Malheur Experiment Station Information for Sustainable Agriculture

Oregon's Malheur County currently grows about 10,500 acres of potato, under contract with potato processors for frozen fries for the fast food industry. There is virtually no production for fresh pack, open market, or storage on the grower's farm. There is also no production of varieties for making potato chips. Because of severe aphid pressure leading to virus infection, there is no potato seed production in the irrigated northeastern part of Malheur County. Harvest begins in late July, to provide potatoes to processing plants straight from the field. The early harvested fields, about 4,700 acres, are mostly furrow irrigated. For late harvest, September through October, about 5,800 acres are mostly sprinkler irrigated. Average yield is 425 100-lb sacks (or cwt) per acre, and the varieties grown are mainly 'Russet Burbank', 'Shepody', and 'Ranger Russet'.

Small acreages of some newer varieties are contracted by processors each year to study the profitability of writing contracts for more acres of the newer varieties. To replace an existing processing variety, a new potato variety needs to have several outstanding characteristics. Total yield should be at least as high as the yield of 'Russet Burbank'. The percentage of USDA No. One tubers must be high, and the tubers need to have low sugars and high specific gravity for light, uniform fry color. A new variety should be resistant to tuber defects or deformities caused by diseases 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 "early die." Early die is caused by a disease complex of common soil fungi, mainly Verticillium and Fusarium. A late harvest variety should continue to bulk its tubers late in the growing season.

Potato variety development at Malheur Experiment Station in 2000 included an 8-Hill trial of 53 long russet clones from the USDA Agricultural Research Service potato breeding program at Aberdeen, Idaho, the Oregon Preliminary Yield and Oregon Statewide trials, and the Western Regional Early and Late Harvest russet trials.

The five furrow-irrigated potato variety trials were grown in a field of 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 20 lb N/acre were broadcast. On October 12, 1999, the field was ripped with Telone II injected at 22 gal/acre, and the field was bedded on 36-inch row spacing on November 16. A soil test March 30, 2000 showed available nitrate plus ammonia nitrogen totaled 106 lb N/acre in the top 2 ft of soil, 41 ppm extractable P, 484 ppm K, organic matter 1.7 percent, and pH 6.7.

Seed of all varieties was hand cut into 2 oz seed pieces and treated with Tops MZ dust. The Western Regional Early trial was planted April 20, 2000, and the other trials were planted May 1, 2000. 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, and Thimet 20G was metered into the seed furrow at planting at 1.7 oz/100 ft of row. The potato rows were sidedressed to provide 102 lb N/acre, 10 lb Zn/acre, 6 lb Mn/acre, and 2 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 4, 2000.

Potatoes in all the trials had emerged by May 26. Fungicide applications to prevent late blight infection started with an aerial application of Bravo at 1.5 pint/acre on the evening of June 6, and then with Dithane at 4 pint/acre on June 16. Powdered sulfur was applied at 30 lb/acre by airplane July 11, and again on August 3, to control powdery mildew. Vines were flailed off the plants in the early harvest trials on August 21. Western Regional Early Harvest potatoes were lifted August 23 and 24 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 on 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. 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 line based on tuber appearance. Plots with excessive water rot were also noted, to be excluded from the statistical analysis. Tubers were placed into burlap sacks and hauled to a barn where they were kept under tarps until grading, on August 29 and 30. At grading, a 20-tuber sample from each plot was placed into refrigerated storage for processing quality tests.

Vines were flailed off the Western Regional Late, Statewide, Preliminary Yield, and 8-Hill trials on August 29. The potatoes were lifted on September 5 and 7 with a two-row digger that laid the tubers back onto the soil in each row. At harvest, the potatoes in each plot were visually evaluated and plots with excessive water rot were excluded from the statistical analysis. Tubers were graded September 8, 11, and 12, and samples from each plot placed into storage. The storage was kept near 100 percent relative humidity and the temperature was gradually reduced to 45°F. Tubers were removed from storage November 14 through 30 and evaluated for tuber quality traits, specific gravity was measured, and ten tubers per plot were cut lengthwise and examined for internal defects. Center slices from ten tubers were fried for 3.5 minutes in 375^oF 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.

The summer of 2000 was not intensely hot, with the highest temperature 102°F on August 2. The heat was prolonged, however. During June, July, and August, there were 7 days 100°F or higher, and 56 days 90°F or hotter. Daytime high temperatures over 86°F are stressful for potato, and 70 days between June 1 and August 31 had high temperatures of 86°F or above. Powdery mildew was found on the foliage of potatoes in the trial on July 6. Powdery mildew is often a problem on potato in Malheur County, and was widespread in 2000. The unusually hot, dry weather in June allowed the pathogen to infect the crop, and the prolonged hot, dry weather in July and August favored the spread of powdery mildew and made control difficult in potato and other crops. Dry weather prevented late blight from developing in 2000.

Hot weather also increases evapotranspiration. The monthly total pan evaporation in 2000 measured at the U.S. Weather Bureau Class A pan at Malheur Experiment Station exceeded the 52-year average for the month of June by 21 percent, July by 14 percent, and August by 25 percent. To prevent tuber defects associated with water stress, irrigations were applied when Watermark soil moisture sensors in the crop root zone indicated that the soil water potential would fall below -60 centibar the following day if an irrigation was not applied. The more frequent irrigations, the higher than normal soil temperature due to the prolonged heat, and frequent crops of potato in the field's rotational history, led to the development of water rot, especially in a low spot in the field. Water rot reduced the yield of all the furrow-irrigated potato variety trials in 2000.

8-Hill Trial

In the 8-Hill trial of early selections of long, russeted varieties, 53 clones were tested (Table 1). The line 'A96003-23' yielded a total of 647 cwt, with 90 percent No. 1 grade tubers, with high specific gravity of 1.099 g/cm^-3 and average fry color of 50.3 percent light reflectance. The line 'A96079-2' yielded 426 cwt total, with 79 percent No. 1 grade, with acceptable fry color and specific gravity, but did produce some tubers with knobs. Only 'A96003-23' and 'A96079-2' had high enough yield and were sufficiently free from defects to warrant growing them at this site again.

Preliminary Yield Trial

In the Preliminary Yield Trial, 76 lines were compared to 'Russet Burbank', 'Ranger Russet', 'Shepody', 'Norkotah', and 'Atlantic' (Table 2). The Oregon potato variety selection committee kept 12 lines for another year, advancing them to the Statewide trial for 2001. Six of the lines, 'AO92019-4', 'AO94004-3', 'AO96160-3', 'AO96165-2', 'AO96165-9', and 'AO96262-1', appear in the entry list. The other six had excessive water rot at this location and data are not shown. Of the six lines with data for this location, 'AO92019-4', 'AO96125-9', 'AO96165-2', and 'AO96165-9' had mediocre total yield and/or dark fry color. The lines 'AO94004-3' and 'AO96160-3' both yielded over 400 cwt, produced over 80 percent No. 1 grade tubers, and had high specific gravity and light fry color.

Oregon Statewide Trial

In the Oregon Statewide Trial, the lines 'AO87277-6', and 'AO91812-1' graduated out (Table 3).The line 'AO87277-6' will move into the variety release procedure as a fresh market variety named 'Wallowa Russet'. 'AO92017-6' graduated to the Western Regional Early and Late Harvest trials for 2001, and 'AO94110-203' was retained for another year in the Statewide trial. The line 'AO94110-203' produced a total yield of 488 cwt, with 74 percent No. 1 grade, good specific gravity of 1.095 g/cm^-3, and an average fry color reading of 45 percent light reflectance. 'Zolushka' and 'Catalina' tubers were so irregular that they would have been discarded, but they are of interest because they are varieties that can be grown from true potato seed. They are proprietary varieties that were entered by Bejoseeds, and will be grown from cut seed again in the 2001 Oregon Statewide Trial. All of the other clones were discarded following this trial.

Western Regional Early Harvest Trial

In the Western Regional Early Harvest trial, 'ATX9202-3RU' had 436 cwt total yield, which was significantly higher than the check varieties 'Ranger Russet' and 'Shepody' (Table 4). The line 'ATX9202-3RU' had acceptable specific gravity and fry color, and no dark ends. All of the other varieties produced unacceptable dark fry color, or had dark ends. In the Western Regional Late Harvest trial, none of the entries matched 'Russet Burbank' for total yield, except 'A9045-7', with 459 cwt total yield (Table 5). The line 'A9045-7' produced 80 percent U.S. No. 1 grade tubers, and appeared to be a productive variety without excessive tuber defects. In the Western Regional Early and Late Harvest trials, 'A8792-1', 'PORTGNP3-138', 'PORTGS124-1', and 'PORTGS129-1' were advanced out of the trial, and all of the other entries will remain in the trials for 2001 to be evaluated an additional year.

Table 1. 8-Hill Trial early selection 'Aberdeen' clones: yield, grade, and processing quality, Malheur Experiment Station, Oregon State University, Ontario, OR, 2000.

Table 2. Preliminary Yield Trial: yield, grade, and processing quality, Malheur Experiment Station, Oregon State University, Ontario, OR, 2000.

*advanced to Statewide, also advanced were AO96060-1, AO96065-7, AO96164-1, AO96176-3, AO96177-6, and AO96272-1.

Table 3. Oregon Statewide Trial: yield, grade, and processing quality, Malheur Experiment Station, Oregon State University, Ontario, OR, 2000.

		U.S. No. 1									Average
Variety	Total  yield	Percent No. 1	Total	>12 oz	4 to 12 oz	<4 oz	U.S. No. 2	Cull	Length-to- width ratio	Specific gravity	fry color, light reflectance	Sugar  ends
	cwt/acre	%	--------------------------cwt/acre------------------------------								%	%
Russet Burbank	448	42	186	29	157	98	140	19	2.43	1.078	34.3	33
Ranger Russet	377	62	235	79	156	38	94	8	1.99	1.095	45.3	0
Shepody	388	59	228	102	126	48	103	8	1.72	1.084	42.4	26
Norkotah	373	73	274	46	228	24	58	9	1.88	1.067	19.7	3
Atlantic	502	82	411	194	216	49	17	23	1.06	1.095	49.1	0
AO87277-6	359	65	234	36	198	64	49	13	2.04	1.090	45.7	0
AO89128-4.1	416	58	247	77	170	34	118	17	2.11	1.093	49.0	1
AO89128-4.2	434	44	190	2	194	159	79	6	2.26	1.092	52.5	0
AO91812-1	428	70	299	18	281	93	17	18	1.00	1.088	48.4	0
AO92007-2	415	65	271	79	192	72	58	14	2.15	1.083	35.2	5
AO92017-6	398	58	231	40	191	74	87	5	2.03	1.083	41.9	5
COO93031-3	455	73	336	172	164	39	61	19	2.39	1.075	32.6	10
AO92252-1	353	67	237	28	209	53	56	6	2.13	1.097	44.7	3
AO94110-203	488	74	361	92	268	47	66	14	1.88	1.095	45.0	0
AO94117-201	509	60	320	155	165	48	106	34	1.78	1.087	42.9	4
AO94171-2	412	64	265	46	219	57	76	13	1.92	1.087	35.7	0
AO95115-3	338	62	215	28	187	83	25	14	2.05	1.089	44.8	3
AO95115-6	347	72	251	58	193	47	9	40	1.90	1.068	32.0	6
AO95135-5	502	73	369	141	229	40	68	25	1.76	1.080	40.6	3
Zolushka	458	58	268	50	217	151	31	9	1.40	1.083	33.6	5
Catalina	451	55	249	37	212	143	53	6	1.40	1.078	34.9	10
Mean	421	64	270	72	199	70	65	15	1.87	1.085	40.5	6
LSD (0.05)	78	10	81	49	56	35	32	NS	0.17	0.007	6.0	15

Table 4. Western Regional Early Harvest Trial: yield, grade, and processing quality, Malheur Experiment Station, Oregon State University, Ontario, OR, 2000.

Table 5. Western Regional Late Harvest Trial: yield, grade, and processing quality, Malheur Experiment Station, Oregon State University, Ontario, OR, 2000.

		U.S. No. 1									Average
Variety	Total  yield	Percent No. 1	Total	>12 oz	4 to 2 oz	<4 oz	U.S. No. 2	Cull	Length-to- width ratio	Specific gravity	fry color, light reflectance	Sugar  ends
	cwt/acre	%	--------------------------cwt/acre-----------------------------								%	%
Russet Burbank	466	41	187	28	159	9	184	33	2.88	1.0774	31.3	91
Ranger	335	63	207	55	151	5	71	21	2.23	1.0909	41.7	3
Norkotah	327	79	260	56	204	4	23	19	1.93	1.0703	19.9	3
A8792-1	343	67	228	49	180	7	51	16	1.78	1.0837	42.2	5
A8893-1	350	69	241	121	120	5	55	19	2.16	1.0730	34.0	6
A9014-2	300	71	211	111	101	4	50	13	2.03	1.0874	54.0	1
A9045-7	459	80	368	98	270	6	45	10	1.93	1.0898	38.3	0
AC87079-3	274	69	185	76	110	3	41	27	2.12	1.0890	36.4	16
A90586-11	319	63	197	1	196	13	24	12	1.89	1.0876	34.1	11
AC87138-4	384	69	265	50	215	10	38	13	1.99	1.0853	37.1	1
AC89536-5	271	71	195	31	164	7	25	8	2.05	1.0898	40.3	3
ATX9202-3RU	381	69	265	44	220	9	39	19	1.85	1.0780	42.2	1
Mean	351	68	234	60	174	7	54	18	2.07	1.0835	37.6	12
LSD (0.05)	72	8	57	48	46	NS	40	NS	0.21	0.0031	3.5	8

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Malheur Agricultural Experiment Station

Last updated  Tuesday June 28, 2011.