2006 Onion Variety Trials

Malheur Experiment Station

Information for Sustainable Agriculture

2006 ONION VARIETY TRIALS

Clinton C. Shock, Erik B. G. Feibert, and Lamont D. Saunders
Malheur Experiment Station
Oregon State University
Ontario, OR

Lynn Jensen
Malheur County Extension Service
Oregon State University
Ontario, OR

Krishna Mohan
University of Idaho
Parma, ID

Introduction

The objective of the onion variety trials was to evaluate yellow, white, and red onion varieties for bulb yield, quality, and single centers. Eight early season varieties (six yellow, two white) were planted in March and were harvested and graded at the end of August. Forty-three full-season varieties (33 yellow, 6 red, and 4 white) were planted in March, harvested and weighed in September 2006, and were graded and fully evaluated out of storage in January 2007. Each year, growers and seed industry representatives have the opportunity to examine the varieties at our annual Onion Variety Field Day and during onion grading in early January.

Methods

The onions were grown on an Owyhee silt loam previously planted to wheat. In the fall of 2005, the wheat stubble was shredded, and the field was irrigated and disked. Soil analysis indicated the need for 100 lb phosphate/acre, 100 lb sulfur/acre, 2 lb copper/acre and 1 lb/acre of boron, which were broadcast in the fall of 2005 after disking. The field was then moldboard-plowed, groundhogged, roller-harrowed, fumigated with Telone® C-17 at 20 gal/acre, and bedded.

A full-season trial and an early maturing trial were conducted adjacent to each other. Both trials were planted on March 23 in plots 4 double rows wide and 27 ft long. The early maturing trial had 8 varieties from 3 seed companies (Table 1) and the full-season trial had 43 varieties from 10 seed companies (Table 3). The experimental designs for both trials were randomized complete blocks with five replicates. A sixth nonrandomized replicate was planted for demonstrating onion variety performance to growers and seed company representatives.

Seed was planted in double rows spaced 3 inches apart at 9 seeds/ft of single row. Each double row was planted on beds spaced 22 inches apart with a customized planter using John Deere Flexi Planter units equipped with disc openers. The onion rows received 3.7 oz of Lorsban 15G® per 1,000 ft of row (0.82 lb ai/acre), and the soil surface was rolled on March 24. Onion emergence started on April 14. On May 15, alleys 4 ft wide were cut between plots, leaving plots 23 ft long. From May 17 through May 19, the seedlings were hand thinned to a plant population of two plants/ft of single row (6-inch spacing between individual onion plants, or 95,000 plants/acre).

The onions were managed to try to avoid yield reductions from weeds, pests, diseases, water stress, and nutrient deficiencies. Weeds were controlled with an application of Prowl® at 1 lb ai/acre on April 28. On May 9, Goal® at 0.1 lb ai/acre, Buctril® at 0.3 lb ai/acre, and Select® at 0.25 lb ai/acre were applied. On May 17, Goal at 0.2 lb ai/acre and Buctril at 0.3 lb ai/acre were applied. On May 30, Goal at 0.2 lb ai/acre, Buctril at 0.3 lb ai/acre, and Select at 0.25 lb ai/acre were applied. After lay-by the field was hand weeded as necessary. Thrips were controlled with aerial applications of the following insecticides: June 12, Warrior®; June 18, Warrior plus Lannate®; July 1, Carzol®; July 17, Warrior plus Mustang®; July 24, Carzol; July 29, Warrior plus MSR; August 10, Warrior plus Lannate. Carzol was applied at 0.69 lb ai/acre, Warrior at 0.03 lb ai/acre, Lannate at 0.45 lb ai/acre, Mustang at 0.05 lb ai/acre, and MSR at 0.5 lb ai/acre.

The trial was furrow irrigated when the soil water tension at 8-inch depth reached 25 cb (1 cb = 1 kPa)(Shock et al. 2005). Starting in mid-June, soil water tension was monitored by six granular matrix sensors (GMS, Watermark Soil Moisture Sensors Model 200SS, Irrometer Co. Inc., Riverside, CA) centered at 8-inch depth below the onion row. The sensors were automatically read three times a day with an AM-400 meter (Mike Hansen Co., East Wenatchee, WA). The last irrigation was on August 23.
The field was sidedressed with 100 lb of nitrogen/acre as urea and cultivated on May 25. On June 21, the field was sidedressed with 100 lb N/acre as urea. An onion root tissue analysis on July 14 showed the need for potassium. On July 21, potassium at 20 lb/acre was water run during a routine irrigation.

Onions in each plot were evaluated subjectively for maturity by visually rating the percentage of onions with the tops down and the percent dryness of the foliage. The percent maturity was calculated as the average percentage of onions with tops down and the percent dryness. The early maturing trial was evaluated for maturity on August 7 and August 21 and the full-season trial on August 22 and September 7. The number of bolted onion plants in each plot was counted.

Onions in each plot of the full-season trial were evaluated subjectively for severity of symptoms of iris yellow spot virus (IYSV) on August 22. Each plot was rated on a scale of 0 to 5, where 0 = no symptoms and 5 = over 80 percent foliage dried out due to symptoms.

After grading of the early maturing trial, 10 randomly chosen bulbs from each plot were shipped via UPS ground to Vidalia Labs International in Collins, Georgia. The bulb samples were analyzed for pyruvic acid content on September 6. Bulb pyruvic acid content is a measure of pungency with the unit being micro mols pyruvic acid per gram of fresh weight. Onion bulbs having a pyruvate concentration of 5.5 or less are considered sweet according to Vidalia Labs sweet onion certification specifications.

In early September, bulbs from one of the border rows in each plot of both trials were rated for single centers. Twenty-five consecutive onions ranging in diameter from 3.5 to 4.25 inches were rated. The onions were cut equatorially through the bulb middle and, if multiple centered, the long axis of the inside diameter of the first single ring was measured. These multiple-centered onions were ranked according to the diameter of the first single ring: "small double" had diameters less than 1.5 inches, "intermediate double" had diameters from 1.5 to 2.25 inches, and "blowout" had diameters greater than 2.25 inches. Single-centered onions were classed as a "bullet". Onions were considered functionally single centered for processing if they were a "bullet" or "small double."

Onions from the middle two rows in each plot in the early maturity trial were lifted, topped by hand, and bagged on August 21. On August 23 the onions were graded. The onions in the full-season trial were lifted on September 8 to field cure. Onions from the middle two rows in each plot of the full season trial were topped by hand and bagged on September 13. The bags were put in storage on September 18. Before being placed into storage each bag was weighed. The storage shed was ventilated to maintain air temperature as close to 34°F as possible. Onions from the full-season trial were graded out of storage on January 3 and 4, 2007.

During grading, bulbs were separated according to quality: bulbs without blemishes (No. 1s), split bulbs (No. 2s), neck rot (bulbs infected with the fungus Botrytis allii in the neck or side), plate rot (bulbs infected with the fungus Fusarium oxysporum), and black mold (bulbs infected with the fungus Aspergillus niger). The No. 1 bulbs were graded according to diameter: small (<2.25 inches), medium (2.25-3 inches), jumbo (3-4 inches), colossal (4-4.25 inches), and supercolossal (>4.25 inches). Bulb counts per 50 lb of supercolossal onions were determined for each plot of every variety by weighing and counting all supercolossal bulbs during grading. The red varieties were evaluated subjectively during grading for exterior thrips damage during storage. The bulbs from each red variety plot were rated on a scale from 0 (no damage) to 10 (most damage) for damage on the bulb surface, without removing the outer scales.

Varietal differences were compared using ANOVA and least significant differences at the 5 percent probability level, LSD (0.05). Regression analyses of yield against IYSV ratings were conducted on both the data from 2005 (Shock et al. 2006) and the current year's data.

Results

Both environmental stress and pest stress limited onion performance at Ontario in 2006. The weather was cooler than normal, with fewer growing degree days than average until May 20. After May 20 the weather was warmer than average. Heat for the season exceeded norms, especially in July. A heat wave had maximum air temperatures equal to or greater than 100°F from July 21 to July 29. Thrips and IYSV were particularly damaging during the 2006 season.

Varieties are listed by company in alphabetical order. The LSD (0.05) values at the bottom of each table should be considered when comparisons are made between varieties for significant differences in performance characteristics. Differences between varieties equal to or greater than the LSD value for a characteristic should exist before any variety is considered different from any other variety in that characteristic.

Since 2003, several experimental varieties were named. In 2004 Nunhems 'SX 7000ON' and 'SX 7002ON' were named 'Bandolero' and 'Montero', respectively. Global Genetics '6001' was named 'Maverick'. In 2005, Seminis 'XP5646' was named 'Orizaba', 'XP5813' was named 'Affirmed', and 'EX5843' was named 'Monarchos'. In 2006, D. Palmer 'DPS 1405' was named 'Generation X', 'DPS 1406' was named 'Evolution', and 'DPS 3052' was named 'Shiraz'. Nunhems 'NUN7004ON' was named 'Arcero', 'NUN7200ON' was named 'Grand Coulee', and 'NUN7008ON' was named 'Joaquin'. Varieties are all listed by name in the results. The experimental numbers are useful for comparing results from previous years.

Early Maturing Trial
The percentage of "bullet" single centers averaged 30.0 percent and ranged from 4.0 percent for 'Western Giant', to 66.6 percent for Montero (Table 1). The percentage of onions that were functionally single centered averaged 49.8 percent and ranged from 14.0 percent for Western Giant to 87.8 percent for Montero.

Total yield at harvest in September 2006 ranged from 496 cwt/acre for 'EX7106' to 727.5 cwt/acre for 'Exacta' (Table 1). Exacta, 'Ovation', and 'Spanish Medallion' were among the varieties with the highest total yield.

Marketable yield out of storage ranged from 466 cwt/acre for EX7106 to 691 cwt/acre for Exacta (Table 2). Colossal yield ranged from 9.7 cwt/acre for Montero to 166 cwt/acre for Exacta.

Full-season Trial
The percentage of "bullet" single centers averaged 43.4 percent and ranged from 3.3 percent for 'White Wing', to 89 percent for Generation X (Table 3). The percentage of onions that were functionally single centered averaged 66.6 percent and ranged from 13.3 percent for 'Snowflake' to 97.3 percent for Generation X. Generation X, 'Ruby Ring', 'Cometa', Grand Coulee, 'Ringleader', Arcero, and 'Koala' had higher than 90 percent functionally single-centered bulbs.

Total yield at harvest in September 2006 ranged from 377 cwt/acre for Shiraz to 834.8 cwt/acre for 'Tequila' (Table 3). Tequila, 'T-433', 'Ranchero', 'Harmony' and 'Charismatic' were among the varieties with the highest total yield.

Total yield out of storage ranged from 288.9 cwt/acre for Shiraz to 771 cwt/acre for OLYS05N5 (Table 4). Varieties OLYS05N5, Tequila, Joaquin, Charismatic, and Harmony were among the varieties with the highest total yield. Marketable yield ranged from 163.8 cwt/acre for Shiraz to 714 cwt/acre for Joaquin. Varieties Joaquin, EX5819, Harmony, and Charismatic were among the varieties with the highest marketable yield. Supercolossal onion yield ranged from 0 cwt/acre for many varieties to 28 cwt/acre for Tequila. Varieties Tequila, Joaquin, Evolution, Harmony, and 'Sweet Perfection' were among the varieties with the highest super-colossal yield. Colossal onion yield ranged from 0 cwt/acre for several varieties to 184 cwt/acre for Joaquin. Varieties Joaquin, Charismatic, Tequila, Evolution, and OLYS05N5 were among the varieties with the highest colossal yield.

Iris Yellow Spot Virus (IYSV)
Subjective ratings of IYSV symptom severity for the full-season varieties, on a scale from 0 to 5, ranged from 1.6 for Joaquin and OLYS05N5 to 4.1 for Generation X (Table 3). Average total onion yield by variety was closely related to the average IYSV symptom severity in 2005 and 2006 (Figs. 1 and 2). In general, varieties with a lower severity rating had higher total yield. Clearly, the relative onion variety tolerance to the effects of IYSV has become a major factor in onion productivity.

References

Shock, C.C., R. Flock, E. Feibert, C.A. Shock, A. Pereira, and L. Jensen. 2005. Irrigation monitoring using soil water tension. Oregon State University Extension Service EM 8900.

Shock, C.C., E.B.G. Feibert, L.D. Saunders, L. Jensen, and K. Mohan. 2006. 2005 Onion Variety Trials. Oregon State University Agricultural Experiment Station Special Report 1070:42-53.

Table 1. Onion multiple-center rating and pyruvate concentration for early maturing varieties, Malheur Experiment Station, Oregon State University, Ontario, OR, 2006.

			Multiple center			Single center
Seed company	Variety	Bulb color	Blowout	Intermediate double	Small double	Functional^a	Bullet	Pyruvate concentration
			------------------------------- % ---------------------------------					µmoles/g FW
Nunhems	Renegade	Y	60.7	17.3	12.7	22.0	9.3	6.3
	Montero	Y	8.0	4.2	21.2	87.8	66.6	7.3
Sakata	Ovation	Y	34.6	18.8	17.0	46.7	29.7	6.9
	Spanish Medallion	Y	25.3	16.0	23.3	58.7	35.3	7.0
	Western Giant	Y	61.3	24.7	10.0	14.0	4.0	7.6
Seminis	Exacta	Y	43.3	22.0	21.3	34.7	13.3	7.5
	Orizaba	W	13.3	20.0	30.7	66.7	36.0	6.6
	EX7106	W	18.7	13.3	22.0	68.0	46.0	6.4
LSD (0.05)			16.3	NS	11.1	14.3	10.6	NS

^aBullet + small double.

Table 2. 2006 performance data for early maturing varieties, Malheur Experiment Station, Oregon State University, Ontario, OR, 2006.

Variety	Bulb color	Total yield	Marketable yield by grade					Bulb counts >4¼ in	Non-marketable yield			Maturity on Aug. 21
			Total	>4¼ in	4-4¼ in	3-4 in	2¼-3 in		Total rot	No. 2s	Small
		--- cwt/acre ---		----------- cwt/acre ------------				#/50 lb	%	-- cwt/acre --		%
Renegade	Y	602.1	516.3	3.1	72.7	417.0	23.4	33.1	0.6	71.3	11.14	67
Montero	Y	502.1	483.4	0.0	9.7	451.4	22.4	---	0.6	0.75	15.1	62
Spanish Medallion	Y	693.3	674.8	2.7	135.2	512.4	24.5	38.9	0.3	8.54	7.97	52
Ovation	Y	700.5	685.7	0.0	102.4	555.0	28.3	---	0.1	3.28	11.14	48
Western Giant	Y	596.5	548.8	1.6	51.0	470.7	25.5	31.5	0.3	36.88	9.2	65
Exacta	Y	727.5	691.0	8.1	165.6	497.1	20.2	29.4	0.8	21.39	9.41	63
Orizaba	W	591.9	563.1	0.0	31.5	489.2	42.4	---	1.2	10.59	11.07	34
EX7106	W	496.0	465.9	0.0	16.0	378.1	71.7	---	1.0	4.9	20.18	27
LSD (0.05)		140.0	146.9	NS	42.3	NS	19.8	NS	NS	14.9	NS	8.9

Table 3. Total yield at harvest, bulb multiple-center rating, and iris yellow spot virus rating for long season varieties, Malheur Experiment Station, Oregon State Univ., Ontario, OR, 2006.

		Bulb color	Multiple center			Single center		Iris yellow spot virus rating^b
Seed company	Variety		Blowout	Intermediate double	Small double	Functional^a	Bullet
			--------------------------- % --------------------------					0 - 5
A. Takii	Ruby Ring	R	0.7	2.7	28.7	96.7	68.0	3.7
	T-433	Y	42.4	27.2	22.4	30.4	8.0	2.5
	9003G	Y	16.0	34.0	30.0	50.0	20.0	2.9
Bejo	Calibra	Y	12.7	25.4	28.7	61.9	33.2	3.0
	Crocket	Y	34.7	28.7	28.0	36.7	8.7	3.4
	Snowflake	W	64.0	22.7	8.0	13.3	5.3	2.1
	Red Bull	R	23.3	21.3	27.3	55.3	28.0	4.0
	Sedona	Y	30.7	20.7	29.3	48.7	19.3	2.8
	Talon	Y	16.7	13.3	28.0	70.0	42.0	3.4
	White Wing	W	58.7	18.7	19.3	22.7	3.3	1.9
Crookham	Harmony	Y	10.7	14.7	14.7	74.7	60.0	2.6
	Sweet Perfection	Y	20.0	27.3	20.7	52.7	32.0	2.5
	OLYS05N5	Y	12.7	14.0	24.7	73.3	48.7	1.6
D. Palmer	Mesquite 06	Y	36.7	21.3	28.7	42.0	13.3	2.5
	Tequila	Y	24.0	21.3	22.0	54.7	32.7	2.0
	Generation X	Y	1.3	1.3	8.0	97.3	89.3	4.1
	Evolution	Y	3.3	9.3	17.3	87.3	70.0	2.1
	Shiraz	R	41.1	17.2	23.8	41.7	17.9	4
Global Genetics	Maverick	Y	21.3	18.0	28.0	60.7	32.7	2.7
	Ringleader	Y	2.7	5.3	13.3	92.0	78.7	2.6
	Varsity	Y	7.3	11.3	30.7	81.3	50.7	2.8
	6093	Y	6.0	8.0	19.3	86.0	66.7	3.5
Nunhems	Cometa	W	1.3	2.0	20.0	96.7	76.7	2.0
	Granero	Y	10.0	18.0	23.3	72.0	48.7	2.3
	Montero	Y	3.3	10.7	22.7	86.0	63.3	3.0
	Pandero	Y	22.0	18.0	24.0	60.0	36.0	2.5
	Ranchero	Y	14.0	12.0	28.0	74.0	46.0	2.7
	Sabroso	Y	2.7	10.0	29.3	87.3	58.0	3.2
	Salsa	R	40.0	15.3	22.0	44.7	22.7	3.8
	Vaquero	Y	6.0	16.0	17.3	78.0	60.7	2.9
	Arcero	Y	4.0	4.7	14.0	91.3	77.3	3.5
	Grand Coulee	Y	1.3	3.3	18.0	95.3	77.3	3.9
	Joaquin	Y	6.0	10.0	20.7	84.0	63.3	1.6
Rispens	Solid Gold	Y	26.0	22.0	31.3	52.0	20.7	3.8
	Silver Princess	W	49.3	14.0	17.3	36.7	19.3	2.8
	Red Castle	R	32.7	12.0	22.7	55.3	32.7	3.3
Sakata	XON-450Y	Y	32.7	17.3	26.0	50.0	24.0	2.3
Seminis	Affirmed	Y	12.0	16.7	26.7	71.3	44.7	1.8
	Charismatic	Y	23.3	21.3	30.7	55.3	24.7	1.9
	Mercury	R	24.7	22.7	33.3	52.7	19.3	3.3
	Monarchos	Y	1.3	10.7	29.3	88.0	58.7	2.2
	EX5819	Y	19.3	19.3	28.0	61.3	33.3	2.3
Zetaseeds	Koala	Y	3.4	6.0	14.1	90.6	76.4	3.5
	LSD (0.05)		9.5	9.2	11.4	12.3	12.8	0.42

^aBullet + small double
^bSubjective symptom severity rating: 0 = no symptoms, 5 = over 80% leaf area dried out due to symptoms.

Table 4. Performance data for experimental and commercial onion varieties graded out of storage in January 2007, Malheur Experiment Station, Oregon State University, Ontario, OR.

Seed company	Variety	Bulb	Total yield	Marketable yield by grade					Bulb counts >4¼ in	Non-marketable yield						Maturity				Thrips damage^a
		color		Total	>4¼ in	4-4¼ in	3-4 in	2¼-3 in		Total rot	Neck rot	Plate rot	Black mold	No. 2s	Small		Aug. 22	Sept. 7	Bolters
			--- cwt/acre ---						#/50 lb	----- % of total yield -----				-- cwt/acre --		%			#/plot
A. Takii	Ruby Ring	R	338.7	284.7	0.0	0.0	52.5	232.2		4.6	1.4	2.9	0.4	0.8	35.8	70		93	0.0	1.2
	T-433	Y	709.7	550.1	1.8	120.7	408.8	18.8	28.3	10.9	7.5	3.4	0.0	74.3	7.3	22		42	0.0
	9003G	Y	544.4	510.0	0.0	4.2	445.3	60.5		3.6	2.9	0.7	0.0	1.9	13.0	33		65	0.0
Bejo	Calibra	Y	496.5	462.8	0.0	0.0	377.6	85.2		1.0	0.2	0.8	0.0	14.0	15.0	29		59	0.0
	Crocket	Y	485.9	411.3	0.0	2.5	323.2	85.5		4.9	1.9	2.7	0.3	36.0	14.4	47		76	0.0
	Snowflake	W	484.2	437.7	0.0	0.0	328.7	109.0		3.7	2.9	0.8	0.0	18.2	12.6	37		62	0.0
	Red Bull	R	430.9	388.7	0.0	0.0	266.1	122.7		2.6	1.5	1.1	0.0	12.6	18.6	43		71	0.0	0.8
	Sedona	Y	558.3	481.2	0.0	3.9	433.0	44.3		7.3	5.5	1.8	0.0	26.9	9.3	29		66	0.0
	Talon	Y	387.8	353.6	0.0	1.7	225.2	126.8		4.7	3.0	1.6	0.0	2.3	13.6	74		93	0.0
	White Wing	W	508.1	361.9	0.0	8.0	281.9	72.1		10.2	7.5	2.7	0.0	78.8	14.9	62		84	0.0
Crookham	Harmony	Y	731.9	671.3	14.6	141.6	493.5	21.6	35.0	7.6	4.3	3.1	0.2	1.0	6.3	24		48	0.0
	Sweet Perfection	Y	691.3	572.9	13.9	145.0	395.1	18.9	34.1	10.0	5.7	3.3	1.0	42.9	7.7	36		51	0.0
	OLYS05N5	Y	770.8	664.0	7.6	166.8	466.9	22.7	34.9	12.4	9.9	2.5	0.0	4.6	7.4	14		25	0.0
D. Palmer	Mesquite 06	Y	707.2	622.5	10.9	139.5	445.6	26.5	34.0	4.3	1.9	2.1	0.2	43.4	11.1	20		43	0.2
	Tequila	Y	740.5	645.3	27.6	170.7	423.3	23.7	29.8	6.2	3.1	2.9	0.2	42.5	6.5	27		45	0.0
	Generation X	Y	488.4	426.4	0.0	3.3	371.3	51.8		9.5	6.8	2.3	0.4	6.8	7.6	46		73	0.0
	Evolution	Y	694.4	639.2	16.2	169.6	437.9	15.5	33.8	5.9	4.2	1.7	0.0	10.1	5.0	19		38	0.0
	Shiraz	R	288.9	163.8	0.0	2.6	52.7	108.4		2.0	0.7	1.3	0.0	86.9	32.5	47		76	0.0	0.8
Global Genetics	Maverick	Y	668.2	578.6	3.9	116.3	439.3	19.1	39.0	9.1	3.9	4.5	0.7	21.9	5.9	36		61	0.0
	Ringleader	Y	583.1	543.4	1.5	64.6	454.7	22.7	34.9	5.4	3.6	1.8	0.0	2.3	7.1	34		65	0.0
	Varsity	Y	509.7	485.6	0.0	10.6	426.8	48.3		2.0	1.1	0.9	0.0	6.5	7.4	56		79	0.0
	6093	Y	583.0	532.1	0.0	20.5	472.8	38.8		5.7	2.9	2.8	0.0	8.7	9.68	28		63	0.0
Nunhems	Cometa	W	726.5	682.6	2.6	79.0	572.0	28.9	39.5	4.5	3.2	1.1	0.1	2.7	8.9	24		54	0.6
	Granero	Y	670.7	632.3	0.0	49.3	554.5	28.5		4.2	2.3	1.9	0.0	5.9	4.2	27		60	0.2
	Montero	Y	543.8	506.4	0.0	17.5	431.3	57.5		4.8	3.2	1.6	0.0	3.8	7.6	65		85	0.0
	Pandero	Y	623.0	575.2	3.2	48.8	483.8	39.4	32.4	5.0	2.6	2.4	0.0	9.0	7.3	25		56	0.0
	Ranchero	Y	677.2	631.0	1.8	110.6	489.4	29.2	28.3	4.7	4.1	0.5	0.0	8.1	6.6	32		59	0.0
	Sabroso	Y	499.4	477.3	0.0	0.0	395.0	82.3		2.4	1.5	1.0	0.0	0.0	10.1	36		70	0.0
	Salsa	R	383.7	326.3	0.0	0.0	237.6	88.7		2.5	1.2	1.3	0.0	32.5	14.9	52		78	0.0	1.8
	Vaquero	Y	643.8	595.4	2.0	52.3	509.3	31.8	25.2	5.8	4.6	1.1	0.1	3.8	7.2	31		64	0.0
	Arcero	Y	620.3	588.6	0.0	39.9	514.7	34.0		3.1	2.8	0.4	0.0	1.7	9.2	38		67	0.0
	Grand Coulee	Y	418.9	390.1	0.0	1.6	272.3	116.2		3.6	3.1	0.6	0.0	0.3	13.2	46		81	0.0
	Joaquin	Y	738.0	713.5	16.2	184.2	496.7	16.5	35.7	1.9	1.2	0.7	0.0	5.9	4.9	14		32	0.0
Rispens	Solid Gold	Y	316.1	245.6	0.0	0.0	106.4	139.2		3.2	2.0	1.2	0.0	35.4	24.7	45		72	0.0
	Silver Princess	W	475.6	289.3	1.6	3.3	221.4	63.0	32.4	14.5	9.0	5.5	0.0	113.0	7.4	31		63	0.0
	Red Castle	R	355.4	274.6	0.0	0.0	173.1	101.5		2.3	1.5	0.8	0.0	50.7	22.3	34		70	0.0	0.0
Sakata	XON-450Y	Y	696.2	624.4	12.6	142.7	439.7	29.3	31.7	4.3	2.8	1.5	0.0	30.9	9.0	24		54	0.0
Seminis	Affirmed	Y	671.4	632.2	1.8	105.1	500.6	24.7	28.3	4.2	2.0	2.2	0.0	2.6	8.3	25		53	0.0
	Charismatic	Y	736.4	669.6	10.4	177.6	450.7	31.0	35.2	5.8	4.4	1.4	0.0	17.0	9.3	18		49	0.0
	Mercury	R	332.2	286.4	0.0	0.0	123.1	163.3		3.9	2.7	1.1	0.0	14.6	19.1	77		91	0.0	2.6
	Monarchos	Y	630.4	596.8	0.0	45.4	524.7	26.6		2.3	1.5	0.8	0.0	12.2	6.7	27		58	0.0
	EX5819	Y	730.4	681.0	7.4	86.7	554.3	32.6	29.2	4.3	3.1	1.1	0.0	12.6	5.7	26		58	0.0
Zetaseeds	Koala	Y	545.0	484.6	0.0	22.6	417.3	44.8		8.3	4.8	3.6	0.0	7.6	9.4	32		64	0.0
	LSD (0.05)		81.1	82.3	7.2	36.0	79.9	21.4	NS	4.6	3.8	2.4	NS	18.6	6.7	10.7		7.5	0.2	0.6

^aThrips damage on the surface of red onions at the end of the storage January 3 and 4: 0 = least damage, 10 = most damage.

Onion yield across varieties was inversely related to IYSV symptoms in 2005.

Onion yield across varieties was inversely related to IYSV symptoms in 2005.

Figure 1. Average onion total yield by variety as a function of the average observed iris yellow spot virus symptoms in 2005. Virus ratings were based on subjective evaluations (0 = no symptoms, 5 = highest damage). Each data point is the average of the yield of five plots of each variety compared with the average observed symptoms. Malheur Experiment Station, Oregon State University, Ontario, OR, 2005.

Onion yield was inversely related to IYSV symptoms in 2006.

Figure 2. Average onion total yield by variety as a function of the average observed iris yellow spot virus symptoms in 2006. Virus ratings were based on subjective evaluations (0 = no symptoms, 5 = highest damage). Each data point is the average of the yield of five plots of each variety compared with the average observed symptoms. Malheur Experiment Station, Oregon State University, Ontario, OR, 2006.