Induced Polyploidy: A Tool for Forage Species Improvement

Abstract

Polyploidy means having more than two basic sets of chromosomes. Polyploid plants may be artificially obtained through chemical, physical and biological (2n gametes) methods. This approach allows an increased gene scope and expression, thus resulting in phenotypic changes such as yield and product quality. Nonetheless, breeding new cultivars through induced polyploidy should overcome deleterious effects that are partly contributed by genome and epigenome instability after polyploidization. Furthermore, shortening the time required from early chromosome set doubling to the final selection of high yielding superior polyploids is a must. Despite these hurdles, plant breeders have successfully obtained polyploid bred-germplasm in broad range of forages after optimizing methods, concentration and time, particularly when using colchicine. These experimental polyploids are a valuable tool for understanding gene expression, which seems to be driven by dosage dependent gene expression, altered gene regulation and epigenetic changes. Isozymes and DNA-based markers facilitated the identification of rare alleles for particular loci when compared with diploids, and also explained their heterozygosity, phenotypic plasticity and adaptability to diverse environments. Experimentally induced polyploid germplasm could enhance fresh herbage yield and quality, e.g., leaf protein content, leaf total soluble solids, water soluble carbohydrates and sucrose content. Offspring of experimentally obtained hybrids should undergo selection for several generations to improve their performance and stability.

Enhanced morphologic traits and medicinal constituents of octaploids in Satureja mutica, a high-yielding medicinal savory

“…Thus, the genome size of tetraploids is almost twice as large as diploids (Blakesley et al, 2002). Genome size in D. rotundifolia and D. anglica with three levels of diploid, tetraploid, and octaploid were 2.73, 5.34, and 11.12 pg, respectively, indicating a direct relationship between ploidy level and genome size (Rauf et al, 2021). However, there are reports that the size of the genome does not increase directly as the ploidy level increases.…”

Improving Abiotic Stress Tolerance of Forage Grasses – Prospects of Using Genome Editing

“…Thus, there is ample genetic variation still to be exploited within the genetic resources of perennial ryegrass. Induced polyploidization is also widely exploited in forage crop breeding as one of unconventional techniques to develop new superior yielding and abiotic stress tolerant breeding material [246][247][248].…”

Genetic relationship and diversity of cultivars and breeding lines of tetraploid Italian ryegrass (Lolium multiflorum Lam.) and its hybrids with Lolium‐Festuca complex based on genome‐wide allele frequency

“…Nevertheless, the genetic diversity within each accession of tetraploid cultivars was not significantly different from that of the diploid cultivars. It should be noted that if the heterozygosity within a population unit is consistent, the heterozygosity of a tetraploid individual will be higher than in that of a diploid, because polysomy at each locus can be expected in a tetraploid (Rauf et al, 2021). However, breeding within a limited range of material may decrease the genetic diversity within a cultivar, as is observed in diploids.…”