Integrating genomic selection and genome editing strategies to accelerate potato breeding

"As a staple food, the potato (Solanum tuberosum L.) plays an important role in human nutrition and it is currently the third most important food crop after rice and wheat. However, the potato crop faces high production losses caused mainly by biotic factors. With the advent of cutting-edge technologies suitable for potatoes, there is an increasing possibility to accelerate genetic progress and variety generation. To contribute to the implementation of genomic strategies to accelerate potato breeding, three different approaches were used. First, whole genome regressions were conducted using additive and dominant allele dosage models for late blight and common scab resistance in tetraploid potatoes. Multiple Single Nucleotide Polymorphisms (SNPs), contribute to late blight resistance, uncovering the introgression history for this trait whereas an unreported locus with a sizable contribution to common scab resistance was detected. Prediction accuracy assessments demonstrated that 90% of the genetic variance could be captured with an additive model, demonstrating the applicability of genomic prediction for tetraploid potato breeding. Second, a genome editing approach was implemented to breakdown the S-RNase -based self incompatibly in diploid potatoes. New S-RNase allelic variants, with flower-restricted expression, were identified in two self-incompatible (SI) diploid potatoes and mapped to chromosome I in a low recombination region. A dual single-guide RNA strategy was used to generate S-RNase knock-out lines producing premature stop codons on each targeted S-RNase allele. Self-compatibility was achieved in T0 knock-outs and stable transmitted to T1 lines. Additionally, Cas-9 free plants were also obtained. Plasticity in the self-compatible response was also observed in wild-type lines, presumably associated with non-stylar and environmental factors. Third, validation of the IPI-O4 -mediated suppression of the RB-based late blight resistance was conducted using in vivo and in vitro approaches. The hypersensitive response (HR) was confirmed when IPI-O1 was co-infiltrated with the RB gene from Solanum bulbocastanum using a heterologous system. However, HR was observed when IPI-O1 and IPI-O4 were infiltrated in transgenic potato lines carrying a synthetic RB gene containing a Coiled-Coil (CC) domain from S. pinnatisectum. Further work should be conducted to confirm this un-reported interaction. Similarly, we could not validate CC-dimerization using yeast-two hybrid assays and therefore more extensive experiments should be conducted to confirm this result. Ultimately, these genomic approaches open a new window to accelerate the generation of new potato varieties. Genomic selection strategies along with targeted mutagenesis will expand the boundaries of both approaches, reducing the potato breeding cycle considerably while maintaining genetic diversity, and providing access to genomic regions with low or null recombination in potatoes."--Pages ii-iii.