Introgression of bacterial wilt resistance from Solanum melongena to S . t uberosum through asymmetric protoplast fusion

Bacterial wilt (BW) caused by Ralstonia solanacearum is an important disease of many plant species especially Solanaceae. To compensate for lack of BW resistance in cultivated potato, we fused UV-treated protoplasts of a resistant eggplant variety with protoplasts of a susceptible potato clone to obtain 32 somatic hybrids. Although asymmetric protoplast fusion has the potential to transfer traits from distant species, introgression frequency and preference of alien fragments remain obscure, as well as the genetic basis for control of a trait. In the present research, the genome components of 32 somatic hybrids were determined by parent-specific SSRs. Each hybrid had integrated from one to eight alien chromosome fragments, providing a foundation for selection of BW resistance transmitted from eggplant. When the selected eggplant sequences were aligned with potato genome sequence it showed a similarity of 46.7 %, suggesting a large genetic distance between these two species. The results also revealed that introgression of eggplant fragments is non-selective, which may allow any part of alien chromosomes to be integrated. Distribution of eggplant loci in individual hybrids suggested a possible relationship between markers emk03O04, emi04P17 and emd13E02a and BW resistance, which are potential loci that control target traits and therefore deserve further investigation. With genome-wide selection of parent-specific molecular markers and sequence alignment, the present research substantiated interspecific introgression of a trait lacking in potato. Moreover, an efficient strategy was established to estimate genomic components of the somatic hybrids, and to explore the candidate loci that associate with target traits.