Reinventing Potato at the Diploid Level

The outcrossing polyploid nature of cultivated potato has hindered the use of genomics resources to dissect the genetic basis of agronomically important traits.  Reversion to the diploid level allows us to apply powerful tools toward this effort. Parthenogenesis generates diploid cultivated potatoes, which can then hybridize to wild relatives, most of which are diploid.  While most diploid potatoes are self-incompatible, the dominant Sli gene, found in a wild relative, allows self-pollination.  We are using this gene to create the first series of recombinant inbred line (RIL) populations in potato for mapping traits of interest to breeders, including yield components, processing quality, and disease resistance.  As we self-pollinate lines to create RILs, SNP markers indicate that the approach to homozygosity is slower than expected.  The most prevalent challenge during inbreeding is male sterility.  In the field, F3 and F4 families vary in vigor and fertility, but the most vigorous families are not necessarily the highest-yielding.  We have also created another diploid genetic resource, an F2 population produced by self-pollinating a hybrid between a cultivated doubled monoploid (DM1-3) and an inbred self-compatible wild species clone (M6). This population is a genetic resource that segregates for many traits.  For example, using genome-wide SNP markers, we mapped both yellow flesh and pigmented skin color to their known locations on chromosomes 3 and 10.