Resistance to frost and tuber soft rot in near-pentaploid Solanum tuberosum - S. commersonii hybrids

The objectives of the present study were to evaluate the tolerance to low temperatures and tuber soft rot in sexual near-pentaploid hybrids between incongruent 2x (1EBN) Solanum commersonii (CMM) and 4x (4EBN) S. tuberosum (TBR). For freezing resistance, killing temperatures both under non-acclimated and un- der acclimated conditions were determined using the ion leakage procedure. Values for the hybrids were dis- tributed between the wild and cultivated parental values. Some hybrids displayed an acclimation capacity close to 2.5°C, typical of hardy species. Artificial inoculation of tubers with Pectobacterium carotovorum ssp. carotovorum (formerly Erwinia carotovora ssp. carotovora) provided evidence of variability in disease response. Highly resistant hybrids were identified. After conventional phenotypic selection, wild genome content was estimated based on the presence of CMM-specific AFLP fragments. Seven primer combinations were used (Eco-AGG/Mse-CAA; Eco-ACC/Mse-CAT; Eco-ACT/Mse-CAC; Eco-ACT/Mse-CAG; Eco- ACT/Mse-CAA; Eco-ACT/Mse-CAT; Eco-AGG/Mse-CAG). The percentages of CMM-specific AFLPs ranged from 4.3% to 56.7%, with an average value of 28.1%. AFLP analysis was employed for the selection of the hybrids to be used for further breeding objectives.