Genotype and variable nitrogen effects on tuber yield and quality for red fresh market potatoes in Minnesota

Potato (Solanum tuberosum) production generally requires added nitrogen (N), which is costly and potentially environmentally damaging. One path to limiting N application is breeding N efficient potatoes. Effective use of nitrogen, across crops, is typically characterized in terms of yield. However, tuber quality characteristics affect potato marketability, especially for red fresh market potatoes. While optimal N rates maximize yield, the genotype-specific effect of N on tuber quality traits is unclear. In order to highlight quality traits effected by N, identify germplasm with lower N requirements, and determine optimal N rates for red-skinned clones, we conducted a variable N rate experiment over two years in Minnesota. Eight red fresh market genotypes were grown in RCB factorial design with five nitrogen application rates ranging from 0 to 81.6 kg/ha. Best linear unbiased estimates were calculated for yield, skin color, skin set, and tuber shape. The models for yield and quality traits included significant genotype by N rate interaction effects, suggesting that there is variation in the way clones respond to N. Established varieties were more responsive to added N than breeding lines. Similarly, established varieties tended to produce more oblong tubers under higher N conditions, while the breeding lines remained round. Color traits also responded to N in a genotype-specific way, while the interaction effect for other traits depended on unmeasured environmental factors. No clone exhibited increased yield above the 54.4 kg/ha rate. Our results suggest that the 81.6 kg/ha rate produced less favorable phenotypes for all traits.