Genetics and cytogenetics of the potato

Tetraploid potato (Solanum tuberosum L.) is a genetically complex, polysomic tetraploid (2n = 4x = 48), highly heterozygous crop, which makes genetic research and utilization of potato wild relatives in breeding difficult. Notwithstanding, the potato reference genome, transcriptome, resequencing, and single nucleotide polymorphism (SNP) genotyping analysis provide new means for increasing the understanding of potato genetics and cytogenetics. An alternative approach based on the use of haploids (2n = 2x = 24) produced from tetraploid S. tuberosum along with available genomic tools have also provided means to get insights into natural mechanisms that take place within the genetic load and chromosomal architecture of tetraploid potatoes. This chapter gives an overview of potato genetic and cytogenetic research relevant to germplasm enhancement and breeding. The reader will encounter findings that open new doors to explore inbred line breeding in potato and strategic roads to access the diversity across the polyploid series of this crop’s genetic resources. The text includes classical concepts and explains the foundations of potato genetics and mechanisms underlying natural cytogenetics phenomena as well as their breeding applications. Hopefully, this chapter will encourage further research that will lead to successfully develop broad-based potato breeding populations and derive highly heterozygous cultivars that meet the demands of having a resilient crop addressing the threats brought by climate change

Effect of genotype on chromosome variation in tissue-culture of inbred and outbred rye

To examine the effect of genotype on the nature of the cytological variation induced in culture, plants were regenerated from cultured immature embryos of six genotypes (lines A-F) of rye (Secale cereale L.). The variation observed differed among the six lines and was generally consistent with the donors. Regenerants of line A were consistent with the donor, cv. Ailes, in that chromosome translocations appeared at high frequencies. No structural or numerical variation was observed in the B chromosomes of line B. Two of the four inbred lines studied were very stable in culture. Inbred line D was also stable except for a translocation in the regenerants. In inbred line F, variation was observed in the donors and the regenerants. An examination of chiasma frequency and distribution indicated that the regenerated plants generally had higher chiasma frequencies and more distally localized chiasmata than the donors. Line F was exceptional in that the regenerants had more interstitial chiasmata. The elevation in chiasma frequency was not as great, or statistically as significant, as the change in distribution. These results provide further evidence that the nature of cytological variation observed in regenerated plants is genotype-dependent and that, in addition to numerical and structural chromosome variation, shifts in chiasma frequency and distribution, and therefore in genetic recombination, can occur as a result of somaclonal variation