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breeding work, ploidy manipulation is a valuable tool for improving crop quality or production and polyploids promote evolution history significantly ( Adams and Wendel, 2005 ; Leitch and Bennett, 1997 ; Otto and Whitton, 2000 ). Polyploidization often

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formation of unreduced gametes in lantana and potential implications of this trait for lantana ploidy manipulation, particularly triploid generation and selection for sterile lantana development. Materials and Methods Plant materials. Ten

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) ( Ferguson et al., 2009 ). Increasing the ploidy, either spontaneously or by manipulation, can therefore increase fruit size in some kiwifruit selections. However, fruit size is only one attribute of fruit quality, and many other quality attributes will be

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Traditional genetic manipulation methods have proven ineffective or irrelevant for many citrus breeding objectives. Alternative approaches to Citrus genetic improvement are now available as a result of technological developments in genetics and tissue culture. For example, mapping DNA marker polymorphisms should lead to identifying markers closely linked to important loci, thereby facilitating early selection and minimizing costs associated with plant size and juvenility. Genetic transformation methods allow trait-specific modification of commercial cultivars. By selecting beneficial variants from sectored fruit chimeras and the recovering plants via somatic embryogenesis, the problems of nucellar embryony and the hybrid nature of commercial cultivar groups can be avoided. Induced mutagenesis from mature vegetative buds may overcome these problems, as well as juvenility. Ploidy level manipulation in vitro can increase the number and diversity of tetraploid breeding parents, leading to the development of seedless Citrus triploids and mitigating sterility, incompatibility, and nucellar embryony.

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Traditional methods of genetic manipulation have proven ineffective or irrelevant for many citrus breeding objectives. Alternative approaches to genetic improvement of citrus are now available as a result of technological developments in genetics and tissue culture. Mapping DNA markers on the Citrus genome should lead to identification of markers closely linked to important loci, thereby facilitating early selection and minimizing costs associated with plant size and juvenility. Genetic transformation methods provide opportunities for trait-specific modification of commercial cultivars. The selection of beneficial variants from sectored fruit chimeras, and the recovery of plants via somatic embryogenesis, can overcome the problems of nucellar embryony and the hybrid nature of commercial cultivar groups. Induced mutagenesis, using mature vegetative buds, may overcome size and juvenility, as well as nucellar embryony and hybridity. Ploidy level manipulation in vitro provides methods to overcome sterility, incompatibility, and nucellar embryony, and it can increase the number and diversity of tetraploid breeding parents available for development of seedless citrus triploids.

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Phytophthorainfestans is the casual agent of late blight and is a major threat to potato production worldwide. There are no curative control agents available and resistance genes offer promise in controlling late blight. To date, the primary source of late-blight resistance has been from hexaploid (6x) [4 Endosperm Balance Number (EBN)] Solanum demissum. Mexican diploid (2x) (1EBN) Solanum species possess a wealth of late-blight resistances, but have been neglected due to crossing barriers. Manipulation of EBN and ploidies should allow integration of 2x (1EBN) germplasm into cultivated potato. Synteny between late-blight resistance loci from Solanum species of disparate ploidies and EBNs may facilitate the identification of unique resistance alleles and loci. Isolate MSU96 (US8/A2) of P. infestans revealed a late-blight resistance locus (Rpi1) from 2x(1EBN) S. pinnatisectum (PI 253214) that mapped to chromosome seven (MGG 265:977-985). MSU96 was also avirulent on the late-blight differential R9-Hodgson 2573 (LB3), revealing the presence of the avirulence gene for R9 originating from S. demissum. To test the relationship between Rpi1 and R9, we evaluated a family segregating for R9 and revealed that it does not map to chromosome seven. The independent inheritance of R9 and Rpi1 indicates that Rpi1 is a unique resistance locus. We are conducting a variety of crossing schemes to introgress Rpi1 into cultivated potato.

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provided by tetraploid parents combines with a gamete containing one set of chromosomes provided by diploid pollen and forms a triploid zygote ( Acquaah, 2007 ). After identification of ploidy levels from induction treatments, diploid, triploid, and

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In vitro ploidy manipulation for crop improvement Front Plant Sci. 11 722 https://doi.org/10.3389/fpls.2020.00722 Zadoo, S.N. Khoshoo, T.N. Roy, R.P. 1976 Cytogenetics of cultivated bougainvilleas VII: Origin and evolution of ornamental

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and Whitton, 2000 ). The manipulation of ploidy can also be a valuable tool for plant breeding programs. Polyploids often generate variants that may contain useful characteristics and provide a wider germplasm base for breeding studies ( Ramanna and

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R . ‘Fragrant Affinity’ may restore fertility ( Contreras et al., 2007 ). In vitro regeneration protocols provide an excellent mechanism for the manipulation of ploidy level, mutation treatment, and transgenic applications. In vitro shoot

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