RUSSET NORKOTAH Texas Selection 223

	Description
	Tuber Shape	Oblong to Long
	Eyes	Shallow evenly distributed eyes
	Skin	Smooth medium russet
	Flesh	White
	Plant	Medium sized upright vine with white flowers

Russet Norkotah is a early-maturing potato released in 1987 by North Dakota State University(APJ 65:597-604, 1988). It is primarily a fresh market potato with good boiling and baking qualities. It is widely adapted to the western U.S. and performs especially well in the SLV. Selections were made at Texas A & M in the early 1990's. Five selections survived grower trials. The Texas selections were first selected in a field with very high early dying / verticilium pressure. Then they were further selected for heat resistence, vigor and tuber type. Texas line selections will have greater vine growth, yield and early dying tolerance with excellent tuber appearance and percentage of U.S. #1's.

Advantages of Line 223: Excellent tuber appearance. High Yields.

Plant/roots Plants are fast emerging with a medium to large, slightly upright vine and white flowers; it has a determinate growth habit. All the Texas selections have a slightly bigger vine than the standard. The selections root system is more developed and extensive than the standard Norkotah. They are susceptible to hail damage, but better than the standards.

Tubers are white flesh, long to slightly oblong with medium to heavy russeted skin. Eyes are shallow, numerous and well distributed; medium specific gravity (1.085). Although not considered suitable as a processing potato, it will fry directly from the field.

Yield potential 450 to 500 cwt. range with a high percentage of No. l's.

GROWING SEASON MANAGEMENT

Pre-planting considerations Tubers have a medium dormancy. Whole or cut seed is acceptable. However, cut seed often is preferred since the increased stem number helps prevent over sizing of tubers late in the season. Closer seed spacing also will help control tuber size. Avoid prolonged warming (usually no more than 60 F for two weeks) to minimize excessive sprouting and physiological aging. Pre-cutting seed a month or more before planting also can add physiological aging. Avoid planting seed in cool soils; delayed emergence can aggravate rhizoctonia stem cankering and result in poor fertilizer uptake. Plant this cultivar 4 to 6 inches deep in a broad well shaped hill to control late season greening.

Fertility (soil test basis; lbs/acre)

Selection 223

Apply total fertilizer in the following range: N(180-200#), P(l20-200#), K(O-40#). Performance in alkali soils is moderate. Pre-plant N applications (110- 140#) are critical for early vine growth necessary to support maximum yields; high N rates do not delay tuberization. Sprinkler applied N should be in the 40 to 90# range at a rate of 15# per application.

Irrigation Irrigation interval at the maximum ET is 2.5 days. Drought tolerance is poor; significant yield reduction occurs if plants are moisture stressed. Adequate irrigation applied at short intervals coupled with high early season fertility will help this cultivar develop necessary vine growth prior to tuberization. After tuberization, vine growth often slows dramatically. Subsequent rapid tuber bulking and early vine senescence results in minimum late season water requirements. Growers should strive to avoid late season over watering since it creates ideal conditions for expression of many diseases such as blackleg or leak.

Pest control

Weeds All selections compete fair against weeds but is not sensitive to any major herbicides. Better vine size gives them better weed competition than the standards.

Insects Standard insect control measures generally are effective but time and rotate insecticides properly because of high aphid preference and virus spread.

Fungicides Three to five fungicide applications may be necessary to control foliar early blight.

Tuberization/bulking Tuber set is light to medium, high in the hill. Greening may be a problem without good hill management. Tuber bulking occurs in a short interval during early to mid-season at an extremely rapid rate. Russet Norkotah is moderately resistant to blackspot and resistant to growth cracks, second growth and hollow heart.

Vine Kill Average days from planting to vine kill are 95 to 110. Vine killing usually is not required. However, if senescence is not complete, vines are killed easily; adequate skin set occurs in 12 to 21 days. Tubers can become large late in the season, so close monitoring is necessary after early August.

STORAGE MANAGEMENT

Russet Norkotah generally has few storage problems, but leak, blackleg and silver scurf can become serious. This cultivar is not considered a long-term storage potato. It should be marketed by mid-March because tuber dehydration can result in pressure bruises and blackspot development.

DISEASE REACTION

Soil-borne disease problems such as leak and silver scurf can be serious so be judicious with irrigations (especially late season) and fungicides and/or disinfectants may be necessary..

Bacterial Ring Rot symptom expression is erratic and difficult to see under most circumstances. Symptoms are mild and tend to appear only after vines begin senescing (90 + days after planting). Reaction to PVY infection is mild to latent. The selection 3 is more latent in expressing PVY than the standard. Infected plants are difficult to detect early in the growing season, but usually express mild symptoms that become somewhat more detectable as the plants age. Infected plants tend to die by mid-season with potentially significant yield losses when PVY incidence is high.

Toxic-seed piece-decay syndrome is characterized by severe plant wilting just prior to tuberization, when the plants are switching from seed piece nutrition to their root system. Plants appear wind burned with dehydrated leaf margins in the upper canopy. A light brown, jelly-type rotted mass is all that is left of the seed piece 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.

Field	Storage
Foliar early blight: Susceptible	Tuber early blight Moderate
Verticillium wilt: Moderate	Bacterial soft rot Susceptible
Blackleg Susceptible	Fusarium dry rot Susceptible
Seedpiece decay Susceptible	Leak (Pythium) Susceptible
Leafroll virus Susceptible	Pink rot (Phytophthora) Susceptible
Leafroll Net necrosis Susceptible	Silver scurf Susceptible
PVY, PVX Susceptible	Rhizoctonia scurf Moderate
Bacterial ring rot Susceptible
Common Scab Moderately Resistant

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