Different methods of somatic hybridization have been proposed namely the physical and chemical method of fusion techniques. (i) The bulk method is simple, convenient, inexpensive and less labour consuming (no pedigree record is to be kept). Flowers should be selected at proper stage. There are two main causes of hybrid breakdown, viz. Share Your Word File The F1 hybrid was sterile. lack of pollen germination, insufficient growth of pollen tube to reach ovule and inability of male gamete to unite with egg cell. 4. There are two cultivated species of oat, viz. The F1 hybrids were sterile in all the three crosses. (iii) Sometimes undesirable genes are closely linked with desirable one and get transferred to the new variety. The total number of possible different single crosses produced by a given number of inbreeds can be calculated by the formula n(n-1)/2 where n is the number of inbreeds. (3) Creation of new crop plants (Table 28.4). role in the development of plant genetic engineering. Role of biotechnology in castor improvement 3.1. This method was first proposed by Harlan and Pope (1922). The method is used for the transfer of a dominant gene. In such hybrids, recombination between chromosome segments during meiosis may lead to production of gametes with deletions or duplications. Some of the following biotechnology tools which play vital role in agriculture biotechnology are- Therefore, crop improvement through biotechnological approaches, appears to be time effective and alternative approach. Essay # 2. Molecular markers. 8). Triticale is the example of new crop which has evolved from an intergeneric cross between Triticum aestivum and Secale sereale and combines good characters of both the species. Both these new species are grown for commercial cultivation. Distant crosses are associated with problems of cross incompatibility, hybrid inviability, hybrid sterility and hybrid breakdown. white oat (Avena sativa) and red oat (Avena byzantiana). Lolium, and Festuca. Single crosses give the maximum degree of hybrid vigour but due to weak inbreeds, little amount of seed is produced. In cotton, commercial interspecific hybrids have been developed both at tetraploid and diploid levels but between cultivated species only. In another words, failure of male and female gametes to unite to form zygote in interspecific and intergeneric hybrids is known as cross incompatibility. Interspecific hybridization gives rise to three types of crosses, viz. (vii) Harvesting and storing the F, seeds. Hybrid breakdown hinders the progress of interspecific gene transfer. The hybrid sterility refers to the inability of a hybrid to produce viable offspring. In this method the corolla of the selected flowers is opened and the anthers carefully removed with the help of fine-tip forceps. Wide crossing or distant hybridization has been used in the genetic improvement of some crop plants. It is used when the desirable character is not found within the species of a crop. The paper concentrates on recent developments of biotechnology use in the seed industry. Following are the important precautions while performing this method: i. Rimpu (1890): Produce the first intergeneric hybrid triticale which have greater potential … The branch of science that deals with crop improvement is called biotechnology. diploid (2n = 24), tetraploid (2n = 48) and hexaploid (2n = 72). Hybridization is an important method of combining characters of different plants. Stebbins termed it as criptic structural hybridity. ... 2017, Crop improvement: new approache s and . Today, it is the most common method of crop improvement, and the vast majority of crop varieties have resulted from hybridization. Commercial hybrids are produced by this method. modern ... poppy, cotton etc. It is the sixth step. Now-a-days this method is employed in improvement of both self and cross-pollinated crops where varieties are deficient in one or two aspects. In distant hybridization transfer of characters is not as simple as in intervarietal crosses. anthers are sterile and do not produce any viable pollens! Interspecific crosses in the genus Brassica were made by several workers. Avena sativa (2n = 42) x A. byzantiana (2n = 42) → F1 plants are fully fertile. But intergeneric crosses are always sterile. It can be defined as a cross among inbreeds, clones or sibbed lines without control of pollination. Seeds are stored properly with original tags. […] The segregation pattern ofF 1 hybrids produced by distant hybridization in segregating generations are different from the intervarietal hybrids. 2. The following techniques are useful in obtaining zygotes from distant crosses: Genetic differences exist among parents in a species for cross compatibility. Hybridization does not change genetic contents of organisms but it produces new combination of genes. These crosses generally have wider adaptation. Improved hybrid cultivars have been developed through the use of wild species mainly in sugarcane, potato and some forage crops. The sterility caused by structural differences between the chromosomes of two species can be overcome by doubling the chromosome number of the hybrid through colchicine treatment. The F1 plants are mated together as (A × B) × (C × D) and (E × F) x (G × H). Some examples of intergeneric hybridization are given below: The first intergeneric cross was made in the family Gramineae between bread wheat (Triticum aestivum, 2n = 42) and rye (Secale cereale 2n = 14) by Rimpau around 1890 in Sweden. Chromosomes in such hybrids have normal pairing at meiosis and as a result the F1 plants are fully fertile. Process is continued as in F3 generation. Share Your PPT File. This technique is successful in maize – Tripsacum crosses, where maize style remains receptive even after cutting. Emasculation is not required in unisexual plants but it is essential in bisexual or self-pollinated plants. (ii) Hybridization has to be done for each backcross. (iii) Unfavourable interaction among embryo, endosperm and maternal tissues. This was done effectively by use of hybridization and biotechnology. The F1 cross between such species would be heterozygous and vigorous. Types 4. Essay # 7. Three crosses were made among three species namely cabbage (Brassica oleracea), rapeseed (B. campestris) and black mustard (B. nigra). High yielding transgressive segregants were obtained after 4 backcrosses. Different methods of somatic hybridization have been proposed namely the physical and chemical method of fusion techniques. In sugarcane, cold tolerance has been transferred from wild species in USA. 2000-10000 F2 plants are space planted. In such cases, growth regulators should be used to accelerate the pollen tube growth or to prolong the viability of pistil. More compatible parents should be selected for use in wide crosses. deletions, duplications, translocations and inversions which cause absence of pollen formation or formation of nonfunctional or abortive pollens. This is the most common method used for transfer for oligogenic character like disease resistance. The emasculated flowers are tagged just after bagging. There is rarely seed set in this cross. Short statured oil palms resulted from interspecific hybrids. 3. The first natural hybridization was recorded by Cotton Mather (1716) in corn. Transfer of some genes from one species into the genome of the other species is known as introgressive hybridization. (iv) This method is suitable for studies on the survival of genes and genotypes in populations. It is also known as intraspecific hybridization. ROLE OF WIDE CROSSES IN CROP IMPROVEMENT Wide crosses are generally used to improve crop varieties for disease resistance, pest resistance, stress resistance, quality, adaptation, yield etc. Grafting of interspecific hybrid on to the cultivated species helps in making the cross successful. Selected material becomes so large that handling of the same becomes very difficult. The first two New World species belong to tetraploid group (2n = 52) and the last two Old World species to the diploid group (2n – 26). In both these species chromosomes of A and B genomes are common and as a result the F1 hybrids are partially fertile. In grape, hardier vines have been developed through the use of wild species Vitis amurensis in the breeding programme. In most of the wide crosses, hybrid sterility is the major problem. Now Triticale is commercially grown in countries like Canada and Argentina. Another example is garden strawberry which has evolved from a natural interspecific cross between American octaploids Fragaria cliloensis and F. virgineana in a botanical garden. Meiosis in F1 leads to formation of 13 bivalents and 13 univalents. Fully fertile interspecific crosses have been observed between some species in cotton, wheat, oats and soybean as given below: There are four cultivated species of cotton viz. When the F1 plants were treated with colchicine, a fully fertile tetraploid (2n = 48) was obtained which resembled cultivated species (N. tabacum). The natural or artificial process that results in the formation of hybrid is known as hybridization. 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. Pollen grains are collected in petridishs (e.g., Wheat, cotton etc.) ... Department of Horticulture, College of Agriculture and Biotechnology, Zhejiang University and Key Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Ministry of Agriculture, B502 of Agri.‐Biotech. Selected superior plants in III year are space planted to study the individual plant. It is an effective means of transferring desirable genes into cultivated plants from related species and genera. New variety is tested in replicated field trials along with the variety A as check. In tobacco, yields were increased by the use of wild species Nicotianci debneyi. The plants which do not have a dominant allele at each locus or which are not homozygous for all recessive alleles would be weak and sterile. F1 hybrids between two genera are always sterile. For example, tolerance to cold in rye, wheat, onion, potato, tomato, grapes, strawberry and peppermints etc. Role of environment is almost negligible. Hence when reciprocal cross is made, the maize styles (ear silks) have to be reduced in length by cutting so that the Tripsacum pollen tube can reach the ovule. These types may not be necessarily the best yielding types. This leads to non-pairing or reduced pairing of chromosomes resulting in following meiotic abnormalities: i. Scattering of chromosomes throughout spindles during metaphase I. ii. 5. 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). Crosses between these two species are fully fertile. Intergeneric crosses of barley (Hordeum) were attempted with some species of Avena, Phleum, Dactylis, Alopercunis, Triticum. Harland (1940) made a cross between Asian cultivated diploid (Gossypium arboreum, 2n = 26) and American wild diploid (G. thurberi, 2n = 26). Trials of superior lines are confirmed. Techniques like alien addition and alien substitution may also be effective. For example, resistance to rust and black arm in cotton; mosaic virus, wild fire, black-fire, blue mould, black root rot, and Fusarium wilt diseases in tobacco; sereh disease in sugarcane; late blight, leaf roll and virus x in potato; rust and eye spot in wheat; and yellow mosaic virus in okra have been transferred from wild species of these crops into cultivated species (Table 28.2). The selected BC1 plants again backcrossed to A till a desirable type having good qualities of A and disease resistance of B is obtained (Fig. (c) Fully sterile in different crop species. It requires lot of time and money. This method is also known as the mass or population method. Interspecific hybridization leads to introgression which refers to transfer of some genes from one species into the genome of another species. After any one of the above-mentioned crosses, seeds are tested, multiplied and distributed. Resistance to jassids and boll weevil in cotton, leaf chewing insects in peanut, and aphids in strawberry has been transferred from their wild species to cultivars (Table 28.2). Essay # 6. But the new species thus developed had roots like cabbage and leaves like radish, which was a useless combination. Hybridization was first of all practically utilized in crop improvement by German botanist Joseph Koerauter in 1760. In F2, the favourable combination of dominant and recessive genes is broken due to segregation and recombination. Hybridization was first of all practically utilized in crop improvement by German botanist Joseph Koerauter in 1760. B is then donor or non-recurring parent and A is recipient or recurring parent. Pedigree Method and Back-Cross Method | Breeding, Hybridization: Frequently Asked Questions | Methods | Plant Breeding, Essay on Plant Tissue Culture: History, Methods and Application. Seeds are space planted and single plant selection is done (F7 generation). The bags are tied to the base of the inflorescence or to the stalk of the flower with the help of thread, wire or pins. diploid (2n = 26) and tetraploid (2n = 52). A 35 cm long rubber tube or belt is stretched over the side of the container, and when in use this tube is tied around the peduncle of the head. DDH 2 in Karnataka and Pha 46 in Maharashtra. Main features of interspecific hybridization are given below: 1. Cytoplasmic male sterility has been transferred from wild species to cultivated ones in wheat, barley, cotton, tobacco, ryegrass and several other crops. The crosses between G. max and G. Soja are fully fertile. Plants are chosen for hybridization and F1 seeds are produced. The main barriers to the use of distant hybridization include: These problems along with their remedial measures are discussed below: Inability of the functional pollens of one species or genera to effect fertilization of the female gametes of another species or genera is referred to as cross incompatibility. Wide hybridization A critical requirement for crop improvement is the introduction of new genetic material into the The time varies from species to species. (ii) During early segregating generations, very little work and attention is needed, which gives the breeder more time to concentrate on other breeding projects. Hybridization Methods of Plant Breeding in Cross-Pollinated Crops. Procedure 4. Wide hybridization involves hybridization between cultivated species and their wild relatives. But N. sylvestris can cross with N. tabacum. The F1 was sterile which was made fertile through colchicine treatment. Because interspecific hybridization involves two species of the same genus, it is also termed as intrageneric hybridization. In such situations, the F1 plants are partially fertile and partially sterile. Our mission is to provide an online platform to help students to share notes in Biology. In such situation either reciprocal cross should be made or the style should be cut to normal size before pollination. Genetically modified crop plants. Preliminary yield test are conducted (F9). Yields of sugarcane and octaploid strawberries have been increased by the use of their wild species. There are several methods of improvement of self-fertilized crops by hybridization. Chemical method is commonly used technique using polyethylene glycol . In some wide crosses, fertilization occurs and zygote formation also takes place. F1 plant is backcrossed with the recurrent parent; variety A and BC: plants (back cross first generation) plants are raised. Treatment of F1 with colchicine resulted in the production of fertile amphidiploid (2n = 48) which was similar to cultivated species N. rustica. The methods of crop variety improvement are hybridisation, genetic engineering etc. After inserting the panicle inside the container a cork is fitted in the hole to close it. in 1980. G. arboreum (2n = 26) x G. herbaceum (2n = 26) → F1 plants are fully fertile. Agriculture biotechnology is defined as that is used for livestock and crop improvement. Increase in yield has been reported in several crops such as Vigna, Zea, Ribes, vanilla, Arachis, potato and tobacco through interspecific hybridization. 4. Further breeding in these hybrids is carried out according to either pedigree or bulk method. Biotechnology encompasses a number of tools and elements of conventional breeding techniques, bioinformatics, microbiology, molecular genetics, biochemistry, plant physiology, and molecular To combine the desired characters into a single individual, and. In general bulk period is allowed up to F5 generation). Plant tissue culture also one of the applications of biotechnology used to improve crops and used to increase the speed or efficiency of the breeding process, to improve the accessibility of existing germplasm and to create new variation for crop improvement. Interspecific hybridization is more successful in vegetatively propagated species like sugarcane and potato than in seed propagated species. DISTANT HYBRIDIZATION FOR CROP IMPROVEMENT Submitted by: Pawan Nagar M.Sc. Improvement in yield has also been achieved through the use of wild species in some crops. The main cause of hybrid sterility is lack of structural homology between the chromosomes of two species. In some cases, pollen tube is short and style is very long, due to species difference. Welcome to BiologyDiscussion! iii. Normally 20-50 families may be retained at the end of F5 generation. Triticale is the amphidiploid obtained from crosses between wheat and rye. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. Genomic variation of new cultivars selected from distant hybridization in Lilium. 2.5 Somatic hybridization. The book is an invaluable source of information for advanced students, teachers, and research scientists in the field of plant breeding, genetic engineering, plant tissue culture, and general plant biotechnology. 3. In cotton, there are two types of species, viz. biotechnology is the term used in crop and livestock improvement through biotechnology tools. (Horti.) The hexaploid wheat (2n = 42) has several species. 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). Wide or distant hybridization has been widely used as an important tool of chromosome manipulation for crop improvement. Semi-dwarf wheat has obtained from Triticum x Agropyron hybrid derivatives. Distant crosses are more successful in more closely related species or genera than in less closely related species or genera. Disclaimer Copyright, Share Your Knowledge Some of the following biotechnology tools which play vital role in agriculture biotechnology are- This method is widely used for the development of varieties in self-pollinated crops. Wide or distant hybridization has been widely used as an important tool of chromosome manipulation for crop improvement. (ii) The breeder is enable to exercise his skill and judgement in selection and therefore the method is less satisfying to him. 2. This procedure has been used for developing many improved varieties of sugarcane, potato etc. Transfer of characters controlled by recessive genes is very difficult in interspecific crosses. Seeds are multiplied and released for cultivation. G. hirsutum (2n = 52) x G. barbadense (In = 52) → F1 plants are fully fertile. Types of Hybridization Based on the taxonomic relationship of the two parents, hybridization may be classified into two broad groups. This technique has been successfully used in Triticum, Hordeum, Phaseolus, Nicotiana, Gossypium, Lycopersicon, Trifolium, Cucurbita and several other species. the improvement of few crop species is primarily based on interspecific hybridization example like Sugarcane. 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. The cytoplasm mix, obtained offers the opportunity of producing hybrids. Treatment of F1 plants with colchicine resulted in the production of fertile amphidiploid (2n = 52) which was similar to upland cotton (G. hirsutum). 9). Use of wild root stocks, in commonly grafted crops such as citrus, rubber, grape, pistachio and peach has eliminated many insect pests and diseases of these horticultural crops. Such crosses are rarely used in crop improvement because of various problems associated with them. Role of Distant Hybridization in Crop Improvement: Wild species or wild genetic resources are the potential sources of desirable genes for various characters of crop plants. 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