POTATO ( Solanum tuberosum )

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					POTATO (Solanum tuberosum)                            R. V. James, W. R. Stevenson, J. P. Helgeson and G.
                                                             T. Haberlach
               Early Blight; Alternaria solani                         Department of Plant Pathology
    Late Blight; Phytophthora infestans               University of Wisconsin-Madison, Madison, WI 53706
                         .
       EVALUATION OF POTATO BREEDING SELECTIONS TO IDENTIFY FIELD RESISTANCE
TO EARLY BLIGHT AND LATE BLIGHT, 1997: A separate trial was placed in the two outer rows of
the variety evaluation trial to evaluate a group of backcross-2 progeny obtained from J. Helgeson,
USDA/ARS Plant Resistance Laboratory, UW-Madison for reaction to early and late blight. These lines
were all obtained from crosses with J101 K6, a progeny line from the cross of a somatic hybrid between
Solanum bulbocastanum and S. tuberosum (J101) backcrossed to Katahdin (K). J101 K6 was backcrossed
to Atlantic and a group of progeny lines from this backcross were tested in an attempt to map the
resistance coming from S. bulbocastanum. One of these lines, J101K6A22 is also the parent of a key
mapping backcross-3 population. These materials segregate nicely for late blight and early blight resistance
Three small tubers were planted for each plot of each test line and they were separated within the row by
two Dark Red Norland seedpieces. The trial was maintained and evaluated as described for the larger trial.
Tubers from selected plots were dug by hand.

     Weather conditions throughout June, July and August contributed to heavy early blight and late blight
(US#8 genotype) pressure in this plot. By the time of the last rating on September 2, many lines exhibited
100% foliage infection by one or both pathogens. Since no fungicide was used in this plot, both diseases
were unimpeded by foliar sprays and, once established, disease progress was rapid. The standard Katahdin
exhibited early blight symptoms on over 15% of the foliage and late blight symptoms on over 61% of the
foliage by the August 25 rating. Several breeding selections exhibited early blight susceptibility similar to
Katahdin, although there were many selections with greater early blight susceptibility than Katahdin. While
several selections exhibited similar late blight susceptibility to Katahdin, there were several selections that
exhibited no late blight symptoms up to vinekill. These promising selections included J101 K6 A2, J101 K6
A6, J101 K6 A21, J101 K6 A27, J101 K6 A42A, J101 K6 A42B, J101 K6 A46, J101 K6 A48, J101 K6
A49, J101 K6 A51, J101 K6 A61, J101 K6 A68 and J101 K6 A70. Several selections with low early blight
and late blight severity includedJ101 K6 A4, J101 K6 A5, J101 K6 A15 and J101 K6 A22.




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Table 1.        Severity of early and late blight infection..
                                                                       Percent foliage infection 1
Cultivar or                                       Early Blight (alone)                  Late Blight (alone)                                Combined
breeding selection 7/1                   7/8 7/14 7/21 7/28 8/4 8/8 8/14 8/25 9/2 8/4 8/8 8/14 8/25 9/2                            8/4    8/8 8/14 8/25 9/2
 1                            ........
     Ckatahdin.................... 0.5   0.3   2.3   3.6 6.0     6.5    6.2   26.0   15.6     --   0.0   0.0   9.6   61.1     --    6.5    6.2   46.9    80.2   100.0
 2                            ........
     cR4#203900................. 0.8     1.0   1.3   5.5 6.2     8.8   13.5   43.1   36.8     --   0.0   0.0   0.0   47.9     --    8.8   13.5   43.1    79.8   100.0
 3                            ........
     J101 K6 A1................ 0.0      0.0   0.0   0.3 2.6     3.6    7.3   53.1   37.5     --   0.0   0.5   0.0   62.5     --    3.6    7.8   53.1    97.7   100.0
 4                            ........
     J101 K6 A2................ 0.0      0.5   1.0   2.6 3.6     4.7    6.8   29.9   59.7   88.3   0.0   0.0   0.0    0.0    0.0    4.7    6.8   29.9    59.7    91.9
 5                            ........
     J101 K6 A4................ 0.0      0.3   0.0   2.1 2.9     5.5    7.8   12.5   18.7   45.8   0.0   0.0   0.0    0.3    2.6    5.5    7.8   12.5    19.8    62.5
 6                            ........
     J101 K6 A5................ 0.0      0.0   0.5   3.1 2.1     5.7    3.4    9.4   22.6   44.1   0.0   0.0   0.0    0.8    6.8    5.7    3.4    9.4    25.7    64.1
 7                            ........
     J101 K6 A6................ 0.0      0.5   1.6   3.9 3.9     9.9   13.5   40.6   54.2   73.4   0.0   0.0   0.0    0.0    0.0    9.9   13.5   40.6    54.2    73.4
 8                            ........
     J101 K6 A7................ 0.0      0.0   1.3   2.9 6.5    13.0   29.2   58.9   67.7     --   0.0   0.0   0.0   13.3     --   13.0   29.2   58.9    92.4   100.0
 9                            ........
     J101 K6 A9................ 0.3      0.0   0.9   3.4 2.6     7.3    9.9   21.5   40.6   67.7   0.0   0.0   0.0    1.0    2.6    7.3    9.9   21.5    43.4    78.1
10                            ........
     J101 K6 A11.............. 0.3       0.8   1.6   5.7 10.9   49.3   85.9   89.3     --     --   0.0   0.0   1.0     --     --   49.3   85.9   91.4    99.0   100.0
11                            ........
     J101 K6 A12.............. 0.0       0.0   0.8   7.0 7.5    36.9   44.1   79.4   62.5     --   0.0   0.0   0.0    0.0     --   36.9   44.1   79.4    74.7    99.7
12                            ........
     J101 K6 A13.............. 0.0       0.5   1.0   4.2 7.5    18.2   72.9   93.8     --     --   0.0   0.0   0.0     --     --   18.2   72.9   93.8   100.0    99.7
13                            ........
     J101 K6 A15.............. 0.0       0.0   0.0   0.8 1.0     1.6    3.1    7.5   12.5   59.4   0.0   0.0   0.0    0.4    9.4    1.6    3.1    7.5    42.4    87.5
14                            ........
     J101 K6 A16.............. 0.0       0.0   0.5   4.7 3.9    17.2   48.8   64.1   23.4     --   0.0   0.0   0.0    1.2     --   17.2   48.8   64.1    48.4    99.5
15                            ........
     J101 K6 A17.............. 0.0       0.0   0.8   0.3 1.0     5.2    5.7   21.9   45.3   81.3   0.0   0.0   0.0    0.8    0.0    5.2    5.7   21.9    49.5    89.6
16                            ........
     J101 K6 A19.............. 0.0       0.0   0.3   2.3 3.4     4.7    8.8   16.7   37.5   58.3   0.0   0.0   0.0    0.0    3.9    4.7    8.8   16.7    37.5    64.6
17                            ........
     J101 K6 A21.............. 0.0       0.0   0.7   1.6 2.3     8.8    9.0   20.8   54.2   83.3   0.0   0.0   0.0    0.0    0.0    8.8    9.0   20.8    54.2    83.3
18                            ........
     J101 K6 A22.............. 0.0       0.0   0.3   1.6 2.1     3.4    5.2   10.9   13.5   31.2   0.0   0.0   0.0    4.2    4.2    3.4    5.2   10.9    20.8    45.8
19                            ........
     J101 K6 A24.............. 0.0       0.0   0.3   1.6 2.9     7.8   20.8   46.9   28.1     --   0.0   0.0   6.0   51.0     --    7.8   20.8   52.1    97.9   100.0
20                            ........
     J101 K6 A27.............. 0.3       0.5   0.5   2.6 3.4     7.3   15.1   30.9   70.8   94.5   0.0   0.0   0.5    0.0    0.0    7.3   15.1   33.0    70.8    96.1
21                            ........
     J101 K6 A28.............. 0.0       0.0   1.2   2.1 4.2     6.5    7.0   25.0   12.5     --   0.0   0.0   0.0   38.3     --    6.5    7.0   25.0    51.2   100.0
22                            ........
     J101 K6 A29.............. 0.0       0.3   0.0   4.2 4.2    12.0   30.2   27.1   14.1     --   0.0   0.0   0.3   66.7     --   12.0   30.2   27.1    84.4   100.0
23                            ........
     J101 K6 A33.............. 0.5       0.8   1.0   4.4 4.2    12.5   25.0   60.4   37.5     --   0.0   0.3   0.0   62.5     --   12.5   25.0   60.4    95.3   100.0
24                            ........
     J101 K6 A36.............. 0.0       0.0   0.5   1.3 1.8     8.3   10.9   72.2   62.5     --   0.0   0.0   0.0    0.0     --    8.3   10.9   72.2    95.8   100.0
25                            ........
     J101 K6 A37.............. 0.0       0.3   1.6   4.7 9.9    17.7   36.8   75.8   18.8     --   0.0   1.6   1.2   62.5     --   17.7   39.9   81.5    95.6   100.0
26                            ........
     J101 K6 A40.............. 0.0       0.0   0.3   2.3 4.7    18.7   40.6   90.6   18.8     --   0.0   0.0   0.0   12.5     --   18.7   40.6   90.6    97.7   100.0
27                            ........
     J101 K6 A42A .......... 0.0         0.0   0.0   2.3 3.6     8.3    9.9   38.5   37.5   91.1   0.0   0.0   0.0    0.0    0.0    8.3    9.9   38.5    37.5    91.1
28                            ........
     J101 K6 A42B........... 0.0         0.0   0.3   2.6 3.4     9.1   17.7   29.5   54.9   95.3   0.0   0.0   0.0    0.0    0.0    9.1   17.7   29.5    54.9    96.4
29                            ........
     J101 K6 A44.............. 0.0       0.3   0.3   2.9 5.5    21.0   45.6   61.3     --     --   0.0   0.0   0.3     --     --   21.0   45.6   63.4   100.0   100.0
30                            ........
     J101 K6 A45.............. 0.0       0.0   0.3   1.6 2.9     5.2    6.2   17.7   15.6   52.1   0.0   0.0   0.5    6.2   37.8    5.2    6.2   20.5    29.2    76.7
31                            ........
     J101 K6 A46.............. 0.0       0.3   0.5   3.9 4.4    15.6   48.6   85.9     --     --   0.0   0.0   0.0     --     --   15.6   48.6   85.9   100.0   100.0
32                            ........
     J101 K6 A48.............. 0.3       0.0   0.0   1.3 3.9     3.4    7.3   26.0   40.3   90.9   0.0   0.0   0.0    0.0    0.0    3.4    7.3   26.0    40.3    90.9
33                            ........
     J101 K6 A49.............. 0.0       0.0   1.6   2.9 3.4     7.3   21.5   49.3   81.3     --   0.0   0.0   0.0    0.0     --    7.3   21.5   49.3    87.5   100.0

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                                                                     Percent foliage infection 1
Cultivar or                                     Early Blight (alone)                  Late Blight (alone)                                                 Combined
breeding selection 7/1                 7/8 7/14 7/21 7/28 8/4 8/8 8/14 8/25 9/2 8/4 8/8 8/14 8/25 9/2                                            8/4     8/8 8/14 8/25 9/2
34                                 ........
     J101 K6 A51.............. 0.0 0.3 0.3                  2.9 9.4 46.0 83.9 93.8               --   --    0.0 0.0     0.0      --     -- 46.0 83.9 93.8 100.0 100.0
35                                 ........
     J101 K6 A57.............. 0.0 0.5 0.3                  5.2 4.4       6.8 20.5 35.8 18.8          --    0.0 0.0     0.0 12.5        --   6.8 20.5 35.8 97.4 100.0
36                                 ........
     J101 K6 A60.............. 0.0 0.3 0.0                  3.4 6.0       8.1 14.1 43.8          --   --    0.5 1.0     3.1      --     --   9.1 15.1 56.3 99.7 100.0
37                                 ........
     J101 K6 A61.............. 0.0 0.0 0.5                  3.1 5.5 28.6 58.3 92.7               --   --    0.0 0.0     0.0      --     -- 28.6 58.3 92.7 100.0 100.0
38                                 ........
     J101 K6 A62.............. 0.0 0.3 0.0                  2.3 3.9       7.8 12.5 27.1          --   --    0.0 0.0     6.2      --     --   7.8 12.5 42.4 99.5 100.0
39                                 ........
     J101 K6 A68.............. 0.0 0.0 0.3                  3.9 6.0 18.7 40.3 85.4               --   --    0.0 0.0     0.0      --     -- 18.7 40.3 85.4 99.5 100.0
40                                 ........
     J101 K6 A70.............. 0.0 0.0 0.3                  1.0 2.6       4.7 7.8 15.6 32.3 53.1            0.0 0.0     0.0 0.0       0.0    4.7 7.8 15.6 32.3 67.7
     Pr > F 2 .........................< 0.01 0.17 < 0.01 < 0.01< 0.01 < 0.01 < 0.01 < 0.01 < 0.01 0.02    0.49 0.49 < 0.01 < 0.01 < 0.01 < 0.01 < 0.01 < 0.01 < 0.01 < 0.01
     LSD (P = 0.05) 2 .......... 0.3 NS 1.1
                                   ........                 1.8 3.9 15.7 25.1 27.2 32.3 38.8                NS NS       3.7 28.6 14.6 15.7 25.1 28.0 29.6 14.9

1    Severity rated on a Horsfall-Barratt scale of 0 (no infection) to 11 (all foliage and stems dead). Ratings were converted to percentages. Combined foliage infection was assessed first. Then
     amount of early and late blight were estimated separately (the separate estimates do not necessarily add up to the combined infection figure as they were done independently).
2    Analysis of variance was performed on data, and Fisher's protected least significant difference (LSD) was calculated. NS = not significant at the P = 0.05 (or P = 0.10) level. * = Differences
     between pairs of treatments were significant at P = 0.10 (but not at P = 0.05).




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Table 2. AUDPC of potato breeding selections.

                                                                                   Relative AUDPC 1
                                                   Early Blight Alone                          Late Blight Alone
 Breeding Selection                            Early                Full                   Early                     Full               Combined
 1   CKatahdin ...................  ............... 0.053             ---                  0.029                       ---                  0.272
 2   cR4#203900.................    ............... 0.079             ---                  0.000                       ---                  0.276
 3   J101 K6 A1................     ............... 0.054             ---                  0.003                       ---                  0.295
 4   J101 K6 A2................     ............... 0.046          0.192                   0.000                    0.000                   0.207
 5   J101 K6 A4................     ............... 0.032          0.091                   0.000                    0.004                   0.103
 6   J101 K6 A5................     ............... 0.026          0.089                   0.000                    0.012                   0.106
 7   J101 K6 A6................     ............... 0.071          0.213                   0.000                    0.000                   0.213
 8   J101 K6 A7................     ............... 0.106             ---                  0.000                       ---                  0.329
 9   J101 K6 A9................     ............... 0.046          0.155                   0.000                    0.007                   0.166
10   J101 K6 A11..............      ............... 0.250             ---                  0.003                       ---                  0.468
11   J101 K6 A12..............      ............... 0.175             ---                  0.000                       ---                  0.367
12   J101 K6 A13..............      ............... 0.190             ---                  0.000                       ---                  0.429
13   J101 K6 A15..............      ............... 0.014          0.091                   0.000                    0.000                   0.136
14   J101 K6 A16..............      ............... 0.135             ---                  0.000                       ---                  0.286
15   J101 K6 A17..............      ............... 0.031             ---                  0.000                       ---                  0.172
16   J101 K6 A19..............      ............... 0.037          0.134                   0.000                    0.005                   0.138
17   J101 K6 A21..............      ............... 0.043          0.183                   0.000                    0.000                   0.183
18   J101 K6 A22..............      ............... 0.024          0.066                   0.000                    0.019                   0.087
19   J101 K6 A24..............      ............... 0.073             ---                  0.018                       ---                  0.310
20   J101 K6 A27..............      ............... 0.059             ---                  0.002                       ---                  0.239
21   J101 K6 A28..............      ............... 0.045             ---                  0.000                       ---                  0.194
22   J101 K6 A29..............      ............... 0.081             ---                  0.001                       ---                  0.271
23   J101 K6 A33..............      ............... 0.102             ---                  0.001                       ---                  0.331
24   J101 K6 A36..............      ............... 0.078             ---                  0.000                       ---                  0.325
25   J101 K6 A37..............      ............... 0.142             ---                  0.011                       ---                  0.383
26   J101 K6 A40..............      ............... 0.143             ---                  0.000                       ---                  0.390
27   J101 K6 A42A...........        ............... 0.057          0.188                   0.000                    0.000                   0.188
28   J101 K6 A42B ...........       ............... 0.062          0.223                   0.000                    0.000                   0.213
29   J101 K6 A44..............      ............... 0.134             ---                  0.001                       ---                  0.364
30   J101 K6 A45..............      ............... 0.033          0.095                   0.002                    0.074                   0.135
31   J101 K6 A46..............      ............... 0.148             ---                  0.000                       ---                  0.393
32   J101 K6 A48..............      ............... 0.039          0.168                   0.000                    0.000                   0.168
33   J101 K6 A49..............      ............... 0.079             ---                  0.000                       ---                  0.294
34   J101 K6 A51..............      ............... 0.237             ---                  0.000                       ---                  0.462
35   J101 K6 A57..............      ............... 0.073             ---                  0.000                       ---                  0.292
36   J101 K6 A60..............      ............... 0.071             ---                  0.016                       ---                  0.320
37   J101 K6 A61..............      ............... 0.180             ---                  0.000                       ---                  0.421
38   J101 K6 A62..............      ............... 0.053             ---                  0.019                       ---                  0.295
39   J101 K6 A68..............      ............... 0.144             ---                  0.000                       ---                  0.388
40   J101 K6 A70..............      ............... 0.032          0.083                   0.000                    0.000                   0.127
     Pr > F 2 .........................
                                    ..............< 0.01           <0.01                   <0.01                    <0.01                   <0.01
     LSD (P = 0.05)2 ...........   ................ 0.052          0.078                   0.012                    0.024                   0.082
     1.    Relative area under the disease progress curve. Data for each observation date are plotted on a graph and the relative area under the line is
           calculated for each treatment providing a measure of the relative severity of disease throughout the season. A disease rating of 100% foliage
           infection for the entire season would produce a value of 1.0. All relative AUDPC values are expressed as the proportion of this value. Either
           decreased disease severity or later disease development will contribute to lower relative areas under the disease progress curve. Early season early
           blight AUDPC includes data from July 1-July 29; Full season early blight AUDPC is July 1-August26; Early season late blight AUDPC is July
           22-August 12; Full season late blight AUDPC is July 22-August 26. AUDPC for combined defoliation combines early blight ratings through
           July 15 and combined foliage infection ratings for the rest of the season.


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2.   Analysis of variance was performed on data, and Fisher's protected least significant difference (LSD) was calculated. NS = not significant at the P
     = 0.05 (or P = 0.10) level. * = Differences between pairs of treatments were significant at P = 0.10 (but not at P = 0.05).




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