Plant Breeding Definition

Plant breeding is the scientific process of modifying a plant's features to generate desired qualities. The nutritional value of food for both people and animals has been improved using it. The purpose of plant breeding is to create crop varieties with superior and distinctive features for a range of uses. The agricultural traits that are most frequently discussed are those that relate to biotic and abiotic stress tolerance, grain or biomass yield, end-use quality characteristics like the taste or the concentrations of specific biological molecules (proteins, sugars, lipids, vitamins, fibers), and ease of processing (harvesting, milling, baking, malting, blending, etc.).

Plant breeding may be done using a variety of ways, from a straightforward selection of plants with desired traits for propagation to more sophisticated molecular procedures that draw on an understanding of genetics and chromosomes. Qualitative or quantitative qualities which a plant will have depends on its genes. Plant breeders work to produce specified results in their plants, including maybe a new plant kind. In the process, they reduce the genetic diversity of that variety to a select few biotypes.

Gardeners, farmers, and expert plant breeders working for institutions like government agencies, colleges, industry groups for certain crops, or research facilities are just a few of the people that engage in it on a global scale. According to international development organizations, developing new types of crops that are more productive, disease-resistant, drought-tolerant, or regionally tailored to various locales and growing circumstances is crucial for maintaining food security.

According to recent research, without plant breeding, Europe would have produced 20% less arable crops over the last 20 years, using up an extra 21.6 million hectares of land and releasing 4 billion tonnes of carbon. Currently, new kinds of wheat are being developed for northern France by crossing wheat species developed for Morocco with plants. Southern Germany is currently the primary region where soybeans are farmed, as opposed to the south of France in the past.

Genetics and Plant Breeding

The "father of genetics" is Gregor Mendel (1822-1844). With the use of studies on plant hybridization, he came up with the rules of inheritance. Plant breeding study was sparked by genetics to increase agricultural output.

To produce a desired phenotype, plants may be genetically modified by introducing a chosen gene or genes or by destroying a gene via RNAi. Transgenic plants are often used to describe plants with a gene added. They are referred to as cisgenic plants if the native promoter is not employed in conjunction with the genetic alteration genes of the species or a crossable plant. Due to the fact that just a small portion of the plant's genome is changed, genetic modification may sometimes yield a plant with the desired characteristic or traits more quickly than traditional breeding.

History

Since the very beginning of agriculture, people have been breeding plants. Humans started to distinguish between different levels of excellence in their field plants not long after the first domestication of cereal grains and began to store seeds from the finest plants to sow new crops. These rudimentary selecting techniques served as the forerunners of early plant-breeding practice practices.

The outcomes of early plant breeding techniques were obvious. Today's variations are so different from their ancestors in the wild that they cannot thrive there. In fact, in some instances, the cultivated forms are so radically different from their wild counterparts that it is even impossible to determine who their forebears were. From an evolutionary perspective, these amazing changes were made by the first plant breeders in a very short period of time, and the pace of change was likely higher than for any previous evolutionary event.

By using pea plants to illustrate the fundamentals of heredity in the middle of the nineteenth century, Gregor Mendel established the foundation for scientific plant breeding. In the early 20th century, progress was made in using the rules of genetic inheritance to enhance plants as they were more defined. One of the most important findings from the brief history of scientific breeding is that there is an immense richness of genetic variation present in the world's plants and that just a beginning has been made in using its potential.

Classical Plant Breeding

The practice of choosing reproducing plants with desired traits and eradicating or "culling" those with less desirable traits is selection, one of the main methods used in plant breeding.

Deliberate interbreeding (crossing) between closely or distantly related individuals is another method for creating new crop varieties or lines with advantageous traits. When plants are crossed, features or genes from one variety or line are introduced into a different genetic background. For instance, a mildew-resistant pea may be crossed with a pea that yields well but is vulnerable to mildew in order to add mildew resistance without sacrificing high yield. To guarantee that the offspring were most similar to the high-yielding parent, offspring from the cross were crossed with that parent again (backcrossing). The offspring of that cross would next undergo yield testing (also known as the selection, as previously mentioned), and plants with high yields of resistance to mildew would also be further improved. To create inbred variants for breeding, plants may also cross with one another. By using pollination bags, pollinators may be kept out.

Homologous recombination between chromosomes is a key component of classical breeding that produces genetic variation. The traditional plant breeder may also utilize a variety of in vitro methods, such as protoplast fusion, embryo rescue, or mutagenesis (see below), to create diversity and create hybrid plants that do not naturally exist.

Breeders have attempted to breed the following characteristics into agricultural plants:

• Increased nutrition, better flavor, or greater attractiveness are higher-quality examples.
• Crop yield that is higher
• Heightened resistance to environmental stresses such as drought, high heat, and salt
• A defense against germs, fungi, and viruses
• A greater ability to tolerate insect infestations
• Elevated herbicide toleration
• The longer time spent storing the produced crop

Modern Plant Breeding

Applied genetics, which includes biology, cytology, physiology, pathology, entomology, and statistics, is the basis of modern plant breeding. Additionally, it has created its own technologies.

In plant breeding, several different genes may sometimes affect a desired characteristic. Numerous genes may be mapped using techniques like DNA fingerprinting or molecular markers. This enables plant breeders to check a vast population of plants for individuals that have the desired characteristic. Instead of visual recognition of the expressed characteristic inside the plant, the screening is based on the presence or absence of a certain gene as determined by laboratory processes.

Types of Plant Breeding Processes

1. Introgression Breeding or Backcrossing

Backcrossing is a technique that is sometimes used by crop breeders. A plant that has the desired feature-let's say, mildew resistance-is crossed with a plant that possesses all other desirable qualities but lacks the desired trait. To ensure that the desired characteristic is the sole modification to the original variety, there is a quality control process. For instance, a mildew-resistant pea may be bred with a high-yielding pea. The offspring of a plant is the next generation. Then, all of the offspring are crossed to the high-yielding parent and tested for mildew resistance. Repeating this process many times, always crossing back to the parent with the highest yield and choosing the offspring that is mildew-resistant. This procedure guarantees that the offspring will mostly resemble the high-yielding parent while also gaining the mildew-resistant trait from the other parent.

2. Inbreeding

Some plants may produce fertilizer on their own, depending on the species. Inbred varieties are created as a result, which is the same from generation to generation. It is beneficial in three ways since it keeps the original traits: for study, as new, true-breeding cultivars, and as the parents of hybrids.

3. Hybrid Breeding

Here, two distinct inbred types are crossed to create offspring with stable traits and hybrid vigor, which is much more productive than either parent.

4. Mutation Breeding

There are genetic mutations that occur naturally all around the globe. These haphazard instances may be exploited to develop new types if they are discovered and judged to be an improvement. As an alternative, plants may be deliberately exposed to chemicals or radiation in order to promote mutations.

5. Molecular Marker-Assisted Selection

There is a significant contrast between this and traditional backcrossing, inbreeding, and hybridization procedures. Breeders choose plants by verifying the information on the genes the plants received from their parents, as opposed to choosing attractive plants based on how they seem or grow. This takes some of the uncertainty out of breeding, much like having a guide to a strange place. Before reproducing the plant, scientists may be sure the gene is there rather than simply assuming it is.

6. Genetic Engineering

The strong building design is included in the blueprints of engineers who create skyscrapers or bridges. Similar to humans, plants may be genetically modified to acquire desired features. Transgenic or genetically modified organisms (GMOs) are the plants that arise.

7. Gene Editing

Through the use of cutting-edge genetic tools like CRISPR-Cas9, breeders may directly alter certain genes. It has razor-sharp accuracy and targets highly certain plant traits.

Steps in Plant Breeding

Since the practice of plant breeding was first developed between 9000 and 11000 years ago, it has undergone several modifications. The stages involved in using the contemporary plant breeding technique are as follows: -

1. Collection of Variability

All breeding techniques use variation as their foundation. The first phase is gathering germplasm, which is a collection of plants or seeds representing all potential alleles for every gene in a particular crop. Even wild variations and farmed species relations are included in this collection.

2. Evaluation and Parent Plant Selection

In order to choose parent plants with the necessary traits, the germplasm is assessed. We anticipate that the hybrid offspring will combine these traits. For instance, a crop of plants with a high protein content may be chosen and bred with a plant with a greater level of disease resistance.

3. Cross-Hybridization between Selected Parents

The third phase involves cross-breeding the parents to create pure lines of offspring. The traditional method of transferring pollen from one plant to the stigma of another is used in this laborious and time-consuming procedure. Despite the effort put forward, just one or two of every few hundred offspring exhibit the optimal mix of traits.

4. Selection and Evaluation of Superior Recombinants

After evaluating the developed offspring, those who possess the appropriate mix of traits are self-pollinated to achieve homozygosity.

5. Testing, Publication, and Commercialization of New Cultivars

The new lines are cultivated in testing plots where their agronomic characteristics, such as quality, yield, disease resistance, etc., are examined. Then, in order to reflect the many agroclimatic zones around the nation, these crops are grown in fields there. The crops are made available for commercial sale to the general population after successful testing.

Goals

Typically, a plant's ideal form combines the most desirable traits possible in the eyes of the plant breeder. These traits may include resistance to pests and diseases, tolerance to heat, soil salinity, or frost, appropriate size, shape, and maturity timing, as well as a variety of other general and specific traits that facilitate better acclimatization to the environment, ease of growing and handling, higher yields, and higher quality. Plant breeders must take aesthetic attractiveness into account. Therefore, the breeder must consider the several features that make the plant more effective in achieving the objective for which it is cultivated rather than focusing emphasis on any one quality, which is unusual. Many essential crops have been modified to tolerate better harsh weather conditions linked to global warmings, such as drought or heat waves, and plant breeding is an important strategy in increasing global food security.

The Function of Plant Breeding in Organic Farming

In instances when such poor performance may be partly due to cultivating poorly-adapted cultivars, some organic agriculture detractors contend that it yields too little to be a practical alternative to conventional agriculture. Despite the fact that the production settings found in organic vs. conventional farming systems are greatly different owing to their unique management practices, it is believed that over 95% of organic agriculture is based on types that have been conventionally adopted. The main difference between organic and conventional growers is the number of inputs available to manage the growing environment. It is essential for this industry to breed types that are specially tailored to the special requirements of organic agriculture in order for it to thrive. This necessitates selecting qualities like:

• Efficient use of water
• Efficiency in the utilization of nutrients, especially nitrogen and phosphorus
• Competitive weed market
• Mechanical weed control tolerance
• Disease/insect resistance
• Early maturity (as a defense mechanism against certain pressures)
• Tolerance to abiotic stresses (such as salt, drought, etc.)

Few breeding programs now focus on organic agriculture, and those that did until recently tended to use indirect selection (i.e., selection in conventional conditions for characteristics thought to be crucial for organic agriculture). A given genotype may, however, operate quite differently in each habitat owing to an interaction between the environment and the genes (see gene-environment interaction) since the differences between organic and conventional settings are so great. If this interaction is strong enough, an essential attribute needed for the organic environment could not emerge in the artificial environment, leading to the selection of people who are ill-suited to it. Advocates of organic breeding currently support the use of natural selection (i.e., selection in the target environment) for several agronomic characteristics to guarantee the identification of the best suitable cultivars.

Despite the restriction on genetically modified organisms, there are several traditional and contemporary breeding strategies that may be used for crop enhancement in organic agriculture. For instance, controlled crosses between individuals allow for the natural recombination and transmission of desired genetic diversity to seedlings. The breeding process may be significantly accelerated by using marker-aided selection as a diagnostic tool to make it easier to identify offspring that have the desired trait(s). This method has shown to be very effective for introducing resistance genes into novel backgrounds and for selecting several resistance genes pyramided into a single person. Unfortunately, many significant features, particularly those that are complicated and regulated by several genes, lack molecular markers at this time.

Issues and Concerns

1. Breeding and Food Safety

Future challenges for plant breeding include a scarcity of arable land, harsher farming environments, and the need to maintain food security, which entails being able to feed the world's population adequately. To enable global access, crops must be able to develop in a variety of conditions, which requires finding solutions to issues like drought tolerance. The idea has been put up that plant breeding, with its capacity to choose certain genes and enable crops to operate at a level that produces the desired results, is a process that may lead to worldwide solutions. The disappearance of native varieties and landraces, which have variety and might include genes helpful for future climate adaptation, is one problem confronting agriculture.

Conventional breeding reduces heterogeneity between genotypes and trait plasticity within genotypes on purpose. Crops cannot respond to a changing climate or other biotic or abiotic stimuli when there is uniformity.

2. Rights of Plant Breeders

The rights of plant breeders are an important and contentious topic. Commercial plant breeders, who aim to safeguard their creations and recoup fees via national and international agreements based on intellectual property rights, dominate the development of new kinds. The variety of linked problems is intricate. Critics of the increasingly stringent regulations contend that commercial breeders are significantly restricting people's ability to develop and trade seed on a regional scale through a combination of technical and economic pressures, which in turn reduces biodiversity. Breeders' rights are still being worked on, for instance, by trying to extend the time that varieties are protected.

Definitions used in intellectual property laws for plants sometimes involve genetic homogeneity and a consistent look across generations. Contrary to conventional agronomic use, which views stability in terms of how constant a crop's yield or quality is over time and between places, these legal definitions define stability. Regulations in Nepal will only permit uniform varieties to be issued or registered as of 2020. Since many landraces and evolutionary plant populations are polymorphic, they do not adhere to these criteria.

3. Stresses on Environment

Cultivars that are uniform and genetically stable may not be able to handle environmental changes and brand-new stressors. Finding variants of the crop that are resistant to drought conditions and low nitrogen levels is one method that plant breeders are ensuring crops function under these circumstances. This clearly shows the importance of plant breeding for agriculture's survival in the future since it allows growers to generate crops that are more resilient to environmental stress and so increase food security. Plant breeders are engaged in breeding for resistance to frost, persistent snow cover, frost drought (desiccation from wind and sun radiation under frost), and high soil moisture levels in winter in locations that endure hard winters like Iceland, Germany, and farther east in Europe.

4. Prolonged Procedure

It's crucial to remember that breeding does not happen quickly while trying to treat a disease. On average, it takes at least twelve years from the moment humans first become aware of a new fungal disease danger before a crop is released that is resistant to that infection.

5. Maintaining Certain Conditions

The maintenance and propagation of newly developed plant breeds and cultivars are necessary. Asexual reproduction is used to propagate certain plants, whereas sexual reproduction is used to increase others. To preserve the integrity of the plant breed outcomes, seed-propagated cultivars need strict control over seed supply and production practices. To avoid contamination from other plants or seed mixing after harvest, isolation is required. The usual method of isolating plants is by planting them far apart, although for certain crops (most often employed for creating F1 hybrids), plants are housed in greenhouses or cages.

6. Nutritional Value

Classical or genetic engineering plant breeding in the modern day both have their problems, especially when it comes to food crops. What matters most in this regard is the issue of whether breeding may impair nutritional value. Scientific evidence suggests that by favoring certain elements of a plant's growth, other aspects may be slowed down, even if there has yet to be a lot of actual study in this area. The nutritional analysis of vegetables conducted in 1950 and 1999 was compared in a study published in the Journal of the American College of Nutrition in 2004 under the title Changes in USDA Food Composition Data for 43 Garden Crops, 1950 to 1999. It revealed significant declines in six of the 13 nutrients measured, including 6% of protein and 38% of riboflavin. There were also decreases in ascorbic acid, iron, phosphorus, calcium, and other elements. The study carried out at the University of Texas at Austin's Biochemical Institute came to the following conclusion: "We suggest that any real declines are generally most easily explained by changes in cultivated varieties between 1950 and 1999, in which there may be trade-offs between yield and nutrient content."

Because it is a practical method for raising the nutritional content of crops and pasture, plant breeding may help ensure global food security. Since 1960, there have been improvements in the nutritional value of forage crops as a result of the use of analytical chemistry and rumen fermentation technology. This science and technology allowed breeders to quickly screen thousands of samples, which allowed them to find a high-performing hybrid. With only a 1% increase in vitro dry matter digestibility (IVDMD), a single Bos Taurus, generally known as a beef cow, reported a 3.2% rise in daily gains. The genetic improvement was mostly in vitro dry matter digestibility (IVDMD), which resulted in an increase of 0.7-2.5%. This advancement suggests that plant breeding is a key strategy for preparing agriculture for the future and enabling it to operate at a higher level.

7. Yield

The necessity for food production to rise along with the population is obvious. To reach the goals set out in the World Summit on Food Security Declaration, it is predicted that food production must grow by 70% by the year 2050. More crops can no longer be planted, however, due to the destruction of agricultural land. Through plant breeding, new plant kinds may sometimes be created that boost production without requiring more acreage. This is shown by the fact that food output has doubled per capita in Asia. In addition to the usage of fertilizers, this has been accomplished through growing superior crops that are adapted to the region.

Hybrid Crops in India

1. Rice and Wheat

Production of rice and wheat both greatly expanded throughout the 1960s. Wheat types that are semi-dwarf were created by Norman E. Borlaug. Two of the hybrid wheat cultivars produced in India are Sonalika and Kalyan Sona. The IR86 (International Rice Research Institute) and Taichung Native I (from Taiwan) semi-dwarf wheat types were used. The more productive semi-dwarf rice cultivars, Jaya and Ratna, were subsequently introduced.

2. Sugarcane

Officinarum is a native of South India, whereas Saccharum Barberi is from North India. Although Officinarum has larger stems and more sugar, it does not thrive in North India. To get the ideal traits of both (higher sugar content, thicker stems, and capacity to thrive in North India), these two types were crossed.

3. Millets

In India, hybrid varieties of maize, jowar, and bajra have been successfully created. These cultivars have good yields and are drought-resistant.

Plant Breeding for Improved Food Quality

Crops are cultivated using the biofortification technique to have increased concentrations of vitamins, minerals, and lipids. Malnutrition is an issue that can be solved as a result. The following goals for the breeding program were taken into consideration:

• Quality and quantity of the protein
• Oil quality and quantity
• Contains vitamins
• Nutrition quality and quantity

Several examples of biofortification:

• Enhanced maize With lysine and tryptophan in equal amounts, Atlas 66 wheat, has a high protein level.
• Rice with added iron has five times as much iron.
• More vitamins and minerals are present in vegetable crops like spinach and carrot.
• Bitter gourd with added vitamin C.