By early testing, the breeder is in a position to discard some lines that are inadequate in hybrid performance and wasteful expenditure on these lines is avoided. A double modified single cross is the hybrid progeny from two single crosses, each developed by crossing two related inbred. The remnant half seeds from the superior parental plants are mixed and grown in isolation for random mating during the third year. 2) Many progeny selection schemes are complicated and involve considerable work. Methods of mixed (cross) pollination . No great subsequent changes were made. The remaining 20% of abiotically pollinated species is 98% by wind and 2% by water. In case of cross pollinated species the mass selected varieties are heterozygous and heterogeneous. (i) Simple recurrent selection or recurrent selection for phenotype, (ii) Recurrent selection for general combining ability, (iii) Recurrent selection for specific combining ability. The performance of synthetics can be improved by one further breeding cycle. Similarly by growing progenies of 8 to 58 plants, range of genetic variability can be established. Those that are pollinated by the wind have long stamens and pistils with small or no petals.Plants that use self pollination, such as Self-Pollination of individual plants within single plant progenies grown is the most common procedure used to develop inbred lines. 105, 110, 194, 290 Inbreeding depression has not been reported in melon 237, 252 and most varieties have been developed by selection and controlled inbreeding. This is done by selecting the strain with the most favorable characteristics then back-crossing it with itself or a parent plant until the resulting phenotype becomes consistent. • In other words, formation of a seed by union of the male and the female gametes from the same plant • also refered as autogamy. Cross-pollination is found in both angiosperms and gymnosperms and facilitates cross-fertilization and outbreeding. Advanced generations of such heterotic crosses often show stabilized yields. 1) There is no control on pollination and plants are allowed to open pollinate, thus selection is based on maternal parent only. In cross-pollinated species, a cyclical selection approach, called recurrent selection, is often used for intermating. +(D x H)/n. Selﬁng F 2 plants produces F 3 plants, and so on. Since cross-pollinated species are naturally hybrid (heterozygous) for many traits and lose vigour as they become purebred (homozygous), a goal of each of these breeding methods is to preserve or restore heterozygosity. Notify me of follow-up comments by email. Methods for breeding cross-pollinated species include mass selection, recurrent selection, family selection and synthetics. (With Methods)| Industrial Microbiology, How is Cheese Made Step by Step: Principles, Production and Process, Enzyme Production and Purification: Extraction & Separation Methods | Industrial Microbiology, Fermentation of Olives: Process, Control, Problems, Abnormalities and Developments. TOS4. In its simplest form it consists of. Selection Methods in Plant Breeding Based On Mode of Reproduction - Selection of Cross-pollinated Crops - Half-sib Selection With Progeny Testing. Now it is also used in self pollinated species. (iv) Based on mean performance of top-crosses of the four inbreeds: (A x variety) + (B x variety) + (C x variety) + D x variety/4. Nilsson and his associates in Sweedish Seed Association, Svalof Sweeden (1890) refined the single plant selection. Recurrent selection was originally developed as a method of breeding in cross pollinated species. Many lines are so poor in seed yield, pollen production, etc., that they cannot be used in a programme to produce single cross hybrid seed. On the basis of the progeny performance, the best parental individuals are identified. Under this model it should be possible to derive a pure line from the F1 which should be equal to F1 in the performance and thus this heterosis will be fixable. Oldest breeding method for cross pollinated crops. This method has been named as mass-pedigree method by S.S. Rajan in India. Usually, they involve open pollinated varieties, synthetics, double crosses, etc., selected for yield performance, maturity, resistance to diseases and pests. Lowe in 1927. All Rights Reserved. According to this hypothesis, each dominant allele contributes equally to heterosis and the recessive alleles contribute nothing. 3) The selection cycle is usually of the two years. Open-pollinated seeds of the selected individual plants are divided into two halves. Second year replicated progeny row trial is conducted using one set of half seeds from each plant. This becomes Syn 1 generation. Selfed seed from plants with superior test cross progenies are grown population wise separately and inter-crossed to reconstitute two populations which will be now called as A’ and B’. Superior progenies are identified on the basis of performance in this trial. However, it is more commonly used in cross pollinated species than in self-pollinated species. Emasculation is a method of “Artificial Hybridization” generally used to promote cross pollination in plants and avoid self pollination. What are the characters Mendel selected for his experiments on pea plant? Therefore, selection is done for easily observable characteristics such as plant height, ear/type, grain colour, grain size, etc. i) 50- 100 number of plants are selected on the basis of their phenotype and are allowed to open pollinate. (iv) Mass selection is a simple and quick method of crop improvement. This method is mainly based upon the easily observable characters are taken into consideration. This method of selection will only be effective for highly heritable traits. Pollination can be accomplished by cross-pollination or by self-pollination: . 3) It is also used in the selection of new superior recombinant type’s i.e Transgressive breeding. Method of Plant Breeding in Cross Pollinated Plants – Recurrent Selection Recurrent Selection: The initial idea of recurrent selection was independently given by Hayes and Garber in 1919 and East and Jones in 1920. Since selection is based on the phenotype of the plant, it is useful only for characters with high heritability. In self pollinated species, these varieties are a mixture of several pure lines, means homozygous but heterogeneous. But the term recurrent selection was first coined by Hull in 1945. Definition: Recurrent selection is defined as reselection generation after […] In plant crossing is done by placing pollen grain from one genotype (male parent) on to the stigma of flower of another genotype (female parents). The performance of Syn 1 can be estimated by the formula: The yield to be expected, usually increases with the number of components until an optimum is reached. The commonly used breeding methods of self-pollinated plants were developed over a century ago in Europe. our some useful Link's 1) Plant … Selected plants are pollinated by both superior and inferior pollen parents. Existence of self-sterility, self-incompatibility, imperfect flowers, and mechanical obstructions make the plant dependent upon foreign pollen for normal seed set. This would be the case if hybrid vigour were due to true over-dominance or due to tight linkage in the repulsion phase at some incompletely dominant loci. The mating of individuals more closely related than individuals mating at random is known as inbreeding. In this chapter we are concerned with the methods by which new varieties of self-pollinated crop plants originate. Cross-pollination is found in both angiosperms and gymnosperms and facilitates cross-fertilization and outbreeding. However, it suffers from the defect that the weak and inferior progenies pollinate plants in the superior progenies. 4. Part 4: Developing open-pollinated varieties using recurrent selection methods 261 units are related to one another or may even be identical, depending on the selection method used. This completes one cycle and additional cycle (s) may be initiated. Mass selection is often described as the oldest method of breeding. Jenkins and others. The greater variability caused by crossing several components with high general combining ability makes the synthetic varieties more adaptable compared to conventional varieties. Louis De Vilmorin first used it for improvement of Sugarbeet. F2 populations of the single crosses are the most frequently used source populations for line development. Now it is also used in self-pollinated species. A three-way cross is the hybrid progeny from a cross between a single cross and an inbred. Superior gametes are recovered as F2 self’s. Modifications of backcross method have also been suggested for example, in convergent improvement by Richey, there is parallel improvement of two inbred lines by the reciprocal addition of dominant favourable genes present in one line and lacking in the other line. Q. The term ‘synthetic variety’ has come to be used to designate a variety that is maintained from open pollinated seed following its synthesis by hybridization in all combinations among a number of selected genotypes, which have been tested for combining ability. Much evidences suggest that apparent over-dominance is, in fact, due to non-allelic interaction and linkage disequilibrium and that heterosis is mainly a result of the bringing together of unidirectionally dominant alleles distributed between the parental line. Various methods of recurrent selection are used for producing progenies for evaluation, as will be discussed here. 3) It is also used in the selection of new superior recombinant type’s i.e Transgressive breeding. Because cross-pollination and self-pollination occur in insect-pollinated plantings, melons can be handled as a self-pollinated or cross-pollinated crop. The challenge of the plant breeder is to develop better varieties. It is also assumed that the dominance is complete. This method is relatively simple and the selection cycle is of one year only. Method of Plant Breeding in Cross Pollinated Plants – Selection with Progeny Testing With Progeny Testing: In this method initial plants are selected on the basis of their phenotype, but the final selection of plant based on progeny test. The component inbred are crossed in all possible combinations. Two hypotheses have been put forward to explain heterosis. The seeds from individual plants are harvested separately. These composites often show a high order heterosis in F1’s when widely diversed populations are crossed. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. The methods used by plant Planting seed from the F 2 plants will yield an F 2 population, the most diverse generation following a cross, in which plant breeders often begin selection. This method is practised in both self and cross – pollinated crops and plants are selected on the basis of their phenotype of appearance. Share Your PDF File
2) This method is commonly used to correct some specific weaknesses of an established variety (Combination breeding). Share Your PPT File. Plants that use wind for cross-pollination generally have flowers that appear early in the spring, before or as the plant's leaves are emerging. However, it is more commonly used in cross pollinated species than in self pollinated species. Most New Zealand native flowering plants are pollinated by animals most by insects, but some by birds or even bats. 2) This method is commonly used to correct some specific weaknesses of an established variety (Combination breeding). The source material may be random mating populations, synthetic cultivars, single cross, or double cross. Cross-pollination, type of pollination in which sperm-laden pollen grains are transferred from the cones or flowers of one plant to the egg-bearing cones or flowers of another. It … This method is useful for improving such characters as vigour, resistance to diseases, pests and lodging. In this method of breeding, the best individuals with desired characters are selected on the basis of phenotypic performance in a source population. (iii) The produce of mass selected variety is lesser uniform than that of pureline variety. 1) In this method the selection is based on the progeny test and not phenotype of individual plants, hence it is more efficient than mass selection in the identification of superior genotypes. Such populations are characterized by a high degree of heterozygosity with … (iii) Conducting multi-location test with the F1 and F2 generations of varietal crosses and selection of F2‘s showing desirable agronomic features along with least decline in F2. The recurrent selection for general and specific combining ability is equivalent to half sib progeny test. Similar to hybrids, the yield of a synthetic variety generally also decreases after the Syn 2, until an equilibrium is reached which, in partially self-fertile species, depends on selfing rate and inbreeding (minimum depression), but also on the number of components used in the Syn 0. pollination – – often cross-pollinated crops 5. Share Your Word File
Mass selection is used in both self pollinated and cross pollinated species. Following top cross hybrids may be formed: A double top cross hybrid is the progeny of a single cross and a variety. Disclaimer Copyright, Share Your Knowledge
Shull (single crosses) and D.F. Richey and M.T. In absence of reconstitution of a synthetic at regular intervals, the population becomes an open-pollinated variety. Hopkins in 1908 developed this method, extensively used in maize. Hybrid cultivar breeding exploits the phenomenon of heterosis, and is applicable to both self- and cross-pollinated species. The test-cross progenies are then grown for evaluation. (ii) Based on mean performance of the four non-parental single crosses: (iii) Based on mean performance of four lines over a series of single crosses: (A x E) + (A x F) + (A x G) + (A x H) + (B x E) + (B x F) + (B x G) + (B x H)+………. In 1903 Johansen proposed the famous ‘pure line theory’ which states that a pure line is In simple recurrent selection a number of plants are self-pollinated in a source population in first year. The source material may be random mating populations, synthetic cultivars, single cross, or double cross. 52. E. g Cotton, Jute, Sunflower and Castor, etc. © 2021 - Agriculture. The resulting F1 plants and the elite line are testcrossed to a common tester and F1 plants are also selfed. So to avoid inbreeding depression and its undesirable effects, the breeding methods in the crop is designed in such a way that there will be a minimum inbreeding. The constituent entries may not be maintained for reconstituting the composite. Ans. Later, more sophisticated schemes of population breeding have been designed, providing the framework for the development of the quantitative genetics theory. Selection and selfing are continued till desirable homozygosity/uniformity is attained. (Breedi… Plant breeders employ a variety of techniques to improve the genetic composition of the crop and a successful strategy is dependent on the physical, physiological and hereditary characteristics of the plant. Cross-pollination, type of pollination in which sperm-laden pollen grains are transferred from the cones or flowers of one plant to the egg-bearing cones or flowers of another. Each plant receives a blend of pollen from a large number of individuals each having different genotypes. The three important uses of inbreeding in cross-pollinated crops are as follows: (i) To attain uniformity in plant characters. Bruce in 1910 and F. Keeble and C. Pellew in 1910. However, there are situations, where F1 is superior over the better parent. This is inbred x variety hybrid. Before sharing Your knowledge on this site, please read the following:! By animals most by insects, but the term recurrent selection, procedure od mass selection is based heterozygosity. Span of time allow for a rapid breaking up of linkage blocks parental individuals are.! Prediction of double cross performance: the best individuals with desired characters are identified important uses inbreeding! 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