29
A Comparison of A74212-1 Seed Sources and Clonal Variants
K.A. Rykbost and J. Maxwell'
INTRODUCTION
The Oregon potato variety development program has been evaluating two variants
of A74212-1 for several years. A late maturing variant, (A74212-1L), has exhibited more
indeterminate vine habit with profuse flowering, larger tuber size with a greater tendency
for bulging eyes, and a serious susceptibility to skinning damage. This is thought to be
the original clonal selection. An earlier maturing vine type was selected out of seed
increase plots at Powell Butte in 1987. This line, (A74212-1E), appears to have a more
determinate growth habit with less flowering, produces smaller, blockier tubers, and it is
less prone to skinning damage during harvest. The two lines have been compared in
statewide variety trials in Oregon since 1988.
Commercial production of A74212-1 seed began in Central Oregon in 1986. Seed
produced from virus-free, tissue cultured plantlets became available through the Oregon
Foundation Seed Project in 1987. Commercial seed production expanded to other states,
including Colorado, Nebraska, and Wisconsin, in 1989 or 1990. Seed lots were also
maintained by one or two Klamath County growers since 1987. It was thought that seed
lots from the Oregon Foundation Seed Project were derived from A74212-1L. In 1991,
the A74212-1L seed distributed to cooperators for western regional trials raised concerns
about the identity of commercial seed lots in several states. A seed lot comparison was
established at KES in 1992 to attempt to determine the clonal identity of several
commercial seed lots in three states.
PROCEDURES
Seed lots of A74212-1E and A74212-1L were obtained from the Central Oregon
Agricultural Research Center (COARC) at Powell Butte. Four commercial Oregon lots
included nuclear (N), generation II (Gil), and generation IV (GIV), obtained from a
Klamath County seed grower (Klamath), and a commercial generation II (GII) lot from
a Deschutes County grower (Deschutes). Colorado lots were obtained from the San Luis
Valley Research Center (CO-SLV), and a commercial seed grower (CO-Grower). The
other lots included a commercial source from Nebraska and a sample from Texas that
originated from an unknown Colorado seed grower.
1
/ Superintendent/Associate Professor and Biological Sciences Research Technician,
respectively, Klamath Experiment Station, Klamath Falls, OR.
Acknowledgment: Partial funding of this study by the Oregon Potato Commission is
gratefully recognized. The assistance of Oregon Seed Certification personnel in rating
vine types is appreciated.
30
All seed lots were hand cut to 1.5- to 2.0-ounce seedpieces at KES, treated with
thiophanate-methyl fungicide, and suberized at 50 °F and 95 percent relative humidity for
10 days before planting. Seed lots were planted with a two-row assisted-feed planter on
May 18 in a randomized complete block design with four replications. Seed was spaced
at 8.7 inches in 32-inch rows. Individual plots were single rows of 30 hills Cultural
practices are described on page 19. Vines were desiccated with Diquat applied at 1.0
pt/A on September 10. Potatoes were harvested with a one-row digger-bagger on
September 25. All tubers were stored and graded in late November.
Vine type was rated, independently, as early, late, or mixed for each plot in midAugust by six seed certification or research personnel. The result was 24 observations
for each seed source. Blind plot maps were used to secure the identity of seed sources.
Tubers were graded to USDA standards. Forty U.S. No.1 tubers of 8 to 16 ounces from
each plot were measured to determine the length to width ratio.
RESULTS AND DISCUSSION
Vine type differences between seed lots were clearly evident in mid-August. The
COARC late clone and the Klamath GIV lot exhibited a distinctly late vine habit
(Table 1). COARC early clone, Klamath N and GII lots, CO-SLV, CO-Grower, and
Nebraska lots were early maturing vine types. Deschutes GII and Texas seed lots were
more varied in vine type, but appeared to be early. Tuber length to width ratios were
quite uniform for most seed lots. The Klamath GIV lot had a significantly higher ratio
than several other lots. Differences between other lots were not significant.
Yield and tuber size distribution data did not provide a statistical basis for clonal
identity (Table 2). The Klamath GIV lot produced the highest yield and percentage of
tubers over 10 ounces, and the lowest yield and percentage of tubers under 6 ounces.
The COARC early and late clones were nearly identical in yield and size distribution.
The lowest yield and smallest tubers were observed for the Klamath N lot. In total, yield
and size data suggest the Klamath GIV lot was different than several of the other seed
lots, but all other lots were similar in tuber characteristics.
Early and late variants of A74212-1 have been compared in Oregon statewide trials
conducted at Hermiston, Ontario, Powell Butte, and Klamath Falls in each year since
1988. Average yields of U.S. No.1, and under 4-ounce tubers over locations are shown
for each year (Table 3). The early clone has produced a higher yield of No.ls four years
out of five. Tuber size has been consistently smaller for the early selection. These
results clearly show an advantage for the early variant.
The greatest commercial interest in A74212-1 has been in Texas. Seed for this
production has been grown in Colorado and Nebraska. Results of seed lot comparisons
suggest that this seed was the early maturing variant of A74212-1. In view of the relative
performance of variants in Oregon trials; results of seed lot comparisons in this study;
and the fact that commercial interest in Texas appears to have been based on the early
variant; the late maturing variant should be discarded and the early clone pursued.
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Table 1. Emergence, vine maturity ratings and tuber length to width ratios of ten
A74212-1 seed lots grown at the Klamath Experiment Station. 1992.
Seed source
Vine Maturity l
Late
Mixed
Early
Length/Width
ratio
98
97
19
5
3
14
2
5
1.57
1.63
Klamath (N)
Klamath (GII)
Klamath (GIV)
Deschutes (Gil)
98
98
98
98
18
20
2
14
4
2
20
8
2
2
2
2
1.49
1.49
1.73
1.62
CO - Grower
CO - SLV
Texas
Nebraska
98
99
90
97
23
24
16
20
0
0
3
2
1
0
5
2
1.60
1.61
1.51
1.55
Average
CV(%)
97
COARC
COARC
(E)
(L)
Percent
Emergence
LSD(.05)
1
/ Vine maturity ratings - number of individual ratings out of 24 possible.
1.58
5
0.13
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Table 2. Yield and grade of ten A74212-1 seed lots grown at the Klamath Experiment Station,
OR. 1992.
4-6 oz.
Seed Source
Yield U.S. No. is
6-10 oz. > 10 oz.
Total
Yield
No 2s Culls
<4 oz.
Total
cwt/A 144
154
228
238
224
218
596
609
34
27
10
13
8
8
648
658
Klamath (N)
Klamath (GII)
Klamath (GIV)
Deschutes (GII)
258
205
120
155
204
284
228
254
78
143
263
256
540
632
611
665
89
67
24
27
14
4
5
2
2
12
12
14
645
715
652
708
CO - Grower
CO - SLV
Texas
Nebraska
162
185
175
155
255
221
226
310
253
237
171
169
670
643
572
635
45
51
38
40
12
0
0
5
6
7
12
13
733
701
622
693
Average
CV(%)
LSD(.05)
171
25
63
245
21
NS
201
30
88
617
10
NS
44
44
29
6
160
NS
9
98
NS
677
9
NS
COARC
COARC
(E)
(L)
Table 3. Average tuber yield and size distribution of A74212-1E and A74212-1L in Oregon
statewide trials at Hermiston, Powell Butte, Ontario, and Klamath Falls from 1988 to
1992.
Year
A74212-1L
A74212-1E ield U.S. No. is Yield
Yield U.S. No. is Yield Y
> 10 oz.
Total
Bs
4-10 oz.
Bs
4-10 oz.
>10 oz.
Total
cwt/A
1988
342
238
580
35
326
280
606
46
1989
310
207
517
33
183
281
465
23
1990
317
213
531
44
224
264
488
36
1991
363
146
509
30
258
205
463
28
1992 1
368
259
627
50
285
260
545
37
Average
340
213
553
38
255
258
513
34
1
/ No data obtained in Hermiston in 1992.