2007 ONION VARIETY TRIALS

Transcription

1 2007 ONION VARIETY TRIALS Clinton C. Shock, Erik B. G. Feibert, and Lamont D. Saunders Maiheur Experiment Station, Oregon State University, Ontario, OR Lynn Jensen Maiheur County Extension Service, Oregon State University, Ontario, OR Krishna Mohan University of Idaho, Parma, ID Hanu Pappu Washington State University, Pullman, WA Introduction The objective of the onion variety trials was to evaluate yellow, white, and red onion varieties for bulb yield, quality, and single centers. Five early-season varieties (four yellow, one red) were planted in March and were harvested and graded at the end of August. Fifty-four full-season varieties (42 yellow, 8 red, and 4 white) were planted in March, harvested in September 2007, and graded out of storage in January Each year, growers and seed industry representatives have the opportunity to examine the varieties at our annual Onion Variety Field Day in late August and during onion grading in early January. Varieties are evaluated for yield, grade, internal quality, and storability. Methods The onions were grown on an Owyhee silt loam previously planted to wheat. In the fall of 2006 the wheat stubble was shredded and the field was irrigated and disked. Soil analysis indicated the need for 172 lb phosphate (P205)/acre, 100 lb sulfur(s)/acre, 5 lb iron (Fe)/acre, 5 lb manganese (Mn)/acre, 2 lb copper (Cu)/acre, and 2 lb/acre of boron (B), which were broadcast in the fall of 2006 after disking. The field was then moldboard-plowed, groundhogged, roller-harrowed, fumigated with Telone C-I 7 at 20 gal/acre, and bedded. The full-season trial and the early maturing trial were planted adjacent to each other, on March 13, and in plots four double rows wide and 27 ft long. The early maturing trial had 5 varieties from 2 seed companies (Table 1) and the full-season trial had 54 varieties from 8 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. 17

2 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. Planting was done with customized John Deere Flexi Planter units equipped with disc openers. The onion rows received 3.7 oz of Lorsban I 5G per 1,000 ft of row (0.82 lb al/acre), and the soil surface was rolled on March 14. Onion emergence started on March 30. On May 4, alleys 4 ft wide were cut between plots, leaving plots 23 ft long. From May 7 through May 9, the seedlings were hand thinned to a plant population of 2 plants/ft of single row (6-inch spacing between individual onion plants, or 95,000 plants/acre). The onions were managed to minimize yield reductions from weeds, pests, diseases, water stress, and nutrient deficiencies. Weeds were controlled with an application of Prowl at 1 lb al/acre on April 13. On May 18, Aza-Direct at lb al/acre and Success at 0.25 lb ai/acre were applied for thrips control, and Select at 0.25 lb ai/acre and Prowl at 0.24 lb al/acre were applied for weed control. On June 1, Aza-Direct at lb al/acre and Success at 0.25 lb ai/acre were applied for thrips control. Subsequent insecticide applications for thrips control were done aerially: June 16, Lannate at 0.9 lb ai/acre; July 6, Carzol at 1.15 lb ai/acre; July 15, Lannate at 0.9 lb ai/acre and Poast at 0.28 lb ai/acre (grass control); and August 3, Lannate at 0.9 lb ai/acre. The trial was furrow irrigated when the soil water tension at 8-inch depth reached 25 cb (1 cb = I 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 28. The field was sidedressed with urea at 120 lb nitrogen (N)/acre on May 11. On June 11, the field was sided ressed with 100 lb N/acre as urea. 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 21, and the full-season trial was evaluated on August 23. 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) and powdery mildew (Level/lu/a taurica) on August 22. Each plot was rated for both diseases on a scale of 0 to 5, where 0 = no symptoms, I = I to 25 percent of foliage diseased, 2 = 26 to 50 percent of foliage diseased, 3 = 51 to 75 percent of foliage diseased, 4 = 76 to 99 percent of foliage diseased, and percent of foliage diseased. At harvest, 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 18

3 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 had diameters less than 1.5 inches, medium had diameters from 1.5 to 2.25 inches, and large had diameters greater than 2.25 inches. Onions were considered functionally single centered for processing if they were single centered or had a small multiple center. Onions from the middle two double rows in each plot in the early maturity trial were lifted, topped by hand, and bagged on August 21. On August23 the onions were graded. During grading, bulbs were separated according to quality: bulbs without blemishes (No. Is), split bulbs (No. 2s), neck rot (bulbs infected with the fungus Botrytis al/li 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 ( inches), jumbo (3-4 inches), colossal ( inches), and supercolossal (>4.25 inches). 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 onions in the full-season trial were lifted on September 10 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 17. The bags were put in storage on September 26. 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 14 and 15, Varietal differences were compared using analysis of variance. Means separation was determined using Fisher's least significant difference test at the 5 percent probability level, LSD (0.05). The varieties from each of the early maturity and full-season trials were compared for yield, grade, internal quality, and disease expression. Results are listed in tables 1-4 in alphabetical order by company. The LSD (0.05) values in 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. Variety performance will vary by year. Growers are encouraged to review performance over a number of years before choosing a variety to plant. Results Early Maturing Trial The percentage of single-centered bulbs averaged 18.4 percent and ranged from 0.8 percent for 'Renegade', to 44 percent for 'Montero' (Table 1). The percentage of onions that were functionally single centered averaged 27.5 percent and ranged from 1.6 percent for Renegade to 60 percent for Montero. 19

4 Total yield averaged 1,082 cwt/acre and ranged from cwtlacre for 'XON-216' to 1,263 cwtlacre for 'Ovation' (Table 2). Ovation and 'Spanish Medallion' were among the varieties with the highest total yield, marketable yield, and supercolossal yield. Full Season Trial The percentage of single-centered bulbs averaged 32.3 percent and ranged from 1.6 percent for 'Frontier', to 81.6 percent for 'Ringleader' (Table 3). The percentage of onions that were functionally single centered averaged 40.7 percent and ranged from 3.2 percent for 'Peso' to 87.2 percent for 'Generation X'. Generation X, 'Arcero', Ring'eader, 'Joaquin', 'Cometa', 'Harmony', and 'Evolution' had 80 percent or higher functionally single-centered bulbs. Total yield out of storage averaged 1,030 cwtlacre and ranged from cwt/acre for 'DPS 1415' to 1,379.4 cwtlacre for 'Charismatic' (Table 4). Charismatic, 'OLYSO5N5', Harmony, 'Ranchero', and 'Vaquero' were among the varieties with the highest total yield. Charismatic, OLYSO5N5, Vaquero, Ranchero, and Evolution were among the varieties with the highest marketable yield. Supercolossal yield averaged 203 cwtlacre and ranged from zero for Frontier, 'DPS 1413', 'DPS 1414', 'DPS 1418' and 'DPS 1419' to cwt/acre for Charismatic. Charismatic had the highest supercolossal yield followed by 'Maverick', Ranchero, Ringleader, and OLYSO5N5. Iris Yellow Spot Virus (IYSV) Iris yellow spot virus severity in 2007 was substantially lower than in 2005 and The average IYSV severity rating (0-5) for Vaquero in the variety trial was 1.1, 2.9, and 0.6 in 2005, 2006, and 2007, respectively. Onion yields were much higher in 2007 than in 2005 and 2006 (Shock et al. 2006, 2007). The average total yield of Vaquero was 666, 644, and 1,331 cwt/acre in 2005, 2006, and 2007, respectively. In 2007, the subjective ratings of IYSV symptom severity for the full-season varieties (scale of 0-5) ranged from 0.4 for 'Milestone' to 1 for 'Sedona' (Table 3). Powdery Mildew Powdery mildew is a relatively recently discovered onion disease caused by the fungus Level/lu/a taurica. The symptoms are necrotic lesions on the leaf surface with occasional white powdery patches with irregular margins. Powdery mildew is not currently thought to result in economic losses because infestations are occurring very late in the season. At the Malheur Experiment Station, powdery mildew on onions was first noticed in late August of 2006 at very low levels on a few varieties. In 2007, the disease was first observed in mid-august. Subjective ratings of powdery mildew symptom severity for the full-season varieties, on a scale from 0 to 5, ranged from 0 for many varieties to 3.2 for Evolution. Evolution and Joaquin had the most severe powdery mildew symptoms. 20

5 References Shock, C.C., R. Flock, E. Feibert, C.A. Shock, A. Pereira, and L. Jensen Irrigation monitoring using soil water tension. Oregon State University Extension Service EM Shock, C.C., E.B.G. Feibert, L.D. Saunders, L. Jensen, and K. Mohan Onion Variety Trials. Oregon State University Agricultural Experiment Station Special Report 1070: Shock, C.C., E.B.G. Feibert, L.D. Saunders, L. Jensen, and K. Mohan Onion Variety Trials. Oregon State University Agricultural Experiment Station Special Report 1075: Table 1. Maturity and bulb multiple-center ratings for early maturing varieties, Malheur Experiment Station, Oregon State University, Ontario, OR, Seed Maturity Multiple center Single center company Variety color Aug. 21 large medium small functionala single % % Nunhems Renegade Y Montero Y Sakata Ovation Y Spanish Medallion Y XON-216 R LSD (0.05) NS NS abullet + small double. Table 2. Yield and grade performance of early maturing varieties, Maiheur Experiment Station, Oregon State University, Ontario, OR, Seed company Variety Nunhems Renegade Montero Non-marketable Marketable yield by grade. yield counts Total >4% 2%-3 No. Total Total 3 4 in Small >4% in color yield in in - in 2s rot cwt/acre % #/50 lb Y Y Sakata Ovation Y Spanish Medallion Y XON-216 R LSD (0.05) NS NS 21

6 Table 3. multiple-center rating, iris yellow spot virus (IYSV), powdery mildew (PM) rating, maturity, and bolting for full-season varieties, Malheur Experiment Station, Oregon State University, Ontario, OR, Continued on next page. Multiple center Single center Disease severity ratingb Maturity August Seed company Variety large medium small functionala single IYSV PM Bolting color 23 % 0-5 % A. Takii Centerstone Y Frontier Y nac na T-433 Y Milestone Y Ruby Ring R Bejo Calibra Y Crocket Y Desperado Y Delgado Y Peso Y Red Bull R Sedona Y Derby Fl Y BGS 231 Y Crookham Harmony Y Sweet Perfection Y OLYSO3-207 Y OLYSO5N5 Y OLYXOO-23 Y D. Palmer Mesquiteo6 Y Tequilao6 Y Evolution Y Generation X Y DPS1413 Y na na DPSI414 Y na na DPSI4I5 Y na na DPSI4I6 Y na na DPSI417 Y DPSI418 Y na na

7 Multiple center Single center Disease severity ratingb Maturity Seed company Variety large medium small functionala August single IYSV PM color 23 Bolting % 0-5 % D. Palmer DPS14I9 Y DPS3052 R DPS3055 R DPS3058 R DPS3062 R Global Genetics Maverick Y Ringleader Y Outlaw Y Y Nunhems Granero Y Montero Y Pandero Y Ranchero Y Salsa R Vaquero Y Arcero Y Joaquin Y Cometa W Sakata XON-670W W Seminis Affirmed Y Charismatic Y Monarchos Y Mercury R Toluca W Orizaba W LSD (0.05) a single + small double b y5 = iris yellow spot virus; PM = powdery mildew. 0 = no symptoms, I = 1-25% of foliage diseased, 2 = 26-50% of foliage diseased, 3 = 51-75% of foliage diseased, 4 = 76-99% of foliage diseased, and 5 = 100% of foliage diseased. cna = data not available due to variety being fully mature at rating.

8 Table 4. Yield and grade of full-season experimental and commercial onion varieties graded out of storage in January 2008, Malheur Experiment Station, Oregon State University, Ontario, OR. Continued on next page. Seed company Variety color Total yield Marketable yield by grade Non-marketable yield No. Total Neck Plate Total >41% in 441% in 3-4 in 21%-3in Small 2s rot rot rot cwtlacre -- % of total yield A.Takii Centerstone Y Frontier Y T-433 Y Milestone Y Ruby Ring R Bejo Calibra Y Crocket Y Desperado Y Delgado Y Peso Y Red Bull R Sedona Y Derby Fl Y BGS 231 Y Crookham Harmony Y Sweet Perfection Y OLYSO3-207 Y OLYSO5N5 Y OLYXOO-23 Y D. Palmer MesquiteO6 Y Tequilao6 Y Evolution Y Generation X Y DPSI4I3 Y DPSI414 Y DPS14I5 Y DPSI4I6 Y D. Palmer DPSI417 Y counts >414 in #/50 lb Thrips damagea 0-10

9 Seed company Seminis Variety Affirmed Charismatic Monarchos Mercury Toluca Orizaba color Total yield Total Marketable yield by grade >4% in % in 3-4 in 2%-3 in cwt/acre DPS1418 Y DPSI4I9 Y DPS3052 R DPS3055 R DPS3058 R DPS3062 R Global Genetics Maverick Y Ringleader Y Outlaw Y Y Nunhems Granero Y Montero Y Pandero Y Ranchero Y Salsa R Vaquero Y Arcero Y Joaquin Y Cometa W Sakata XON-670W W Y Y Y R w Non-marketable yield No. Total Neck Plate Small 2s rot rot rot --%oftotalyield w LSD (0.05) a Thrips damage on the surface of red onions at the end of the storage January 14 and 15: 0 = least damage, 10 most damage. counts >41/4 in #/50 lb Thrips damagea