Recombinant inbred line (RIL) populations are powerful mapping tools in many crops but have not yet been created using cultivated potato germplasm. We crossed the doubled monoploid cultivated clone DM 1-3 with the self-compatible diploid inbred wild clone M6 to create a diploid F1 hybrid. One F1 plant was self-pollinated to generate a phenotypically diverse F2 population, which was selfed to create 87 RILs. This is the first report of a RIL population developed from a cultivated x wild hybrid in potato. Poor fertility was a significant challenge in creating RILs. Nevertheless, we generated inbred lines that ranged from high to low fertility, vigor, and tuber production. F6 RILs ranged from 98% to 68% homozygosity, based on 2884 SNP markers. Considering the phenotypic variability between the two parents and among the RILs, we expect the RIL population to be valuable for mapping traits important to the potato industry.

We crossed the diploid potato inbred Solanum chacoense clone M6 as a male to the S. tuberosum doubled monoploid cultivated potato DM 1-3 516 R44 to create an F1 population. We then self-pollinated one F1 plant to generate an F2 population. We then self-pollinated F2 plants to begin RIL development. In the fall of 2013, we sowed approximately 50 seedlings of each of 85 F3 families and four weeks later, transplanted 12 seedlings of each to 10 cm square pots filled with soilless potting mix. In most cases, our goal of at least 12 F3 seedlings was achieved, but low seed numbers, poor germination, and low vigor sometimes limited seedling numbers or caused the extinction of a lineage. Plants were maintained in a greenhouse with a 16-hour photoperiod and day/night temperatures of 24/18C. On every plant that flowered, self-pollinations were attempted by holding a pollen capsule over each open flower and vibrating it with an electric toothbrush in which the brush had been replaced by a plastic-coated wire. Pollinations were carried out at least twice per week and in most cases, all flowers on each plant were self-pollinated until berries were observed on at least two inflorescences. A few plants produced hundreds of flowers; at least 100 self-pollinations were attempted on those plants. Performing pollinations across many days was helpful, as pollen shed in some plants varied over time. Berries were collected at least three weeks after pollinating, allowed to ripen at room temperature for three more weeks, and then seeds were extracted in water, air-dried, and stored in a -20C freezer. Additional F3 families were sown and, if available, additional seeds were sown for families that did not generate F4 seeds. This process was repeated for additional generations.

After the F3 generation, we grew 18 plants per family instead of 12. For families that did not produce any selfed berries, additional sowings were made as long as residual seeds were available. Two F2 clones (125 and 159) produced highly fertile F3 families; several F4 families were produced, so three inbred families were produced from each of these two F2 lineages. Otherwise, each F2 plant produced only one recombinant inbred line. Across the course of RIL development, 212 F3 families were generated from 253 F2 plants; 170, 92, and 72 lineages advanced to the F4, F5, and F6 generations, respectively. The RIL population described here is comprised of 87 inbred lines (72 F6, 7 F5, and 8 F4). 

In February 2020, one tuber of each of the 87 RIL clones was planted in a soilless potting mix in 15 cm diameter pots. They were grown in a greenhouse with an 18-hour photoperiod and with 50 cm spacing. Plants were staked as needed throughout the growing period. As each plant flowered, a sample of mature flowers was collected and photographed. On July 2, all pots were harvested and photographed, and then tubers were collected, washed, and photographed.