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

Abstract

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.

Keywords: Diploid potato; F1 hybrids; Heterosis; Homozygosity; Inbred lines; Inbreeding depression; Self-compatibility; TPS.

Fig. 1

Complexity of zygotic outputs in diploid, tetraploid and hexaploids. Assuming a diallelic model with complete dominant A and recessive a at a locus, crossings from heterozygous parental genotypes show genotypic and phenotypic segregation. Ovals represent genotypic segregation, whereas squares represent phenotypic segregation. It clearly shows that an increase in ploidy requires a large progeny population for phenotypic selection

Fig. 2

Diploid Inbred Lines development in potato. The flow chart demonstrates the major steps and selection of desired clones in early selfing generations through genetic analysis to develop elite inbred lines

Fig. 3

Schematic representation of reinventing vegetatively propagated tetraploid potato into a diploid inbred based TPS hybrid crop