A diploid, fertile, self-compatible and essentially homozygous Solanum tuberosum potato breeding line comprising plants having an average tuber yield expressed in grams of fresh weight of at least 200 grams per plant, wherein plants of said line have a level of homozygosity that is above 75% when testing 100 loci, obtainable by a method comprising: (a) providing a first potato plant, which first potato plant is a plant of a first diploid, self-compatible, fertile and essentially homozygous S. tuberosum potato line selected from NCIMB accession number 41663, NCIMB accession number 41664, NCIMB accession number 41665, or NCIMB accession number 41765, representative seeds of said lines having been deposited with the NCIMB, Aberdeen, Scotland under breeders reference AGVD1, AGVD2, AGVD3, and AGVD17 respectively, wherein said self-compatibility trait is due to the presence of a S-locus inhibitor (Sli) gene; (b) providing a second S. tuberosum potato plant, wherein said second potato plant is a plant of a diploid potato line which may have any level of homozygosity, said line of said second potato plant comprising plants having an average tuber yield expressed in grams of fresh weight of at least 200 grams per plant; (c) cross pollinating said first and second potato plant to provide seeds and collecting said seeds to thereby provide an offspring generation in the form of a hybrid offspring seed; (d) growing said hybrid offspring seed into a population of hybrid offspring potato plants and selecting from said population plants producing tubers at a yield expressed in grams of fresh weight of at least 200 grams per plant, and (e) selfing said hybrid offspring potato plant for between 1 to 8 selfings, thereby selecting for fertile offspring to thereby provide a diploid, self-compatible and essentially homozygous potato breeding line comprising plants having an average tuber yield expressed in grams of fresh weight of at least 200 grams per plant, wherein plants of said line have a level of homozygosity that is above 75%, and wherein said self-compatibility trait is due to the presence of said S-locus inhibitor (Sli) gene. (a) providing a first potato plant, which first potato plant is a plant of a first diploid, self-compatible, fertile and essentially homozygous S. tuberosum potato line selected from NCIMB accession number 41663, NCIMB accession number 41664, NCIMB accession number 41665, or NCIMB accession number 41765, representative seeds of said lines having been deposited with the NCIMB, Aberdeen, Scotland under breeders reference AGVD1, AGVD2, AGVD3, and AGVD17 respectively, wherein said self-compatibility trait is due to the presence of a S-locus inhibitor (Sli) gene; (b) providing a second S. tuberosum potato plant, wherein said second potato plant is a plant of a diploid potato line which may have any level of homozygosity, said line of said second potato plant comprising plants having an average tuber yield expressed in grams of fresh weight of at least 200 grams per plant; (c) cross pollinating said first and second potato plant to provide seeds and collecting said seeds to thereby provide an offspring generation in the form of a hybrid offspring seed; (d) growing said hybrid offspring seed into a population of hybrid offspring potato plants and selecting from said population plants producing tubers at a yield expressed in grams of fresh weight of at least 200 grams per plant, and (e) selfing said hybrid offspring potato plant for between 1 to 8 selfings, thereby selecting for fertile offspring to thereby provide a diploid, self-compatible and essentially homozygous potato breeding line comprising plants having an average tuber yield expressed in grams of fresh weight of at least 200 grams per plant, wherein plants of said line have a level of homozygosity that is above 75%, and wherein said self-compatibility trait is due to the presence of said S-locus inhibitor (Sli) gene.