The remnant half seeds from the superior parental plants are mixed and grown in isolation for random mating during the third year. (iv) Mass selection is a simple and quick method of crop improvement. Most New Zealand native flowering plants are pollinated by animals most by insects, but some by birds or even bats. (iii) In cross pollinated crops, large numbers of plants have to be selected for bulking, because small sample will lead to inbreeding depression. Cross-pollination is found in both angiosperms and gymnosperms and facilitates cross-fertilization and outbreeding. However, probably most breeders use a method that is intermediate between these two systems. Crossing of two F 1 plants (or selfing an F 1) yields an F 2 plant (F 1 × F 1 = F 2). 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. Content Guidelines 2. Mass selection is a simplest , common and oldest method of crop improvement, in which large number of plants of similar phenotype are selected and their seeds are harvested and mixed together to constitute the new variety. This procedure has been called as ‘early testing’ originally proposed by M.T. A modified single cross is the hybrid progeny from a three- way cross which utilizes the progeny from two related inbred as the seed parent and an unrelated inbred as the pollen parent. Ear-to-row selection is a half-sib method in which one location's yield trial is grown in isolation and is pollinated by selected male plants … The commonly used breeding methods of self-pollinated plants were developed over a century ago in Europe. Oldest breeding method for cross pollinated crops. 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’. This method is as effective as recurrent selection for gca when additive gene action predominates, and is as effective as recurrent selection for sea when non-additive effects are of major importance. This becomes Syn 1 generation. Similarly by growing progenies of 8 to 58 plants, range of genetic variability can be established. An increase of the mean performance of the F1 combinations. (iii) To develop suitable inbred lines in production of hybrids and synthetics. The simplest version of population breeding is the mass selection method applied to cross-pollinated species, in which the improved population is directly used as a cultivar. 3) The selection cycle is usually of the two years. The test crosses of F1 plants that exceed the elite line by tester are presumed to have obtained superior gametes from the source population. The components of a synthetic variety could be inbred (usually), clones, mass selected populations or various other materials. No great subsequent changes were made. Selection methods. This method helps to know the superiority of plants, whether due to environment or genetic variation. 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. Save my name, email, and website in this browser for the next time I comment. Basically, the selection procedure of the best progenies was optimized, particularly with the development of agricultural experimentation based on the publications of Fisher . In order to maintain performance in subsequent generations, mass selections have been found to be sufficient in maize. Harvey in 1949 aims at simultaneous improvement of two heterozygous and heterogenous populations (designated as A and B). The details of the steps involved in development of composite variety are as follows: (i) Screening of diverse germplasm by evaluation at multi-locations/years to identify the sources having adaptability, desirable agronomic attributes and resistance to major diseases and tolerance/resistance to serious insects. our some useful Link's 1) Plant … A spectacular example of such divergence is provided by the monkeyflowers Mimulus cardinalis and Mimulus lewissii , which are pollinated … Stadler in 1944, is based on the premise that if superior zygotes occur with a frequency of p2, superior gametes would occur with a frequency of p. The procedure involves crossing an elite line with a random sample of pollen of plants from a source population. Sexual reproduction in plants happens via the flowers, it takes place in two successive processes which are the pollination and the fertilization, it is the formation of offspring by the fusion of gametes while asexual reproduction is the formation of offspring without the fusion of gametes.. Application of Pedigree Method: 1) Selection of desirable plants from the segregating population in self- pollinated crops. 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. 2) Inbreeding may be avoided to certain extent by selecting sufficiently large number of progenies. Method of Plant Breeding in Cross Pollinated Plants – Selection with Progeny Testing. Methods of mixed (cross) pollination . Mass selection is often described as the oldest method of breeding. Answer Now and help others. However, it is generally agreed that heterosis is not fixable in the homozygous state. However, it is more commonly used in cross pollinated species than in self pollinated species. These composites often show a high order heterosis in F1’s when widely diversed populations are crossed. 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. The question regarding the most favourable number of genotypes the Syn 0 should be composed of cannot be clearly answered, because the evidence from research and practice is too divergent. iii) Several phenotypically superior plants are selected from the superior progenies and selected plants are permitted to open pollinate. In this method of breeding, the best individuals with desired characters are selected on the basis of phenotypic performance in a source population. TOS4. What are modifications of mass selection? The component units are maintained so that the synthetic may be reconstituted at regular intervals. Our mission is to provide an online platform to help students to share notes in Biology. Empirical studies have led to contradictory estimates of the correlation between the performance of lines at early and late selfing generations. 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. This method is useful for improving such characters as vigour, resistance to diseases, pests and lodging. This method is practiced in both self and cross pollinated crops and plants are selected on the basis of their phenotype of appearance. Hull in 1945. The three important uses of inbreeding in cross-pollinated crops are as follows: (i) To attain uniformity in plant characters. ii) A single row of 10-50 plants i.e a progeny row, is grown from each selected plant. Recurrent Selection. When the animal visits another flower, some of this pollen comes off onto the stigma pollination has occurred. However, it suffers from the defect that the weak and inferior progenies pollinate plants in the superior progenies. Hybrid cultivar breeding exploits the phenomenon of heterosis, and is applicable to both self- and cross-pollinated species. The component inbred are crossed in all possible combinations. Following top cross hybrids may be formed: A double top cross hybrid is the progeny of a single cross and a variety. This method is practised in both self and cross – pollinated crops and plants are selected on the basis of their phenotype of appearance. If plants evolve to utilize different pollinators, prezygotic isolation will build up due to reduced cross-pollination (Grant, 1981). This clearly demonstrated the difference between effect of selection in cross and self-pollinated crops. Recurrent selection was originally developed as a method of breeding cross pollinated species. The cyclical selection was developed to increase the frequency of favorable genes for quantitative traits. Shull in 1909 suggests a mechanism based on heterozygosity and therefore, is not fixable in the homozygous state. Plant species where normal mode of seed set is through a high degree of cross-pollination have characteristic reproductive features and population structure. Before sharing your knowledge on this site, please read the following pages: 1. Pedigree selection is a widely used method of breeding self-pollinated species. The greater variability caused by crossing several components with high general combining ability makes the synthetic varieties more adaptable compared to conventional varieties. This reduces the efficiency of selection. In this number of plants are selected and they are open pollinated and the individual plants are harvested separately. The characteristics such as the height of the plant, size and colour of the grain etc. The challenge of the plant breeder is to develop better varieties. If all the dominant alleles are concentrated in one parent, and the counterpart recessive alleles in another parent, the F1 will be equal to the parent having all the dominant alleles. Recurrent selection was originally developed as a method of breeding in cross pollinated species. In absence of reconstitution of a synthetic at regular intervals, the population becomes an open-pollinated variety. Therefore, selection is done for easily observable characteristics such as plant height, ear/type, grain colour, grain size, etc. This method includes progeny selection on ear to … +(D x H)/n. F1 will have a value of 4. Methods for breeding cross-pollinated species include mass selection, recurrent selection, family selection and synthetics. Cross-pollination, also called allogamy, occurs when pollen is delivered from the stamen of one flower to the stigma of a flower on another plant of the same species. According to this hypothesis, hybridity/heterozygosity is superior to either homozygote and this state of heterozygosity has a stimulating effect upon the physiological activities of the organism leading to superiority of Aa over AA or aa. (iii) The produce of mass selected variety is lesser uniform than that of pureline variety. Therefore, it is obvious that I0 plants should already be tested for their combining ability and plants or lines should be used as components, the inbreeding depression of which is not as strong as in the I5. Because cross-pollination and self-pollination occur in insect-pollinated plantings, melons can be handled as a self-pollinated or cross-pollinated crop. This is a modification of pedigree method. (v) This method is applicable to both self and cross pollinated species. Jenkins in 1935. A modified three-way hybrid is the progeny of a single cross as female parent and another single cross between two related inbred. Specific combining ability is also estimated. Method of Plant Breeding in Cross Pollinated Plants – Hybridization. Those that use insects as pollinators tend to have brightly colored flowers and an attractive scent. The performance of synthetics can be improved by one further breeding cycle. Share Your PPT File. This completes original selection cycle. This was proposed by G.H. No progeny test is conducted. At maturity superior plants based on phenotypic performance are selected. It is also assumed that the dominance is complete. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. In this chapter we are concerned with the methods by which new varieties of self-pollinated crop plants originate. Jones (double crosses). • Selection is done for easily observable characters like height, grain color, seed size, disease resistance, insect resistance etc. The progeny rows are evaluated for desirable character and superior are identified. 5. As an animal reaches into a flower for its reward, it brushes against an anther, and some of the pollen sticks to its body. 1) There is no control on pollination and plants are allowed to open pollinate, thus selection is based on maternal parent only. The superior progenies are identified. This method involves crossing two different species of plants to obtain desirable traits from both species. Advanced generations of such heterotic crosses often show stabilized yields. 3) It is also used in the selection of new superior recombinant type’s i.e Transgressive breeding. i) 50- 100 number of plants are selected on the basis of their phenotype and are allowed to open pollinate. A single cross is a hybrid progeny from a cross between two unrelated inbred. Mass selection is based on the maternal parent only and there is no control on the pollen (♂) parent. Which part of the male reproductive system store the sperm? The pioneering work on hybrid maize was done by G.H. Though gamete selection is not used as extensively as pedigree and backcross methods, it does have some intrinsic features, and consequently, is included in some breeding programmes. Of the above four methods, method (ii) is found to give more accurate results. 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. Concept of composite varieties (in maize) originated in India. 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. Comstock, H.F. Robinson and P.H. The term heterosis, coined by G.H. Jenkins in 1935. Two types of artificial selection also are often applied: (1) destruction of plants that carry undesirable major genes and (2) mass techniques such as harvesting when only part of the seeds are mature to select for early maturing plants or the use of screens to select for increased seed size. The testing for combing ability is the decisive criterion for a synthetic variety by which it can be distinguished from a conventional variety of a cross-pollinating species, which originates in a continuous selection of individuals and subsequent progeny tests. Usually, they involve open pollinated varieties, synthetics, double crosses, etc., selected for yield performance, maturity, resistance to diseases and pests. The selected plants are pollinated by both superior and inferior pollen parents. (ii) In cross pollinated species, there is no control on the pollination. Here a no. Definition of Hybridization: The mating or crossing of two plants of dissimilar genotype is known as hybridization. Emasculation is a method of “Artificial Hybridization” generally used to promote cross pollination in plants and avoid self pollination. Self-pollination: • Transfer of pollen from an anther to a stigma within the same flower or to a stigma of another flower on the same plant. 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. Existence of self-sterility, self-incompatibility, imperfect flowers, and mechanical obstructions make the plant dependent upon foreign pollen for normal seed set. However, there are situations, where F1 is superior over the better parent. Mass selection method is used to breed a plant with cross-pollination. Q. These are usually developed from open-pollinated varieties or other heterozygous populations or germplasm which have originally not been subjected to inbreeding or have not been elaborately tested for their combining ability. Check Answer Share Your PDF File This method is mainly based upon the easily observable characters are taken into consideration. Mass selection is a method of crop improvement for both the self-pollinated and the cross pollinated plants. In cross-pollinated species, a cyclical selection approach, called recurrent selection, is often used for intermating. (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. Odisha JEE 2006: Simplest selection of cross pollinated crop is (A) Selection (B) Introduction (C) Mass selection (D) None of the above. iv) Small progeny rows are again grown from the selected plants, and the process of selection is repeated. 4. Plant breeding - Plant breeding - Breeding self-pollinated species: The breeding methods that have proved successful with self-pollinated species are: (1) mass selection; (2) pure-line selection; (3) hybridization, with the segregating generations handled by the pedigree method, the bulk method, or by the backcross method; and (4) development of hybrid varieties. Several similar plants are selected from the progenies and allowed to open pollinate thus selection process is repeated. 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. In plant breeding nearly homozygous lines are produced by continued self-fertilization accompanied by selection for five to six generations. For example, in simple mass selection in a highly cross-pollinating species, the selected S 0 plants … This method has been named as mass-pedigree method by S.S. Rajan in India. Mass selection is used in both self pollinated and cross pollinated species. This can also be an advantage in that varieties can be selected for local performance. However, it is more commonly used in cross pollinated species than in self pollinated species. Welcome to BiologyDiscussion! Thus, strictly speaking, selfing is not an integral component of simple recurrent selection, rather it is done only to prevent crossing from the inferior pollen grains before the plants reach to selection stage. 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. Genotypes that are identified for above average performance in these tests are continued in the selfing and selection nursery. The high additive genetic variance existing in a new population makes mass selection a relatively efficient method of selection. 3) It is simple and easy. The improved population may be … In the above cross, if each dominant allele, contributes 1 unit and the recessive allele, 0 unit, then the P1 will have a value of 4 and P2, a value of 0. Various methods of recurrent selection are used for producing progenies for evaluation, as will be discussed here. Second year replicated progeny row trial is conducted using one set of half seeds from each plant. The constituent entries may not be maintained for reconstituting the composite. This very method is called line breeding when selection is based on progeny tests and a group of progeny lines is composited. The many generations grown within a limited span of time allow for a rapid breaking up of linkage blocks. A double modified single cross is the hybrid progeny from two single crosses, each developed by crossing two related inbred. General combining ability and additive gene effects play predominant role in exploitation of these populations. The pollen of animal-pollinated plants has a rough surface to help it stick to a pollinator He obtained commercial seed lot of princess variety of bean. Thus , time requirement for selection is twice as that of mass selection. Definition: Recurrent selection is defined as reselection generation after […] 1) Population improvement 1) Without progeny testing 1) Mass selection 2) With progeny testing 1) Progeny selection 2) Recurrent selection 2) Hybrid varieties 3) Synthetic varieties Methods of breeding in cross pollinated crops. The assumption is that the combining ability of a line is determined early in its development and will change relatively little in subsequent generations of inbreeding and selection. Is called line breeding when selection is the most common procedure used to correct some specific of! 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