36
A74212-1, A High Yielding, Russet-Skinned
Oregon Selection Adapted to the Klamath Basin.
K. A. Rykbost, G. E. Carter and J. Maxwelll
INTRODUCTION
Russet Burbank, which accounts for the majority of production in the
Klamath Basin, requires a long frost-free season to achieve high yields and
suitable size. Typically only a small percentage of the crop makes the 7080 count carton grade which commands the highest price. Up to 30 percent of
Russet Burbank crops grade out as B's or culls under Klamath Basin conditions.
In 1981 an Oregon selection, A74212-1, was evaluated at KES for the
first time. In succeeding years this selection has demonstrated exceptional
yield potential at KES and other locations. A high percentage of the
A74212-1 crop has graded U.S. No. I's in the 70-80 and 90 count sizes.
Grade out for B's and culls has been about 15 percent of total production.
Skin netting and thickness is
A74212-1 is not without deficiencies. less than for Russet Burbank. In organic soils the netting may be unacceptable. In small commercial trials, skinning damage at harvest has resulted
in the development of excessive disease in storage on more than one
occasion.
Seed decay problems have been experienced in research and
commercial plantings.
Poor stands have resulted in excessive tuber size
which compounds the potential for harvest damage.
In 1987 and 1988 several cultural management experiments were conducted
at KES to identify practices that would minimize weaknesses in A74212-1.
This report will summarize the performance of A74212-1 at KES over eight
years, and identify cultural management practices that will enhance the
chances for the successful commercialization of this seedling following its
official release.
I. VARIETY SCREENING TRIAL PERFORMANCE
Procedures:
Screening trials conducted from 1981 through 1988 included large numbers
of entries in a randomized complete block design with three or four replications. Plots were single rows with 12 to 30 hills. Planting dates ranged
from May 15 to June 10 and vine desiccation dates from September 1 to September 15. Seed spacings were 12 inches in 32-inch rows. Standard cultural
practices for Russet Burbank production were followed.
1/ Superintendent/Associate Professor, Associate Professor
Emeritus, Experimental Biology Technician, respectively,
Klamath Experiment Station.
37
Results and Discussion:
In each year since 1981 A74212-1 exceeded Russet Burbank in yield of
No. l's by a minimum of 90 cwt/A (Table 1). More detailed analyses of 1988
performance are presented in the report on the Oregon Statewide Trial. In
the 1987 Statewide trial A74212-1 produced 366 cwt/A of No. l's over 6
ounces, compared with 151 cwt/A for Russet Burbank.
High specific gravity is not an essential quality for all fresh market
crops. Early maturing russets, red-skinned varieties and white-skinned
fresh market varieties are usually much lower in specific gravity than
Russet Burbank. However, for russeted varieties to successfully replace
Russet Burbank as an acceptable baking variety, relatively high specific
gravity will be a prerequisite. A74212-1 has demonstrated the ability to
achieve acceptable solids content when managed under conditions appropriate
for Russet Burbank.
II. RESPONSE OF A74212-1 TO SEED SPACING AND N-RATE
Procedures:
In 1987 A74212-1 and other selections were planted at seed spacings of
6, 9, and 12 inches in 32-inch rows on May 26. - Individual plots were one
Vines were desiccated on September 22 and plots were
row, 15 feet long.
harvested on October 5. Standard cultural practices were followed.
In 1988 A74212-1 and nine other entries were evaluated in two separate
experiments for their response to seed spacing and nitrogen fertilization
rates. Procedural details will be presented later in this report.
Results and Discussion:
In several screening trials A74212-1 exhibited plant stands of 80
percent or less. In combination with low planting density, this resulted in
the production of very large tubers, some of which would be unacceptable
for fresh markets. High nitrogen rates undoubtedly contributed to excessive
size and reduced specific gravity.
In both 1987 and 1988 increasing plant populations increased total and
No. 1 yields markedly (Table 2). Increased seed spacing consistently
reduced yields of all classes up to 10-ounce and increased the percentage
and yield of off-grade tubers. The 1987 crop exhibited roughness with
increasing percentages of No. 2's and culls at lower populations. In 1988
off-grade tubers were a much smaller percentage of total yields, but a
similar response was observed.
The closest seed spacing tested was the most economical in both years,
even under a high seed price situation. While relatively high yields are
possible at low populations, excessive tuber size enhances the risk of harvest and handling damage. Large tubers used for seed may contribute to poor
stands due to inadequate eye distribution and hence "blind" seed pieces.
Appropriate management of seed spacing will be essential for optimum performance of A74212-1 for seed and fresh market crops.
38
In 1988 the
The response of A74212-1 to nitrogen rate is less clear.
However,
yield of No. 1's increased at higher nitrogen rates (Table 3). this increase was achieved by a shift in tuber size distribution toward
excessive size, more susceptible to harvest damage. In view of a tendency
for difficulty in killing vines and obtaining adequate resistance to harvest
damage, a yield sacrifice may be justified. Additional data are needed to
clarify this question.
III. RESPONSE OF A74212-1 TO SEED SOURCE AND CUTTING TIME
Previous experiences with poor stands and seed decay may have been due to
isolated seed management factors, a genetic weakness in A74212-1, or a combination of both. This experiment compared a range of seed from nuclear to
the equivalent of foundation class, under two management regimes that would
be expected to affect seed decay problems differently.
Procedures:
Five sources of A74212-1 seed were either cut, treated with TOPS 2.5 D,
and suberized for 10 days prior to planting or cut, treated and planted the
Three of the sources were stored at KES under identical
following day.
conditions from October, 1987, until planting. A factorial randomized comIndividual plots were
plete block design with four replications was used. two rows, 30 feet long. Seed spacing was 8.7 inches and nitrogen rate was
180 lb. N/A.
The seed lot designated as 'Deschutes C.' was 100 percent tubers in
excess of 10 ounces, most of them with at least one fusarium dry rot lesion.
Several exhibited other fungal or bacterial diseases. Other seed lots were
2- to 12-ounce size with very little evidence of storage diseases. All lots
were hand cut to 1.5- to 2.0-ounce seed size and batch treated with TOPS 2.5
D. Cutting knives were only disinfected between lots and no effort was made
to sort and discard diseased pieces,,either at cutting time or at planting.
Seed was stored at approximately 55 F and 90 percent R.H. prior to planting
The potatoes were planted on May 20, desiccated on September 12, and
harvested on September 31. All tubers were weighed in the field and
approximately 120-pound samples per plot were stored and graded in early
November.
Results and Discussion:
Emergence data were obtained 31 days and 46 days after planting (Table
4). KES and Deschutes C. lots were slightly slower to emerge. Cutting time
did not affect emergence rate or final stands, in spite of differences in
disease inoculum and a period of cool and wet weather between planting and
emergence. Final stands were similar and acceptable for all seed lots.
Crop vigor was excellent throughout the growing season. Except for the
Oregon Foundation Seed Project (OFSP) nuclear lot, senescence set in by
early September. The OFSP lot maintained lush growth and continued flowering until vine desiccation and frost stopped vine growth in mid September.
Vines in this seed lot were not completely desiccated at harvest.
-
39
Yields were exceptionally high for all treatments. The average yield of
No. l's was nearly doubled that achieved by Russet Burbank in several
adjacent experiments. The OFSP lot was slightly, but not statistically,
higher in yield of No. l's and total yield than other seed sources. Cutting
time did not affect yield or tuber size distribution. The fusarium infected
Deschutes C. source was equivalent in performance to other seed sources.
High levels of fusarium infection in one seed lot did not reduce stands,
yields, or quality, in a season when stand and yield problems were
experienced in a few commercial fields of Russet Burbank.
Excessive vine vigor in nuclear seed is consistent with observations
from other research and suggests that reduced nitrogen fertilization rates
may be appropriate for nuclear seed which is relatively pathogen-free.
Procedures:
IV. RESPONSE OF A74212-1 TO SEED TREATMENT
The Deschutes C. seed source, highly infected with fusarium dry rot, was
used exclusively. Seed was hand cut to 1.5- to 2.0-ounce seed piece size on
May 19. Knives were not disinfected during cutting and no attempt was made
to sort and discard fusarium infected material. After cutting, appropriate
quantities of seed were batch treated with nine different treatments. One
batch remained untreated.
The experiment was a randomized complete block design with 10 treatments
and four replications. Individual plots were two rows, 30 feet long.
Potatoes were planted on May 20, desiccated on September 12, and harvested
on October 5. All tubers from both rows were weighed in the field and approxately 60-pound samples per plot were stored and graded in early
November.
Results and Discussion:
Treatment of cut seed with Spotless resulted in delayed emergence, phytotoxic injury to emerged plants, a slight reduction in yield, and a significant effect on tuber size distribution (Table 5). A reduction in tuber
set appears to be responsible for the dramatic shift in size distribution.
The TOPS-Rovral treatment also reduced final stands slightly.
The highest yield of No. l's occurred in the untreated control. This is
surprising for a seed lot with a high level of fusarium infection, particularly when a period of cool, wet conditions followed planting. However,
failure to observe stand and yield effects under adverse conditions is an
indication that A74212-1 has some level of tolerance to fusarium infection
in seed.
40
SUMMARY AND CONCLUSIONS
Over a period of eight years the A74212-1 selection has demonstrated
outstanding yielding ability in the Klamath Basin. Management of cultural
practices to control tuber size will be very important for successful comA combination of relatively high plant
mercialization of this seedling.
populations and modest nitrogen rates maintained appropriate size distribution for fresh markets.
A74212-1 has a thinner skin than Russet Burbank. A 1987 experiment at
KES demonstrated a greater susceptibility to skinning damage at harvest for
A74212-1 at 10 days after topkilling. One commercial experience in the
Klamath Basin in 1988 confirmed the importance of delaying harvest until
skin maturity is adequate to resist damage. It seems likely that seed decay
problems experienced in the past were at least partially caused by damage at
harvest and subsequent infection by fungal and or bacterial diseases. The
use of a fungicide on crops at storage loading time would reduce the risk of
storage disease losses.
The A74212-1 selection has experienced very little hollow-heart, brown
center, or other physiological disorders. Hollow-heart was observed extensively in the 1988 Oregon Statewide Trial in a number of entries, but not
at all in A74212-1, even in very large tubers. A74212-1 has apparent field
resistance to early blight and the early dying complex. In 1988 trials
A74212-1 was susceptible to root-knot nematodes and tuber infection with
spraing.
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Table 1. Performance of A74212-1 vs. Russet Burbank in Klamath Experiment
Station Statewide Variety Trials 1981-1988.
A74212-1
RUSSET BURBANK
TOTAL
YIELD
YEAR
1981 1982
1983 1984
1985 1986
1987 1988
Average
YIELD
NO l's
cwt/A 1.085
1.090
1.077 1.074
1.079 1.075
1.080
294 300
233
371
283 390
209
320
412
441
421
495
397
535 ,
370
463
471 524
484 634
510
621 495 626
1.085
300
442
TOTAL
YIELD
YIELD
NO l's
cwt/A SPECIFIC
GRAVITY
1.079
SPECIFIC
GRAVITY
398
395
409
539
414 546
405
573
546
460
1.081
1.083
1.070
1.076
1,068
1.066
1.079
1.075
Table 2. Effect of seed spacing on yield and size distribution of A74212-1
at the Klamath Experiment Station.
SEED SPACING
inches
YEAR
YIELD NO #1's
YIELD
4-6 oz 6-10 oz >10 oz TOTAL B's NO 2's CULLS TOTAL
cwt/A
1987
6.0
9.0
12.0
92
80
53
161
143
107
216
191
154
469
414
314
55
49
39
43
57
72
47
47
45
613
568
470
1988
6.8
8.7
12.0
133
119
92
246
174
177
230
262
252
609
555
521
59
58
40
19
34
31
7
10
16
694
657
607
Table 3. Effect of nitrogen rate on yield and size distribution of A74212-1
at the Klamath Experiment Station, 1988.
YIELD
, YIELD NO l's N RATE
(lb N/A) 4-6 oz 6-10 oz >10 oz TOTAL B's NO 2's CULLS
TOTAL
cwt/A
130
160
190
115
74
81
171
177
172
171
236
255
457
487
508
54
46
42
49
26
25
7
22
2
567
581
577
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Table 4. Effects of seed source and cutting,time on A74212-1, Klamath Experiment Station, 1988.
YIELD EMERGENCE
YIELD NO.1's
CUTTING 4-6 oz 6-10 oz >10 oz TOTAL B's NO 2's TOTAL JUNE 20 JULY 5
TIME
%
cwt/A
SEED
SOURCE
KES
Powell Butte
Klamath C.
Deschutes C.
OFSP Nuclear
Pre-
Pre-
Pre-
Pre-
Pre-
149
175
152
153
128
228
•261
266
259
290
195
134
160
152
206
572
570
578
564
624
55
63
71
64
57
12
10
15
13
35
641
643
671
642
721
70
89
83
77
92
89
93
91
89
96
KES
Powell Butte
Klamath C.
Deschutes C.
OFSP Nuclear
Fresh
Fresh
Fresh
Fresh
Fresh
109
176
195
151
143
265
276
227
221
315
217
155
111
181
175
590
606
532
552
633
55
68
86
65
63
21
11
20
13
20
673
688
648
633
716
66
92
85
74
93
92
97
94
93
97
129
247
205
144
581
135
166
191
588
555
558
629
55
66
78
65
60
16
10
18
13
27
657
666
660
638
719
68
91
84
76
93
91
95
93
91
97
82
82
91
95
Source Main Effect:
KES
Powell Butte
Klamath C.
Deschutes C.
OFSP Nuclear
175
174
152
136
269
246
240
302
Cutting Time Main Effect:
Pre-Cut
Fresh Cut
CV(%)
LSD(.05)
Table 5.
151
155
261
261
169
168
582
583
62
67
17
17
664
672
17
38
13
51
32
NS
9
NS
23
22
56
13
9
NS
Effect of seed treatment on A74212-1, Klamath Experiment Station, 1988.
SEED
TREATMENT
Control
Gypsum
TOPS 2.5 D
TOPS - Rovral
TOPS - Rizolex
Captan 7.5
Spotless
TOPS - Anchor
TOPS - Manzate
TOPS - Benzimidazole
Average
CV(%)
LSD(.05)
YIELD YIELD NO l's EMERGENCE
4-6 oz 6-10 oz >10 oz TOTAL B's NO 2's TOTAL JUNE 20 JULY
cwt/A
%
167
173
169
157
201
167
71
174
192
156
196
191
173
188
233
198
91
220
186
201
204
173
178
132
113
151
326
101
73
171
566
537
520
476
547
515
488
495
451
528
72
81
102
93
89
86
42
88
136
70
6
15
29
10
43
55
29
23
42
38
652
637
654
602
689
691
578
619
653
667
163
18
42
188
23
63
162
34
79
512
13
99
86
27
34
29
69
29
644
10
NS
68
68
78
63
82
84
48
78
80
75
72
--
91
90
88
82
90
90
83
89
87
87
88