3 edition of Gametophytic apomixis, hybridization, and polyploidy in Crataegus (Rosaceae). found in the catalog.
Gametophytic apomixis, hybridization, and polyploidy in Crataegus (Rosaceae).
Nadia Joan Talent
Written in English
Pseudogamous gametophytic apomixis in flowering plants can be a flexible type of asexual reproduction because pollination is required. Ploidy-level changes are possible if a meiotically reduced egg cell develops by parthenogenesis or if a meiotically unreduced egg cell is fertilized. In North American Crataegus, pseudogamous gametophytic apomixis exists among polyploids in several taxonomic sections of the genus, and many hybrids have been identified. Polyploidization and selection for apomixis have been attributed to diploid-diploid hybrids, but evidence for that evolutionary process is slight. Ploidy-level increases and hybridization may instead result from apomixis, which possibly occurs occasionally in diploids. This thesis explores the taxonomic distribution of ploidy levels in Crataegus and how the ploidy levels of seeds relate to the breeding systems of the parent plants.Quantification of nuclear DNA amounts by flow cytometry revealed the ploidy levels of various tissues. The ploidy levels of the embryo and endosperm in seeds revealed whether sexual or apomictic reproduction and fertilization occurred. Inter-ploidy pollinations between different taxonomic series were compared with intra-taxon and open pollinations.These results greatly expand what is known about the formation of endosperm in Rosaceae, and the mechanism differs from what is thought to occur in related genera. Triploid hybrids may be a vital, although sometimes ephemeral, factor in maintaining gene flow from sexual diploids to apomictic tetraploids. Diploid-triploid-tetraploid-diploid gene flow appears to be possible, with pentaploid and hexaploid derivatives. One exceptional seed appears to indicate rare apomixis in a diploid, and a hypothetical model is proposed to explain the greater success of apomixis in polyploids of Rosaceae than in diploids.Some post-pollination crossing barriers apparently exist in the genus. Triploids formed from diploid mothers in some diploid-tetraploid inter-serial pollinations, and tetraploids formed from some triploid-diploid inter-serial pollinations. Tetraploid-diploid pollinations produced hybrids only if the mother plant was a largely sexual tetraploid. Fertilization of unreduced egg cells was also indicated by pentaploid and hexaploid embryos, and rare pentaploids and hexaploids occur as adults. A largely sexual tetraploid also produced diploids when pollinated from a diploid species, consistent with parthenogenesis in sexual embryo sacs.
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rence of gametophytic apomixis. In tribe Colurieae polyploidy is widespread, and allopolyploidization events have been in-ferred from molecular data in the Geum L. group (Smedmark & al., , ). Gametophytic apomixis . Gametophytic apomixis, asexual reproduction involving megagametophytes, occurs in many flowering-plant families and as several variant mechanisms. Developmental destabilization of sexual reproduction as a result of hybridization and/or polyploidy .
ROSACEAE: Maloideae Crataegus spp.. Crataegus (hawthorn) and the closely related genus Mespilus pose challenging problems for taxonomists and evolutionary biologists because of the occurrence of hybridization, polyploidy, and apomixis. Audio Books & Poetry Community Audio Computers, Technology and Science Music, Arts & Culture News & Public Affairs Non-English Audio Spirituality & Religion. Librivox Free Audiobook. Full text of "Polyploidy and apomixis in .
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Babcock EB, Stebbins GL () The American species of Crepis: Their relationships and distribution as affected by polyploidy and apomixis.
Carnegie Gametophytic apomixis Wash Publ – Google Scholar Băra II. Gametophytic apomixis is strongly correlated with the occurrence of hybrid and polyploid com- plexes.
It was formerly thought to be a direct result of hybridization or increased level of ploidy. Today, all. Apomixis is a method of reproduction to generate clonal seeds and offers tremendous potential to fix heterozygosity and hybrid vigor.
The process of apomictic seed development is complex and Cited by: 2. Gametophytic apomixis (Stebbins, ) is a common term for all types of apomixis where the maternal seed embryo develops from the egg cell of a well-developed embryo sac, without fertilization.
Gametophytic. Maheshwari used the following simple classification of types of apomixis in flowering plants. Nonrecurrent apomixis: In this type "the megaspore mother cell undergoes the usual meiotic divisions. Full Text; PDF ( K) PDF-Plus ( K) Citing articles; Polyploidy in Crataegus and Mespilus (Rosaceae, Maloideae): evolutionary inferences from flow cytometry of nuclear DNA amounts.
Nadia Cited by: Knowledge and models concerning the genetic basis of apomictic reproduction are summarized, as well as effects upon apomixis of changes of chromosome number and of hybridization.
In the author's opinion, the constituents or elements of apomixis. Apomixis in Plants presents a comprehensive review of different aspects of asexual seed formation in plants.
This is important in plant research since apomixis could greatly facilitate breeding in important. curs, it is associated with polyploidy and with heterozygos-ity, which suggests a hybrid origin (Nogler ; Carman ). The distributions of polyploidy and apomixis within the hawthorns, the details of the mechanisms, and the suc-cess rate of apomictic reproduction, as well as the extent of hybridization.
Apomixis, the asexual reproduction via seed, has many potential applications for plant breeding by maintaining desirable genotypes over generations. Since most major crops do not express natural apomixis, it is useful to understand the origin and maintenance of apomixis in natural plant systems.
Here, we review the state of knowledge on origin, establishment and maintenance of natural apomixis. by apogamety). Gametophytic apomixis is overwhelmingly associated with polyploidy, and hybridization is also often apparent.
Some triploids with gametophytic apomixis are extremely successful, but the majority of plants with gametophytic apomixis. Gametophytic apomixis (Stebbins, ) is a common term for all types of apomixis where the maternal seed embryo develops from the egg cell of a well-developed embryo sac, without fertilization.
where f asex is the female fitness of asexual individuals and f sex that of the sexual individuals, and m is the respective male fitness quotient (Mogie, ).If m = 1, then the f quotient must only exceed 05, or, in other words, asexual seed set needs to exceed only half of that of the sexual individuals to increase the frequency of apomixis.
Developmental genetics of gametophytic apomixis. or are lethal in diploid progen 45, 46, suggesting that the relationship between apomixis and polyploidy might be structural rather than functional.
Other evidence, however, suggests a functional role for partial or complete genome duplications. induces apomixis. Hybridization. Developmental genetics of gametophytic apomixis Olivier Í Leblanc, Enrico Perotti and Ueli Grossniklaus Some higher plants reproduce asexually by apomixis, a natural way of cloning through seeds.
Apomictic. In North American Crataegus, pseudogamous gametophytic apomixis exists among polyploids in several taxonomic sections of the genus, and many hybrids have been identified. Polyploidization and selection for apomixis have been attributed to diploid--diploid hybrids. Partitioning Apomixis Components: Principle and Consequences.
The apomixis components were believed to be strictly under control of “one major locus,” eventually generating an apomictic. Crataegus (hawthorn) is one of the largest genera in the predominantly woody Rosaceae tribe Pyreae (Campbell et al.
In North America, over 60 of the approximately species include polyploid individuals (Talent & Dickin-son ). Both gametophytic apomixis and hybridization. Hawthorns and medlars are closely related genera in Rosaceae subfamily Maloideae, whose taxonomy remains poorly understood.
Gametophytic apomixis occurs in polyploids, and. Apomixis is relatively common in the polyploid species of Pennisetum, especially those in the tertiary gene pool.
Apomixis has been reported in polyploids (triploid and higher) of both the x = 8 and x = 9. Global and fine scale molecular studies of polyploid evolution in Crataegus L.
(Rosaceae) Doctor of Philosophy Eugenia Yuk Ying Lo Graduate Department of Ecology and Evolutionary Biology .26 Apomixis in Crop Improvement. January ; DOI: /_26, In book: Plant Biology and BiotechnologyVolume I: Plant Diversity, Organization, Function and Improvement (pp. The relationship between polyploidy and breeding system is of critical importance for understanding evolution and improving the taxonomy of large Rosaceous genera.
Reviewing the data available for the family and for tribe Pyreae (formerly subfamily Maloideae) in particular, it appears that hybridization, pseudogamous gametophytic apomixis, polyploidy.