Malheur Experiment Station Information for Sustainable Agriculture

Malheur County currently grows about 9,500 acres of potatoes, with an average yield of 402 cwt/acre. Potatoes are grown under contract with potato processors for frozen products for the food service industry. There is very little production for fresh pack or open market, and growers do not have storages on their farms. There is also no production of varieties for making potato chips. There is no potato seed production in Malheur County because high populations of aphids result in virus infection. The varieties grown are mainly 'Shepody', for early harvest and 'Ranger Russet' and 'Russet Burbank' for late harvest. Harvest begins in July, providing potatoes to processing plants straight from the field. The early-harvested fields, about 3,000 acres, are mostly furrow irrigated. For late harvest, August through October, about 6,500 acres are mostly sprinkler irrigated.

Small acreages of some new varieties are contracted by processors each year to study the feasibility of writing contracts for the new varieties. To displace an existing processing variety, a new potato variety needs to have several outstanding characteristics. The yield should be at least as high as the yield of 'Russet Burbank'. The percentage of U.S. No. 1 tubers must be high, and the tubers need to have low reducing sugars for light, uniform fry color and high specific gravity. A new variety should be resistant to tuber defects or deformities caused by diseases, water stress, and heat. It should begin to bulk its tubers early if it is a variety for early harvest. Or, if it is a late-harvest variety, it should be resistant to early vine death, known as the "early die" syndrome. Early die is caused by a disease complex of common soil fungi, mainly Verticillium and Fusarium. A late-harvest variety should continue tuber development late in the growing season.

Potato variety development trials at Malheur Experiment Station in 2001 included an 8-Hill trial of 110 long russet clones from the USDA Agricultural Research Service (ARS) potato breeding program at Aberdeen, Idaho; the Oregon Preliminary Yield trial with 95 entries; the Oregon Statewide trial with 20 entries; the Western Regional Early-harvest Trial with 17 entries; and the Western Regional Late-harvest trial with 17 entries.

The five potato variety trials were grown under sprinkler irrigation on Owyhee silt loam, where winter wheat was the previous crop. The wheat stubble was flailed, the field was irrigated, and disked, then 100 lb P/acre and 50 lb N/acre were broadcast. In the fall, the field was ripped with Telone II injected at 22 gal/acre, and the field was bedded on 36-inch row spacing. A soil test taken on April 17, 2001 showed available nitrate plus ammonia was 89 lb N/acre in the top 2 ft of soil, and the top ft of soil had 24 ppm extractable P, 262 ppm K, 1 percent organic matter, and pH 7.6.

Seed of all varieties was hand cut into 2-oz seed pieces and treated with Tops-MZ- Gaucho dust. The Western Regional Early-harvest trial was planted April 12, 2001, and the other trials were planted April 19 and 20. The 8-Hill trial was unreplicated, the Preliminary Yield Trial had two replicates, and the Statewide, Western Regional Early-harvest, and Western Regional Late-harvest trials each had four replicates. Plots were planted using a two-row cup planter with seed spacing 9 inches in the row, with rows 36 inches apart. The potato rows were sidedressed to provide 60 lb N/acre, 50 lb K/acre, 50 lb S/acre, 25 lb Mg/acre, 8 lb Zn/acre, 1 lb Mn/acre, and 1 lb B/acre. After planting, hills were formed over the rows with a Lilliston rolling cultivator. Prowl at 1 lb ai/acre plus Dual at 2 lb ai/acre, in 30 gal/acre spray mix, was applied and incorporated with the Lilliston on May 1. Matrix herbicide was applied at 1.2 oz/acre on May 7.

Potatoes in the Western Regional Early-harvest Trial had full emergence by May 15, and later planted potatoes had full emergence by May 25. Fungicide applications to prevent late blight infection started with an aerial application of Ridomil Gold and Bravo at 1.5 pint/acre on June 14, and then with Dithane at 4 pint/acre on June 22. Powdered sulfur was applied at 30 lb/acre by airplane on July 14, and again on July 28, to control powdery mildew.

The sprinkler system was operated 18 times, with scheduling based on soil water potential measured with 6 Watermark soil moisture sensors (Irrometer Co. Inc., Riverside, CA) logged by a Hansen AM400 (M. K. Hansen Co., East Wenatchee, Wa). The AM400 unit was read daily through the summer to anticipate crop water needs, and an irrigation was applied when the average soil moisture in the potato root zone approached -60 kPa.

A petiole test taken on June 26 showed nutrient deficiencies were developing. Fertilizer was injected into the sprinkler line during an irrigation on July 3 to supply 20 lb N/acre, 0.25 lb Mn/acre, and 0.2 lb B/acre. A petiole test taken on July 11 showed nutrient deficiencies, so fertilizer was injected into the sprinkler line again on July 19 to supply 20 lb N/acre, 10 lb S/acre, 5 lb Mg/acre, 0.25 lb Zn/acre, and 0.25 lb Mn/acre. Vines were flailed in the early-harvest trial on August 13, and in the late-harvest trials on September 19.

Western Regional Early-harvest potatoes were lifted August 21 with a two-row digger that laid the tubers back onto the soil in each row, and potatoes were visually evaluated in the plots. Visual evaluations included observations of desirable traits, such as a high yield of large, smooth, uniformly shaped and sized, oblong (or "blocky") to long, attractively russetted tubers, with shallow eyes evenly distributed over the tuber length. Notes were also made of tuber defects such as growth cracks, knobs, curved or irregularly shaped tubers, pointed ends, stem-end decay, stolons that remained attached, folded bud ends, rough skin due to excessive russetting, pigmented eyes, or any other defect, and a note to keep or discard the clone based on tuber appearance. Tubers were placed into burlap sacks and hauled to a barn where they were kept under tarps until grading. At grading, a 20-tuber sample from each plot was placed into refrigerated storage for processing quality tests.

The potatoes in the Preliminary Yield trial were dug on September 26, and the potatoes in the Western Regional Late-harvest, Statewide, and 8-Hill trials were dug on September 27 with the two-row digger. At harvest, the potatoes in each plot were visually evaluated. Tubers were graded and a 20-tuber sample from each plot was placed into storage. The storage was kept near 90 percent relative humidity and the temperature was gradually reduced to 45°F.

Tubers were removed from storage November 20 through 30 and evaluated for tuber quality traits. Specific gravity was measured using the weight-in-air, weight-in-water method, and 10 tubers per plot were cut lengthwise and examined for internal defects. Center slices from 10 tubers were fried for 3.5 min in 375°F soybean oil. Percent light reflectance was measured on the stem and bud ends of each slice using a model 577 Photovolt Reflectance Meter (Seradyn, Inc., Indianapolis, IN), with a green tristimulus filter, calibrated to read 0 percent light reflectance on the black standard cup and 73.6 percent light reflectance on the white porcelain standard plate.

Dry weather kept late blight from developing in 2001. No powdery mildew or mite problems were observed in the field, probably due to the sprinkler irrigation keeping the canopy environment moist. Precipitation for April through September was 2.13 inches. Potato evapotranspiration, Et_c, was measured using a U.S. Bureau of Reclamation Agrimet station at the Malheur Experiment Station. The crop Et_c for the early-harvest trial totaled 21.5 inches, and the trial received 22.0 inches of irrigation plus precipitation, or 102 percent of Et_c. For the late-harvest trials Et_c totaled 26.8 inches, and the trials received 27.4 inches of irrigation plus precipitation, or 102 percent of Et_c.

8-Hill Trial

Eight hills were grown of each of 110 clones selected for long, russeted tubers from the Aberdeen ARS potato breeding program. Of the 110 clones, the top 20 were selected, based on tuber type, yield, and grade, for processing quality determination (Table 1). Several of the clones had high yields, good processing quality, and were sufficiently free from defects to warrant growing them in future trials. The clone 'A97210-10' yielded a total of 1,003 cwt, with 81 percent U.S. No. 1 grade tubers, with specific gravity of 1.092 g/cm³ and average fry color of 50.2 percent light reflectance. The clone 'A97019-2' yielded 993 cwt total, with 88 percent U.S. No. 1 grade, with specific gravity 1.102, and fry color 44 percent light reflectance.

Preliminary Yield Trial

In the Preliminary Yield Trial, 95 numbered clones were compared to 'Russet Burbank', 'Ranger Russet', 'Shepody', 'Norkotah', and 'Umatilla Russet' (Table 2). The Oregon potato variety selection committee kept 12 clones to advance to the Statewide trial for 2002. The clones that were kept, 'AO96382-3', 'AO97178-1', 'AO97318-2', 'AO97133-2', 'AO97278-3', 'AO97303-2', 'AO97109-3', 'AO97118-3', 'AO97131-3', 'AO97143-1', 'AO97171-4', and 'AO97175-13', are marked with a asterisk in the entry list. These clones yielded well over the four locations (Hermiston, Klamath Falls, Ontario, and Powell Butte), had high percent U.S. No. 1 grade tubers, and had high specific gravity and light fry color needed for processing.

Oregon Statewide Trial

In the Oregon Statewide Trial, five clones, 'AO94110-203', 'AO96160-3', 'AO96164-1', 'AO96176-3' and 'AO96177-6' were kept by the variety selection committee (Table 3). 'AO94110-203' will advance to the Western Regional Early and Late Harvest trials for 2002. 'AO94110-203' produced a total yield of 690 cwt/acre, with 84 percent U.S. No. 1 grade, good specific gravity of 1.108 g/cm³, and an average fry color reading of 46 percent light reflectance. 'AO96160-3' produced total yield of 582 cwt/acre, with 90 percent U.S. No. 1, specific gravity of 1.100 g/cm³, and fry color of 51 percent light reflectance. 'AO96164-1' produced total yield of 602 cwt/acre, with 80 percent U.S. No. 1, specific gravity of 1.098 g/cm³, and fry color of 50 percent light reflectance., 'AO96176-3' produced total yield of 612 cwt/acre, with 86 percent U.S. No. 1, specific gravity of 1.088 g/cm³, and fry color of 47 percent light reflectance. 'AO96177-6' produced total yield of 605 cwt/acre, with 77 percent U.S. No. 1, specific gravity of 1.104 g/cm³, and fry color of 47 percent light reflectance. 'Russet Burbank' had 55 percent sugar ends, far more than any other variety.

Western Regional Early-harvest Trial

In the Western Regional Early-harvest trial, 'A8893-1' with 619 cwt/acre total yield, 'A90586-11' with 612 cwt/acre, 'AC87138-4' with 573 cwt/acre, 'AC87079-3' with 572 cwt/acre, 'Russet Burbank' with 568 cwt/acre, and 'A9045-7' with 564 cwt/acre were among the highest total yields (Table 4). All of those clones except 'Russet Burbank' had acceptable specific gravity and fry color, and no sugar ends. 'Russet Burbank' produced 10 percent sugar ends. In production of marketable tubers (the total of U.S. No.1 plus U.S. No. 2 grades) 'A8893-1' with 579 cwt/acre, 'A90586-11' with 538 cwt/acre, 'A9045-7' with 529 cwt/acre, and 'AC87079-3' with 521 cwt/acre were among the highest. 'Russet Burbank' produced 110 cwt/acre cull tubers, which was significantly more culls than any other variety in this trial. 'AC87138-4' produced 47 cwt/acre cull tubers.

Western Regional Late-harvest Trial

In the Western Regional Late-harvest trial, among the highest for total yield, 'A90586-11' with 738 cwt/acre, 'AC87079-3' with 679 cwt/acre, 'A8893-1' with 678 cwt/acre, and 'A9045-7' with 678 cwt/acre (Table 5). The clone 'A90586-11' with 668 cwt/acre marketable yield, 'A8893-1' with 649 cwt/acre, 'A9045-7', with 646 cwt/acre, and 'AC87079-3' with 631 cwt/acre produced among the highest marketable yields. The clones 'A8893-1', 'A9014-2', 'AC87079-3', 'AC87138-4', 'TXNS102', and 'TXNS296' were advanced out of the trial, and 'AC91014-2', 'AO92017-6', and 'ATX9202-3RU' were dropped from further testing. All of the other entries will remain in the trials for 2002 to be evaluated an additional year. 'Russet Burbank' had 45 percent sugar ends, more than any other variety.

Table 1. Yield, grade, and processing quality of the top 20 clones out of 110 early selections in an unreplicated 8-Hill Trial, Malheur Experiment Station, Oregon State University, Ontario, OR, 2001.
 

Table 2. Preliminary Yield Trial: yield, grade, and processing quality of potato varieties grown at the Malheur Experiment Station, Oregon State University, Ontario, OR, 2001.

*Advanced to 2002 Statewide Trial based on the results from four locations.

Table 3. Oregon Statewide Trial: yield, grade, and processing quality of potato varieties grown at the Malheur Experiment Station, Oregon State University, Ontario, OR, 2001.