Interspecific potato somatic hybrids between Solanum tuberosum and S-cardiophyllum, potential sources of late blight resistance breeding

Solanum cardiophyllum Lindl. (PI 341233) (2n = 2x = 24, 1EBN) is a diploid wild potato species highly resistant to late blight, the most serious disease of potato. However, it poses a problem of sexual incompatibility with common potato. So to circumvent this problem, in this study, we developed interspecific potato somatic hybrids between cultivated S. tuberosum dihaploid C-13 and wild species S. cardiophyllum via protoplast fusion. Out of 26 regenerants, only 4 were confirmed as true somatic hybrids containing both parental genomes based on molecular markers and phenotypes. Somatic hybrids were identified by RAPD, ISSR, SSR, AFLP and cytoplasm (chloroplast and mitochondrial genomes) type molecular markers. Intermediate phenotypes of somatic hybrids were confirmed by leaf, flower and tuber traits. Late blight resistance of the hybrids was assessed by challenge inoculation of P. infestans under controlled conditions. Somatic hybrids were found tetraploid by flow cytometry, exhibited high pollen stainability by acetocarmine staining and formed berries and viable seeds after crossing with a common potato variety. Somatic hybrids possessed diverse cytoplasm types (W/alpha, W/gamma and T/beta) as assessed by chloroplast and mitochondrial genome-specific markers. Further, cluster analysis based on the Jaccard's coefficient of molecular profiles generated by all above markers showed genetic distinctness in somatic hybrids and parents. Taken together, these interspecific somatic hybrids with diverse cytoplasm background have potential to be employed in potato breeding programmes to widen the cultivated gene pool through conventional and molecular methods.