Seedless Table Grapesfor the Willamette Valley

Agricultural Experiment StationOregon State University

Special Report 893April 1992

Seedless Table Grapesfor the Willamette Valley

Delbert D. Hemphill Jr., W.A. Sheets, and Lloyd W. Martin

Agricultural Experiment StationOregon State University

Abstract

Table or dessert grape varieties have been tested at the North WillametteResearch and Extension Center (NWREC) since 1968. This planting included manyseedless varieties from breeding program:3 across the country. In 1987, weestablished a planting devoted exclusively to seedless grapes, including manyrecent releases from breeding programs. Grapes of Vitis vinifera, Vitis labrusca,and hybrids of these and other Vitis species were planted on a deep, fertile soiltypical of the Willamette Valley floor. Variety characteristics, including relativefruit maturity, disease susceptibility, and hardiness are listed.

Authors

Delbert D. Hemphill, Jr. is Professor of Horticulture at NWREC, 15210 NEMiley Rd., Aurora, Oregon. W. A. Sheets is Chair Agent, Washington County,Oregon, Cooperative Extension Service. Lloyd W. Martin is Professor ofHorticulture and Superintendent of NWREC.

The authors wish to thank Ray Ethel!, Lon Rombough, and Ivan Holm fortheir assistance in obtaining starts of many of the grape varieties.

Disclaimer

The use of either generic chemical or trade names does not constitute anendorsement by the Oregon State University Agricultural Experiment Station orCooperative Extension Service. Always check with your Extension Service orpesticide consultant for current pesticide registrations and restrictions onapplication.

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SEEDLESS TABLE GRAPES FOR THE WILLAMETTE VALLEY

Delbert D. Hemphill, Jr., W. Arden Sheets, and Lloyd W. Martin

Interest in table or dessert grapeshas increased greatly in recent years asconsumers have sought alternatives tothe limited range of types available inthe supermarket. Gardeners seekinformation on varieties adapted to theclimate of the Willamette Valley, withthe intention of growing their owngrapes for table, juice, or raisinproduction. Farmers have expressedinterest in plantings for direct marketingor desire to grow grapes with differentflavor characteristics and ripening timesthat might find a place in local markets.

The North Willamette Researchand Extension Center (NWREC)established a vineyard in 1968, withboth seeded and seedless varieties ofEuropean (Vitis vinifera), American(Vitis labrusca and other species), andhybrid types. Observations from thistrial were published in 1976 asAgricultural Experiment Station Circularof Information 655, authored by W. A.Sheets. This publication is now out ofprint.

In response to increased interestin seedless grape varieties for table andraisin use, we established a secondplanting at NWREC in 1987, devotedexclusively to seedless grapes. SinceOregon State University does not havea grape breeding project, varieties werecollected from states with activebreeding programs, primarily California,New York, and Arkansas. We wereparticularly interested in early-ripeningvarieties that would mature before theonset of the fall rainy season.

The objective of this publicationis to help the potential grower identifyvarieties of Vitis vinifera, V. labrusca,and hybrids of these and other species,that produce acceptable quality fruitwhen grown in the Willamette Valley.

Both the well-adapted varieties, and allothers tested, are listed for the sake ofcompleteness.

Establishment Procedure

Most varieties were planted inthe spring of 1987 with plants rootedfrom hardwood cuttings taken theprevious winter. Plants were set fivefeet apart in rows 10 feet apart, withthree plants per cultivar. An eight-footgap was left in the row at the boundarybetween varieties. The planting is onlevel, valley-floor soil at about 100 feetelevation. The soil is a Willamette siltloam, moderately well-drained, withabout 3 percent organic matter and apH of 5.5. All varieties planted in 1987through 1989 are included in Table 1.

Insect, Disease, and Weed Control

Aside from honeybees andyellow-jackets feeding on ripening fruit,insects have not been a problem and noinsecticides have been used. The majorpotential disease problems are powderymildew (Uncinula necator) and bunchrot (Botrytis cinerea). Acceptablecontrol of powdery mildew wasobtained with two applications oftriadimefon. No controls were used forbunch rot; rot did not develop until theadvent of fall rains.

Chemical herbicides such assimazine, diuron, and dichlobenil wereused to control all weeds in a three-footwide strip beneath the trellis. Aftergood weed control was established, asingle annual application of any one ofthese herbicides in early spring wassufficient for control of most weeds.Occasional hand-hoeing was necessaryfor blackberry and other perennials. A

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strip of fine fescue turf grass ismaintained between the rows byregular mowing.

The greatest pest problem hasbeen birds, both migratory starlings andresident robins and other species. Noattempt was made to control birds.

Irrigation

The planting was sprinkler-irrigated several times during the firsttwo summers after establishment.From 1989 on, no irrigation has beenused. The turf appeared to competefor available water and may havehelped in controlling grapevine vigorand hastening fruit maturation.

Fertilizer

Prior to planting, a 10N-8.7P-16.7K fertilizer was applied at 1000pounds per acre. Since then,maintenance applications of 50 poundsnitrogen per acre, as urea or ammoniumnitrate, have been made in May. Thishas been more than adequate to obtaingood vine vigor, but is somewhatlimiting for the grass sod.

Training and Pruning

The trellis consists of 8-foot-long, five-inch diameter, posts setevery 18 feet in the row and markingthe boundary between varieties. Heavy(No. 9) galvanized wire was attached tothe top of the posts, about six feetabove ground, and at the four-footlevel. A steel T-type fencepost was setat each plant; the wires were alsosecured to these posts.

A single shoot (trunk) wasvertically trained to the fencepost in thefirst and second years of establishment.The shoot was topped a few inchesbelow the top wire and side shootswere secured to the trellis wires with

plastic tie tape. Side shoots werepruned back to two to three bud spursafter the second winter. These shootswere then used to establish the four-arm (cane) Kniffen system of pruning(Figure 1).

Since the second winter,dormant pruning has consisted ofremoving all current-season growthexcept for four well-exposed canes,each having about 10 buds. Also, ashort renewal spur of one to two budsis left near the base of each cane toprovide well-placed canes for trainingthe following year. This system isstandard for all varieties, although somemight have responded more favorablyto a different trellising method or to agreater or lesser number of retainedbuds.

Most of the varieties evaluatedhave great vine vigor at this site.Summer training and pruning wasnecessary to provide exposure of thefruiting area to sun, to increase airmovement, and to keep canes out ofthe sodded row middles. Bailing twinesecured to the top of the posts is usedto support canes arising from the lowertwo arms. Hedging is done in mid-summer, taking care to leave at least10 leaves, on average, beyond the fruitclusters.

Evaluation of Fruit Maturity

Grape maturity is often estimatedby measuring the soluble solids contentof the juice with a refractometer orhydrometer. These measures areaccurate indicators of sugar content butnot of perceived sweetness. The tastesensation of "sweetness" is a complexfunction of sugar content, pH, totalacid content, and other flavorcomponents and varies amongindividual tasters. Rather than reportsoluble solids at various dates, we havegiven a subjective maturity rating,based on our combined judgment as towhen the grapes had the right balance

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of sugars, acids, and other flavorcomponents for good dessert quality.

Cold Hardiness

The relatively mild winters of theWillamette Valley have not providedmany tests of winter hardiness.However, experience from othergrowing areas has indicated that manyseedless varieties of Vitis vinifera, orhybrids of vinifera and native Americanspecies, are less cold hardy thanvarieties derived from native species.

The freeze event of December,1990 provided an unusual test of grapebud survival, but did little damage tovine trunks. The minimum temperaturereached 0°F (-18°C) on December 21and did not exceed 10°F for a six-dayperiod. The maximum temperature alsoremained below freezing during thisperiod. Most seedless varietiesexperienced significant loss of primarybuds, those most responsible for fruitproduction.

Table 2 lists the relativehardiness of most varieties in the trialand includes many seeded varietiesfrom other grape plantings at NWRECfor comparison. The reader should becautioned that these observations arebased on only a single freeze and maynot reflect varietal performance underdifferent climatic conditions.

Mildew Susceptibility

In 1991, no attempt was madeto control mildew in order to obtainsome observations on relativesusceptibility to this important disease.Powdery mildew attacks foliage, fruit,and canes, but is of most concernwhen the fruit is infected. Mildewedberries are prone to splitting, tend todevelop a tough skin, and fail to sizeand accumulate sugar normally. Insevere cases, the immature berries willdry out and fall from the cluster.

Native American varieties are generallyconsidered to be nearly resistant topowdery mildew, vinifera varieties verysusceptible, and hybrid varietiesintermediate in susceptibility.

Mildew pressure was severe in1991, resulting in complete crop loss insome varieties. Relative susceptibilityto mildew is listed in Table 2. Seededvarieties from other plantings areincluded for comparison. Among theseedless varieties, Canadice and Einset,both hybrids, compared favorably withnative American seeded varieties inresistance to mildew infection of thefruit.

As with the hardiness ratings,the mildew susceptibility ratings arebased on observations in a singleseason. Relative performance ofvarieties may differ somewhat in otherseasons with different diseasepressure.

Figure 1. Four-cane Kniffen trainingsystem.

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Table 1. Origin, parentage, and description of seedless table grapes evaluated at the North Willamette Researchand Extension Center 1987-1991.Variety Origin Parentage Type Season'. Color Slipskin"Beauty CA Scolorkerteck kiralynoje x Black Kishmish V Blue NoBronx NY (Goff x lona) x Sultanina L M Red NoCanadice NY Bath x Nimrod L E Red NoCentennial CA Gold x Q25-6 V E White NoChallenger MO Unknown, NY material? L ME Red NoConcord Seedless Sport of Concord? L M Blue YesDawn CA Gold x Perlette V M White NoDelight CA Scolorkerteck kiralynoje x Sultanina V M White No

Dora Jones Unknown, NY material? L ME White NoEinset NY Fredonia x Canner L E Red YesEmerald CA Emperor x Pirovano 75 V VL Green NoFiesta CA Complex, includes Calmeria, Red Malaga,

SultaninaV L White No

Flame CA Complex, includes Cardinal, Sultanina,Red Malaga

V ME Red No

Fresno CA Complex, includes Calmeria, Sultanina,Red Malaga

V ME White No

Glenora NY Ontario x Russian Seedless L M Blue NoHimrod NY Ontario x Sultanina L E White No

Interlaken NY Ontario x Sultanina L E White NoLakemont NY Ontario x Sultanina L L White NoMars AR Island Belle x Ark. 1339 L E Blue YesNY 36095 NY Ontario x Sultanina L ME White NoNY 36289 NY (Hubbard x self) x Interlaken L ME White NoNY 36661 NY Bell x Interlaken L ME White NoNY 47616 NY Bath x (Fredonia x Black Monukka) L E Blue YesNY 65.479.1 NY (Muscat Hamburg x Hubbard) x L M Blue Yes

(Ontario x Black Monukka)NY 65.483.2 NY (NY 10782 x Muscat Hamburg) x L ME Blue Yes

Suffolk RedNancy Unknown, NY material? L ME White NoPatio Green Unknown, NY material? L M White NoPerlette CA Scolorkerteck kiralynoje x Sultanina V E White NoReliance AR Ontario x Suffolk Red L E Red NoRemaily NY Lady Patricia x (Ontario x Russian Seedless) L L White NoRuby Seedless CA Emperor x Pirovano 75 V VL Red NoSovereign Coronation BC Unknown L E Blue YesSuffolk Red NY Fredonia x Russian Seedless L M Red NoThompson (Sultanina) 7 From Asia minor V L White NoThornton 7 Unknown, NY material? L ME White NoV52131 ON Seibel 8357 x Bronx L ML Blue NoVanessa ON Seneca x (Bath x Interlaken) L ML Blue NoVenus AR Alden x NY 46000 L ME Blue YeszV = vinifera or European type; L = labrusca or American types. Many of the cultivars are hybrids but tendto resemble one species more closely than the other.

YV E = very early - ripe by September 1 in most years.E = early - ripe by September 10 in most years.M = medium - ripe by September 20 in most years.ML = medium late - ripe by September 30 in most years.L = late - ripens in October.VL = very late - usually does not ripen fully in Willamette Valley.

xSlipskin refers to a non-adherent, tough skin that separates readily from the pulp. Example: Concord.Thompson Seedless is an example of a non-slipskin type.

""Foxy refers to the Concord-like flavor characteristic of most labrusca grapes and many hybrids.

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Table 1.{continued}Remarks

Large, long clusters with small, crisp, neutral-flavored berries. Very large clusters possible with cluster thinning.Medium, scraggly bunches; soft, mealy-textured berry. Tends to alternate bearing and berries crack in rain.Medium, compact, well-filled cluster; small to medium berry with spicy flavor. Low vigor, tends to overbear.Large, loose cluster; large, oval berry with mild Muscat flavor. Tends to crack and rot during wet autumn.Medium, scraggly cluster; teardrop-shaped berry; some seeds. Can be flat-tasting with unappealing texture.Small cluster; Concord flavor with smaller berry and cluster.Large, well-filled clusters; medium-large, crips berry. Less prone to cracking and bunch rot than Centennial.Medium cluster; small to medium berry with slight Muscat flavor. Low vigor with short-jointed canes. Lesscracking and rot than its sibling Perlette.Small cluster; small, slightly oval berry; neutral to slightly foxy flavor; like Himrod.Small to medium cluster; small to medium berry; crisp and spicy.Medium cluster with small to medium berry; berries soft and high acid. Remains green at maturity.Variable cluster size; small, crisp berry. Very susceptible to mildew.

Large, loose cluster with good resistance to bunch rot; medium berry with excellent texture. Vines veryvigorous, can be excessive.Medium cluster; medium berry; crisp, spicy. Mediocre set.

Cluster and berry size variable. Berries crisp with tender skin; tendency to crack in wet weather.Large, loose cluster with small to medium, tender berries. Variable set. Slightly foxy. Clusters can be largeand uniform with girdling or gibberellin.Medium cluster with medium berry. Slightly foxy. Firmer berry and smaller, better-filled cluster than Himrod.Large, well-filled cluster; medium berry. Retains green color at maturity. Higher acid than Interlaken.Large, loose cluster; large berry with a few seed traces; foxy flavor. Few clusters per vine.Small cluster; small berry with pink blush, neutral flavor.Small to medium cluster; medium to large berry; flavor like Niagara.Very small berry and cluster. Flavor like Interlaken.Small cluster and berry; like Concord Seedless but sweeter, less foxy. Few clusters per vine. Low vigor.Medium, tight cluster; medium berry; fairly crisp for slipskin; non-foxy.

Medium cluster; medium-small berry. Like NY Muscat in flavor and color.

Long, loose cluster; resembles Himrod.Loose cluster; small berry; neutral flavor.Medium, scraggly cluster; poor set; small to medium berry, very crisp. Very mildew susceptible.Medium berry and cluster; occasional seeds; flavor varies from foxy to an excellent fruitiness; firm berries.Large cluster, berry; pink blush; firm texture; heavy crop. Can taste flat; tends to crack in wet weather.Large, loose cluster; medium-large berry with neutral flavor. Tends to crack and rot in wet weather.Small cluster; medium berry; foxy.Large, loose cluster with medium to large berry of good texture. Poor color development except in full sun.Medium cluster; medium, oval berry; crisp, neutral flavor.Medium cluster; medium berry; resembles Interlaken.Long, scraggly cluster can improve with thinning; resembles Glenora; tart flavor makes it a good pie grape.Medium cluster, berry; crisp for slipskin; neutral flavor. Yield decline with age due to few canes near trunk.Medium cluster; large, soft berry; some hard seeds; foxy, fruity, to slightly Muscat in flavor.

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Table 2. Relative mildew susceptibility, primary bud cold hardiness, and overall rating of grape varietiesat the North Willamette Research and Extension Center, 1990-1991.Variety Mildew' Hardiness'' Overall ratinc'Seedless Table GrapesBeauty 4 4 4Bronx 4 3 5Canadice 1 1 1Centennial 4 2 2Challenger 2 3 2Concord Seedless 1 1 4Dawn 4 3 3Delight 5 4 3Dora Jones 4 ND NDEinset 1 1 2Emerald 5 3 5Fiesta 5 5 5Flame 5 4 1Fresno 5 3 2Glenora 3 2 3Nimrod 3 2 3Interlaken 4 2 3Lakemont 3 2 4Mars 2 1 2Nancy 2 ND NDNY 36095 2 ND NDNY 36289 2 ND NDNY 36661 3 2 3NY 47616 2 2 2NY 65.479.1 3 ND 2NY 65.483.2 2 ND 2Patio Green 2 ND NDPerlette 5 4 5Reliance 2 2 2Remaily 2 1 3Ruby 5 4 5Sovereign Coronation 2 1 2Suffolk Red 3 2 4Thompson 5 4 5Thornton 3 2 3V52131 2 1 3Vanessa 3 1 2Venus 3 2 3

'Susceptibility to powdery mildew on a five point scale with 5 = most susceptible (nearly 100% croploss), 1 =least susceptible (no significant damage to fruit).

'Primary bud loss in December, 1990, freeze. Five point scale with 5 = greater than 80% loss, 4 = 60-79% loss, 3=40-59% loss, 2=20-39% loss, 1 = less than 20% loss.

'Five point scale with 1 = most suited to the Willamette Valley. Includes disease susceptibility,hardiness, cluster appearance and berry quality.

ND: Not determined; insufficient observation.

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Table 2.LcontinuedVariety Mildew Hardiness Overall ratingSeeded American and Hybrid GrapesAlwood 2 1 3Aurore 2 2 5Blue Star 1 1 2Buffalo 2 1 2Caco 1 1 4Campbell Early 1 1 3Cardinal 5 4 4Cayuga White 1 1 2Concord 1 1 4Diamond 1 1 4Edelweiss 2 1 3Elizabeth 2 1 3Fredonia 1 1 3Golden Muscat 2 1 2Kendaia 2 1 2Lady Patricia 4 2 4Lucille 2 1 5Monticello 1 3 4Moored 1 1 3Niagara 1 1 4NY 30454 4 2 2NY Muscat 3 2 2Ontario 2 1 4Portland 2 1 3Price 3 1 3Rosea Belle 1 1 2Schuyler 3 1 3Seneca 5 1 2Seyval 2 1 2Swenson Red 3 1 2Utah Giant 5 3 4VanBuren 1 1 2Verdelet 1 2 4Worden 2 1 3

Seeded Vinifera Wine GrapesChardonnay 4 3 3Gamay (Napa ► 3 5 5GewOrztraminer 3 5 3Grenache 3 5 5Muscat blanc 5 5 5Pinot blanc 5 4 3Pinot noir 5 4 3Riesling 5 2 3Sauvignon blanc 4 3 3Semillon 4 2 4Sylvaner 4 4 4Zinfandel 5 5 5

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Adaptation to the Willamette Valley

An overall score for each variety,based on suitability for growing in theWillamette Valley, is found in Table 2.The major factors considered wereearliness, fruit set, hardiness, flavor,and berry size. For those who wish togrow grapes without spraying forpowdery mildew, the best choicesamong seedless table grapes areCanadice, Einset, Mars, and SovereignCoronation. The grower willing toimplement a regular spray program formildew control should also considerCentennial, Dawn, Delight, Flame, andReliance. These varieties haveoutstanding fruit quality but aresusceptible to powdery mildew. Thevarieties Nimrod, Interlaken, andThornton are very similar in maturity(early), cluster type, flavor, and and aremoderately resistant to powderymildew. However, they often havepoorly formed clusters and poor fruitset. The NY numbered lines 47616,65.479.1, and 65.483.2, also appearto be well-adapted to the WillametteValley, but obtaining cuttings or rootedplants may be a problem.

Plant Variety Protection Act

Most newly released grapevarieties are protected by the PlantVariety Protection Act. Propagationand sale of these varieties without alicense and payment of royalties isprohibited. Release of many numberedlines from breeding programs is alsoprohibited. The North WillametteResearch and Extension Center is notlicensed to propagate patented varietiesand does not sell cuttings of thesevarieties to the public. Varieties andlines in the planting which are knownto be protected include Centennial,Dawn, Einset, Mars, Reliance, and theNY lines 47616, 65.479.1, and65.483.2. Most of these varieties areavailable from licensed nurseries in thearea.

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