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Potato varieties Russet Burbank, Umatilla, and Shepody were grown in two side by side field trials at the Malheur Experiment Station in 1997 under sprinkler irrigation. Tubers were dug September 18 and 19, graded, and a twenty tuber sample of each variety was placed in refrigerated storage. The stored samples were removed October 7 and specific gravity, sugar percentages, and fry color were measured. The varieties Russet Burbank, Umatilla, and Shepody differed significantly for most measured parameters. Umatilla had good yield, high percent number one tubers, low production of under four ounce tubers compared to Russet Burbank, less dark stem-end fry color, and higher tuber solids than Russet Burbank or Shepody.
Russet Burbank is the old industry standard variety for processing, is late maturing and keeps well in storage. Russet Burbank has many defects such as a tendency to produce sugar ends (tubers with excess levels of reducing sugar that fry too dark), excessive small tubers, too many misshapen tubers, and inconsistent performance. Consequently, newer varieties are being developed for the processing industry. Shepody, a recently adopted variety for processing, has good internal qualities of low reducing sugar and high specific gravity; it bulks the tubers faster and can be harvested sooner than Russet Burbank; and produces more large tubers. Shepody has had problems with low specific gravity when grown in the Treasure Valley of eastern Oregon and southwestern Idaho. Umatilla is a new variety (AO82611-7) selected by the variety development program led by Al Mosley at Corvallis, with Ken Rykbost at Klamath Falls, Steve James at Powell Butte, Oscar Gutbrod at Corvallis, Dan Hane at Hermiston, and Joey Ishida, Eric Eldredge, and Clint Shock at Ontario. Consistently across locations and years, Umatilla has yielded as well as Shepody and Russet Burbank and has processing quality better than Shepody. The trials reported here were conducted to compare Umatilla to Russet Burbank and Shepody for tuber yield, grade, and processing quality.
Materials and Methods
Potato varieties Russet Burbank, Umatilla, and Shepody were planted May 2, 1997, in alternating three row strips, separated by border rows of Russet Burbank. The order of the three rows of varieties in each plot was random. The Statewide Variety Trial in the same field also included four replicates of each of these three varieties, and received the same management. Treated 2 oz seed pieces were planted 9 inches apart in the row with rows spaced 36 inches apart. Admire at 19 oz/acre was applied in the seed furrow at planting. Standard cultural practices of weed control and fertilizer were followed. Urea was sidedressed after planting at 114 lb N/ac. Both trials were irrigated with solid set sprinklers. Solution 32 fertilizer was applied through the sprinkler system June 25 to supply 85 lb N/acre. Matrix herbicide was applied at 0.25 oz ai/acre on June 10. The crop was protected from insects, diseases, and mites by aerial applications: on June 24, June 30, and July 7, Bravo at 0.19 gal/acre plus Thiodan at 0.25 gal/acre, Dithane at 0.4 gal/acre on July 21, August 13 Dithane at 0.5 gal/acre, plus Kocide at 0.25 gal/acre, plus sulfur at 5 lb/acre, and August 22, sulfur at 3.4 lb/acre plus Comite at 0.29 gal/acre.
The potato vines were destroyed with a flail mower September 8, and tubers were lifted with a mechanical potato digger and picked by hand into burlap sacks September 17-19. The sacks of potatoes were stored under tarps on pallets in a barn until they were graded on September 26 and 29. Twenty tuber samples were taken of each variety in each plot from the Comparison Trial, and placed in refrigerated storage. On October 7 the samples were taken to the J.R. Simplot fresh laboratory in Caldwell, Idaho, to measure specific gravity, fry color, and percentages of sucrose and reducing sugars. Yield, grade, and processing quality data were evaluated using ANOVA. Where significant differences were present, the LSD was calculated.
Results and Discussion
On June 19, Russet Burbank plants were 20 inches tall, 30 inches wide, dark green color, in bud stage with 12 fully expanded leaves, and a good set of tubers averaging 1 inch long. Umatilla plants were 18 inches tall, 23 inches wide, medium green color, in bud stage with 13 fully expanded leaves and tubers 1/4 inch diameter. Shepody plants were 19 inches tall, 26 inches wide, lighter green color than the other two varieties, with first flowers blooming, 14 fully expanded leaves per stem, and tubers 1/2 inch long. The potato plants all developed uniformly, and no nutritional imbalance, insect, disease, mite, or weed problems were present to limit crop growth and development.
Umatilla and Shepody produced significantly more US Number One tubers over 12 oz than did Russet Burbank (Table 1). Umatilla and Shepody produced significantly fewer 4-6 oz, and more 6-12 oz US Number One tubers than Russet Burbank. Russet Burbank produced significantly less marketable yield, more tubers less than 4 oz, and lower total yield than Umatilla or Shepody. No significant differences between varieties were measured for US Number Two size categories, rot, and percentage of US Number One tubers.
Percentage of Number One tubers over 12 oz was significantly less with
Russet Burbank than Umatilla or Shepody. A significant difference was detected
between each variety in specific gravity, with Russet Burbank the lowest
in total solids, followed by Shepody, and Umatilla with the highest tuber
total solids. A significantly greater percentage of Russet Burbank tubers
darkened excessively when fried, than did Umatilla or Shepody.
Table 1. Two comparisons of Russet Burbank, Shepody, and Umatilla potato yield and processing quality, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1997.
||Tuber grade||Total yield|
|US Number One||US
< 4 oz
|Percent US Number One||Tuber
|Dark fry colors|
|4-12 oz||> 12 oz||Total|
|Statewide Variety Trial|
|Average of trials|
NS: not significant