Production Location Affects Tuber Shape Phenotype of Late-Season Russet Selections and Cultivars from the Northwest Potato Variety Development Program (NWPVDP)

Potato tuber length-to-width ratio (L/W) is an important trait for consumer visual acceptance, pack-out efficiency, French fry production, and waste recovery. In the U.S. Northwest Potato Variety Development Program (NWPVDP), L/W accounts for 13% of the overall postharvest score. Selections with L/W ≥ 1.8 are preferred for maximum raw-product recovery (≥ 7.6-cm-long fries). However, tuber shape often depends on production location. Our objectives were to (1) model the effects of production location on L/W using 26 years of historical data from the NWPVDP, and (2) quantify the variability in tuber shape phenotype of selected NWPVDP varieties across production locations (WA, ID, OR). A mixed linear model demonstrated that tuber L/W was strongly affected by location, year, and location-by-year interactions (40% of total variation), while variety and variety-by-location accounted for 43% of total variation. L/W of the 227-284-g tubers of twenty-two released varieties from the NWPVDP averaged 1.65, 1.70, and 1.92 for WA, OR, and ID, respectively, and ranged from a low of 1.51 and 1.53 (cvs. Payette Russet & Palisade Russet) to a high of 2.06 and 2.12 (cvs. Ranger Russet & Echo Russet) across locations. The round phenotype of Palisade was stable across locations, leading to consistently low fry recovery (84% FW). By contrast, Payette tubers were invariably round in WA and OR, but elongated when grown in ID. The elongated phenotypes of Echo and Ranger from all locations ensured maximum fry recovery (94 to 95% FW), despite the relatively high variation in L/W (9–13%) attributable to location. Collectively, our results suggest an opportunity for genetic selection of L/W that are stable across locations for market specific reductions in shape waste. Future work should focus on identifying key mechanisms which are impacted by production environment for improved stability of L/W. Furthermore, cultural management strategies should be optimized for L/W consistency and usability by all sectors of the potato industry.