Evaluation for chipping and tuber soft rot (Erwinia carotovora) resistance in potato clones from unilateral sexual polyploidization (2x x 4x)

The aim of this work is the evaluation of tetraploid potato clones with germplasm from S. chacoense and S. phureja for chipping and resistance to tuber soft rot (Erwinia carotovora subsp. carotovora). Tetraploid potato clones were obtained via 2n eggs through 2x-4x crosses. Cytological mechanisms were investigated in the diploid hybrid 2n-egg producer used as parent in the unilateral sexual polyploidization scheme; the omission of the second meiotic division and cytokinesis failure at the end of meiosis were identified with a genetic consequence equivalent to second division restitution (SDR). Tuber marketable yield, specific gravity and chip-processing ability evaluated at harvest and after cold storage with and without reconditioning were higher in some clones as compared to the S. tuberosum tetraploid parent. Tuber soft rot resistance, contributed by S. chacoense, was successfully transferred to the 4x level. After inoculation with Erwinia carotovora subsp. carotovora. and estimation of the rotted area, one tetraploid clone proved to be resistant and three partially resistant. The genetic value of exotic germplasm and sexual polyploidization strategy are discussed in relation to potato improvement.