The nature of apomixis in cassava (Manihot esculentum, Crantz).
نویسنده
چکیده
Apomixis in cassava is formed by aposporic embryo sacs which arise from cells in nucellus or from cells in the sexual embryo sac. There is an association between sterility and apomixis. It seems that sterility caused by defected meioses triggers a specific gene for exhibiting apomixis. This apomictic mechanism is favoured by natural selection since it offers an escape from lethality and provides a perpetuation of the current genotype.
منابع مشابه
Cassava, Manihot esculenta Crantz, genetic resources: origin of the crop, its evolution and relationships with wild relatives.
About 98 species of Manihot are known. All of them are native to the New World and are concentrated in four regions in Brazil and Central America. All the Manihot species so far examined have 2n = 36 chromosomes. Interspecific hybrids between cassava and its wild relatives show relatively normal meiosis, and further generations can be obtained. Electrophoresis shows affinity among wild species ...
متن کاملEmbryonic, Meiotic and Molecular Analysis of Apomictic Cassava (Manihot esculenta Crantz)
Apomixis genes have been successfully transferred to cassava by hybridizing it with the wild species, M. glaziovii. An interspecific hybrid of cassava and M. glaziovii was left for open pollination during three subsequent generations. Seven sibs and their maternal progenitor of the fourth generation were genotyped using five microsatellite loci previously developed for cassava. All sibs were id...
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A new species was synthesized artificially by chromosome doubling of an interspecific hybrid between cassava and Manihot anomala. The ensuing polyploid type exhibits an apomictic nature and maintains its morphological characteristics in the progeny. It showed a 29% frequency of multiembryonic sacs in its examined ovules whereas the multiembryonic sacs were absent in the diploid type.
متن کاملApomixis and cassava.
Apomixis means seed formation without fertilization. In cassava (Manihot esculenta) it is an alternative to reproduction by cuttings, which normally transmits pathogens and leads to an accumulation of viral and bacterial diseases. Apomixis also assures preservation of heterosis and avoids genetic segregation. It occurs in wild relatives of cassava and has been transferred successfully from Mani...
متن کاملWild Manihot species: botanical aspects, geographic distribution and economic value.
A total of 98 Manihot species have been recognized in the genus. All of them are native to the tropics of the New World, particularly Brazil and Mexico. The cultigen, Manihot esculenta Crantz (cassava), grows throughout the lowland tropics. Wild species vary in growth habit from acaulescent or short shrubs to tree-like. Because of their adaptations to different conditions, they are gene reservo...
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ورودعنوان ژورنال:
- Hereditas
دوره 134 2 شماره
صفحات -
تاریخ انتشار 2001