The number of selected progenies should be reasonable so that preliminary yield trial with 25-100 progenies can be done. Pollinators that visit these flowers will facilitate pollination and can improve the yield per plant. 3. Breeding methods in self-pollinated crops ⢠1. 3. 4. Share Your PDF File
⢠In terms of breeding system, self-pollination is an extreme form of inbreeding, ⢠rapidly restores homozygosity of the genotypes in generations following a chance cross- pollination (hybridization) in nature or an artificial hybridization. Back-cross method is useful for production of isogenic lines, i.e., the lines of a crop which are identical in their genotype except for one gene. Survivability of any gene or a particular genotype can be studied in this method. ... Pure-line selection method is used to breed a plant with self-pollination. Pedigree breeding is a method of genetic improvement of self-pollinated species in which superior genotypes are selected from segregating generations and proper records of the ancestry of selected plants are maintained in each generation. So this method drastically reduces the time period required to develop a new variety. After seed set and maturation, the F1 seeds are harvested separately from each plant individually. As an animal reaches into a flower for its reward, it brushes against an anther, and some of the pollen sticks to its body. This method has been used to a limited extent due to lack of popularity. There is no rust resistance test, the plants are selected only on resemblances with recurrent parent A, and again back-crossed with recurrent parent. This method is simple, convenient and less expensive. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. Genetic consequences of repeated back-crossing: Repeated back-crossing results in decreasing the frequency of heterozygosity by 50% in each subsequent generation and rapid increase in homozygote, upto 98% by sixth back cross progeny, will be achieved. The method is generally used for handling segregation generation may be grouped into three categories. 4. A tomato plant does not need other tomato plants nearby to pollinate its flowers and produce fruit. Through the maintenance of pedigree record the breeder may be able to obtain the information about inheritance of characters. TOS4. This is because a tomato flower is perfect, meaning that it contains both male and female parts. *Autogamy: Pollen from the anther is deposited on stigma of same flower. The variety is tested in replicated yield trial along with the variety A as check. In pedigree method, individual plants are selected from F2 and the subsequent generation and their progenies are tested. In case of Bajra, Tift 23A, a male sterile line which was susceptible to downy mildew has made resistant through back-cross method. These isogenic lines are useful for studying the effect of individual genes. During the entire operation, a record of the entire parent’s offspring relationship is kept, is known as pedigree record. (3) The long period of bulking may be helpful for natural selection to change the composition of population. The hybridization is done among two selected parents, after emasculation one become female parent and another male parent. Before sharing your knowledge on this site, please read the following pages: 1. The lines are evaluated for some important characteristics in addition to yield, disease resistance, etc. The new variety is not superior in performance than the existing variety except the introduction of single character. The above mentioned criteria are evaluated for these lines. Which part of the male reproductive system store the sperm? Pure line selection ⢠3. The mechanism is seen most often in some legumes such as peanuts.In another legume, soybeans, the flowers open and remain receptive to insect cross pollination during the day.If this is not accomplished, the flowers self-pollinate as they are closing. Single seed descent. Answer Now and help others. Pedigree method is useful in selection of new superior recombinant types from a hybridization programme. Open-Pollinated . During this process the record of parents as well as off-springs is kept, for which it is known as pedigree method. Once a recurrent parent taken in a back-cross method may get replaced by another superior variety of high yielding ability. Share Your PPT File. Hybridization is done between the selected parents with the desirable attributes. In Pedigree method, a detailed record of the relationship between the selected plants and their progenies is maintained as a result of this each progeny in every generation can be traced back to the F2 plant from which it originated, such record is known as pedigree record or pedigree. 1) Selection of desirable plants from the segregating population in self- pollinated crops. 2. However, it is more commonly used in cross pollinated species than in self pollinated species. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. Individual plants with desirable characteristics are selected; disease and lodging susceptible progenies to be eliminated, and also the progenies with undesirable characters are rejected even from the selected plants. Firstly, the selected plants are self-pollinated in recurrent selection, whereas they are open pollinated in progeny selection. But there are greater chances of error, since more number are to be recorded. Disclaimer Copyright, Share Your Knowledge
Comparison between the transfer of dominant and recessive gene during back- cross method: Quantitative characters are governed by polygenes such as grain size, plant height, maturity time, etc. Thus each progeny can be traced back to the F3 progeny or F2 plants, from which it originated. Breeding Self-Pollinated Crops Selection Methods Pure-line Selection Pure-line selection, like mass selection, begins with a heterogeneous population of homozygous plants. 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. If the progenies show variation then the individual plants are selected. Therefore it is also known as individual plant selection⦠In some cases, the plant will produce both male and female flowers, like squash or pumpkin plants. Progeny in the 3 rd row in the F6 plot selected from the progeny in the 14 th row of the F5 plot. Poor progenies may be simply marked discard. So the selection for that recessive gene requires the F2 generation, i.e., selfing is needed after every two back-crosses, and testing for the presence of that character has to be done in that generation. 3) It is also used in the selection of new superior recombinant typeâs i.e Transgressive breeding. This method gives maximum importance on the breeder to use his/her skill and judgement about the selection of plants and progenies. Seed multiplication is done and distributed to the farmers. The parents are selected in this programme as the previous one, only difference is that the rust resistance is a recessive gene controlled character: The recurrent parent is used as female parent and hybridized with the rust resistant donor plant. Specific Objectives Theory By the end of the course, the students will be able to i. learn breeding procedures in self and cross pollinated crops ii. Progeny in the 4 th row in the F4 plot, selected from the progeny in the 7 th row of the F3 plot. People new to gardening or those without the time or inclination to fuss with plants often choose self-pollinating vegetables due to their ease of propagation compared to those that require insect, wind or artificial pollination by a human. These plants are selected and back-crossed with recurrent parent. On the basis of choice of parents, the type of cross will be of two types â it will be simple cross or complex cross. Features of Recurrent Selection: The line which is superior to the best commercial variety may be released as new variety. Most New Zealand native flowering plants are pollinated by animals most by insects, but some by birds or even bats. Pure line selection is a method in which new variety is developed by selection of single best plant progeny among traditional varieties or land races. The variety or species from which the cytoplasm is to be transferred is used as female parent. Back cross method. Procedure for transferring a recessive gene will be different from that of dominant gene, as the recessive gene will be expressed only in homozygous condition. Except the characters of disease resistance other characters can also be transferred by the back-cross method. This method is applicable to any self-pollinating crop like cereals, legumes and oil seeds. Inheritance of characters is not individually maintained as in pedigree method. 2) This method is commonly used to correct some specific weaknesses of an established variety (Combination breeding). Individual plant progenies of selfed plants are grown separately. Welcome to BiologyDiscussion! In self-pollinating plants, anther and stigma mature at the same time. Progeny obtained from plant number 7 selected in F2, Progeny from plant No.4 selected from F3 progeny , derived from the plant No.7 selected in F2. Preliminary yield trial with three or more replications is conducted to identify few superior lines. 7. Secondly, the progeny of selected plants are intermated in all possible combinations in this method, whereas they are open pollinated in progeny selection. The system of alternate back-crossing and selfing goes on till the desired results are obtained. What is Pureline â Definition? There are some alternatives for selection in a segregating population of self-pollinated plants, including the Bulk method and Bulk within F 2 progenies. But for determining the pedigree of a progeny the breeder has to consult the records of the preveious year. Generally, each cross is given a number. Plant species where normal mode of seed set is through a high degree of cross-pollination have characteristic reproductive features and population structure. The pollen of animal-pollinated plants has a rough surface to help it stick to a pollinator 2. In addition each progeny in F4 and the subsequent generation is assigned the row number of the progeny in the preveious generation from which it was derived. Progeny from plant No 8, selected from the F5 progeny, derived from the plant N0.2 selected from the F4 progeny of the plant No.4 selected from F3 progeny of the Plant No.7 selected in F2. 5. both stamen and pistil in the same bloom) and readily transfer pollen from the stamen to the pistil with even the gentlest breeze. This brings resistance but with undesirable characters like more fibre, low sugar, thin stem, etc. For interspecific transfer of genes, back-cross method is widely used for crop improvement. 1. In U.S.A the barley varieties like Arivat, Beecher, Glacier and Gem have been originated from a bulk population derived from cross Atlas x Vaughn, the bulk was maintained in this case for 7 generations. 4. 3) The pedigree record must be accurate. Individual plant progenies of F5 generation are planted according to recommended commercial seed rate. As the recurrent parent is an established variety, so it is not necessary to test the yield performance which ultimately saves five years-time, as well as expenses. 2. Later a technolgy of two-lines using environmental genetic male sterility (EGMS) counting on photoperiod (PGMS) and temperature (TGMS) sensitivity to induce sterility was in practice. At this stage, selection is done among the progenies, because there would be no genetic variation within progenies. 5. ï¶ Mass selection is a method of breeding in which individual plants are selected on the basis of phenotype from a mixed population, their seeds are bulked and used to grow the next generation. Plants are selected against rust resistance and also the characters of variety A. When the animal visits another flower, some of this pollen comes off onto the stigma pollination has occurred. Such kind of modification would produce new variety which won’t be like the recurrent parent. The undesirable progenies are rejected. As this method requires more time to get the effect of natural selection for developing a new variety and the lack of using any skill of breeder for selection of superior types, this method is less used by the breeder for crop improvement. The object of hybridization is to combine desirable genes found in two or more different varieties and to produce pure-breeding progeny superior in ⦠1. This method is most useful as transgressive segregation for yield and other quantitative characters may be recovered in addition to improvement of specific characters. using back-cross method. From 15-30 selected F1 plants, the F2 seeds are collected to get a reasonable size of F2 population and variation. Each progeny should have about 30 or more plants. Individual plant progenies are grown. The multiple characters can be transferred in a stepwise method. This number is given to those homozygous lines that are included in preliminary yield trials. 4. ï¶ Pureline refers to the homogenous progeny of a self pollinated homozygous plant. Ans. Now it is also used in self pollinated species. This method takes less time than bulk method to release a new variety. The flowers that are self-pollinated and they can produce the viable seeds are self-compatible, and the flowers which are self-pollinated but the pollen grains do not function properly on the carpels of the same plant are termed self-incompatible. Our mission is to provide an online platform to help students to share notes in Biology. Rigid selection is done for resistance to stem rust and the characteristic of variety A. This method does not change the genotype of the popular established variety, only it helps a single desirable character to be transferred in the existing variety. 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