Creation of long-day adapted tetraploid potatoes from crosses of Solanum tarijense females with Andigena males

T-type is a common chloroplast DNA type among modern potato varieties (Solanum tuberosum), their progenitor Chilean tuberosum, and a diploid wild species S. tarijense. To recreate Chilean tuberosum, we made 983 pollinations between 10 accessions of T-type chloroplast DNA-holding S. tarijense used as females and 32 Andean tetraploid landraces (Andigena) used as males, from which 14 tetraploid hybrids were obtained. These interspecific hybrids grew vigorously with long stolons, flowered well with high male and female fertilities, and matured 1 month later than modern varieties. Seedlings of selfed and sib-crossed interspecific hybrids were artificially selected for tuber yield under long days. The selected clones were grown in the field, of which two clones produced over 1 kg of edible tubers per plant. These results lend experimental support to the hypothesis that the Chilean tuberosum originated by selection for long-day adaptability from tetraploid hybrids that occurred by fertilization of a 2n egg of S. tarijense and n pollen of Andigena.