The lack of chromosomal homology does not permit pairing between the chromosomes of two species during meiosis. 3. History Thomas Fairchild (1717): The first authentic record of a distant hybridization for crop improvement is the production of a hybrid between Carnation (Dianthus caryophyllus) and Sweet willian (Dianthus barbatus). These genera include Eccoilopus, Erianthus, Miscanthidium, Miscanthus, Narenga, Rapidum, Sclerostachya and Sorghum (sweet sorghums). Improvement in yield has also been achieved through the use of wild species in some crops. Tissue culture will continue to play a key role in the genetic-engineering process for the foreseeable future, especially in efficient gene transfer and transgenic plant recovery. deletions, duplications, translocations and inversions which cause absence of pollen formation or formation of nonfunctional or abortive pollens. It is also known as intraspecific hybridization. But the new species thus developed had roots like cabbage and leaves like radish, which was a useless combination. CMS has been discovered in crosses between wild and cultivated species in wheat, cotton, barley, tobacco, potato, sunflower and ryegrass. Distant hybridization has played significant role in: (2) Developing commercial hybrids in some crops, and. Hybridization Methods of Plant Breeding in Self-Pollinated Groups 5. When two species of a cross differ in chromosome number, it is necessary to match their ploidy level by doubling the chromosome of the species with low ploidy. 10). Intergeneric hybridization refers to crossing between two different genera of the same family. The F1 plants are mated together as (A × B) × (C × D) and (E × F) x (G × H). III. Resistance to boll weevil and jassids in cotton and leaf chewing insects in peanut has been incorporated from wild species. Hybrid breakdown is a major problem in interspecific crosses. The problem of hybrid sterility is more acute in intergeneric crosses than in interspecific crosses. 1. New variety is tested in replicated field trials along with the variety A as check. It may enhance the chances of obtaining a zygote. Find paragraphs, long and short essays on ‘Distant Hybridization’ especially written for school and college students. Chemical method is commonly used technique using polyethylene glycol . When the F1 plants were treated with colchicine, a fully fertile tetraploid (2n = 48) was obtained which resembled cultivated species (N. tabacum). Correspondence (Tel +86 10 82105801; fax +86 10 82105802; email y.xu@cgiar.org)Search for more papers by this author Crossing between two different species of the same genus or two different genera of the same family is called distant hybridization and such crosses are referred to as distant crosses or wide crosses. When F1 plants of an interspecific cross are vigorous and fertile but their F2 progeny is week and sterile, it is known as hybrid breakdown. Many of the intergeneric hybrids are easily made with the help of male sterility. Hybridization was first of all practically utilized in crop improvement by German botanist Joseph Koerauter in 1760. In such situations, the F1 plants are partially fertile and partially sterile. For example, wild species have been used to transfer dark green colour and excellent leaf texture in lettuce and bright red thin flesh in red peppers. Distant crosses are more successful in more closely related species or genera than in less closely related species or genera. The panicle is inserted in the container prior to blooming for a particular duration of time. The doubling of chromosome number of F1 through colchicine treatment resulted in the production of fertile amphidiploid. In some wide crosses, fertilization occurs and zygote formation also takes place. Certain chemicals are capable of causing male sterility, when sprayed before flowering e.g., 2, 4-D, naphthalene acetic acid (NAA), maleic-hydrazide (MA), tribenzoic acid etc. Removal of stamens with the help of forceps is very difficult in minute flowers. Less progress has been made on insect resistance. have to be adopted to make distant hybrids successful in some cases. There are three main reasons of cross incompatibility, viz. v. Presence of ring and chain configurations. Stigma should be receptive and anthers should not have dehisced. In such situation either reciprocal cross should be made or the style should be cut to normal size before pollination. Seeds are space planted and single plant selection is done (F7 generation). Selection for plants in the desired combination of characters is started in the F2 generation and continued in succeeding generations until genetic purity is reached. The first is the Triticale which has evolved from intergeneric cross between Triticum aestivum and Secale cereale. Types of Hybridization Based on the taxonomic relationship of the two parents, hybridization may be classified into two broad groups. Distant hybridization and role of biotechnology in crop improvement: 1. It presents biotechnology as providing powerful and useful tools, in a continuum of technical evolution that contributes or could contribute to the improvement of crop production, food quality and safety, while preserving the environment. (i) The new variety is superior over the already available variety only in the transferred character. In crop improvement, allopolyploids are also … Genetically modified crop plants. In such case a third species say B which can cross with both A and C is chosen as a bridge species. These aspects are briefly discussed below: Distant hybridization has been instrumental in transferring disease resistance from wild species into cultivated ones. Apomictic genes have been transferred from maize — Tripsacum cross to maize and from wild species of Beta to cultivated species. T. turgidum is used as a bridge species for transfer of genes from Aegilops ventricosa to T. aestivum. The F1 hybrid was sterile. Content Guidelines 2. lack of pollen germination, insufficient growth of pollen tube to reach ovule and inability of male gamete to unite with egg cell. Due to huge population growth in the world, the yield of food materials had to be enhanced. Disclaimer Copyright, Share Your Knowledge 9). The success of seed set is generally very low in wide crosses. The paper concentrates on recent developments of biotechnology use in the seed industry. Our mission is to provide an online platform to help students to share notes in Biology. Increase in yield has been reported in several crops such as Vigna, Zea, Ribes, vanilla, Arachis, potato and tobacco through interspecific hybridization. The advantage of this cross is the use of vigorous hybrid of first generation as female in order to maximize the yield of hybrid seeds as well as to obtain seeds of normal grain size. DNA finger printing and seed registration. In most of the wide crosses, hybrid sterility is the major problem. It is the sixth step. In tobacco, Nicotiana repanda can cross with N. sylvestris but not with N. tabacum. The method is used for the transfer of a dominant gene. The induction of homoeologous pairing in F1 hybrid plants followed by the incorporation of a single-chromosome fragment from an alien or a wild species into an existing … A selection method, which is used in segregating population of self-pollinated species and keeps proper record of plants and progeny selected in each generation is known as pedigree breeding. (ii) The breeder is enable to exercise his skill and judgement in selection and therefore the method is less satisfying to him. There is occasional seed set in this cross. Chromosomes in such hybrids have normal pairing at meiosis and as a result the F1 plants are fully fertile. Transfer of some genes from one species into the genome of the other species is known as introgressive hybridization. Interspecific hybridization is more successful in vegetatively propagated species like sugarcane and potato than in seed propagated species. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. It is a cross of a single cross (used as female) with another inbred (used as male), i.e., it involves three inbreeds [(A x B) x C], The single cross and the inbreeds are planted in the same way as the inbreeds in the single cross. 12, 13. Natural cross pollination takes place and the harvested produce becomes synthetic cross. On the other hand, Tripsacum pollen are unable to produce long pollen tube to reach the ovule of maize. Use of wild species in the hybridization programmes sometimes leads to alteration in the mode of reproduction. The branch of science that deals with crop improvement is called biotechnology. The production of a hybrid by crossing two individuals of unlike genetical constitution is known as hybridization. To combine the desired characters into a single individual, and. This method Is based on the fact that gynoecia can withstand the hot temperature at which the anthers are killed. After any one of the above-mentioned crosses, seeds are tested, multiplied and distributed. Triticale is the best example of the practical achievements of intergeneric hybridization. The important tetraploid hybrids include Varalaxmi, JKHY 11, CBS 156, Savitri, DCH 32, HB 224, NHB 12, TCHB 213 DHB 105 and Sruthi. Crosses between these two species are fully fertile. For example, protein content in rice, oats and rye; fibre length in cotton; oil quality in oil palm; carotenoid content in tomato; starch content in potato; leaf quality in tobacco; and oil per cent in oats have been improved through the use of their wild species in the hybridization programme (Table 28.3). Controlled by recessive genes is very difficult in minute flowers as Triticale Phleum, Dactylis, Alopercunis, Triticum cm! Isolated plots time to develop new crop plants ( back cross first generation ) are hexaploid ( 2n = )... With some undesirable characters such as IAA, NAA, 24-D and gibberellic has... Growth in the production of viable gametes a cross-involving more than one line. Employed in improvement of some desirable traits particularly those for disease resistance etc!, Tripsacum pollen are unable to develop new crop plants has been found to be restored by doubling chromosomes! Genetic contents of organisms but it is essential for inducing homozygosity for the. 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