Potato Variety Trials 2005

 

 

Eric P. Eldredge, Clinton C. Shock, and Lamont D. Saunders

Malheur Experiment Station

Oregon State University

Ontario, OR

 

 

Introduction

New potato varieties were evaluated for their productivity and suitability for processing. Potatoes are grown under contract in Malheur County for potato processors to produce frozen products for grocery outlets and the food service industry. There is very little production for fresh pack or open market, and very few growers have potato storage buildings on their farms. There is also no production of varieties for making potato chips.

 

The varieties grown for processing in Malheur County, Oregon, are mainly ‘Ranger Russet’, ‘Shepody’, and ‘Russet Burbank’. Harvest begins in July, providing potatoes to processing plants directly from the field. Yield of harvests later than mid-August may be limited by the “early die” syndrome, which causes early senescence of the vines of susceptible varieties, especially Shepody and Russet Burbank. Early die is caused by a complex of soil pathogens, including bacteria, nematodes, and fungi, particularly Verticillium wilt. Early die is worse when the rotation between potato crops is shorter.

 

Small acreages of new varieties or advanced selections are sometimes grown under contract to study the feasibility of expanding their use. 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 the currently contracted varieties. The tubers need to have low reducing sugars for light fry color, and high specific gravity. A new variety should be resistant to tuber defects or deformities caused by disease, water stress, or heat.  It should begin tuber bulking early and rapidly if it is a variety for early harvest. Late-harvest varieties should be resistant to early die.

 

Potato variety development trials at the Malheur Experiment Station (MES) in 2005 included the Western Regional Early Harvest Trial with 22 entries, the Western Regional Late Harvest Trial with 22 entries, the Oregon Statewide Trial with 23 entries, the Oregon Preliminary Yield Trial with 120 entries, a Malheur Preliminary Yield Trial of 4 lines selected in previous 8-Hill trials at MES, an 8-Hill trial of 55 clones from the USDA Agricultural Research Service (ARS) potato breeding program at Aberdeen, Idaho, and a Specialty Trial of 28 colored-flesh potato varieties. Through these trials and active cooperation with other scientists in Idaho, Oregon, and Washington, promising new lines are bred, evaluated, and eventually released as new varieties.

 

 

Materials and Methods

 

Seven potato variety trials were grown under sprinkler irrigation on Owyhee silt loam, where winter wheat was the previous crop and potato had not been grown for the past 17 years. A soil test on September 16, 2004 showed 48 lb nitrogen (N)/acre in the top 2 ft of soil, and 52 lb available phosphate (P₂O₅), 1,462 lb soluble potash (K₂O), 48 lb Sulfate (SO₄), 3,348 ppm calcium (Ca), 491 ppm magnesium (Mg), 125 ppm sodium (Na), 3 ppm zinc (Zn), 7 ppm iron (Fe), 6 ppm manganese (Mn), 0.5 ppm copper (Cu), 0.6 ppm boron (B), organic matter 4.2 percent, and pH 8.2 in the top foot of soil. The soil was too wet to work or fumigate in the fall due to 0.56 inch of rain in September followed by 2.03 inch of rain in October. Vapam^® was applied on March 9 at 75 gal/acre using solid set sprinklers and 1.12 inch of water to apply and seal the fumigant. Fertilizer N at 110 lb/acre and sulfur (S) at 100 lb/acre were broadcast on April 6, and the field was bedded on 36-inch row spacing.

 

Seed of all varieties was hand cut into 1.2- to 1.5-oz seed pieces and treated with Tops-MZ^®+Gaucho^® dust 1-2 weeks before planting and placed in storage to suberize. Potato seed pieces were planted in single row plots using a 2-row cup planter with 9-inch seed spacing in 36-inch rows. Red potatoes were planted at the end of each plot as markers to separate the potato plots at harvest, except in the colored-flesh trial where 'Russet Norkotah' was used as the marker.

 

The Western Regional Early Harvest Trial was planted on April 13, 2005. The Statewide Trial, the Malheur Preliminary Yield Trial, the 8-Hill Trial, and the Oregon Preliminary Yield Trial were planted on April 18. The Western Regional Late Harvest and the Specialty Trial were planted on April 19. The 8-Hill trial was unreplicated with plots 8 seed pieces long, the Oregon Preliminary Yield Trial and the Specialty Trial plots were 20 seed pieces long with 2 replicates, and the Statewide, Western Regional Early Harvest, and Western Regional Late Harvest Trials each had 4 replicates with plots 30 seed pieces long.

 

After planting, hills were reformed over the rows with a Lilliston rolling cultivator. Prowl^® at 1 lb ai/acre plus Dual^® at 2 lb ai/acre were applied as a tank mix for weed control on May 2 and were incorporated with 1.7 inch of rain over the next 10 days. Irrigation was applied 27 times (Fig. 1), from June 6 to September 9, with scheduling based on crop evapotranspiration (ET_c) estimated by the U.S. Bureau of Reclamation using data from an AgriMet weather station at MES. Water was measured using an inline flow meter (McCrometer, Hemet, CA).

 

Fungicide applications to control early blight and prevent late blight infection started with an aerial application of Ridomil Gold^® and Bravo^® at 1.5 pt product/acre on June 13. On June 18 Endura^® fungicide at 10 oz product/acre plus Dithane^® at 2 lb product/acre plus Folo Spray 20-20-20 was applied. Dithane at 2 lb product/acre plus liquid sulfur at 6 lb S/acre was applied on June 28. Bravo at 1.5 pt product/acre was applied on July 20. Dithane at 2 lb product/acre plus Tanos^® at 8 oz product/acre was applied on July 28, and on September 6 Bravo was applied at 1.5 pt product/acre. On August 20, liquid sulfur at 6 lb S/acre was applied to prevent two-spotted spider mite infestation.

 

Petiole tests were taken every 2 weeks from June 17 and fertilizer was injected into the sprinkler system during irrigation to supply the crop nutrient needs. A total of 142 lb N/acre, 17 lb P₂O₅/acre, 32 lb K₂O/acre, 45 lb SO₄/acre, 7.5 lb Mg/acre, and 0.4 lb Zn/acre were applied through the sprinkler lines.

 

Vines were flailed in the Western Regional Early Harvest Trial on August 15. Western Regional Early Harvest Trial potatoes were lifted August 22 with a two-row digger that laid the tubers back onto the soil in each row. Visual evaluations included observations of desirable traits, such as a high yield of large, smooth, uniformly shaped and sized, oblong 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. Notes to keep or discard the clone were recorded based on the overall appearance of the tubers.

 

Tubers were placed into burlap sacks and hauled to a barn where they were kept under tarps until grading. After grading, a 20-tuber sample from each plot in the Western Regional Early Harvest Trial was evaluated for tuber quality traits for processing. Specific gravity was measured using the weight-in-air, weight-in-water method. Ten tubers per plot were cut lengthwise and the 10 center slices 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 Photovolt Reflectance Meter model 577 (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.

 

The vines were flailed on the late harvest trials on September 27. The vines of most entries had died by August 30. Potatoes in the Western Regional Late Harvest Trial were dug on October 4. The Specialty Trial tubers were dug on October 5, the Oregon Preliminary Yield Trial on October 5-6, the 8-Hill Trial on October 6-7, and the Statewide Trial on October 7. At each harvest, the potatoes in each plot were visually evaluated as described above. Tubers were graded and a 20-tuber sample from each plot was placed into storage. The storage temperature was gradually reduced to 45°F. Tubers were removed from storage November 2 through 17 and evaluated for tuber quality traits, specific gravity, and fry color as described above. Data from all trials were analyzed with the General Linear Models analysis of variance procedure in NCSS (Number Cruncher Statistical Systems, Kaysville, UT) using Fisher's Protected LSD means separation at the 95 percent confidence level.

Results and Discussion

 

Spring weather at MES in 2005 was cool and wet, followed by summer weather similar to 2004, and similar to the 10- and 60-year averages. No disease or mite problems were observed in the field. Compared to 2004 potato trials at this location, overall yields were greater by about 33 percent, and specific gravity of the tubers was higher.

 

Precipitation for May 1 through September 30 was 1.57 inch, the crop ET_c for the late-harvest trials totaled 30.2 inch, and the trials received 28.58 inch of irrigation plus precipitation, or 94.6 percent of ET_c (Fig. 1). The incremental increases in the irrigation plus rainfall curve show the 27 sprinkler irrigations applied during the growing season.

 

Soil water potential at the seedpiece depth was allowed to become drier at the end of the growing season, after the vines died on the early maturing entries, by applying frequent sprinkler irrigations of short duration, as shown in Figure 1. This was necessary to avoid swollen lenticels and the associated possibility of rotting tubers of early maturing entries, while continuing to supply a portion of the ET_c requirement for late maturing entries in shallow moisture increments.

 

All Trials

Hollow heart, brown center, internal brownspot, and vascular discoloration are common potato internal defects that vary by variety.  These defects often do not occur at MES and were not observed in any of the potato varieties tested at Ontario in 2005.

 

Western Regional Early Harvest Trial

In the Western Regional Early Harvest Trial, the clone producing the highest total yield was 'MWTX2609-2Ru' with a total yield of 802 cwt/acre (Table 1). That clone had specific gravity below 1.080 g cm^-3, a desirable level for processing. The clones that were among the highest in production of marketable tubers for processing (U.S. No.1 plus U.S. No. 2 grades) were 'AO96164-1' with marketable yield of 651 cwt/acre, 'A95409-1' with marketable yield of 641 cwt/acre, and 'TXA549-1Ru' with marketable yield of 634 cwt/acre. Those three clones also had acceptable specific gravity for processing, of 1.080 g cm^-3 or higher.

 

Western Regional Late Harvest Trial

The highest total yield In the Western Regional Late Harvest Trial was produced by MWTX2609-2Ru, with 722 cwt/acre (Table 2). 'ATX91137-1Ru', 'A93157-6LS', TXA549-1, AO96164-1, 'A92030-5', 'Ranger Russet', 'AO96160-3', and 'CO95086-8Ru' were among the highest clones in production of U.S. No. 1 tubers, ranging from 92 to 80 percent. In production of total U.S. No. 1 tubers, among the highest were TXA549-1Ru, A93157-6LS, Ranger Russet, A95409-1, 'A96104-2', AO96164-1, and ATX91137-1Ru ranging from 570 to 495 cwt/acre. MWTX2609-2Ru and Russet Burbank produced significantly more U.S. No. 2 tubers than other clones in this trial. In this late-harvest trial, specific gravity of A92294-6 and 'CO95172-3Ru' were among the highest, and all clones except Russet Norkotah, which is not a processing variety, had specific gravity acceptable for processing into frozen potato products. The clone A93157-6LS has advanced to imminent release.

 

Oregon Statewide Trial

In the Oregon Statewide Trial, six clones marked with an asterisk were retained by the variety selection committee (Table 3). The clone AO96160-3 will stay in the statewide trial and in the Western Regional Trial, 'AO96141-3’ will advance to the Western Regional Trial, and AO96305-3, 'AO96365-2', and 'AO98282-5' will be maintained in the Statewide Trial in 2006. At this location in 2005, AO98205-5, AO96370-2, Russet Burbank, AO99108-5, Ranger Russet, and AO96365-2 produced among the highest total yields. Among the clones producing a high percentage of U.S. No. 1 tubers were AO99099-3, AO96305-3, AO98133-2, AO98307-6, AO98123-2, COO00254-9, AO96164-1, and AO98268-5. Russet Burbank produced 84 cwt/acre cull tubers, significantly more culls than any other entry, and had 13 percent sugar ends.

 

Oregon Preliminary Yield Trial

In the Preliminary Yield Trial, 116 numbered clones were compared to Russet Burbank, Ranger Russet, Shepody, and Russet Norkotah (Table 4). The Oregon potato variety selection committee kept 14 clones, based on their performance at Hermiston, Klamath Falls, Powell Butte, and Ontario, to advance to the Statewide Trial for 2006. The clones that were advanced were: 'AO98086-1', 'AO98104-1', 'AO98129-4', 'AO98170-4', 'AO99178-2', 'AO99179-1', 'AO99179-4', 'AO99192-2', 'AO00018-3', 'AO00024-7', 'AO00057-2', 'AO00076-4' – depending on taste evaluation, 'AO00088-11', and 'AO01012-4'. These clones yielded well across the four locations (Hermiston, Klamath Falls, and Powell Butte data are not shown in this report), had a low incidence of undesirable characteristics, had high percent U.S. No. 1 grade tubers, and had high specific gravity, light fry color, and resistance to developing sugar ends in response to stress.

 

Malheur Preliminary Trial

This was the third year for the Malheur Preliminary Trial, a cooperative project by MES and the USDA/ARS. Four clones from previous 8-Hill trials at Malheur were selected for their adaptation to the high early die disease pressure, heavy soil texture, and the hot, dry climate of Treasure Valley. These clones were compared to Russet Burbank, Ranger Russet, and Shepody (Table 5). The clones 'A00551-50LB', 'A0068-5', 'A97320-1', and 'COA00329-1' had specific gravity above 1.080 g cm^-3, a level desirable for processing. The clone 'COA00329-1' produced 5 percent sugar ends.

 

8-Hill Trial

Eight hills were grown of each of 55 clones selected for long, russet tubers from the Aberdeen ARS potato-breeding program, including 4 clones with the LB suffix signifying that they were bred for resistance to late blight. The 55 clones were evaluated for tuber type, yield, grade, and processing quality (Table 6). The clones 'A99093-14', 'A01025-19', 'A01024-7', 'COA01082-4', 'A01302-64LB', 'A01010-3', 'A01007-2', 'A01590-60', 'A01010-1', 'A99109-5', 'A01025-13', and 'A99076-7' had high total yield and produced 80 percent or higher of U.S. No. 1 tubers, with specific gravity higher than 1.080 g cm^-3 and light fry color suitable for processing.

 

Specialty Preliminary Trial

This was the first year for a colored-flesh potato variety trial at MES (Table 7). Potato tubers with red to yellow carotinoid or red, blue, and purple anthocyanin pigments are of interest because of the anti-oxidant properties of those pigments in human nutrition. The clones 'POR01PG20-12', 'POR01PG22-1', 'PA97B36-3', 'POR00PG4-1', 'POR01PG16-1', 'POR01PG45-5', 'POR02PG2-4', 'POR02PG5-1', 'POR02PG12-1', 'POR02PG26-11', and 'POR02PG37-2' will advance to the Statewide Specialty Trial for 2006.The clones 'POR02PG26-6' and 'POR02PG2-4' had the highest yields of the 26 clones, far higher than the check varieties 'Yukon Gold' and 'All Blue'. The clone POR02PG26-6 produced 1,339 cwt/acre of tubers that were irregular shapes, with yellow skin with pink eyes, and a light yellow flesh. The clone POR02PG2-4 produced 1,174 cwt/acre of round tubers with a purple-red skin and purple-red to mottled-red flesh. Both clones had a good size distribution for fresh market, but both also had tubers that adhered to the stolons.

 

 

Figure 1. Crop evapotranspiration (ET_c) and sprinkler irrigation applied (plus rain) to potato variety trials, Malheur Experiment Station, Oregon State University, Ontario, OR, 2005.

 

Table 1. Western Regional Early Harvest Trial potato yield, grade, and processing quality, Malheur Experiment Station, Oregon State University, Ontario, OR, 2005.