RUSSET NORKOTAH

RUSSET NORKOTAH SELECTION 3

RUSSET NORKOTAH SELECTION 8

 

 

Prepared by Susie Thompson, Ph.D. and Robert D. Davidson, Ph.D., Department of Horticulture & Landscape Architecture, San Luis Valley Research Center, Colorado State University

 

This profile was developed for production in the San Luis Valley. While some guidelines may be appropriate regardless of growing area, fine-tuning for specific production locales is recommended.

 

Russet Norkotah is an early maturing cultivar released in 1987 by North Dakota State University (APJ 65:597-604, 1988). Primary use is for the fresh market, and it is particularly suited for baking. It is widely adapted in North America and performs very well in the San Luis Valley. In order to address the weaknesses of standard Russet Norkotah including a high requirement for nitrogen fertility and weak vines, Dr. David Holm began a concerted effort in 1991 to identify superior genotypes able to withstand stress situations more favorably. After several years of evaluation, two lines stood out in offering advantages in reduced nitrogen requirements and in stress situations.

 

Vine maturity of Selection 3 is later by about seven days when compared to the standard. Vine maturity for Selection 8 is early, although intermediate between the standard and Selection 3. Application for U.S. Plant Variety Protection has been made for the two selections (Colorado Russet Norkotah Selection 3 - PV#9800256; Colorado Russet Norkotah Selection 8 - PV#9800255).

 

Plant/roots: Plants emerge quickly with a medium, slightly upright vine and white flowers. Selection 3 vines are medium to large, and more upright than those of the standard or Selection 8. Selection 3 blooms more heavily than the standard and the flowering period is longer. All have a determinate growth habit. Root systems for standard Russet Norkotah and Selection 8 tend to be shallow and concentrated. Selection 3 has a medium sized root system. The selections are not as susceptible to hail damage as standard Russet Norkotah, and will demonstrate some recovery following such an event.

 

Tubers: Tubers have white flesh, are long and blocky with medium to heavy russet skin. Eyes are shallow, numerous and well distributed. Specific gravity levels are medium (1.080). Although not considered a processing cultivar, Russet Norkotah will fry directly from the field.

 

Yield potential: Yield potential varies from 450 cwt per acre to 500 cwt plus, with proper management. All produce a high percentage of US No. 1 tubers.

 

GROWING SEASON MANAGEMENT

Pre-planting considerations: Tubers have medium dormancy. Some producers have indicated that Selection 3 has slightly longer dormancy than the standard. Whole or cut seed is acceptable, however, cut seed may be preferred as the increased stem number aids in limiting oversized tubers late in the season. Tuber size is also controlled through closer within-row seed spacing. Avoid prolonged warming of seed to minimize excessive sprouting and physiological aging (no more than two weeks at 60 F). Precutting may age seed physiologically, as well, but research in Colorado indicates this may not be a significant problem if proper storage conditions after cutting are utilized. Avoid planting seed in cool soils, since delayed emergence may aggravate Rhizoctonia stem canker and result in reduced fertilizer uptake. Plant 4 to 6 inches deep in a broad, well-shaped hill to minimize late season greening. Selection 3 will perform better at the deeper planting depth.

 

Fertility: Apply total fertilizer in the range: N(210-230#), P(120-200#), K(0-40#) for standard Russet Norkotah. Performance of Selection 8 has been maximized with applications in the range: N(160-180#), P(120-170#), K(0-40#). For Selection 3, applications in the range of: N(130-150#), P(100-150#), K(0-40#) are suitable. Pre-plant N applications are critical for the early vine growth necessary to support maximum yields, particularly for standard Russet Norkotah (110-140#). This should be reduced to a range of 80-100# for the selections. Sprinkler applied N should be in the range of 90 to 100# for the standard, 80# for Selection 8, and 40-70# for Selection 3. All may benefit from applications at a rate of 7-10# per application, but not exceeding 20# per application. High N rates will delay tuberization of Selection 3 resulting in misshapen tubers, skin-set problems, etc. under short growing seasons. Performance in alkali soils is reduced for the standard.

 

Irrigation: The interval at the maximum ET is approximately 2.5 days. Drought tolerance of Selection 8 is similar to the standard. However, due to a larger vine, but similar rooting characteristics, producers may prefer to shorten the interval to 2 days and decrease application rates slightly to match ET, in order to avoid moisture stress. The selections may require prolonged irrigation later in the season, when compared to the standard due to slightly later vine maturity, however, once vine senescence has begun, water needs must be monitored closely. Producers should strive to avoid late season over-watering, since it creates ideal conditions for expression of many diseases such as blackleg, pink rot and leak. The selections may display tuber malformations, skin set problems, and deep eyes if irrigation is erratic, temperatures are extremely high, or nitrogen fertility excessive.

 

Pest Control

Weeds: The selections compete better with weeds than standard Russet Norkotah. No sensitivities to major potato herbicides have been demonstrated by the standard, or the selections.

Insects: Standard insect control measures are suitable, however timing and rotation of pesticides are important due to preference by aphids and virus spread. It is especially important to continue applications into late season for the selections since vines remain succulent and green longer than the standard.

Fungicides: Three to five fungicide applications may be necessary to control foliar early blight for standard Russet Norkotah. Due to the later maturity, susceptibility to foliar early blight and Verticillium wilt are slightly less for the selections when compared to the standard.

 

Tuberization/bulking: Tuber set is light to medium and high in the hill. Greening may be a problem without proper hill conformation. Tuber bulking occurs in a short interval during early to mid-season at an extremely rapid rate. Russet Norkotah is moderately resistant to blackspot bruise. The selections are somewhat susceptible to growth cracks, deep eyes, misshapen tubers and hollow heart if not appropriately managed. Physiological pigmentation (internal purpling) may appear in tubers of all if proper planting depths, hill conformation and sound nitrogen fertility management are not adhered to.

 

Vine Kill: Average days from planting to vine kill are 95 to 110. Unlike standard Russet Norkotah, vine kill may be required for the selections. Adequate skin set occurs in 14 to 21 days. Tubers may become excessively large late in the season, so close monitoring is warranted by early August.

 

STORAGE MANAGEMENT

Russet Norkotah and the selections generally have few storage problems. However, leak, pink rot, blackleg and silver scurf may become serious when proper field and storage management are not practiced. Russet Norkotah is not considered a long-term storage cultivar. Due to a propensity for pressure bruise and blackspot bruise development, consider marketing prior to March 1. A note; some producers feel that they may be able to store Selection 3 slightly longer due to stronger dormancy.

 

DISEASE REACTION

Potato early dying, caused by Verticillium dahliae is a problem in some years, but can be easily confused with natural vine senescence. It is not as prevalent for the selections when compared to the standard. Soil-borne diseases such as leak, pink rot and silver scurf can be quite common and serious.

 

Bacterial ring rot symptom expression is erratic and may be difficult to see under some circumstances for Russet Norkotah. Symptoms can be mild and tend to appear only after vines begin senescing (90+ days after planting). Expression for the selections is adequate and similar to the standard. Reaction to PVY infection is mild to latent. Infected plants are difficult to detect early in the growing season, but usually become somewhat more detectable as the plants age. Yield losses due to PVY will be in the 30-40% range for individual plants based on research conducted in the Pacific Northwest and in Colorado. Expression of symptoms may be delayed for the selections when excessive N is applied.

 

Toxic seedpiece decay syndrome is characterized by severe plant wilting just prior to tuberization, when the plants are switching from seedpiece nutrition to the root system. Plants appear windburned with dehydrated leaf margins in the upper canopy. A light brown, jelly-type rotted mass is all that is left of the seedpiece and brown streaks may be visible in the lower stem. Normally the plant recovers within a couple of weeks. This problem may be present when early season wet conditions are linked with warm weather. Toxic seedpiece decay syndrome is rarely seen in the selections.

 

 

Field

Foliar early blight Susceptible - Moderately susceptible for the selections

Verticillium wilt Susceptible - Moderately susceptible for the selections

Blackleg Susceptible

Seedpiece decay Susceptible

Leafroll virus Susceptible

Leafroll net necrosis Resistant

PVY Susceptible, latent reaction possible

PVX Susceptible

Common scab Moderately resistant

Powdery scab Resistant

Bacterial ring rot Susceptible

Late blight Susceptible

 

Storage

Tuber early blight Moderately resistant

Bacterial soft rot Susceptible

Fusarium dry rot Susceptible

Pythium leak Susceptible

Pink rot (P. erythroseptica) Susceptible

Silver scurf Susceptible

Rhizoctonia scurf Moderate

 

Disease reaction ratings = susceptible, moderately susceptible, moderate, moderately resistant and resistant.

 

 

Spring 1999