Erwinia resistance in backcross progenies of Solanum tuberosum x S. tarijense and S. tuberosum (+) S. commersonii hybrids

The resistance to tuber soft rot caused by Erwinia carotovora of Solanum tuberosum x S. tarijense and S. tuberosum (+) S. commersonii hybrids and their backcrosses is reported. A number of resistant diploid sexual hybrids and tetraploid/hexaploid somatic hybrids were selected. Backcross progenies were obtained through 2x x 4x crosses involving a resistant diploid hybrid and tetraploid S. tuberosum, and through 4x x 4x crosses between a resistant somatic hybrid and S. tuberosum. The hybrids showed high variability in terms of resistance to tuber soft rot. The resistance of progeny from 2x x 4x backcrosses was similar to that of the parental sexual hybrid. By contrast, the resistance of genotypes deriving from 4x x 4x backcrosses was reduced compared with the resistant somatic hybrid. In general, tuber characteristics of the backcross hybrids improved considerably as compared with their parents, and tuber yield per plant was good.