Potato clone variation in blackspot and soft rot susceptibility,redox potential,ascorbic acid,dry matter and potassium

Tubers of 11 potato clones were compared for susceptibility to blackspot and soft rot, redox potential, ascorbic acid, dry matter, and potassium content. Evaluations were made before and after 6 mo storage at 3.9C. Clonal behavior was generally consistent over 2 yr. Significant differences occurred among clones for each factor except redox potential. Blackspot and soft rot were positively correlated in 5 of 8 comparisons. Neither blackspot nor soft rot was correlated with ascorbic acid or redox potential. Blackspot was positively correlated with dry matter in the fall but not after storage and was negatively correlated with potassium. Soft rot evaluated in air or air plus 8% CO₂ was positively correlated with dry matter in only 2 of 8 comparisons. Soft rot susceptibility did not increase with storage when inoculated discs were incubated in air but did increase when the discs were incubated in air plus 8% CO₂. Ascorbic acid was negatively correlated with redox potential only before storage and decreased to varying degrees in all clones during storage.