Cytogenetics Research,Production of Aneuploids,E.R. Sears,Haploid Wheat Pollen,Parthenogenetic,Trisomics,Tobacco

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Production and Uses of Haploids Production and Uses of Haploids Introduction Production of Haploids Anther and Microspore Culture Ovule Culture Chromosome Elimination Somatic Reduction and Chromosome Elimination Mechanism of Chromosome Elimination Detection or Identification of Haploids Use of Haploids in Plant Breeding Programmes Use of Haploids in Species with Disomic Inheritance Hybrid Sorting in Haploid Breeding Some high Yielding Crop Varieties through Hybrid Sorting Using Anther Culture

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Cytogenetics Research
Haploids have been found to be useful in various areas of cytogenetics research, including the following : (i) production of aneuploids, (ii) determination of basic chromosome number and (iii) determination of the nature of polyploidy. For instance, in wheat initially monosomics were produced by E.R. Sears by pollinating a haploid wheat plant by the pollen from a normal wheat plant. The monosomics in this case presumably resulted due to functioning of eggs with restitution nuclei deficient for any individual chromosome. in potato, haploids were used for the production of trisomics using one of the following procedures : (i) isolation of Parthenogenetic aneuhaploid offspring following 4x × 2x crosses : (ii) isolation of aneuploids from 3x × 2x crosses, where 2x is a haploid. In both the schemes, a number of trisomics with 2n = 25 could be obtained.

In tobacco, several nullisomics were derived from haploids obtained from monosomics, which could not produce nullisomics on selfing due to sterility. Haploids have also been used for the production of alien barley addition and substitution lines in a crop like wheat.

A study of meiosis in haploids also gives evidence for the original basic chromosome number in a species or a genus. For instance, in pearl millet (Pennisetum typhoides), occurrence of some pairing (upto two bivalents in some cells) suggested that the basic chromosome number may be x=5. Similar evidence is also available in maize, which is, therefore, considered to be an archaic tetraploid. In potato also, chromosome behavious of dihaploids (2n=2x=24) suggested that the base number is x=12 and that potato is an autotetraploid. Chromosome behaviour of monoploids in potato (2n = x = 12) formed only univalents confirming this conclusion.

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Comparison of Pedigree and Bulk Methods of Conventional Plant Breeding Production of Spontaneously Doubled Haploids for Breeding Use of Haploids in Species with Polysomic Inheritance Analytical Breeding in Potato Two Breeding Schemes Using 2n Gametes in Potato Analytical Synthetic Breeding for Potato Limitations to Haploid Breeding Other Uses of Haploids Mutation Research Gametoclonal Variation Cytogenetics Research Evolutionary Studies Genetic Studies