Advances and perspectives in the generation of polyploid plant species

Whole-genome duplication (polyploidy) occurs frequently and repeatedly within species of plants. According to the source of the genomes giving origin to a polyploid plant species, these are classified into allopolyploid (when two or more genomes are combined through either intraspecific or interspecific hybridization) and autopolyploid (when a single genome becomes duplicated). According to the time period in which polyploidy occurred plant species are classified as paleopolyploid (ancient polyploids), mesopolyploid (less ancient polyploids), and neopolyploid (recent polyploids). Many plant species appearing as diploid are actually paleopolyploids (ancient polyploids) derived from at least one event of whole-genome duplication followed by a process known as diploidization, which consists in massive gene loss and genomic reorganization (diploidized paleopolyploids). Many polyploid species of plants have been shown to present morphological and physiological characteristics making them further attractive for industry than their lower ploidy level counterparts. Polyploidy is a fundamental but relatively underexplored biological process. With the aim of understanding the factors involved in the formation of polyploid plant species, many studies have been carried out on synthetic polyploidy obtained by mitotic inhibitors and hybridization. However, the rapid progress of genetic engineering techniques makes genetic modification (GM) to become a feasible strategy for obtaining polyploid plants. In this review we discuss advances made about factors known to influence plant polyploidy and we suggest that in a future, this knowledge could be used for generating polyploids in vitro by GM and for crop improvement.