Diploid inbred-based hybrids: fast-forward breeding approach in potatoes

Following the identification of the self-compatibility gene (Sli) in diploid potatoes two decades ago, the breeding of inbred based diploid hybrid potatoes made its way. Tetraploid potatoes have a long history of cultivation through domestication and selection. Tetrasomic inheritance, heterozygosity and clonal propagation complicate genetic studies, resulting in a low genetic gain in potato breeding. Diploid hybrid TPS potato breeding, similar to the developments in hybrid maize, was pursued as an alternative to the genetic improvement of potatoes. However, several challenges, like self-incompatibility and high inbreeding depression associated with diploid potatoes, must be overcome to develop inbred lines in potatoes. Moreover, the inbred lines must retain good fertility and vigour for hybrid breeding. Good progress has been made by creating di-haploids of popular varieties, mapping self-incompatibility inhibitor gene, understanding the genetic basis of inbreeding depression, and identifying genomic regions for deleterious alleles and fertility. Further, the genome sequencing of diploid inbred lines has revealed the genetics of key traits associated with potato breeding. This article discussed these insights and summarized the progress of diploid hybrid TPS potato breeding. Recent advances in genetic and genomic research and genome editing technology have shown promise for this technology's success and far-reaching implications.