A. Mosley, D. Hane, S. James, K. Rykbost, C. Shock and B. Charlton
Introduction
Oregon released COO83008-1 as RUSSET LEGEND in the spring of 1998 in
cooperation with Colorado, Washington, Idaho and the ARS. Oregon selected
COO83008-1 from a Colorado cross between Century Russet and WNC672-2 performed
by Dr. D. Holm at the San Luis Valley Research Center, Colorado State University.
Production recommendations for Russet Legend are currently limited by lack of commercial grower reports. However, the information situation is rapidly improving for selected production areas. The following points are based mostly on Oregon observations.
Plant and Tuber Characteristics
Legend vines are typically slightly smaller and later maturing than
Russet Burbank (Table 3). Flowers are bright white and profuse. Plants
tend to have slightly fewer stems and to set slightly fewer tubers than
Russet Burbank, consequently, Legend tubers are noticeably larger (Table
2).
Russet Legend tubers mature late. Tuber shape ranges from oblong to long depending on the growing area. In the Columbia Basin, especially on sandy soils, tubers tend to be shorter and rounder than desirable (length to width ratios of 1.50 to 1.65 compared to 1.75 to 1.90 for Russet Burbank). Tubers are usually longer, thinner and more attractive in short season areas such as eastern Idaho. Soil type may have a strong effect on tuber shape in long season areas. In general, heavier soil seems to favor length. Interactive effects between soil and climate on Russet Legend tuber conformation are not well understood.
Compared to Russet Burbank, Legend tubers are larger, darker, more russeted and shallow-eyed, and more uniform in size and shape (Table 3). They also typically show higher oven dry solids and more protein and vitamin C but lower levels of reducing sugar, sucrose and glycoalkaloids than Russet Burbank.
Legend is relatively resistant to blackspot and shatter bruise, hollow heart, brown center and second growth, and sugar-ends compared to Russet Burbank (Table 4).
Diseases and Disorders
Legend has occasionally shown extreme susceptibility to stem-end discoloration.
The problem seems to be physiological in nature and related to unusually
large stolon size and immaturity at harvest. We suspect that stolons must
be well dried to allow good tuber-plant separation at harvest. Crop and
tuber maturity seems to be especially important for consistently satisfactory
results with Russet legend. Therefore, we recommend thorough vine kill
and an interval of three weeks between vine kill and harvest when possible.
First-time Legend growers should not store large quantities without a good understanding of Legend stem-end behaviour in the immediate production area. If you must store, harvest only mature tubers. Any stem-end problems should show up shortly after harvest and increase in severity in early storage. Stem-end discoloration in Legend typically does lead to excess storage decay under normal conditions.
We have heard but not yet tested a rumor that later generations of Legend seed, Generation 4 or 5 for example, are less susceptible to stem-end discoloration than earlier generations. This theory seems reasonable, since higher generation numbers would usually produce earlier-maturing, less vigorous vines because of increased disease levels. We have also heard that the fungicide metalaxyl reduces stem-end discoloration in Legend but have personally seen no supporting evidence; we do not understand why fungicides might work. Due to lack of evidence, our best current recommendation is simply to promote good vine kill, tuber maturity and stolon desiccation before harvest. Reduced nitrogen and water late in the season would improve vine kill and maturity.
Legend has shown fairly good resistance to tuber late blight (Table 6) symptoms compared to Ranger Russet, Shepody, Russet Norkotah and Russet Burbank. It is resistant to metribuzin injury and scab and slightly resistant to Verticillium wilt but very susceptible to potato virus Y (PVY) (Table 5). Plants are susceptible to potato leafroll virus (PLRV) and to tuber net necrosis, therefore good seed and aphid control are highly recommended. Tubers are also susceptible to Fusarium dry rot and bacterial soft rot. Legend response to rootknot nematode and corky ring spot is similar to that of Russet Burbank.
Yield and Grade
Legend typically produces total yields 3 to 8 percent lower than Russet
Burbank but U.S. No.1 yields 10 to 30 percent higher (Table 1, 2). Tubers
tend to be larger than Russet Burbank
Processing Quality and Tuber Composition
Russet Legend is an excellent choice for frozen processing. Starch
content is consistently higher than Russet Burbank and fry color is lighter
(Table 1,2). Russet Legend tends to have slightly higher levels of protein
and vitamin C than Russet Burbank (Table 7).
Russet Legend is perhaps the best-tasting russet-skinned baker currently grown in the U.S.
Seed Spacing
Optimum seed spacing will depend on growing conditions and location.
Legend tubers tend to average about 2 ounces heavier than those of Russet
Burbank. Consequently, research at the Klamath Experiment Station has shown
that optimum Legend plant populations average about 25% higher than for
Russet Burbank. For example, growers who space Russet Burbank 10 to 11
inches apart should leave only 7 or 8 inches between Legend seedpieces.
This 25% rule of thumb probably applies to most production areas in the
Pacific Northwest for both commercial and seed crops. Seed crops are typically
planted much closer than commercial crops in order to reduce tuber size
and the incidence of oversized or blind seedpieces.
Fertilization
Trials at the Klamath, Ontario and Hermiston branch stations have shown
Legend nitrogen fertility requirements to be similar to those of Russet
Burbank. That is, yield and quality peaked at about 150, 200 and 240 lbs.
of N/acre, respectively, at the three sites. We suspect that typical Russet
Burbank patterns will also suffice for P, K and other elements as well.
Length of season and irrigation regime strongly influence nitrogen requirements.
Irrigation
Irrigation models currently used for Russet Burbank and other varieties
should suffice for Russet Legend. However, Legend is notably less sensitive
than Russet Burbank to moisture stress disorders including second growth
and dark-end fries (sugar-ends).
Disease and Pest Control
Legend is susceptible to PVY, PLRV and net necrosis, so good insect
control is highly recommended. Russet Burbank recommendations for insects,
diseases, nematodes and weeds should be satisfactory for Legend. Legend
is resistant to metribuzin injury at normal rates.
Vine Killing and Harvest
Because of potential stem-end discoloration, good vine kill and a delay
of at least three weeks between application and harvest are highly recommended
for Legend. Bruise-free harvest and handling will reduce losses to tuber
early blight and Fusarium dry rot.
Storage
Few varieties store long-term as well as Russet Burbank. Russet Legend
has a shorter dormancy period than Russet Burbank and will produce sprouts
up to three inches long by March at Hermiston while Russet Burbank is barely
peeping. Russet Legend probably should be sprout-treated no later than
January in non-seed storage.
Related References:
1. Rykbost, K.A., and J. Maxwell.
1995. Potato cultivar response to seed spacing and nitrogen fertilizer
rates. Crop
research in the Klamath Basin,
1994. Oregon State University AES Special Report 949.
2. Shock, Clint, Erik Feibert, and Monty Saunders. 1994. Irrigation management for potato varieties: Variety tolerance to deficit irrigation. Oregon State University AES Special Report 936. pp. 70-81.
3. Shock, Clint, Erik Feibert, and Monty Saunders. 1995. Cultural practices for new potato varieties. Part I. Irrigation management for potato varieties: variety tolerance to deficit irrigation. Oregon Potato Commission, 1994-1995 Research Progress Reports: pp 112-120.
4. Shock, Clint, Erik Feibert, and Monty Saunders. 1995. Cultural practices for new potato varieties. Part I. Nitrogen fertilization for potato varieties grown under sprinkler irrigation, 1994 trial. Oregon Potato Commission, 1994-1995 Research Progress Reports: pp 112-120.
Table 1. Yield and Quality Characteristcs of COO83008-1 (Russet Legend)
and
Russet Burbank at Three Locations, Tri-State Trials, 19891