Breeding value of 2n pollen (diplandroids) in tetraploid x diploid crosses in potatoes.

The relative breeding value of first division restitution (FDR) and second division restitution (SDR) 2n male gametes from diploids, and n (2x) gametes from tetraploids were compared. This was done by measuring tuber yield of 105 4x families obtained from 4x x 2x (FDR), 4x x 2x (SDR), and 4x x 4x crosses at two locations. All tetraploid families obtained from 4x x 2x (FDR) matings exhibitedheterosis (the mean of the F1 exceeded that of the higher yielding parent), and outyielded other tetraploid families and 4x cultivars at both locations. The tuber yield of 4x x 2x (SDR; families was higher than that of the families derived from 4x x 4x matings, although the 2x parents had significantly lower yield than tetraploid parents. Specific combining ability (S.C.A.) was found to be significant when families obtained from each category (4x x FDR, 4x x SDR and 4x x 4x) were analyzed individually. Both general combining ability (G.C.A.) (2x) and S.C.A. were significant when families obtained from: 1) 4x x FDR plus 4x x SDR; 2) 4x x FDR plus 4x x 4x; and 3) all categories, were analyzed. Only S.C.A. was found to be significant when 4x x SDR and 4x x 4x families were analyzed together. Consistent results were obtained at each of, and over, the two locations. These results strongly demonstrated that FDR gametes were superior in breeding value to either SDR or n (2x) gametes, and were more homogeneous, Gametes formed by SDR might be superior to n (2x) gametes although they were as heterogeneous. Distinct yield differences between 4x x FDR and 4x x SDR families plus the significant G.C.A. (2x) detected when these two categories were compared, substantiated the cytological interpretation of genetically distinct modes of diplandroid formation.