The United States Potato Genebank Holding of cv. Desiree is a Somatic Mutant of cv. Urgenta

Genome-wide markers enable routine confirmation of whether varieties are true-to-type, and when they are not, to infer their identity. The objective of this study was to determine the basis of a previously described chromosome translocation, tr8-7, which was apparently polymorphic among holdings of the tetraploid potato (Solanum tuberosum L.) cultivar Desiree. Through analysis of publicly available genotype data from North American and European tetraploid potato germplasm, we resolved a longstanding mistaken identity of the United States Potato Genebank holding of Desiree, which is actually a somatic mutant of its maternal parent, cv. Urgenta. Comparison of multiple holdings revealed that tr8-7 was a somatic mutation that occurred at least 25 years ago and was maintained in isolated lineages. Holdings from other institutions lacked tr8-7 and were confirmed as Desiree by trio analyses, suggesting that the mixup affected the United States Potato Genebank and institutions that received Desiree from there. In the face of inevitable mutations and human error, we recommend validation of potato germplasm collections with pedigree and genomic information. To that effect, we provide molecular markers to distinguish the varieties investigated in this study.