Abstract
Polyploidy has the utmost importance in horticulture for the development of new ornamental varieties with desirable morphological traits referring to plant size and vigor, leaf thickness, larger flowers with thicker petals, intense color of leaves and flowers, long lasting flowers, compactness, dwarfness and restored fertility. Polyploidy may occur naturally due to the formation of unreduced gametes or can be artificially induced by doubling the number of chromosomes in somatic cells. Usually, natural polyploid plants are unavailable, so polyploidy is induced synthetically with the help of mitotic inhibitors. Colchicine is a widely used mitotic inhibitor for the induction of polyploidy in plants during their cell division by inhibiting the chromosome segregation. Different plant organs like seeds, apical meristems, flower buds, and roots can be used to induce polyploidy through many application methods such as dipping/soaking, dropping or cotton wool. Flow cytometry and chromosome counting, with an observation of morphological and physiological traits are routine procedures for the determination of ploidy level in plants.
Highlights
Polyploidy was first discovered in 1907 and was thought to be responsible for increasing the number of genomic copies that are heritable [1]
Chromosome doubling through colchicine by using different application methods has been obtained in many ornamental crops such as lily, salvia, phlox, gladiolus, petunia and marigold (Tables 1–4)
Polyploidy causes a wide range of effects on plants, but these effects depend upon species and range of different ploidy level within a same species, degree of heterozygosity and rely on various mechanisms that are related to gene dose effects, gene silencing, regulation of specific traits and gene interaction [32]
Summary
Polyploidy was first discovered in 1907 and was thought to be responsible for increasing the number of genomic copies that are heritable [1]. Polyploidy leads to changes in gene dosage that causes chromosomal rearrangements, epigenetic remodeling and reunion of divergent gene regulatory hierarchies These changes may bring out novel variations or may result in speciation and reproductive isolation [5]. Phenotypic and genetic changes in plants caused by polyploidy may occur due to an increase in cell size, allelic diversity (level of heterozygosity), gene silencing and gene dosage effect or because of epigenetic and genetic interactions. Extra copies of genes provide a protection against inbreeding depression and single locus deleterious mutation effects Another important benefit of gene redundancy is found in terms of duplicated gene pairs, in which a member mutates and obtains certain novel function without affecting the essential functions [10]. Asexual reproduction allows the polyploid plants to reproduce even in the absence of their sexual mates [11]
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