413 Amer J of Potato Res (2001) 78:413-419

Jacqueline Lee: A Late-Blight-Resistant Tablestock Variety

D. S. Douches'", K. Jastrzebski', J. Coombs', W. W. Kirk2,

K. J. Felcher', R. Hammerschmidt", and R. W. Chase I

I Dept. of Crop and Soil Sciences, Michigan State University, E. Lansing, MJ48824.

'Dept. of Botany and Plant Pathology, Michigan State University, E. Lansing, MJ48824.

*Corresponding author. David S. Douches, Phone: 517-353-3145; FAX 517-353-5174; dou chesd@msu.edu

ABSTRACT

Jacqueline Lee has a bright golden skin, yellow flesh,

attractive oval shape, and excellent cooking qualities that

make it suitable for tablestock use. In addition, it has

been determined to have a high level of foliar resistance

to the US-8 genotype ofPhytophthora infestans (Mont.)

de Bary under Michigan field and greenhouse conditions.

It is a full-season variety with vine maturity similar to

Snowden. Jacqueline Lee has high yield potential. It has a

high set (14-16 tuberslhill) of medium sized tubers that

leads to 65%-80% marketable yield. Tubers are low in

internal and external defects. It has a scab reaction simi­

lar to Atlantic, and the tubers have been observed to have

a long dormancy.

RESUMEN

Jacqueline Lee es una variedad de papa de pieI

amarilla brillante para consumo fresco, tuberculos de

forma oval muy atractivos y de excelente calidad de

cocimiento. Esta variedad tiene altos niveles de resisten­

cia foliar al genotypo US-8 de Phytophthora infestans

(Mont.) de Bary, tanto en invernadero como en condi­

ciones de campo, esta evaluacion fue hecha en Michigan,

USA. Jacqueline Lee es una variedad con alto potencial

de rendimiento y maduraclon media tardia similar a

Snowden. Produce un gran numero de tuberculos (14-16

tuberculos/semilla) de tamafio mediano, de los cuales 65­

Accepted for publi cation August 2, 2001. ADDffiONAL KEYWORDS: Solanum tuberosum, potato, Phylophlhora infesums .

80% son tuberculos comercializables. Los tuberculos

tienen resistencia a defectos internos y externos. Tam­

bien tienen resistencia a la sarna (Streptomyces scabies

Thaxter) similar a la variedad Atlantic y dormancia

Iarga,

BACKGROUND

Jacqueline Lee is a new potato variety (Solanum tubero­

sum L.) developed at Michigan State University with resistance

to the US-8 genotype of late blight (Phytophthora injestans

Mont. de Bary). Jacqueline Lee was evaluated as seedling num­

ber MSG274-3. It is a selection from a cross in 1994between the

late-maturing, late-blight-resistant Mexican variety Tollocan and

the early-maturing variety Chaleur (Dejong et al. 1995) for the

purpose of breeding late-blight-resistant cultivars with mid-sea­

son maturity. Jacqueline Lee is named for the daughter of the

breeder.

Jacqueline Lee is an oval/oblong tablestock selection with a

high tuber set. The tubers have a bright skin and a smooth,

attractive app earance with a yellow flesh that is typical of many

European cultivars (Figure 1). The primary merit of this selec­

tion is its strong foliar resistance to the US-8 genotype of late

blight (as determined by four years of field testing) combined

with a vine maturity that is similar to Snowden. Other strengths

of Jacqueline Lee are that the tubers have very low incidence of

internal defects, excellent culinary quality, and a long dormancy.

The pedigree of Jacqueline Lee is described in Figure 2.

The seedling generation was grown in 1994, followed by

two years of selection and seed multiplication at Lake City

Experiment Station, Lake City, MI. Since 1997,it has been tested

in replicated agronomic trials at the Montcalm Research Farm,

Entrican, MI, and in inoculated late blight trials at the Muck Soils

Research Farm, Bath, MI. in 1999it was entered into farm trials

in Michigan as well as commercial seed production

414 AMERICAN JOURNAL OF POTATO RESEARCH Vol. 78

VARIETAL DESCRIPTION

Plant Vme and Foliage:

Growth habit: Medium to tall height,

semi-erect Stems: Anthocyanin weak,

wings are very weak. Leaves:Yellow­ ToUoean green (Royal Horticulture Society { [R.H.S.] Color Chart value 147A)

with thick and short pubescence;

medium-open leaf silhouette; petiole

anthocyanin coloration is absent;

leaf stipules are large. Terminal

leaflets: Narrowly ovate with acumi­

JacquelineLee (MSG274-3)

nate tip and cordate base, with weak

leaflet margin waviness. Primary

leajlets: Four pairs per leaf, lanceo­

late, with acuminate tip and cordate Chaleur

base. Secondary and tertiary

leaflets: five pairs. vine maturity:

full season (similar to Snowden).

Inflorescence: Three to nine

FIGURE 1. Tuber sample of Jacqueline Lee from a field trial at Montcalm Research Farm.

Semi-stellate in shape with a violet color (R.H.S.

Color Chart value 85A). Calyx: Anthocyanin col­

oration absent. Anthers: Broad cone shape with a

yellow-orange color (R.H.S. Color Chart value

17A). Stigma: Capitate and green (R.H.S. Color

Chart value 137C). Fertility: Pollen shed is abun­

dant and female fertility is average. Berry set in the

field is heavy.

Tubers: Shape:Ovaland slightlyflattened. The

average tuber length x width x thickness is 91 mm x

60 mm x 49 mm with an average weight of 170 g.

Skin: Bright with slight flakiness and a yellow color

(R.H.S. Color Chart value 162B).Eyes: Shallow and

evenly distributed with an average 7.3 eyes/tuber;

eyebrows have a slight prominence. Flesh: Yellow

(R.H.S. Color Chart value 160B). Dormancy: Above

average (comparable to Yukon Gold).

rLoman Juanita ~ [ Ac25953 (58-E8-37) Anita--~

USDA21.31-3

Loman CFJ-69-1 { (58-ER-l) HOL-32

BeUeisle

s ebal o

N457

Houmaiwith an average of six per plant; 12 Minn 92-36-5 -{ Minn 17-2

FIGURE 2. florets per inflorescence. Corolla: Pedigree of Jacqueline Lee.

2001 DOUCHES, et al: JACQUEUNE LEE 415

TABLE 1-8cab (Streptomyces scabies) disease reaction from the Scab Nursery at the Michigan Sta te University Soils Farm , East Lansing , MI.

Entry 1998' 2000'

Jacqueline 3.0 3.5 2.5 Yukon Gold 2.7 2.5 2.0 Atlan tic 3.3 3.0 3.3 Snowde n 3.5 3.0 3.0

'Scab Disells e Rating 'Scab Disease Rating 1: Practically No Infection 0: No Infection 2: Low Infection 1: Low Infection <5% 3: Avg, Susceptibility 2: Moderate Susceptibilty 4: High SuoeeptibiJity 3 : Intermediate

5: Severe Susceptibility 4: High Susceptibility 5: Severe Susceptibility

DISEASE RESISTANCE

Replicated field tri als were conducted at the MSU Soils

Farm Scab Nursery to assess resistance to common and pitted

scab . This disease trial is a severe test for scab susceptibility.

From 1998 to 1999, the vari etie s were ranked on a 1-5 scale

based upon a co mbined score for scab coverage and lesion

severity. A rating of 1.0indicates zero to a trace amount of infec­

tion. A mod erate resistance (1.2 - 1.8) corre lates with <10%

infection and surface scab. These two categories are acceptable

levels of scab toleran ce. Susceptibl e lines have greater than 25%

infection with pitted lesions . Scores of 4.0 or greater are found

on lines with >500A! infection and severely pitted lesions . In 2000,

the scale was modified to a 0-5 scale with 0 equal to no infec­

tion; 1 is a low infection «5%); 3 is intermediate susceptibility;

and >4 is highly susceptible. Table 1 compares Jacqueline Lee

to some ch eck vari eti es . Based upon three years of tr ials ,

Jacqueline Lee has an interm ediate susceptibility to scab com­

parable to Atlantic and Snowden. In comparison, Yukon Gold

has slightly less susceptibility to scab. Some check cultivars that

so rt into the resistant category are Russet Burbank, Onaway ,

and Superior ldata not shown).

Foliar late blight trials were conducted at the Muck Soils

Research Farm, Bath, MI, from 1997 to 2000. The entries were

evaluated in 4-hill plots with three replications in a randomized

complete block design. Each year the trial was planted late (i.e.,

early Jun e) and the field was inoculated with a mixture of US-S

isolates of P. infestans in late-July and ratings were taken every

3 to 4 days durin g August. The mixture of isolates used over­

comes all R-genes in detached leaf tests however, in the field R8

and R9 differential lines recorded little to no infection. Under

these conditions most lines were highly susceptible to the US-S

genotype of late blight Table 2 summarizes the foliar late blight

reaction (RAUDPC) for

Jacqueline Lee in com­

parison to susceptible

check varieties . Figure 3

compares the foliage of

Jacqueline Lee and

Snowden approximate­

ly 5 wk after inoculation

with US-8 genotype of

P. infestans at the Muck

Soils Research Farm.

Over four years Jacque­

line Lee was one of the

FIGURE 3. Comparison of foliage from Jacqueline Lee (L) and Snowden (R) 5 weeks after inoculation with the US-8 genotype of P. infestans at the Muck Soils Research Farm, Bath, MI.

416 AMERICAN JOURNAL OF POTATO RESEARCH Vol. 78

TABLE 2-Foliar late blight (Phythopthera infestans)

reaction from. inoculated trials with no fungicide application at the Michigan State Unversity Muck Soils Research Farm, Bath, MI.

RAUDPC Values'

Entry 1997 1998 1999 2000

Jacqueline 1.9 3.8 3.8 0.7 Yukon Gold 19.2 35.8 24.5 27.8 B0718-3 1.9 8.2 7.4 1.2 Atlantic 16.1 34.6 24.3 29.8 Snowden 10.8 35.0 19.3 31.2

LSDo 10.1 5.4 8.4 8.0.05 33DAP 28DAI 28 DAI 39DAI

'Relative Area Under the Disease Progress Curve 2DAI: Days after inoculation.

top lines showing strong foliar resistance comparable to the resis­

tant germplasm B0718-3 (Haynes et al. 1998) and AWN86514-2

(Corsini et al. 1999) both of which are much later in vine matu­

rity. It should be noted that early blight (Alternaria solani) lesions were observed on Jacqueline Lee foliage late in the sea­

son. Kirk, et al. (2001a) evaluated tuber resistance to the US-8

genotype ofP. infestans by injecting a mycelial homogenate into

the tuber periderm at the apical end of the tuber. Based upon

visual examination, Jacqueline Lee had lower tuber susceptibility

rating than other lines and varieties with susceptible foliage.

Jacqueline Lee was also tested in a controlled environment

chamber in the greenhouse in 1998 and 1999following the pro­

tocol of Douches et al. (1997). Table 3 summarizes the data for

Jacqueline Lee. Severity of infection was much higher in the

1998test for B0718-3 compared to 1999. Percent infection of the

foliage and stems 7 days after inoculation was significantly

TABLE 3-Foliar late blight disease reaction in a controlled environment chamber in the greenhouse.

Percent Defoliation (%)'

Entry 1998 1999 Avg.

Jacqueline 10 11 10 B0718-3 82 3 43 Atlantic 34 77 55 Snowden 65 60 63

LSDO.05 45 31 35

'Defoliation was recorded 7 days after inoculation.

2llT"""-------------------, 1988

20

16

10

6

O.L- ---l

LSD....

1899

1101--------------------1

4.35 30

20

10

I 1- _ -0 ......--- ---'• 2llT"""-------------------, 20 2000

LSD..... 4.2216

10

II

o I I

o 33 100

FunglcldI AppIicItIon R8lI(" MInufaeturII'I ~lded AppIicItIon RatI)

FIGURE 4. Response of Jacqueline Lee and Snowden to variable application rates of the standard fungicide, cWorothalonil during three years of inoculated field tests at the Muck Soils Research Farm, Bath, MI.

lower for Jacqueline Lee than for Atlantic and Snowden in both

years and in the combined results. Based on combined results,

B0718-3 was not significantly different from Jacqueline Lee.

Field experiments were conducted with Jacqueline Lee

over three years (1998-2000) at the Muck Soils Research Farm to

evaluate managed fungicide applications to control late blight

under inoculated conditions (Kirk et al. 2001b). The high level

2001 DOUCHES,et al .: JACQUELINELEE 417

TABLE 4-Agronomic performance trials at the Michigan State University Montcalm Research Farm, Erurican; MI.

Yield (mtJh) Percent of Total' Specific Total Days Year US#1 Total US# 1 Bs As OV PO Gravit HII' Cut to Harvest

Jacqueline Lee

1997 32.1 46.6 69 31 68 1 1 1.085 0 20 140 days 1998 42.9 64.6 66 33 66 0 0 1.077 0 40 135 days 1999" 20.0 45.8 44 55 43 0 1 1.079 0 40 140 days 2000" 36.2 54.0 67 31 65 2 2 1.082 0 40 132 days 2000' 46.9 66.5 70 27 65 6 3 1.081 5 40 146 days

Mean 35.6 55.5 63 35 61 2 1.081

Yukon Gold

1997 30.5 32.8 93 7 73 20 1 1.078 16 20 140 days 1998 31.4 35.5 88 10 80 8 2 1.071 0 40 149 days 1999" 27.1 31.3 87 12 77 10 1 1.074 2 40 133 days 2000 46.6 48.4 96 3 62 34 1 1.080 4 40 142 days

Mean 33.9 37.0 91 8 73 18 1.076 6

'Size Distribution: B: < 5.1 em , A:. 5.1- 8.3 em , OV: > 8.3 em, PO: Pickouts. 'HH: HoUow Heart. 'Pota to Early Die symptoms observed. 'Standar d nitrogen rate of 202 kg/ha, 'Higher nitrogen rate of 247 kg/ha,

of foliar resistance to late blight in Jacqueline Lee allowed min­

imal amounts of chemical protectant to be applied to achieve

crop protection (chlorothalonil) (Figure 4). Similar results were

found for the novel chemical protectant fluazinam.

Jacqueline Lee tubers were also evaluated for susceptibility

to Fusarium dry rot (Fusarium sambucinum) and Erwinia soft

rot (Erwinia carotova) . Though resistance was not observed,

the infection level was not unlike other varieties. Infection of the

foliage with PYX, PVY, and PLRV was not observed during field

seed increase or during agronomic trials. No sensitivity to

rnetributzin for Jacqueline Lee was observed when the herbicide

was used at pre-emergence.

AGRONOMIC PRODUCTION

Field experiments were conducted at the Montcalm

Research Farm in Entrican, Ml , to measure total and marketable

yields, determine tuber size distribution, specific gravity,

blackspot bruising and to evaluate tuber appearance, and inci­

dence of external and internal defects. Jacqueline Lee and other

lines and check varieties were planted in a randomized complete

block design with four replications. The plots were 7.01 m in

length and spacing between plants was 30.5 em. Inter-row spac­

ing was 86.4 em. Supplemental irrigation was applied as needed.

Yield was graded into four size classes, incidence of external and

internal defects in tubers >8.3 em diameter or 284 g was

recorded, and samples for specific gravity, chipping, dormancy,

disease tests, bruising, and cooking tests were taken.

Jacqueline Lee is notable for its high set of attractive oval­

shaped tubers with a yellow flesh (Figure 1). These oval shaped,

medium-sized tubers do not fit a typical market class. The tuber

type is more common among European varieties. Four years of

full season agronomic data for Jacqueline Lee in comparison to

Yukon Gold is summarized in Table 4. Total yield for Jacqueline

Lee is high , but the percentage of marketable yield is less than

most round-shaped varieties. Percentage of marketable yield

tends to range between 60% and 800,-0; however, in 1999, only 44%

marketable yield was observed. This subpar performance was

attributed to the severe potato early die symptoms that affected

the tuber sizing in full season varieties like Jacqueline Lee. In the

four years of trials, few off-type tubers were observed (OO/~%).

In addition, a low percentage of oversize (>284g) tubers was

observed (OOAr6%) compared to 8o/~% for Yukon Gold. Tuber

specific gravity ranged from 1.077 to 1.085, while Yukon Gold

was, on average, slightly lower (1.071-1.080). Only an incidental

amount of hollow heart was found in the large-sized tubers. In a

preliminary trial to compare spacing and nitrogen fertilization

levels, Jacqueline Lee responded positively to supplemental

nitrogen side-dress during the season, but not to spacing (25.4

cm vs 35.6 ern).

418 At\1ERICAN JOURNAL OF POTATO RESEARCH Vol. 78

T ABLE 5-Agronomic performance trials from Michigan on-farm. potato trials for' Jacqueline Lee.

Yield (mtJh) Percent of Total ' _ Specific Location US#1 Total US#1 Bs As OV PO Gravity

1999

Tablesto ck Trials" 22.3 36.3 62 37 60 2 I 1.087 Processing Trials" 26.8 46.0 57 38 57 0 4 1.079 St. Joseph Coun ty ' 56.5 82.5 69 31 69 0 0 1.085

2000 Lower Peninsula

Trials ' 36.0 49.5 72 26 64 8 2 1.084 Delta County 59.6 75.2 79 20 56 23 I 1.075

'Size Distribution: B: < 5.1 em, A: 5.1 - 8.3 em, OV: > 8.3 em, PO: Pick­outs . 'Average of thr ee locations: Presqu e Isle, Sanilac, and Delta counties . "Average of four locations: St. Joseph, Allegan, Monro e, and Montcalm counties. 'Average of thr ee harvest dates. 'Average of thr ee locations: Monroe, Bay, and Presque Isle counties .

Jacquelin e Lee was included in four on-farm trials in 2000

(Table 5). The best agronomi c data was collected at the Upper

Peninsula of Michigan site, with 7fJ% marketable yield and 23%

oversize tubers. The three Lower Peninsula locations were aver­

aged and agronomic performance was similar to the trials at the

Montcalm Research Farm location. It should be noted that agro­

nomic perform ance of Jacquelin e Lee was only observed at irri­

gated sites with sandy loam soil types.

Jacqueline Lee has attractive tub ers with few internal

defects making them desirable for the tablestock market. Blind

taste tests were conducted comparing Jacqueline Lee to other

tablestock vari eties such as Russet Burbank, Russet Norkotah,

Superior, and Yukon Gold. Three separate taste tests were con­

ducted in 2000. In each test the tubers were prepared either by

baking, boiling or microwaving. Jacqueline Lee rated high in all

three taste tests (data not shown). In addition, no sloughing or

after-cooking darkening was observed with the cooked tubers .

To evaluate blackspot bruise, two 25-tuber samples were

collected (a composite of four replications) from each line and

variety at the Montcalm Research Farm at the time of harvest

and grading. One sample was placed in 10 C storage overnight

and then tumbled in a hexagon plywood drum 10 times to simu­

late bruise-conducive conditions. The second 25-tuber check

sample was held at room temperature. After holding the tube r

sampl es at ambient indoor temp eratures for 3 wk, the tubers

were peeled in an abrasive peeler and individual tubers were

assessed for the number of blackspot bruises on each potato.

These data from 1999 and 2000are shown in Table 6. The bruise

data are represented in two ways: percentage of bruise-free

potatoes and average number of bruises per tuber. Jacqu eline

Lee has blackspot sus ceptibility similar to Atlantic and Snow­

den (between 1and 2 spots/tuber). Yukon Gold, another yellow­

fleshed variety, was much more tolerant to bruising. The check

samples of Jacqueline Lee have blackspot bruise level between

Atlantic and Snowden (Table 6).

ELECTROPHORETIC PATTERNS

Leaf tissue was sampled from Jacqueline Lee to construct

an electrophoretic fingerprint. The procedures and allelic desig­

nations used are according to Douches and Ludlam (1991). The

transcript for 10 enzyme loci is described below: Mdh­

12121212, Mdh-~~~~, 6-Pgdh-3131s2s2, Idh-1 1111212,

Pgi_1.'2121212, Got-13131313, Got-~~:z5:z5, Pgm_13131313,

Pgm-~22~22, Dia-11111212. This electrophoretic data is

maintained as part of a database with over 200 lines and vari­

eties. The electrophoretic fingerprint is unique to Jacqueline Lee.

CHEMISTRY

Total tuber glycoalkaloids (TGA) were measured on tubers

collected at harvest for three years. These samples were sent to

either Dr. Ken Deahl at the USDNARSIPSI Vegetable Labora-

TABLE fr-Black-spot bruise resul ts of "A"-size tuber samples.

1999 2000

Avg. Spot %Tubers Avg. Spos %Tubers Entry Pe r Tuber Bruise Free Per Tuber Bruise Free

Chec k Sampl es'

Jacqueline 0.4 67 0.5 64 Yukon Gold 0.0 100 0.0 96 Atlantic 1.3 41 0.7 52 Snowd en 0.1 88 0.3 69

Simulated Bruise"

Jacqueline 1.3 22 1.4 12 Yukon Gold 0.1 92 0.4 71 Atlanti c 2.0 20 1.1 41 Snowden 1.1 33 1.1 24

'Tuber samples were collected at harvest , graded, and held until evalua­tion. Samples were abrasive-peeled and score d. 'Tu ber sam ples were collected at harv est, held at 10 C at least 12 hr , and placed in a six-sid ed plywood drum and rotated ten times to produce simul ated bruising. Samples were abr as ive-peeled and scored.

-... ~ ..

2001 DOUCHES, et al. : JACQUELINE LEE 419

TABLE 7-Total glycoalkaloidsl (mg/100 g f resh weight) of foll-haruested tubers from the Michigan State Universi ty Montcalm Research Farm, Entrican, Michigan.

Entry 1998' 1999' 2000' Avg.

Jacqueline Lee 6.5 0.7 6.7 4.7 Atlantic 9.5 1.9 11.4 7.6

'Solid phaseJion pairing extraction (C18) HPLCIPDAdetection . 'USDA-ARS - Deahl. 'Perkins - Maine.

tory or to Brian Perkins at the University of Maine Food Safety

Laboratory for analysis. For these TGA analyses the extraction

and rap id high-performance liquid chromatographic determina­

tion method as des cribed by (Carman et al. 1986) were used .

Table 7 summarizes the TGA data for Jacqueline Lee along with

Atlantic for 1998-2000.

SEED AVAILABILITY

Virus-free tissue culture plantlets of Jacqueline Lee were sent

to Sklarczyk Seed Farm (8714 M32 East, Johannesburg, Ml49751;

phone: 517-731-5452) and Krueger Seed Farm (2797 W. Hawkes

Hwy, Hawks, Ml49743; phone: 517-734-7366). Small amounts of

seed for testing can be obtained from Dave Douches at Michi­

gan State University (517-355-6887, douchesd@msu.edu). Plan t

Variety Protection is being appli ed for Jacqueline Lee.

ACKNOWLEDGMENTS

The development and testing of Jacqueline Lee was sup­

po rted in part by the Michigan Agricultural Experiment Station,

Project GREEEN (Gen erating Research and Extension to meet

Economic and Environmental Needs), Michigan Potato Indus­

try Commiss ion, and the USDA Special Gran t for Potato Breed­

ing/Variety Development. Chris Long, Lynn Buzka, and Jarred

Driscoll provided technical support.

LITERATURE CITED

Cannan. A.S., S.S. Shia, G.M. Ware, O.J. Francis , and G.P. Kirschen­heut er. 1986. Rapid high-performance liquid chromatographic determination of the potato g1ycoalkaloids oc-solanine and oc-cha­conine. J Agric Food Chern 34:279-282.

Corsini, D., J. Pavek, C. Brown, D. Inglis , M. Martin, M. Powelson, A Dor­rance, and H. Lozoya-Saldana 1999. Late blight resistant potato germplasm release AWN86514-2. Am J Potato Res 76(1): 45-49.

DeJong, H., T.R. Tarn, A M. Murphy, G.C.C. Tal, R.H. Bagnall, W.J. Arse­nault, J.H.E. Thorpe, H.W. Platt, DA Young , and H.T. Davies. 1995. AC Chaleur: A new early-maturing cultivar with excellent table quality. Am Potato J 72(7): 393-400.

Douches , D.S., W.W. Kirk, K. Jastrzebski , C. Long, and R. Hammer­sc hmidt. 1997. Greenhouse screen ing of potato var ieties and advanced breeding lines (Solanum tuberosum L.) for suscepti­bility to Phytophthora i nfestans (Mont.) de Bary. Am Potato J 74:75-86.

Douches, D.S.,and K.Ludlam. 1991. Electrophoretic characterization of North American potato varieties. Am Potato J 68:767-780.

Haynes, KG., D.H. Lambert, B.J. Christ, D.P. Weingartner, D.S.Douches, J.E. Backlund, G. Secor, W. Fry, and W. Stevenson. 1998.Pheno­typic stabili ty of resistan ce to late blight in potato clones evalu­a ted at eight sites in the United States. Am J Potato Res 75:211-217.

Kirk, W.W., KJ . Felcher, D.S. Douches, B.A Niemira, and R. Hammer­schmidt. 2001a Susceptibility of potato (Solanum tuberosum L.) foliage and tubers to the US8 genotype of Phytophthora infes­tans. Am J Potato Res 78(4):319-322.

Kirk, W.W., K.J. Felcher, D.S. Douches, J.M. Stein, K.M. Baker, and R. Hanunerschmidt. 2001b. Combining host plant resistance with managed fpngicide appli cations to control potato late blight (PhytophlJiora in,[estan.~): 1) Influence of rate of application of residual contact fungicides. Plant Disease 85:1113-1118.