98:. Different from nucellar embryony, double fertilization occurs via the syngamy of sperm and egg cells, producing a triploid endosperm and a diploid zygotic embryo. In nucellar embryony, embryos are formed asexually from the nucellus tissue. Zygotic and nucellar embryos can occur in the same seed (monoembryony), and a zygotic embryo can divide to produce multiple embryos. The nucellar embryonic initial cells form, divide, and expand. Once the zygotic embryo becomes dominant, the initial cells stop dividing and expanding. Following this stage, the zygotic embryo continues to develop and the initial cells continue to develop as well, forming nucellar embryos. The nucellar embryos generally end up outcompeting the zygotic embryo, rending the zygotic embryo dormant. The polyembryonic seed is then formed by the many adventitious embryos within the ovule (to picture this process, refer to Figure 1). The nucellar embryos produced via apomixis inherit its mother's genetics, making them desirable for citrus propagation, research, and breeding.
150:, the production of fruit without fertilization. Self-incompatible fruits are able to undergo parthenocarpy to yield seedless fruits. In citrus specifically, there have been other modes developed to reduce seeding as well: gibberellic acid enhances ovule abortion and copper sulfate has been shown to reduce seed number in fruit. An example is the ‘Afourer’ mandarin that contains a haploid self-incompatibility system and parthenocarpy. Under conditions where cross-pollination is not present, the ‘Afourer’ mandarin produces a seedless fruit by undergoing parthenocarpy. Where cross-pollination is present, gibberellic acid is applied and produces a decreased seeding fruit.
20:
146:, another reproductive trait within citrus fruits and many seed plants. Self incompatibility is the phenomena where hermaphroditic plants are not able to produce fertile embryos after self-pollination. Self-incompatibility is regulated by the S-loci; if pollen is rendered incompatible, it is determined by its haploid S genotype, or if its sporophyte is rendered incompatible, it would be determined by its diploid S genotype. This is also termed and associated with
29:
23:
Figure 1. depicts the process of nucellar embryony. A) begins with megaspore formation. B) shows the nucellus and forming of cells, nucellar embryonic initial cells, from the nucellus tissue. These initial cells form, divide, and expand. C) The nucellar embryos are developed. If and when a zygote is
129:
An important component of nucellar embryo development is its changing cell wall thickness. Between nucellar embryo's initial cell stage and its dividing and expanding stage, the cells' wall thickens. This most likely occurs due to callose deposition; callose deposition reduces the permeability of a
106:
Nucellar embryos have also been found in polyembryonic Mango varieties, where generally one of the embryos is zygotic and the rest are nucellar. However, there is little research on Mangos undergoing nucellar embryo development as there has on varieties of citrus.
130:
cell and is usually found in the initial cells about to undergo embryogenesis. The initial cells become enlarged, rounded, and divided. During this stage, the initial cell's cell walls thin out, leaving room for the nucleus to become distinguished.
115:
Nucellar embryony is able to occur within both fertilized and unfertilized ovules. Furthermore, instead of using the endosperm as nutritive tissue, it will utilize the surrounding nucellus tissue for nutrition. For example, the
138:
Many seed plants, including citrus fruits, are self-compatible, meaning that they are able to fertilize themselves. Self-compatibility produces a seedy fruit which may be deemed as undesirable to the citrus industry.
120:
undergoes nucellar embryony in both fertilized and unfertilized conditions. But, it has been found that nucellar embryo development, under fertilized or unfertilized conditions, can take place in different positions.
24:
present, the nucellar embryos supersede the zygote. D) The presence of extra embryos formed from the nucellar tissue gives rise to polyembryonic seeds. E) Polyembryonic seeds germinate and develop.
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679:
Gambetta, Giuliana; Gravina, Alfredo; Fasiolo, Carolina; Fornero, Cecilia; Galiger, Sebastián; Inzaurralde, Cristian; Rey, Florencia (2013-12-17).
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which yields consistent results in fruit production. However, this trait can interfere with progress in cross-breeding; most commercial
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Seedless fruits have been made popular as they are sought-after in the citrus industry. To be seedless, a citrus must exhibit
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Plant & Animal
Genomes XI Conference. January 11–15, 2003, Town & Country Convention Center, San Diego, CA
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457:"Adventive Embryogenesis in Citrus I. The Occurrence of Adventive Embryos Without Pollination or Fertilization"
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varieties produce mainly nucellar seedlings which do not inherit any of the traits of the "father" plant.
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Nucellar embryony is important to the citrus industry, as it allows for the production of uniform
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195:"Reproduction in woody perennial Citrus: an update on nucellar embryony and self-incompatibility"
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681:"Self-incompatibility, parthenocarpy and reduction of seed presence in 'Afourer' mandarin"
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86:) are genetically identical to the parent plant, rendering them as clones. By contrast,
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Zhang, Siqi; Liang, Mei; Wang, Nan; Xu, Qiang; Deng, Xiuxin; Chai, Lijun (March 2018).
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416:"Polyembryony in Mango (Mangifera indica L.) Is Controlled by a Single Dominant Gene"
304:"Apomixis: Embryo Sacs and Embryos Formed without Meiosis or Fertilization in Ovules"
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527:"Adventive Embryogenesis in Citrus (Rutaceae). II. Postfertilization Development"
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can produce nucellar cells, also termed initial cells. These additional embryos (
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Wilms, H. J.; Went, J. L. van; Cresti, M.; Ciampolini, F. (1983-01-01).
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74:. During the development of seeds in plants that possess this genetic
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754:"Molecular Genetic Analysis of Nucellar Embryony (Apomixis) in
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from both parents. Most angiosperms reproduce sexually through
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724:"Molecular Genetic Analysis of Nucellar Embryony in Citrus"
619:
Newbigin, E.; Anderson, M. A.; Clarke, A. E. (1993-10-01).
414:
Aron, Y.; Gazit, S.; Czosnek, H.; Degani, C. (1998-12-01).
248:
Aleza, P.; Juárez, J.; Ollitrault, P.; Navarro, L. (2010).
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Spillane, C.; Steimer, A.; Grossniklaus, U. (2001-12-01).
361:"Apomixis in agriculture: the quest for clonal seeds"
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that occurs in certain plant species, including many
134:
Seedless fruits and influence by the citrus industry
574:"D. de Nettancourt Incompatibility in angiosperms"
250:"Polyembryony in non-apomictic citrus genotypes"
66:tissue of the ovule are formed, independent of
455:Wakana, Akira; Uemoto, Shunpei (April 1987).
102:Nucellar embryony outside of citrus varieties
62:, where eventually nucellar embryos from the
8:
90:seedlings are sexually produced and inherit
36:varieties produce mainly nucellar seedlings.
621:"Gametophytic Self-Incompatibility Systems"
78:, the nucellus tissue which surrounds the
58:varieties. Nucellar embryony is a type of
652:
431:
335:
273:
731:Citrus Research Board 2000 Annual Report
572:Končalová, Marie Naděžda (1978-12-01).
525:Wakana, Akira; Uemoto, Shunpei (1988).
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752:Kepiro, Joseph L.; Mikeal L. Roose.
578:Folia Geobotanica et Phytotaxonomica
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488:"Adventive Embryogenesis in Citrus"
473:10.1002/j.1537-2197.1987.tb08672.x
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504:10.1080/00087114.1983.10797645
302:Koltunow, A. M. (1993-10-01).
1:
697:10.1016/j.scienta.2013.09.002
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531:American Journal of Botany
461:American Journal of Botany
433:10.21273/HORTSCI.33.7.1241
377:10.1007/s00497-001-0117-1
365:Sexual Plant Reproduction
211:10.1007/s00497-018-0327-4
16:Form of seed reproduction
685:Scientia Horticulturae
37:
25:
637:10.1105/tpc.5.10.1315
320:10.1105/tpc.5.10.1425
31:
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809:Asexual reproduction
794:Tropical agriculture
144:self-incompatibility
96:double fertilization
760:Poncirus Trifoliata
72:sexual reproduction
804:Plant reproduction
590:10.1007/BF02851938
266:10.1093/aob/mcq148
199:Plant Reproduction
38:
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722:Roose, Mikeal L.
631:(10): 1315–1324.
314:(10): 1425–1437.
118:‘Valencia’ orange
41:Nucellar embryony
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625:The Plant Cell
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308:The Plant Cell
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84:polyembryony
52:reproduction
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762:Using AFLP"
691:: 183–188.
420:HortScience
788:Categories
776:2006-10-26
744:2006-10-26
584:(4): 370.
492:Caryologia
177:References
111:Conditions
705:0304-4238
645:1040-4651
598:1874-9348
551:0002-9122
512:0008-7114
442:0018-5345
385:1432-2145
328:1040-4651
235:254022638
219:2194-7953
155:rootstock
43:(notated
663:12271031
401:23996256
393:24573424
346:12271038
284:20675656
227:29457194
171:Apomixis
165:See also
125:Features
64:nucellus
60:apomixis
606:5868472
559:2443771
275:2944972
88:zygotic
68:meiosis
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159:scion
76:trait
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223:PMID
215:ISSN
70:and
49:seed
693:doi
689:164
649:PMC
633:doi
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539:doi
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332:PMC
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