed 13 varieties of rice from Oryza nivara to develop IR - 36 which was resistant to grassy stunt virus.

The first step in breeding for disease resistance is identifying and screening the available germplasm to find sources of resistance that can be incorporated into commercial varieties.

Herbicides, also commonly known as weed killers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets, while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic mimics of natural plant hormones. A large number of different herbicide classes inhibit photosynthesis by binding to the quinone-binding protein, D-1, to prevent photosynthetic electron transfer. Mostly they interfere with photolysis of water. Thus, option C is correct. Herbicides does not interfere with water absorption, translocation of sugar and CO$ _{2}$ absorption. Thus, other options are wrong.

The shoot tip culture used for obtaining disease free plant without genetical changes. The plant which affected by any contaminant mostly by viruses have saved by shoot tip culture, because shoot tip of any affected plant is less or free from contamination (viruses, bacteria, fungus or others). Plant shoot tip are more efficient to cultivation or differentiation in-vitro because cells of them newly generated and healthy comparison to other parts. 

Rust of wheat is caused by fungus. Diseased plants show rust coloured orange patches on the infected plant part.

Himgiri is a wheat hybrid variety, which yields 26-30 qtls/ha. It is a disease resistance variety to stripe rust or yellow rust. This is Triticum aestivum species. The variety was developed by IARI. Thus, the correct answer is option A.

Breeding for disease resistance is a comprehensive process that requires identifying a source of resistance, planning the hybridization, and rigorously testing the progeny for resistance.

Mutation breeding is associated with Staddler (4), Inbreeding depression with Shull (5), Pureline selection with Johannsen (1), and Intergeneric hybridization with Karpechenko (2).

Ear cockle of wheat is caused by the nematode Anguina tritici, which causes the formation of galls (brown stony structures) in place of grains and distorts the spikelets.