Morphological and molecular evidence of natural interspecific hybridization in the diploid potato Solanum kurtzianum from Argentina

The common potato, Solanum tuberosum L. subsp. tuberosum, is a tetrasomic tetraploid. This subspecies has approximately 220 related tuber-bearing species that constitute a genetic pool of enormous breeding value. The diploid species Solanum kurtzianum Bitter et Wittm., described as resistant to drought and nematodes, grows in northwestern and western Argentina and can naturally hybridize with the related diploids Solanum chacoense Bitter, Solanum spegazzinii Bitter, and Solanum maglia Schltdl., in areas of sympatry. In this species, the variability for morphological phenotypes and pollen-pistil relations in intra- and interspecific crosses is large. To investigate whether S. kurtzianum accessions available at the Germplasm Bank in Argentina belong to one taxon with great morphological plasticity or are hybrid and (or) segregant populations, these and accessions of the other three species were characterized using morphological and molecular (SSR) markers. Data were statistically analyzed with ANOVAs and AMOVA. With univariate ANOVA, only 11 characters out of 33 evaluated were statistically significant among species, With multivariate analyses, the grouping did not reflect a priori taxonomic assignments; when population averages were used, a tendency was observed towards grouping by geographical origin. With the AMOVA, only individuals within accessions were separated. Interspecific hybridization and introgression in areas of sympatry can explain these results.