In such cases, growth regulators should be used to accelerate the pollen tube growth or to prolong the viability of pistil. Thus this is a combursome task. 5. iii. In alfa-alfa, a treatment of even 10 seconds with 57 % alcohol is sufficient to kill the pollen grains. G. hirsutum (2n = 52) x G. barbadense (In = 52) → F1 plants are fully fertile. In such hybrids, recombination between chromosome segments during meiosis may lead to production of gametes with deletions or duplications. Seed production and processing technologies. 4. In some cases, sterility has been found to be associated with completely normal pairing of chromosomes (genie sterility). Interspecific crosses are partially fertile between those species which differ in chromosome number but have some chromosomes in common. In such species, chromosome number may or may not be similar. Hybridization was first of all practically utilized in crop improvement by German botanist Joseph Koerauter in 1760. What are the characters Mendel selected for his experiments on pea plant? The tags are attached to the base of flower or inflorescence with the help of thread. Each F1 plant is a potential source for a new clone. The implications of somatic hybridization in gene transfer in wide crosses and for the induction of genetic variability in various crops are discussed. First B is crossed with C and then the amphidiploid is crossed with A. Bridge crosses have been used in tobacco and wheat. Due to successive self-pollination most of the lines become homozygous and uniform. This is the most common method used for transfer for oligogenic character like disease resistance. 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. All the hybrid seeds of maize to farmers for cultivation are nothing but double crosses. This method is rarely used in crop improvement programmes and that too for transfer of some specific characters into cultivated species from allied genera. In crop improvement programme this type of hybridization is commonly used E. g crossing of two varieties of wheat or other crops. Seeds are multiplied and released for cultivation. Distant crosses are more successful in more closely related species or genera than in less closely related species or genera. (i) The bulk method is simple, convenient, inexpensive and less labour consuming (no pedigree record is to be kept). Several special techniques, viz. During the testing period observations are made on height, tendency to lodge, maturity, disease resistance and quality. The amphidiploid (2n = 56) was named as Triticale. It is needed to transfer the disease resistance from B to A without adversely affecting the good qualities of A. The production of a hybrid by crossing two individuals of unlike genetical constitution is known as hybridization. In India, interspecific hybrids have been developed for commercial cultivation in cotton. Here B is treated as female and A as male. Objectives of Hybridization 3. 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. Triticale also combines good characters of both the parents, viz., grain quality and yield potential of wheat and winter hardiness of rye. Such crosses are rarely used in crop improvement because of various problems associated with them. The bagging is done with the emasculation in bisexual plants and before the stigma receptivity and dehiscence of the anthers in unisexual plants. 4. In such situations, the F1 plants are partially fertile and partially sterile. The methods of crop variety improvement are hybridisation, genetic engineering etc. To combine the desired characters into a single individual, and. (Horti.) Further breeding in these hybrids is carried out according to either pedigree or bulk method. through distant hybridization. Role of interspecific and intergeneric hybridization. Intergeneric crosses between maize and Tripsacum were also attempted. (i) The new variety is superior over the already available variety only in the transferred character. Meiosis in F1 leads to formation of 24 bivalents and 12 univalents. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. Plays a pivotal role in the improvement of the crop species specially the vegetatively propagated ones. The main features of intergeneric crosses are given below: 1. Treatment of F1 plants with colchicine resulted in the production of fertile amphidiploid (2n = 52) which was similar to upland cotton (G. hirsutum). Several modern cultivars of sugarcane have been developed from crosses of Saccharum officinarum with S. spontaneum or S. barberi. 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. A is very good in all characters but disease susceptible and the variety B is disease resistant but very poor in all characters. In the field water is carried in a thermos jug (Fig. But the zygote does not grow. Distant hybridization and role of biotechnology in crop improvement: 1. Sometimes, distant hybrids have several undesirable characters such as non-flowering, late maturity and seed dormancy and useless combinations like Raphanobrassica. 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. Interspecific hybridization is more successful in vegetatively propagated species like sugarcane and potato than in seed propagated species. The gametes with deletions and duplications result in hybrid breakdown. (ii) Inter-varietal or Intraspecific hybridization: The crosses are made between the plants belonging to two different varieties. In tobacco, Nicotiana repanda can cross with N. sylvestris but not with N. tabacum. In vitro techniques, one of the key tools of plant biotechnology, can be employed for overcoming specific problems, viz. Chromosomes in such hybrids have normal pairing at meiosis and as a result the F1 plants are fully fertile. 3. 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