Studies Of Self-incompatibility And Inbreeding Depression In Diploid Potato

Potato(Solanum tuberosum L.)is the most important tuber crop worldwide.Cultivated potato is autotetraploid,propagated from tubers.Potato researchers and breeders have long been challenged by the tetrasomic inheritance and the need for vegetative propagation.To thoroughly solve this problem,an increasing number of studies have focused on reinventing potato as an inbred line-based diploid crop that is propagated by seed.However,self-incompatibility and inbreeding depression severely hamper the development of inbred lines.In this study,we carried out deep research on these two issues,and obtained the following findings.(1)The self-incompatibility in potato is controlled by the highly polymorphic S-RNase alleles.Knock-out of S-RNase by CRISPR/Cas9 system can overcome self-incompatibility.(2)Deleterious mutations are the main factor causing inbreeding depression.Here,we re-sequenced 151 diploid potatoes,and found that the mutation burden in potato is line-specific.(3)We developed a parent-independent genotyping by sequencing method in potato.Using this pipeline,we analyzed three selfing populations and identified 15 genomic regions showing strong segregation distortions.(4)Based on the genotype and phenotype of three selfing populations,we identified nine large-effect deleterious mutations,causing lethality or obvious phenotypic defects.Genetic mapping showed that most of them are located in the genomic regions with high recombination,suggesting it is possible to effectively purge them by sexual propagation.(5)The large-effect deleterious allele arl controls the development of embryo,and it is a rare variation in potato germplasm.