Cytogenetics of plant cell and tissue cultures and their regenerates

Critical Reviews in Plant Sciences (Impact Factor: 4.36). 01/1985; 3:73-112. DOI: 10.1080/07352688509382204

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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