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2003 Late Tri-State Trial Postharvest Evaluations

The Tri-State trial is a part of the cooperative cultivar development program conducted at locations in Washington, Oregon, and Idaho. All official entries in this trial are selected by the Tri-State committee. All entries are grown for full season late harvest in each of the three states to determine how they perform when grown under different management and climatic conditions.

The Washington State Late Harvest Tri-State Trial was grown in conjunction with the Late Regional Trial in a grower cooperator field of Russet Burbank near Connell, WA. The trial received the same management as the rest of the circle. The trial had two check cultivar entries (Ranger Russet and Russet Burbank) and eight test clones. The following summarizes the Washington field results along with postharvest results from all three trial locations.

The postharvest evaluations are intended to identify those clones best suited for the French fry processing industry of the Pacific Northwest. The tuber samples are obtained from the Washington, Idaho and Oregon field trials for evaluations of storage and processing quality in Pullman.

Eight numbered clones and two cultivars were evaluated from each growing location. With the exception of A95109-1, all clones outperformed Russet Burbank when averaged across states. The four highest scoring entries were A94053-5 (28.9/35), A95074-6 (26.0/35), AOA95154-1 (25.5/35) and AOA95155-7 (25.0/35). Three of these clones (A94053-5, AOA95154-1, AOA95155-7), along with AO96164-1, produced the lightest colored fries following 63 days storage at 44 and 40°F, indicating resistance to low-temperature sweetening (LTS).

A94053-5 was among the highest scoring entries in last year’s trial, and along with AO96164-1 and AOA95154-1 produced fries with stem end USDA ratings ranging from “0” to no darker than “1” when grown in WA and ID and stored at 40°F this year, reflecting their resistance to LTS. When grown in OR, these three clones also produced the lightest fries when compared with the other clones; however, fry colors of all OR-grown clones were dark, resulting in an unacceptable USDA 4 rating. The higher tendency of OR-grown clones to sweeten during storage at 44 and 40°F this year was undoubtedly a consequence of heat stress experienced at the Hermiston production site. That said, the three top performing clones (A94053-5, AO96164-1, AOA95154-1) reconditioned (3 wks at 65°F) back to USDA 0 when grown in WA and ID and stored at 40°F, and an acceptable USDA 2 when grown in OR.

A95109-1 and A95409-1 were the lowest scoring numbered clones (18.5/35 and 16.1/35, respectively). These clones produced unacceptably dark and/or non-uniformly colored fries from the 48 and 44°F-stored, OR- and ID-grown tubers. On average, these clones produced the darkest fries of all the numbered clones at any storage temperature.

AOA95155-7 ranked fourth in overall ratings and for processing out of 44°F storage. Its ability to retain at-harvest processing quality when stored at 44°F was variable however, depending on production site. AOA95155-7 also produced mottled fries from all three growing locations at all samplings. Relative to all the other clones, AOA95155-7 was highly resistant to blackspot bruise.

As was evident in last year’s trial, Ranger Russet ranked last in wound-healing ability, but in general all clones wound-healed well. All entries received the same or higher taste panel scores than the standard Russet Burbank.

Averaged over production sites, L/W ratios of the 8- to 10-ounce tubers ranged from 1.62 (A95409-1) to 1.96 (Russet Burbank), which translated into an estimated 67 to 73% yield of 3-inch or longer French fries. While the clones differed significantly in L/W ratios, from a practical standpoint, the differences were insufficient to affect the yield of French fries from this particular size class of tubers.

AO96160-3 produced the largest variability in tuber shape across growing locations, while A95074-6 and AOA95154-1 were the least variable. Resistance to change in tuber shape as affected by variation in climate, length of growing season, soils, etc. is desirable for clones being developed for production in the Pacific Northwest.

Potatoes at WSU, PO Box 646414, Washington State University, Pullman WA 99164-6414, 509-335-9502
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