Transgressive variation. Transgressive Segregation 2022-11-16
Transgressive variation refers to the occurrence of individuals within a population who exhibit traits or characteristics that differ significantly from the norm or average within that population. These variations can be physical, behavioral, or both, and can occur as a result of genetic mutations, environmental influences, or a combination of both.
Transgressive variation is an important concept in biology, as it allows for the potential for evolutionary change and adaptation within a population. In some cases, these variations may provide an advantage to the individual in terms of survival and reproduction, leading to their inclusion in the gene pool of future generations. In other cases, transgressive variations may be disadvantageous or even detrimental to the individual's survival, leading to their eventual elimination from the population.
One example of transgressive variation can be seen in the field of plant breeding, where plant breeders intentionally create new plant varieties by crossing individuals with desired traits in order to create offspring with a combination of those traits. This process can result in the creation of new plant varieties that exhibit traits that are significantly different from their parent plants.
Transgressive variation can also occur naturally within populations, as a result of genetic mutations or environmental influences. For example, some animals may exhibit unusual coloration or physical characteristics due to genetic mutations that occur during development. These variations may provide an advantage to the individual in terms of survival and reproduction, leading to their inclusion in the gene pool of future generations.
Transgressive variation is also an important concept in the field of psychology, where it can be used to explain individual differences in behavior and cognition. For example, some individuals may exhibit unusual or exceptional abilities in certain areas, such as mathematics or music, due to genetic or environmental influences that have resulted in transgressive variation.
In conclusion, transgressive variation refers to the occurrence of individuals within a population who exhibit traits or characteristics that differ significantly from the norm or average within that population. These variations can be beneficial or detrimental to the individual's survival and reproduction, and can occur as a result of genetic mutations or environmental influences. Understanding transgressive variation is important in a variety of fields, including biology, psychology, and plant breeding, as it helps to explain individual differences and the potential for evolutionary change within a population.
Linkage mapping, is usually done in the context of closely related individuals having known relationships, such as the offspring of a controlled cross or the members of a family where the pedigree is known. In India, Agnihotri and Kaushik 2003a, b have reported successful introgression of double-low traits in B. Typically, the first two years are used to produce a vast array of unique F3 to F5-derived RILs that are subsequently screened for up to five more years for yield potential and other desirable agronomic traits. The information on potential PAs can be collected on parental lines that involve screening either a whole crossing block, or a set of frequently used parents. In some cases short parents have tall children for the same reason.
Transgressive Variation for Yield Components Measured throughout the Growth Cycle of Jefferson Rice (Oryza sativa) × O. rufipogon Introgression Lines
At the same time, other critical attributes that contribute to soil moisture conservation during late-season water deficits must be addressed. Major QTLs for resistance of nematode disease have been identified in Acala NemX×Acala SJ-2, Acala SJ-2×Clevewilt, and Pima S-7×Acala NemX Wang et al. These crosses can derive highly resistant lines, even when both parents have a susceptible phenotype. Studies done using MAS to identify nematode resistance are included in Table 17. Breeding approaches based on specific PAs are useful only if defined appropriately in terms of the developmental stage of the plant, the specific attributes of the target environment for which they are adaptive, and their potential role in yield Reynolds and Trethowan, 2007; Mujeeb-Kazi et al.
Drought escape, for example, under water-limited conditions via manipulation of plant phenology is a commonly used genetic approach for relative yield stability Richards, 1991. In the same context, the extreme sensitivity of reproductive processes to drought may result in reproductive failure, which is associated with low HI. Eizenga and Jeremy D. Marker assisted selection MAS can be used to increase the efficiency of NIL development by screening individuals for the presence of the target locus gene in each generation and the absence of extraneous donor DNA throughout the rest of the genome to speed up the return to recurrent parent type. So far, in most plant breeding programs, intraspecific hybridization involving diverse crosses between indica × indica and indica × japonica both tropical and temperate japonica has been used in rice improvement.
Difference between “Transgressive Variations” and “Regressive Variations”
A common refrain about modern plant breeding is the concern about its potential to reduce genetic diversity by increasing selection pressure on the uniform conditions typical of modern agriculture. Resistance can be effectively achieved through transgressive segregation in which a segregating hybrid exhibits novel phenotypes due to the epistatic interactions of genes Rieseberg et al. Molecular markers have become important tools for enhancing the selection efficiency for various pest resistance traits in precision plant breeding. Experimental work toward development and improvement of low erucic acid germplasm for other species is being pursued at global level Rakow and Raney, 2003. . Alleles in LD are co-inherited more often than would be expected by chance alone. Since the number of recombination events in these cases is relatively small, genes or quantitative traits are mapped to large chromosomal blocks, and the resolution is low Mb scale.
Expand This research demonstrates that tiller angle is controlled by a major quantitative trait locus, TAC1 Tiller Angle Control 1 , which was mapped to a 35-kb region on chromosome 9 using a large F 2 population from crosses between an indica rice, IR24, which displays a relatively spread-out plant architecture, and an introgressed line, IL55, derived from japonica rice Asominori. Brassica oil contains few harmful saturated fatty acids and many mono and polyunsaturated fatty acids, which makes it nutritionally superior to most other edible oils Agnihotri et al. Therefore, it is advocated to keep the population heterozygous for quality characters and select plants for these characters in advanced generation. For instance, the height in human beings is one such trait subject to regressive variations. In high concentrations, in nonruminants like swine and poultry, it hydrolyzes to form thiocynates, isothiocynates, or nitriles and can adversely affect iodine uptake by the thyroid gland and can result in weight loss Fenwick et al.
This method works at a population level and relies on LD between an array of linked markers and the functional mutations responsible for trait variation. At the VRN-B1 locus, 35 accessions had winter type allele vrn-B1, and 10 accessions had dominant Vrn-B1 allele. The control of HD is critical for reproductive success and has a major impact on grain yield in Triticeae. Despite it having been an important source of nutrition for animals, there are undesirable components in the meal like glucosinolates, which render them unfit for animal and human consumption. Unfortunately, however, the genes controlling the glucosinolate content in rapeseed are either pleiotropic or linked to the seed-filling stage and have a positive correlation with 1000 seed weight Oliveri and Parrini, 1986.
Under water-limited conditions, superior photosynthesis, accumulation and remobilization of stem reserves, different stress-tolerant enzymes, osmotic adjustment, and so on are important PAs. The use of molecular markers can greatly improve the efficiency of the process, and markers are often used in combination with backcrossing to capture positive transgressive variation for rice improvement. Their analysis suggested that while allelic changes have occurred in modern plant breeding, no apparent loss of genetic diversity or allele number was detected in this collection of varieties. This thus increases the probability of transgressive segregation, ultimately bringing desirable attributes together. It is also used for technical purposes such as lubricants and hydraulic oils, as base chemicals for oleochemistry or biodiesel fuel Shahidi, 1990; Kimber and McGregor, 1995. Patterns of LD in a sample reflect the effects of many historical recombination events over thousands of generations and may therefore permit fine-scale mapping of a trait.
The origins of the experiment were influenced primarily by work conducted in France by early breeders of the fodder beet Hopkins, 1899; Troyer, 1996; Dudley and Lambert, 1992 , and the early focus of this experiment was modification of the corn kernel's chemical makeup. In addition, identification and introgression of QTLs from different AA genome wild species, including from O. Three introgression lines carried O. Natural or artificial selection also contributes to non-random mating among members of a population. This renders strict selection difficult for quality traits in early segregation, especially in light of genotypes for high seed yield possibly being lost.
Detection of such drought-adaptive PAs and the mechanisms involved is laborious, costly, and time consuming; however, the benefits are likely to be significant if successful. Based on the map positions, it can be postulated that HD QTL on 5A may be similar to the VRN1 gene mapped on chromosome 5A in T. Oil is used for human consumption, as salad oil or margarine. Table beet Beta vulgaris L. Epistatic genes may be linked, but their effects must reside at different loci in the genome. In addition, in an F 2:3 family, Wang et al. Commonly used molecular marker assays are designed to detect Single Nucleotide Polymorphisms SNPs , Simple Sequence Repeats SSRs or Restriction Fragment Length Polymorphisms RFLPs.
Although the details vary greatly among breeding programs, Fig. Since attempts to produce commercially-useful quantities of hybrid soybean seed have been unreliable to date, F1 hybrids are typically made by hand and used almost exclusively for breeding purposes. The focus of improving all three components needs to be accomplished through complex physiological attribute-based breeding. A minor locus identified on chromosome 21 was found to be linked with egg production and root galling phenotypes in the F 2 population of Pima S-7×Acala NemX Ulloa et al. In our study, T.