Characterization of the multiple resistance traits of somatic hybrids between Solanum cardiophyllum Lindl. and two commercial potato cultivars.

Interspecific somatic hybrids between commercial cultivars of potato Solanum tuberosum L. Agave and Delikat and the wild diploid species Solanum cardiophyllum Lindl. (cph) were produced by protoplast electrofusion. The hybrid nature of the regenerated plants was confirmed by flow cytometry, simple sequence repeat (SSR), amplified fragment length polymorphism (AFLP), microsatellite-anchored fragment length polymorphism (MFLP) markers and morphological analysis. Somatic hybrids were assessed for their resistance to Colorado potato beetle (CPB) using a laboratory bioassay, to Potato virus Y (PVY) by mechanical inoculation and field trials, and foliage blight in a greenhouse and by field trials. Twenty-four and 26 somatic hybrids of cph + cv. Agave or cph + cv. Delikat, respectively, showed no symptoms of infection with PVY, of which 3 and 12, respectively, were also resistant to foliage blight. One hybrid of cph + Agave performed best in CPB and PVY resistance tests. Of the somatic hybrids that were evaluated for their morphology and tuber yield in the field for 3 years, four did not differ significantly in tuber yield from the parental and standard cultivars. Progeny of hybrids was obtained by pollinating them with pollen from a cultivar, selfing or cross-pollination. The results confirm that protoplast electrofusion can be used to transfer the CPB, PVY and late blight resistance of cph into somatic hybrids. These resistant somatic hybrids can be used in pre-breeding studies, molecular characterization and for increasing the genetic diversity available for potato breeding by marker-assisted combinatorial introgression into the potato gene pool.