The polyploidy and its key role in plant breeding

Abstract

This article provides an up-to-date review concerning from basic issues of polyploidy to aspects regarding the relevance and role of both natural and artificial polyploids in plant breeding programs. Polyploidy is a major force in the evolution of both wild and cultivated plants. Polyploid organisms often exhibit increased vigor and, in some cases, outperform their diploid relatives in several aspects. This remarkable superiority of polyploids has been the target of many plant breeders in the last century, who have induced polyploidy and/or used natural polyploids in many ways to obtain increasingly improved plant cultivars. Some of the most important consequences of polyploidy for plant breeding are the increment in plant organs ("gigas" effect), buffering of deleterious mutations, increased heterozygosity, and heterosis (hybrid vigor). Regarding such features as tools, cultivars have been generated with higher yield levels, improving the product quality and increasing the tolerance to both biotic and abiotic stresses. In some cases, when the crossing between two species is not possible because of differences in ploidy level, polyploids can be used as a bridge for gene transferring between them. In addition, polyploidy often results in reduced fertility due to meiotic errors, allowing the production of seedless varieties. On the other hand, the genome doubling in a newly formed sterile hybrid allows the restoration of its fertility. Based on these aspects, the present review initially concerns the origin, frequency and classification of the polyploids, progressing to show the revolution promoted by the discovery of natural polyploids and polyploidization induction in the breeding program status of distinct crops.

Molecular characterization of red clover genotypes utilizing microsatellite markers

“…Although the most common method for obtaining tetraploids in red clover is colchicine doubling, there are also other methods that could be used for inducing polyploidy, like N 2 O and sexual polyploidization through unreduced gametes. The induced tetraploid forms could exceed their diploid counterparts in many traits like increased disease resistance, persistence, winter hardiness and forage DM yield (Sattler et al, 2016).…”

Genetic mapping in polyploids

“…), also known as the "gigas" effect (Sattler et al, 2016), or their ability to be clonally propagated. We therefore find ourselves in the position of relying on some of the most genetically-complex species to provide us with the basic necessities One may attribute this to their genetic complexity and the fact that few software tools are developed to analyse autopolyploid data (noting that due to the diploid-like inheritance of allopolyploids it is possible to use many of the diploid software tools for those crops).…”

“…Many theories to explain their prevalence among crop species have been proposed, identifying features which may have appealed to early farmers in their domestication of wild species. Such features include their larger organs such as tubers, fruits or flowers (the so-called "gigas" effect) (Sattler et al, 2016), increased heterosis (Comai, 2005), their genomic plasticity (te Beest et al, 2011), phenotypic novelty (Udall and Wendel, 2006), their ability to be clonally propagated (Herben et al, 2017), increased seedling and juvenile vigour (Levin, 1983), the masking of deleterious alleles (Renny-Byfield and Wendel, 2014) or the possibility of seedlessness which accompanies aneuploidy (Bradshaw, 2016). It is currently believed that all flowering plants have experienced at least one whole genome duplication (WGD) during the course of their evolution, with many lineages undergoing multiple rounds of WGD followed by re-diploidisation (Vanneste et al, 2014).…”

Flow cytometric determination of genome size and ploidy level of some frost-resistant cultivars and species of Rhododendron L. native to Asian Russia

“…Fur ther more, the important consequences of polyploidy for plant breeding are increased heterozygosity and hete ro sis as well as enhanced tolerance to both biotic and abiotic stresses (Sattler et al 2016). There are a large number of in du ced polyploid rhododendron cultivars of commercial va lue; however, wild species of Siberia and the Russian Far East have not been involved in the breeding program yet.…”