The postharvest evaluations are aimed at identifying clones from the Tri-State Cultivar Improvement Trials that are best suited for the Pacific Northwest potato industry. Tubers grown as part of the Washington, Idaho and Oregon cultural adaptation portions of these programs are evaluated for processing quality and storability at the potato Postharvest Research Laboratory, WSU, Pullman. Industry input has helped to create the current rating system, which is continually being revised based on industry needs and priorities.

The Late Tri-State Trial had nine clones from each growing location, including the standards, Ranger Russet and Russet Burbank.

At harvest, all clones produced light colored fries, although fry color of A92303-7 and AO89128-4.1 was variable from stem to bud end (9 Photovolt unit difference) from two out of three growing locations.

Two clones, A92303-7 and COO93031-3 had specific gravities at or below the cutoff (1.070) when grown in Oregon.

AO89128-4.1 and -4.2 received the highest specific gravity ratings across all three states. On average, these two clones also received the highest taste-panel ratings.

A92303-7 developed significantly less blackspot bruise than most of the other clones. When grown in Washington and Idaho, tubers of this clone were resistant to soft rot relative to the other entries.

COO93031-3 showed the greatest percentage of tissue loss when inoculated with bacterial soft rot.

The length to width ratios of Ranger and Russet Burbank tubers averaged 1.96 and 1.90 across the Tri-state production sites. With the exception of A89384-12, which had a relatively low L/W ratio, the estimated fry yields of the tri-state clones were comparable to the checks. A89384-10 had the greatest variation in usable fry yield, ranging from 57 to 78%, across the Tri-state production sites. Tuber shape and thus French fry yield of AO89128-4.2, Ranger and Russet Burbank varied the least with region of production. Resistance to change in tuber morphology as affected by variation in climate, length of growing season, soils, etc. is desirable for clones being developed for production in the Pacific Northwest.