PowerPoint Presentation

[Audio] Breeding self-pollinated crops involves the identification of one or a few superior genotypes and their multiplication. This process typically employs specific breeding methods such as mass selection, pure-line selection, pedigree breeding, backcross breeding, and bulk populations..

[Audio] Selection is a crucial step in breeding self-pollinated crops. There are two fundamental requirements that need to be met for this process to operate effectively. Firstly, there must be variation present within the population, meaning that there needs to be a range of different characteristics among the individuals being considered for selection. Secondly, the variation must be heritable, meaning that the characteristics being selected for must be passed down from one generation to the next through the genes..

[Audio] There are two main types of selection. Natural selection occurs due to natural forces such as climate, soil, and biological factors. This type of selection is beyond human control and can result in the survival and reproduction of certain individuals with favorable traits..

[Audio] Breeding self-pollinated species typically requires identifying one or a few superior genotypes and multiplying them. There are several specific breeding methods commonly used for self-pollinated species, including mass selection, pure-line selection, pedigree breeding, backcross breeding, and bulk populations. These methods allow breeders to identify and multiply desirable traits while eliminating undesirable ones. By using these methods, breeders can develop high-yielding and disease-resistant varieties that meet the needs of farmers and consumers..

[Audio] Mass selection is one of the oldest methods of plant improvement. This technique involves selecting a large number of plants with similar phenotypes and mixing their seeds together to create a new variety. The selection process is based solely on the physical characteristics of the plants, such as seed size, disease resistance, plant height, yield components, and seed color. These traits are easily observable and can be used to identify desirable individuals within a population. By combining the seeds of these selected plants, breeders can create a new variety that exhibits improved performance in terms of these desired traits..

[Audio] The improvement in self-pollinated crops through breeding is limited to the genetic variation present in the original population. This means that no new variation is introduced during the breeding process. Breeding can involve both positive and negative selection. In negative selection, we aim to eliminate the least desirable plants, while in positive selection, we focus on preserving the most desirable ones. This results in a more uniform population compared to the original one..

[Audio] Breeding in plants involves selecting desirable traits in parent lines to produce offspring with improved characteristics. This process can be applied to self-pollinated crops, where the focus is on selecting for desirable traits within a single line. The goal is to identify and select individuals with superior qualities, such as increased yields, disease resistance, or improved nutritional content. By selecting for these traits, breeders can develop new crop varieties that better meet the needs of farmers, consumers, and the environment..

[Audio] In plants, some species exhibit self-pollination, where pollen from one flower fertilizes another flower on the same plant. This process can lead to the formation of seeds, which contain the genetic information from both parents..

[Audio] In the first year of mass selection, large numbers of plants exhibiting desirable characteristics such as vigor, plant height, disease resistance, and other agronomic traits are identified. These seeds are then composited to produce the next generation, thereby concentrating the desired traits within the population..

[Audio] Mass selection is a breeding method that offers several advantages. It allows us to improve local varieties, which are often well-suited to specific environments and can thrive under certain conditions. Purification of existing pure-line varieties is also possible through mass selection, eliminating unwanted traits and maintaining desirable characteristics. Moreover, mass-selected varieties tend to be more widely adapted than pure lines, making them suitable for cultivation over a larger area. However, there are some limitations to consider. It's impossible to determine whether a selected phenotype is superior because of its genetic makeup or environmental influences. Furthermore, mass selection does not create new variation; instead, it relies on the existing variability within a population..

[Audio] Pure line selection involves selecting seeds of different sizes and growing them separately to produce progenies that differ in seed size. Johannsen's study with the princess variety of beans demonstrated that this method is effective in selecting for desirable traits. By selecting for larger seeds, we can produce offspring that also have larger seeds, indicating a genetic basis for the trait. This approach allows us to isolate and maintain a specific genotype, which can then be used as a breeding material. However, it is essential to note that pure line selection has limitations, such as limited adaptability and requiring great skill and familiarity with the crop..

[Audio] All the individual plants within a pure-line variety are genetically similar and homozygous, meaning they have the same set of genes. Any variation observed within a pure-line is solely due to environmental factors and is non-heritable. This means that if we were to grow multiple plants from a pure-line variety under identical conditions, they would exhibit the same characteristics..

[Audio] Genetic variation in pure lines originates through three primary mechanisms: mechanical mixture, natural hybridization, and mutation. As a consequence, all plants within a pure line possess the same genotype. Moreover, any variation noticed within a pure line is environmentally caused and non-inherited. This implies that the traits displayed by plants within a pure line are consistent and predictable..

[Audio] Pure line selection has several applications in improving self-pollinated crops. It is used to enhance local varieties by selecting the best individuals within a local variety and breeding them to produce improved offspring. Additionally, it can upgrade old pure-line varieties by introducing desirable traits into these existing varieties to make them more productive or disease-resistant. Furthermore, pure line selection can also be used to improve introduced varieties by adapting them to specific environments or combining their desirable traits with those of local varieties. By using pure line selection, breeders can develop new varieties that better suit the needs of farmers and consumers alike..

[Audio] We select a large number of individual plants based on their phenotypic appearance. These plants should exhibit desirable traits, including a good growth habit, high yield, and disease resistance. Next, we grow the progenies of each plant in a plant-to-row basis, allowing them sufficient space to develop properly. Within each row, we select the best plants, taking into account factors like uniformity, vigor, and overall performance. After harvesting, we bulk the seed while carefully evaluating its quality, generated by each plant. Through this process, we can identify the top-performing lines and utilize them as the foundation for our breeding program..

[Audio] The next step in breeding self-pollinated crops is to test the bulked seed from each individual selected-row in a preliminary yield trial. This involves sowing the seed in a controlled environment and evaluating its performance based on factors such as yield, quality, and disease resistance. The best entries will then be selected and further propagated to produce a larger quantity of seed. Once this is done, we need to evaluate the progenies of these selected entries in a replicated variety trial. This means growing multiple plots of each entry under identical conditions and comparing their performance over several years. The goal is to identify the most outstanding entries and release them as new varieties..

[Audio] Pure lines offer several advantages. They are extremely uniform since all the plants in the variety will have the same genotype. This means that every plant will exhibit the same characteristics, making it easier to identify the variety. Pure lines are also attractive and liked by farmers and consumers due to their consistent quality. Moreover, pure lines are stable and can be tested for many years, ensuring that the variety remains unchanged over time. Furthermore, the variety can be easily identified in seed certification programs due to its extreme uniformity..

[Audio] New genotypes are not created through pure line selection, which means that breeders cannot introduce novel traits or characteristics into the crop. Pure lines also have limited adaptability, making them suitable for cultivation in specific areas only. Selecting pure lines requires great skill and familiarity with the crop, which can be challenging for inexperienced breeders. Breeding involves devoting significant amounts of time, which can be a limiting factor. Once the best available genotype has been isolated, no further improvements are possible..

[Audio] Individual plants from the F2 generation are selected, and then the progenies of each selected plant are reselected in subsequent generations until genetic purity is obtained. This process maintains a detailed record of the relationships between the selected plants and their progenies, allowing each progeny to be traced back to the original F2 plant. This record of parent-offspring relationships is known as a pedigree..

[Audio] Hybridization is a crucial step in generating variability, which sets pedigree selection apart from other methods like mass selection or pure-line selection. This technique was first introduced by H H Lowe in 1927. When selecting for desirable traits, we focus on those with moderate to high heritability, such as seed color, presence of awn, or disease resistance. However, vigor is not an effective trait to select for, as it can be influenced by factors like heterozygosity, genotype-environment interactions, and environmental conditions. When selecting plants in the F2 generation using the pedigree method, careful consideration is necessary..

[Audio] In the pedigree method of breeding, we start by crossing two parents with desirable characteristics. This produces an F1 generation, which is then grown to produce a large quantity of F2 seeds. These seeds are harvested in bulk, and the resulting F2 plants are grown in large numbers, typically ranging from 2000 to 10000 individuals..

[Audio] The bulk method of breeding involves growing the F2 generation in a large plot, harvesting all the seeds, and using them to establish the next generation. No records of ancestry are kept, and natural selection eliminates plants with poor survival value. Artificial selection is also applied through the elimination of plants carrying undesirable major genes and the selection of plants with desirable traits such as early maturity and increased seed size. Single plant selections are then made and evaluated in the same way as in the pedigree method of breeding. The advantages of the bulk population method include its ability to handle large numbers of plants and its efficiency in eliminating inferior plants..

[Audio] The bulk method of breeding self-pollinated crops offers several merits. Firstly, it provides the breeder with ample opportunities to utilize their expertise and judgment in selecting superior plants. This enables them to identify and eliminate inferior plants and their offspring in the early stages of breeding. Furthermore, this approach requires less time compared to the bulk method, allowing breeders to develop new varieties more efficiently..

[Audio] The bulk method of breeding involves handling the F2 generation at normal commercial planting rates in a large plot. The crop is harvested in mass, and the seeds are used to establish the next generation in a similar plot. No record of ancestry is kept. Natural selection tends to eliminate plants with poor survival value. Artificial selection is also applied through the destruction of plants carrying undesirable major genes and mass techniques like harvesting when only part of the seeds are mature to select for early-maturing plants or using screens to select for increased seed size. Single-plant selections are then made and evaluated in the same way as in the pedigree method of breeding. The main advantage of the bulk population method is that it allows breeders to handle very large numbers of plants..

[Audio] The bulk-population method of breeding involves growing the F2 generation at normal commercial planting rates in a large plot. At maturity, the entire crop is harvested and used to establish the next generation in a similar plot. Unlike the pedigree method, no record of ancestry is kept. During this process, natural selection eliminates plants with poor survival value. Artificial selection is also applied through the destruction of plants carrying undesirable major genes and the use of mass techniques like selective harvesting to favor early-maturing plants or larger seeds. Finally, single-plant selections are made and evaluated similarly to the pedigree method. This approach enables breeders to work with large numbers of individuals inexpensively..

[Audio] In the bulk method of breeding, we harvest F2 and subsequent generations in mass or as bulks to raise the next generation. This process continues until the end of the bulking period, typically around F4 or F5. At this point, individual plants are selected and evaluated in a similar manner as in the pedigree method. The bulk-population method differs from the pedigree method mainly in how we handle the generations following hybridization..

[Audio] The bulk method of breeding involves growing F2 populations and harvesting their F3 progenies in bulk without any artificial selection by the breeder. This process is repeated several times until sufficient levels of homozygosity are achieved. Once homozygosity is reached, individual superior plants are selected and threshed separately. The progenies of these selected plants are grown in rows, and the best rows are chosen. Finally, the progenies are tested for yield and evaluated in varietal trials..

[Audio] The merits of bulk selection include its simplicity, convenience, and inexpensiveness. This method does not require keeping pedigree records, which saves time and labor. Additionally, isolating desirable types is easier, and less work and attention are needed in F2 and subsequent generations. However, there are demerits to this method. It takes a much longer time to develop a new variety, and it provides little opportunity for the breeder to exercise their skill or judgment in selection. Furthermore, this method is less efficient than the pedigree method when dealing with highly heritable traits, as it can purge non-selections in early generations..