Interspecific potato somatic hybrids between Solanum malmeanum and S. tuberosum provide valuable resources for freezing-tolerance breeding

Key message Freezing tolerance was transferred to cultivated potato from S. malmeanum by protoplast fusion for the first time, and valuable resources for freezing tolerance breeding were obtained. Freezing stress affects the geographic distribution, growth, and development of potato, resulting in yield loss. Solanum malmeanum, a diploid wild species with strong freezing tolerance, was fused with the freezing sensitive dihaploid S. tuberosum by somatic hybridization. In our study, 980 calli were obtained, and 248 differentiated shoots were obtained from the calli. Parental-specific SSR markers were used to analyse the chromosome composition of the 80 randomly selected regenerated plants, obtaining 51 somatic hybrids. Among them, 44 somatic hybrids were tested with ploidy analysis in the years 2016 and 2020. During subculture, the genomic ploidy levels changed due to the composition of the unstable chromosome in 56.82% of the somatic hybrids. The somatic hybrids showed better freezing tolerance than the cultivated parent. Then, freezing-tolerant somatic hybrids were selected to backcross with cultivars, and we obtained valuable breeding resources with enhanced freezing tolerance and tuberization capacity similar to that of cultivars. The correlation analysis showed that freezing tolerance has no relation with tuberization capacity, which indicates that they are controlled by independent genetic loci.

Automated summary

Freezing tolerance was successfully transferred from S. malmeanum to cultivated potato through protoplast fusion. Valuable resources for freezing tolerance breeding were obtained, and breeding resources with enhanced freezing tolerance and tuberization capacity were obtained. The correlation analysis showed that freezing tolerance is not related to tuberization capacity and they may be controlled by independent genetic loci.