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POTATO (Solanum tuberosum) R. Zhang and B.J. Christ
Early blight; Alternaria solani Department of Plant Pathology
The Pennsylvania State University
University Park, PA 16802
Severity of early blight on potato cultivars and breeding Lines, 2002.
Forty-one potato cultivars and advanced breeding lines were evaluated at the Russell E. Larson Agricultural Research
Center at Rock Springs, PA. Soil type was Hagerstown silty clay loam. The previous crop was clover. Entries were planted on
24 May in a randomized complete block design with four replicates. Plots consisted of a single 10-ft row with a 5-ft break
between treatments. Fifteen seed pieces were hand-planted and spaced 8-in. apart. Each entry was surrounded by the susceptible
cultivar Norland. Fertilization was 695 lb/A of 10-10-5 (N-P-K) banded in the row during planting. Rainfall was 0.92, 5.23,
1.00, 2.15 in. for May after planting, Jun, Jul, and Aug, respectively. The field was irrigated about 0.56, 1.00, 1.25 and 1.45 in.
on 12 Jul, 23 Jul, 30 Jul and 15 Aug, respectively. The inoculum was from nature. Early blight was assessed on 8, 19 and 26
Aug. Each plot was assessed by visually dividing the plot into three sections and assessing the percentage of diseased foliage in
each section. These values were averaged to obtain a mean disease severity value per plot. Plants were vine-killed on 5 Sep and
harvested on 24 Sep. Tubers were graded into size categories and all those greater than 17/8 -in. diameter were weighed to
determine yield. Disease and yield data were subjected to an analysis of variance and Fisher’s protected least significant
difference test. Vine maturities and yields of all cultivars and lines also were recorded on non-replicated plots that were located
in a nearby field that was managed with fungicide sprays to reduce early blight infection. Specific gravity was evaluated for both
diseased and healthy plots (data are not shown here).
Early blight severity was low prior to 1 Aug. Low levels of natural inoculum and low rainfall delayed the onset of disease.
All yields reported here were relatively low when compared with yields in sprayed plots (data not shown). ARS-W96-400061,
B1240-1, Katahdin, W1242, A90586-11, AF1775-2, AF1753-16, Russet Burbank, Brise du Nord, Gem Russet, Snowden,
AF1455-20, Atlantic, and Kennebec all had low levels of early blight, and we consider them moderately resistant. The specific
gravity of Chieftain, Dark Red Norland, Envol, ARS-W-96-40022-5 and W1313, was higher in diseased plots than in healthy
plots. The specific gravity of Shepody was reduced in diseased plots.
Cultivar/Line %EarlyZ >17/8-in yieldX Cultivar/Line %EarlyZ >17/8-in yieldX
blight (cwt/A) blight (cwt/A)
Aquilon ..........................41.3 fghijW 180.3 efghijklm AF1470-6......................55.0 ijklmn 216.8 jklmnopq
Atlantic ..........................16.3 abcd 213.9 jklmnop AF1569-2......................30.0 cdefgh 284.5 rs
Brise du Nord.................13.8 abcd 214.4 jklmnopq AF1753-16....................12.5 abcd 202.7 hijklmnop
Chieftain ........................41.3 fghij 228.6 lmnopqr AF1758-7......................31.3 defgh 188.7 fghijklmn
Dark Red Norland..........98.8 o 163.4 defghijk AF1763-2......................61.3 klmn 165.4 defghijk
Envol..............................100.0 o 140.0 bcdefgh AF1775-2......................11.3 abc 242.0 mnopqrs
Gem Russet....................13.7 abcd 98.9 abc AF1938-3......................41.3 fghij 242.9 mnopqrs
Katahdin.........................8.8 ab 253.4 opqrs AF2133-17....................66.0 lmn 123.3 abcde
Kennebec .......................17.5 abcd 263.0 pqrs ARS-W96-4654-1 ........31.3 defgh 87.7 ab
KeukaGold.....................26.3 abcdefg 252.5 opqrs ARS-W96-400061........7.5 a 159.3 cdefghijk
Roselys...........................47.5 hijkl 277.1 prs ARS-W96-40022-5 ......94.5 o 76.8 a
Russet Burbank..............12.5 abcd 150.1 bcdefghi ATX84706-2Ru............23.8 abcdef 299.0 s
Russet Legend................47.5 hijkl 153.8 cdefghij B1240-1 ........................7.5 a 300.3 s
Russet Norkotah ............70.0 mn 168.7 defghijkl B1425-9 ........................36.5 efghi 219.4 klmnopq
Shepody .........................27.5 bcdefg 194.6 ghijklmno B1523-4 ........................21.3 abcde 293.5 rs
Snowden ........................13.8 abcd 172.9 efghijkl CO86218-2 ...................31.3 abcde 108.1 abcd
Superior..........................57.5 jklmn 244.4 nopqrs NY102 ..........................43.8 ghijk 145.5 bcdefghi
Yukon Gold ...................73.8 n 246.0 nopqrs NY115 ..........................52.5 ijklm 171.1 defghijkl
Ware’s Pride ..................47.5 hijkl 126.8 abcdef W1242 ..........................8.8 ab 237.8 mnopqrs
A90586-11 .....................10.0 ab 136.7 abcdefg W1313 ..........................20.0 abcde 161.0 cdefghijk
AF1455-20.....................15.0 abcd 206.4 ijklmnop
Z
Assessed on 19 Aug.
X
cwt/A = Hundred weight per acre.
W
Means followed by the same letter are not significantly different, Fisher’s protected LSD, P = 0.05.
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