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Polyploidy is a common and important event in plant evolution and polyploidization implies a reorganization of the cellular molecular and biochemical apparatus. Despite its relevance, it is still not clear what the consequences of genome doubling are. Among potato germplasm, primitive and wild species show several ploidy levels (from diploid 2n=2x=24 to hexaploid 2n=6x=72), while the cultivated potato S. tuberosum is an autotetraploid (2n=4x=48) with basic chromosome number x=12, and a haploid genome size of approximately 840 Mbp.

Our group is involved in a wide multidisciplinary program aimed at understanding the events underlying early polyploid formation. Studies range from genetics and epigenetics to morpho-anatomy and stress tolerance. For this reason, through oryzaline treatments we produced polyploids from two diploid potato species, S. bulbocastanumand S. commersonii. So far, our transcriptomic and metabolomic data revealed that cell cycle, DNA and plant metabolism might be altered as a consequence of the increment of genome copies and that stochastic and species-specific changes occur following genome doubling. Our polyploids also showed alterations in genome methylation and we are investigating their potential role in target gene silencing through the analysis of the involved sequences.

We are now expanding the number of genotypes and species of our studies (e.g. S. pinnatisectum, S. phureja, S. multidissectum). We are also producing polyploids through callus induction and shoot regeneration from in vitrotissue culture, exploiting the potential of callus endoreduplication and nuclear fixation to produce regenerant shoots with doubled genomes. The different approaches and species involved in our studies provide us various materials to use in the research of a general trend in the response to genome doubling. 

Polyploidy and ploidy manypulations are also used for practical breeding purposes. Indeed, polyploidization and haploidization may allow to overcome interspecific crossing barriers. Strategies involve crosses between haploids of S. tuberosumand diploid species followed by the restoration of tetraploidy through the use of 2n gametes. This is possible due to the possibility to extract maternal haploids through crosses with pollinator clones of S. phureja, and because several genotypes produce 2n gametes. Alternatively, bridge ploidies are used. 

Overall, these activities will allow us to study the plasticity of plant genomes and to interpret molecular changes associated to polyploidy.