Developing self-compatible diploid potato germplasm through recurrent selection

Most wild and cultivated diploid potato species are self-incompatible, preventing inbreeding and promoting outcrossing. To generate diploid inbred lines, the tuber bearing self-compatible species Solanum chacoense (M6 line) has been used to overcome self-incompatibility. In this study, self-compatibility was introgressed from a set of four diploid self-compatible (SC) donor lines with S. chacoense background into eight introgression species lines to develop a multi-species potato germplasm pool using a recurrent selection (RS) breeding strategy. Concurrently, tuber and adaptation-related traits were selected under Michigan field conditions prior to self-compatibility assessment. After six cycles of RS, we observed a significant increase in self-compatibility (16% in cycle 0-86% in cycle 5) inheritance and improvement of tuber-related traits. Reproductive fitness was increased, reducing male sterility from 32% in cycle 0 to 0% in cycle 5. Progeny with no-flowers decreased from 19 to 3% from RS cycles 0 to cycle 5. Additionally, 4,885 single-nucleotide polymorphism (SNPs) markers were used to access the linkage disequilibrium (LD), heterozygosity, and population structure over the RS population. SNP heterozygosity moderately decreased through the six cycles of RS cycles. Hierarchical clustering and Principal Components Analysis showed that selections become more uniform as the cycles advanced and that LD had been reduced across each potato chromosome. We observed significant increase in earliness for vine maturity in cycle 4. The SC germplasm developed in this study can be used to introgress self-compatibility, select tuber-related traits, and develop inbred lines in F1 hybrid programs using a genetically diverse diploid germplasm.