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Plant Biotechnology
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2020
Plants that have three or more complete sets of chromosomes are commonly known as polyploidy plants. The chromosome numbers can be increased artificially by treating the plant cells with colchicine, which leads to a doubling of the chromosome number. Generally, the main effect of polyploidy is an increase in size and genetic variability. On the other hand, polyploid plants often have lower fertility and slower growth. Instead of relying only on the introduction of genetic variability from the wild species gene pool or from other cultivars, an alternative is the introduction of mutations induced by chemicals or radiation. The mutants obtained are tested and further selected for desired traits. The site of the mutation cannot be controlled when chemicals or radiation is used as agents of mutagenesis. Because the great majority of mutants carry undesirable traits, this method has not been widely used in breeding programs.
Agricultural biotechnology
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2018
Plants that have three or more complete sets of chromosomes are commonly known as polyploidy plants. The chromosome numbers can be increased artificially by treating the plant cells with colchicine that leads to a doubling of the chromosome number. Generally, the main effect of polyploidy is increase in size and genetic variability. On the other hand, polyploid plants often have lower fertility and slower growth. Instead of relying only on the introduction of genetic variability from the wild species gene pool or from other cultivars, an alternative is the introduction of mutations induced by chemicals or radiation. The mutants obtained are tested and further selected for desired traits. The site of the mutation cannot be controlled when chemicals or radiation is used as agents of mutagenesis. Because the great majority of mutants carry undesirable traits, this method has not been widely used in breeding programs.
Genetic resources in agroecosystems
Published in Stephen R. Gliessman, V. Ernesto Méndez, Victor M. Izzo, Eric W. Engles, Andrew Gerlicz, Agroecology, 2023
Stephen R. Gliessman, V. Ernesto Méndez, Victor M. Izzo, Eric W. Engles, Andrew Gerlicz
When it was discovered by modern cytologists that many favorable traits in crop plants were the result of polyploidy, methods were developed to artificially induce it. Through the use of colchicine or other chemical stimulators during the first steps of meiosis, artificial multiplication of the number of chromosomes has become possible. Induced polyploidy has produced some of the most useful lines of wheat, for example, such as the hexaploid Triticum aestivum. Once produced, polyploids themselves can then be used to perpetuate pure lines or develop new hybrids.
The importance and prevalence of allopolyploidy in Aotearoa New Zealand
Published in Journal of the Royal Society of New Zealand, 2020
Anna H. Behling, Lara D. Shepherd, Murray P. Cox
Polyploidy, the heritable phenomenon that generates species with increased chromosomal content, is a major force in evolution (Ren et al. 2018). It is widely accepted that polyploidy encompasses a continuum spanning its two primary classifications, autopolyploidy and allopolyploidy (Tayalé and Parisod 2013; Spoelhof et al. 2017). Autopolyploids, the prefix ‘auto-’ meaning ‘same’, are generated from whole genome duplication within species. Conversely, allopolyploids (‘allo-’, meaning ‘different’) originate from the hybridisation of two or more different species (Comai 2005). This continuum of polyploidy accounts for intermediates whose chromosomes exhibit both homologous (as in autopolyploids) and homeologous (as in allopolyploids) pairing during cell division. Intermediacy in polyploids was described in the seminal works by Stebbins (1947, 1950), who later asserted the inefficiency of selection in duplicated genomes, deeming polyploids to be evolutionary dead-ends (Stebbins 1971). Stebbins’ view, the ‘dead-end hypothesis’, has seen increasing opposition through subsequent discoveries of recurrent polyploidy (Soltis and Soltis 1999), substantial dynamism within polyploid genomes (Scannell et al. 2006; Flagel and Wendel 2009; Parisod et al. 2009; Chester et al. 2012; Wang et al. 2015; Wang et al. 2018) and the presence of an ancestral polyploidy event at the base of the major land plant radiation (Jiao et al. 2011).