Potato vine kill: Stem-end discoloration effects on Russet Burbank

The relationship of potato (cv. Russet Burbank) tuber stem-end discoloration to speed of vine kill and maturity of vines when killed was studied for three years at several sites in Idaho. Discoloration due to leafroll was separately determined. Vine killing with sulfuric acid, dinoseb, endothall and hand pulling produced a range in killing speeds from fast to slow. Vine kill speed alone did not affect amounts of discoloration. Vines that died naturally from frost or other causes had as much discoloration (14% over all treatments) as from any chemical or mechanical vine killing method. The tendency for tuber discoloration increased when vines were less mature when killed.     

Respiration studies on Russet Burbank potato tubers: Effects of storage temperature and chemical treatments

Tubers of Russet Burbank potatoes were stored at 36 F (2.2 C), 42 F (5.6 C), 45 F (7.2 C), 48 F (8:9 C), and 70 F (21.1 C) and respiration rates determined. Chemical treatments 4 with growth regulators were made and respiration rates determined on intact tubers. Tubers stored 42 F (5.6 C) and 45 F (7.2 C) generally respired less and at a more uniform rate than tubers stored at other temperatures. The respiration rate of CIPC and BA (20 ppm) treated tubers was less than the untreated tubers.     

Influence of low fertility and vine killing on sugar development in apical and basal portions of Russet Burbank potatoes

Russet Burbank tubers from plants which died prematurely (low fertility plots) accumulated significantly greater amounts of reducing sugars in storage than tubers from plants which were adequately fertilized. Also, a significantly greater difference in relative amounts of reducing sugars between the apical and basal portions was obtained from tubers of the low fertilizer regime. The basal portion had a three times greater amount of sugars than the apical portion. This is of particular interest to processors of French fries who try to obtain uniformity of color in processed fries. The difference in total reducing sugar accumulation in storage between tubers of high and low fertilizer regimes was greater at the lower storage temperatures. Tubers allowed to mature in the ground (second harvest date) accumulated less sugars in storage than tubers dug shortly after vine kill.     

Blackspot of Russet Burbank potatoes and the carbon dioxide content of soil and tubers

These studies were designed to elucidate the influence of CO₂ on blackspot susceptibility of Russet Burbank potatoes. The influence of tuber CO₂ environment on blackspot was tested. Tubers from 1–4 and 6–8 inches deep in the soil were scored for blackspot and moisture samples were taken from their vicinity. Blackspot was worse in shallow tubers and in tubers from drier soil. Plowing under corn stover, covering the soil with plastic, and excessive irrigation failed to cause blackspot susceptible tubers. Diffusing CO₂ into the soil atmosphere under plastic sheets slightly increased the intensity of spot discoloration but the discoloration was atypical blackspot. Effects on blackspot by changing tuber gases was tested. Tubers whose gases had been evacuated and replaced by O₂, N₂, and CO₂ had lower blackspot scores than untreated tubers. Increasing the time tubers were soaked in water after gaseous evacuation reduced blackspot. Hydration consistently decreased tuber blackspot. In chemical studies, tubers were tested for blackspot and analyzed for CO₂ content. The relationship between tissue CO₂ and blackspot appeared to be inverse. Tuber CO₂ content was not influenced by time of day. Tuber blackspot scores immediately, 1, 3, and 7 hours after digging were the same, but tissue CO₂ content increased linearly with time after harvest.     

Preconditioning and storage of chemically immature Russet Burbank and Shepody potatoes

Russet Burbank and Shepody potatoes of different chemical maturities (i.e. varying sucrose concentrations) at harvest were preconditioned by holding at 15 C for various durations to lower the concentration of reducing sugars to levels acceptable for processing as french fries out of 8 C storage. In chemically immature tubers (i.e. those harvested with a high sucrose), sucrose declined after harvest and stabilized in storage regardless of the preconditioning period. However, there was a temporary small increase in sucrose after harvest in more chemically mature tubers. The concentrations of the reducing sugars glucose and fructose were low at harvest, usually < 1.0 mg g^?1, but increased rapidly during the first 30 to 45 d of storage in tubers with more than 2.0 mg g^?1 sucrose at harvest. Preconditioning for up to 70 d at 15 C either limited the increase in reducing sugars or lowered them more rapidly during storage than when preconditioned for only 14 d. Fresh weight loss of Russet Burbank and Shepody was greater in physically and chemically immature tubers compared to more mature tubers. Extended preconditioning of Russet Burbank and Shepody resulted in minimal additional weight loss.     

Influence of seed placement on Russet Burbank potato yield and grade

Potato seed pieces were hand planted with different spacings in the row and percentages of doubles to determine the effects on total yield and tuber size distribution. The objective was to determine acceptable performance levels for commercial potato planters. Average tuber size increased as the percentage of double seed pieces decreased or as the in-row spacing between single seed pieces increased. Yield of tubers smaller than 113 g was the most sensitive parameter and they increased as in-row spacing decreased and as the percentage of double seed pieces increased. Yield of tubers larger than 283 g increased as in-row spacing increased but only for the first year. Total yield was not affected by the change of in-row spacing or the percentage of doubles.     

Influence of mefluidide on tuber development,maturity, and storage of Russet Burbank and Norland potatoes

Mefluidide {N-[2,4-dimethyl-5-[[(trifluoromethyl) sulfonyl] amino] phenyl] -acetamide}, a chemical with plant growth regulator properties, was applied to the foliage of potatoes (Solanum tuberosum L.) in field experiments to determine its effects on tuber development, maturity, and storage of the cultivars Russet Burbank and Norland. The rate of sucrose loss before harvest was reduced in mefluidide-treated plants. Total and marketable yields generally were lower in treated plants. Specific gravity tended to increase in Russet Burbank with application rates up to 1.0 kg ai/ha mefluidide. Preharvest treatments of mefluidide resulted in an increase in periderm thickness and russeting. However, weight loss during storage was greater in tubers from treated plants. Less sprouting occurred in storage in tubers from mefluidide-treated plants. Mefluidide resulted in a lower anthocyanin content and consequently an undesirable color change in Norland tubers.     

Potato vine kill: Pulling,chemical killing and rolling effects on yield and quality of Russet Burbank

Pulling of potato vines in Idaho was compared to three chemical vine killing methods for a period of three years. Rolling was examined alone or in combination with chemicals. Effects on yield, grade, specific gravity and stem-end discoloration of the Russet Burbank variety were determined. Rolling increased desiccation overall by 6% but was not a satisfactory vine kill method when used alone. Pulling reduced yields by 14% compared to control plots and 7% compared to sulfuric acid treatments. Specific gravity was reduced overall by 0.002 for all vine killing treatments compared to the control. Pulling and rolling did not affect the amount of stem-end discoloration.     

Influence of Foliar-Applied Growth Retardants on Russet Burbank Potato Tuber Production

The potato cv Russet Burbank grows poorly in the semi-arid climate of the High Plains, primarily due to its tendency to produce misshaped tubers. Since gibberellic acid (GA₃) is associated with stem elongation and may be involved in tuber shape, the objective of this study was to determine whether GA₃ biosynthesis inhibitors could improve tuber shape. Prohexadione-Ca and chlormequat-Cl are two well-known such inhibitors. They were applied to ‘Russet Burbank’ at 0, 70, 280, 1,120, 4,480 g/ha when the largest tubers were 20, 60 and 100 g/tuber from 2001 to 2003. Neither compound affected tuber shape. Yields increased 17–20 % by prohexadione-Ca at 280 g/ha and 9–33 % by chlormequat-Cl at 4,480 g/ha. In 2004, prohexadione-Ca at 280 g/ha was applied when the largest tubers were 3, 25, 100, 180, and 370 g to determine a tuber stage response. Yield increased 14 % when applied at 25 and 100 g/tuber growth stages, but the number of misshaped tubers increased from 48 % to 75 %. These two inhibitors did not overcome tuber misshaping and should not be used for that purpose.     

Field performance of transgenic Russet Burbank and Lemhi Russet potatoes

Transformed Russet Burbank and Lemhi Russet clones which contained three different transgene constructs were evaluated for performance under field conditions in Idaho. The transgenic lines were characterized over two growing seasons, using plants grown from both greenhouse produced minitubers (first year) and field grown seed (second year). Individual clones were evaluated for a variety of agronomic and quality properties. Many of the transformed clones showed reduced yield and increases in percent malformed and undersized tubers. Other characteristics, such as specific gravity and fry color, showed less variability. The variation observed in non-transgenic clones regenerated from tissue culture was less than that of the transformed lines. Out of an original population of 57 transgenic lines in tissue culture, maintenance of key agronomic and quality properties of the parental material was observed in only four clones. These results suggest that experiments designed to generate transgenic lines for the marketplace should be initiated with a large number of transgenic clones.     

Cell size in Russet Burbank potato tubers with various levels of nitrogen and soil moisture tensions

Russet Burbank potatoes were grown at levels of added nitrogen of 0, 135, and 270 kg/ha and soil moisture tensions (SMT) of 0.5 and 1.0 atm. With all combinations, there was a consistent gradient of larger to smaller starch-storage parenchyma cells from stem end to bud end of mature tubers. Stem and bud ends of tubers grown at a SMT of 0.5 atm with N had smaller cortical and pith (innermost medullary or water-core) cells than did ends of tubers grown without N. Perimedullary tissues of bud ends of tubers receiving N likewise contained smaller cells than did corresponding tissues of tubers grown without N. No pronounced differences in cell size were found in tissues from the midsections. In bud-end tissue of tubers grown at a SMT of 1.0 atm, there were no consistent differences in cell size with respect to N levels. However, pith, perimedullary, and cortical tissues of the midsections and stem ends of tubers receiving N had smaller cells than did corresponding tissues from tubers without N. The different patterns of cell size in tubers grown at different SMT indicate that the effects of N may be influenced by soil moisure.     

Association of viral,bacterial and fungal pathogens with vascular discoloration of Russet Burbank potato tubers

Russet Burbank potatoes from the 1979 and 1980 crop years, collected from Chicago, IL repack warehouses and retail markets, were sampled for vascular discoloration. The amount of discoloration varied among sampling months and states of origin and decreased from 7.7% in 1979 to 1.6% in 1980. Highest levels of vascular discoloration were detected in December and January samples. Vascular discolored and non-discolored (control) tubers were assayed for the presence of potato leafroll, potato virus X, and beet western yellows viruses by the enzyme-linked immunosorbent assay (ELISA). Tubers were also assayed for 2 subspecies ofErwinia carotovora and forVerticillium albo-atrum andV. dahliae. Potato leafroll virus was detected in 31 of 831 vascular discolored tubers.V. albo-atrum was detected in 1 of 180 discolored tubers. Beet western yellows virus was not detected in discolored or non-discolored tubers. Two subspecies ofE. carotovora and potato virus X were equally common in discolored and non-discolored tubers.     

Seed performance of Russet Burbank potatoes

A three-year study of three planting dates and four harvest dates of Russet Burbank seed potatoes was made to determine their effect on plant vigor, virus leaf roll infection, yield, size distribution and quality. Yields decreased significantly with delayed harvest of the seed crop. The incidence of late season virus leaf roll based on visual symptoms increased significantly with delayed harvests. The risk of a late season virus leaf roll infection increased when a later harvest was combined with a late planting. Seed taken from the earlier harvested plots consistently had earlier and more uniform emergence, the greatest vigor and the highest yields. The effect of planting date and harvest date had little effect on size distribution and no effect on specific gravity.     

Suppression of PLRV Titer in transgenic Russet Burbank and Ranger Russet

Potato varieties Russet Burbank and Ranger Russet were transformed with a cDNA version of the 23 kD coat protein cistron (CP) of the potato leafroll virus (PLRV) using anAgrobacterium-mediated procedure. Clones were assayed for presence of thenpt- II and CP genes by Southern analysis, for expression of CP mRNA by Northern analysis, and for presence of PLRV coat protein in uninoculated and aphid inoculated plants by ELISA and Western blot analysis in uninoculated plants. Two putative Russet Burbank transformants were escapes, lacking eithernptll or CP, while one putative Ranger Russet transformant possessed thenpt- II gene but not the CP gene. In Russet Burbank and Ranger Russet, some transformants had statistically lower virus titer. The lowered titer was consistent throughout assays at three times during primary infection and one assay of secondary infection. The ranking of virus titer across all tests was statistically consistent. Transformants with the lowest secondary titers had virus contents 15 and 31 % of the titers of untransformed controls for Russet Burbank and Ranger Russet, respectively. The virus titer of the two Russet Burbank escapes and the Ranger Russet with only thenpt- II gene did not differ significantly from their respective untransformed controls.     

Specific gravity of Russet Burbank potatoes

Variability in specific gravity of Russet Burbank potatoes was documented in a single 32 hectare field. Maximum variation was 40 units among individual tubers within hills (one unit equals one part in 1000th of specific gravity measurement) and 15 units among hills. Field site variability of 10–15 units was common between sampled grid lines in the field; but bulked samples (truckloads) reduced the sampled variability to 8–10 units. When the samples were taken from bulked lots as opposed to single hill samples, the variability decreased. Grower lots, which were pooled samples from several truckloads, showed specific gravity differences of 2–7 units even though all lots were from the same field. These variations among specific gravity samples should be taken into account when considering total solids content in any lot of potatoes. Degree of russetting of the skin and hollow heart also influenced specific gravity measurements. Measured differences between peeled and unpeeled lots of 10 units in specific gravity corresponded to 2% difference in total solids content. Statistically, the variance of the peeled lot was one half that of the unpeeled lot, therefore, to minimize the measured differences due to skin type, peeled potatoes could be used for the specific gravity measurements.     

Factors influencing reconditioning of Russet Burbank potatoes

Studies were made to determine factors which influence reconditioning of Russet Burbank tubers. Tubers from plants grown under low fertility were more difficult to recondition than tubers from plants adequately fertilized. Low specific gravity potatoes were also more difficult to recondition than high specific gravity potatoes even though the initial sugar content was approximately equal. The stem portion of Russet Burbank tubers lost considerably less sugars than the bud portion during the reconditioning process. It appears that factors which are responsible for high sugar development are also responsible for difficulty in sugar loss. Results also indicate greater difficulty in reconditioning early in the storage period with the loss of sugars becoming easier as the storage season progressed into spring.     

Irrigation and soil temperature effects on Russet Burbank quality

Potato growers in the Pacific Northwest suffer large economic losses in seasons with above normal temperatures, due to excess reducing sugars in tubers, which cause dark-end French fries. Our objective was to study irrigation management effects on potato quality, particularly the factors causing dark-end French fries or sugar-end syndrome. Solid-set sprinkler irrigated plots were established on potatoes at Kimberly, Idaho during the 1987, 1988 and 1989 irrigation seasons, and at Parma, Idaho in 1987 and 1988. Irrigation treatments were high and low frequency (3/week and I/week) and two or three water application amounts referenced to estimated evapotranspiration (ET, ET+20%, and ET-20%). Neither frequency nor amount significantly affected yields. Irrigation frequency had more influence on potato quality than application amount. More frequent irrigation produced slightly higher quality tubers and lower incidence of dark-ends when fried. Soil temperature was inversely related to tuber grade quality and directly related to percentage of sugar-end tubers. Soil temperature was about 0.5 C lower under the high frequency than under the low frequency irrigation regime. On these silt loam soils, allowing available soil water to decline to 50 percent had no adverse affect on yield or quality.