Unraveling the Heterozygosity in Unique Structured Diploid Populations of Potato

Cultivated potato, Solanum tuberosum L. (2n=4x=48), is a vegetatively propagated heterozygous autotetraploid. Due to its asexual propagation and autotetraploidy, potato has a greater probability of retaining deleterious gene mutations than sexually propagated diploids. We constructed three diploid potato populations (one segregating F1 population, two haploid populations) to study biomass production and a complex of phenotypic traits associated with fitness. An F1 mapping population was developed from a cross between the sequenced doubled monoploid Solanum tuberosum Group Phureja DM 1-3 516 R44 and a heterozygous outcrossing Solanum tuberosum Group Tuberosum clone, RH89-039-16. Atlantic and Superior tetraploid cultivars were used to generate haploid populations. These populations were phenotyped in the field for six traits. Yield (total tuber yield – TTY, average tuber weight – ATW and number of tubers per plant – TS), food quality (specific gravity – SPGR), and plant development traits (Vigor, maturity – Mat) were measured. The haploid populations showed extreme phenotypic variation, including a high rate of reduced male fertility. Sixteen different quantitative trait loci (QTL) were identified in the F1 population. These QTL are now being study in a subset of individual F1s with extreme phenotypes. We expect to identify genomic regions closely associated with genes coding for the traits. Our efforts to probe the genetic complexities of potato will serve as a model genomics system for other vegetatively propagated, highly heterozygous crops with similarly intractable breeding systems.