Cytogenetics of plant cell and tissue cultures and their regenerates
ABSTRACT After a short introduction, the cytogenetics of plant cell and tissue cultures and their regenerates will be discussed. In the first section discussion will focus on cytogenetic conditions “in vivo”, i.e., in the original explant: (I) widespread ocurrence of polysomaty as a consequence of endoreduplication; (2) aneusomaty, an important, though rare, cause of chromosome number variation in vivo; (3) occurrence of chromosome structural changes in differentiated tissues, especially in association with aging; (4) mixoploidy and/or gene mutations, either nuclear or organellar, present as mosaics or periclinal chimeras, especially in vegetatively propagated plants. In section two the discussion will follow with nuclear processes at and during callus induction: (1) mitosis induction in diploid (haploid) and endoreduplicated cells and initiation of cell lines with different ploidy levels; (2) chromosome endoreduplication prior to mitosis induction as a mechanism of polyploidization; (3) nuclear fragmentation (amitosis) followed by mitosis, a mechanism responsible for wide chromosome number variation in cultured cells. In the third section the discussion will consider cytogenetic conditions in medium‐ and long‐term culture: (1) stability at the diploid level with emphasis on the genetic makeup of the species; (2) polyploidy, both existing and originated during culture, and its competitive ability in chromosomally heterogeneous cultures; (3) haploidy: origin and fate; (4) aneuploidy: origin, selective advantage of particular karyotypes, etc.; (5) chromosomal and gene” mutations: preexisting vs. induced during culture. In section four the discussion will focus on cell fusion and somatic hybrid cell lines. The two main aspects of protoplast fusion: (1) for gene (cytoplasm) transfer or exchange; and (2) for the production of somatic hybrids by nuclear fusion, will be treated in detail. Section five will consider cytogenetic conditions in regenerated plants. How much of the genetic variation present in in vitro cultures may be incorporated into regenerated plants? In trying to answer this question, the discussion will concern: (I) cell selection during the regeneration process via adventitious shoots or somatic embryos; (2) polyploidy and aneuploidy in regenerates; (3) chromosome number rnosaicism (aneusomaty) a rather frequent occurrence in plants regenerated via adventitious shoots and intrasomatic cell selection; (4) haploidy, diploidy, and polyploidy in pollen‐derived plants; (5) other genetic variation in regenerates; (6) an analysis of the somatic hybrid plants produced so far. Finally, section six will cover ensuring genetic stability: micropropagation. After stressing the genetic continuity of the meristem cell line in higher plants, papers will be discussed which show maintenance of genetic stability in plants developed in vitro from shoot apex cultures, from axillary buds and latent meristems in some plant parts. The review will end with concluding remarks.
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ABSTRACT: The cytogenetic peculiarities of the genesis of apical meristem cells in apomicts were analyzed using some Asteraceae species as an example. It has been revealed that the frequency of aneu- and mixoploids is so high among the plants of these species (up to 30–60% of all plants studied or their progeny) that there is every reason to say that their occurrence in apomicts is regular rather than spontaneous. It has been demonstrated that microgametophyte in aposporous facultative apomict Pilosella officinarum is a relatively stable element of the seed reproduction system in terms of the ploidy level.Cytology and Genetics 01/2011; 45(2):85-96. · 0.29 Impact Factor
Chapter: Somaclonal Variation in Date Palm[Show abstract] [Hide abstract]
ABSTRACT: The exploration of somaclonal variation is an approach that could provide date palm breeding programs with new genotypes. Naturally occurring or induced variants may have superior agronomic quality and/or enhanced performance but could also harbor new traits such as tolerance to drought and salinity or resistance to major diseases i.e. bayoud. This chapter summarizes recent progress in terms of studying and exploring date palm somaclonal variation, and provides an outlook about future applications of this biotechnology in this socioeconomically important crop. KeywordsBiotic and abiotic stress-Bayoud-Conventional breeding-Date palm-Drought- In vitro-selection- Phoenix dactylifera L.-Salt-Somaclonal variation12/2010: pages 183-203;
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ABSTRACT: Astragalus gilvanensis Ranjbar & Nouri sp. nova (Fabaceae) is described and illustrated. It belongs to Astragalus sect. Incani and is endemic to Iran. Its morphological characters, meiotic chromosome number and meiotic behavior were studied. It is a mixoploid plant with the ploidy levels 2n = 2x = 16 and 2n = 4x = 32, consistent with the proposed base number of x = 8. Although the species displayed regular bivalent pairing and chromosome segregation at meiosis, some meiotic abnormalities were observed. The meiotic irregularities included the occurrence of varied degrees of sticky chromosomes in diakinesis to metaphase, laggard chromosomes in anaphase, cytomixis in prophase to telophase, asynchronous nuclei, and binuclear cells.Annales Botanici Fennici 01/2012; · 0.66 Impact Factor