Russet Burbank Potatoes Research Articles

Effects of Green Manure Type and Amendment Rate on Verticillium Wilt Severity and Yield of Russet Burbank Potato.

Increasing restriction of agrochemicals is motivating development of ecology-based cropping systems, including green manures, to manage soilborne diseases. Green manures have shown promise in suppressing Verticillium dahliae, but information about effect of different green manures and optimal application rates remains limited. Therefore, we conducted two single-year field experiments comparing effects of Austrian winter pea (Pisum sativum 'Melrose'), broccoli (Brassica oleracea var. botrytis 'Excelsior'), and Sudan grass (Sorghum vulgare var. sudanense 'Monarch'), amended at 6, 12, or 24 Mg ha-1, on soil populations and root infection by V. dahliae, wilt severity, and yield of Russet Burbank potato. Inoculum density was reduced relative to the nonamended, infested control by all broccoli treatments, Austrian winter pea applied at 12 and 24 Mg ha-1, and Sudan grass applied at 12 Mg ha-1. Root infection was not reduced by any green manure treatment. Median wilt severity was reduced approximately 70% by all green manures applied at 24 Mg ha-1 and 74% by Austrian winter pea applied at 12 Mg ha-1. Tuber yield was reduced approximately 20% in nonamended, V. dahliae-infested controls relative to the noninfested controls. No green manure treatment improved yield relative to the nonamended, infested control.

Microclimate and potential for late blight development in irrigated potato

Application of irrigation water can improve potato growth and tuber yield during periods of deficit rainfall. A variety of water application techniques exist; however, little is known of their relative impacts on potato late blight potential. The effects of sprinkler, sub-surface drip, and surface drip irrigation treatments on microclimate and potential for late blight development were evaluated on Russet Burbank potato over three growing seasons in central Maine. Leaf wetness, air temperature, relative humidity (RH), rainfall and soil temperature were recorded each year. The potential for late blight was assessed with a late blight simulation model. Leaf wetness and RH peaked during night hours, while canopy and soil temperatures were lowest during the same hours. Comparison of observed and simulated blight development revealed a good prediction of potato late blight by the simulation model. The onset of simulated blight severity and final predicted disease level differed among years. Slight differences in simulated disease levels were sometimes observed between irrigated and non-irrigated treatments; however, irrigation application method did not consistently impact microclimatic parameters associated with late blight development. These results indicate that microclimate conducive to late blight development was less impacted by irrigation treatments than by local macroclimatic conditions.

The effect of Bt-transgenic potatoes on the movement of the Colorado potato beetle [Coleoptera : Chrysomelidae

A two-year field study conducted at the Potato Research Centre in Fredericton, New Brunswick, demonstrated a quantifiable residency time for Bacillus thuringiensis (Bt) susceptible adult Colorado potato beetles (Leptinotarsa decemlineata) in a Bt-transgenic potato field. Fifty percent of Bt-susceptible beetles released in a transgenic Russet Burbank (NewLeafTM) potato plot were recaptured 4 to 7 days after release compared to 7 to 11 days for beetles released in a non-transgenic control plot. Beetles survived for long periods of time (up to 31 days) on transgenic potatoes in spite of the crop's toxicity. A significant number of beetles dispersed from transgenic plots. Twenty-five and 30% of the beetles released in the Bt-transgenic plot were recaptured in border rows or trench traps outside the plot indicating a high level of dispersal activity. The long residency time and the high level of dispersal activity could increase the chances of development of a Bt-resistant beetle population. These findings are important to the development of a deployment strategy that will reduce the risk of build-up of Bt resistance in the beetle population.

Discrimination of three fungal diseases of potato tubers based on volatile metabolic profiles developed using GC/MS

Volatiles from the headspace of Russet Burbank potato tubers, non-wounded non-inoculated (N-control), wounded-inoculated-with sterile water (W-control), wounded-inoculated withPhytophthora infestans, Pythium ultimum orBotrytis cinerea, respectively, were sampled at 3 and 6 days after inoculation (dai), using gas chromatography/mass spectrometry (GC/MS).Botrytis inoculated tubers produced two specific volatiles: 2-2-propenyl-l,3-dioxolane and 3, 5-heptadiyn-2-one, while thePythium inoculated tubers produced three: 2-methyl-l-butanol, 2-butanone and 2-methyl-2-butanamine. Similarly, ethoxy-ethene was specific forPhytophthora inoculated tubers. 5-l-methylethylidene-l,3-cyclopentadiene was specific to W-control tubers. Discriminant analysis models based on metabolic fingerprints of metabolites or of mass ions correctly classified 80 to 100% of the observations into respective inoculations/diseases. However, a test-validation correctly classified only 44, 50, 44, 50 and 44% of the fingerprints based on consistent metabolites and 44, 63, 38, 75 and 31% of fingerprints based on mass ions, intoBotrytis, N-control,Phytophthora, Pythium and W-control, respectively. The disease discriminatory metabolite markers and the discriminant models developed here can be used to differentiate the three diseases of Russet Burbank potato tubers, after further validation under commercial conditions.

Some unique benefits with sudangrass for improved U.S. #1 yields and size of Russet Burbank potato

Three studies provided additional knowledge of beneficial effects of sudangrass for yield and quality increases of the Russet Burbank potato. Two of these studies showed significant increases of both U.S. #1 and smooth tubers > 280 g following green manures of sudangrass. These sudangrass (HS-33) effects did not differ from a sorghum-sudan hybrid (Trudan-8). When a sudangrass green manure was compared with a fallow treatment, results of the first study showed mean yield increases of 36% for U.S. #1 tubers > 280 g and yields of a second study by 34% for U.S. #1 tubers. This same sudangrass treatment outperformed green manures of either Austrian winter pea, barley, or sweet corn by increased U.S. #1 yields that ranged from 27% to 61%. By several lines of evidence, these benefits were found to extend beyond the effect of Verticillium suppression. Soil N was significantly increased following green manures of sudangrass, and these increases were in turn negatively correlated with wilt incidence and positively correlated with yields of both U.S. #1 tubers and tubers > 280 g. Additional benefits also included significant increases of tuber grade percentages for marketable tubers and of smooth tubers > 280 g. Benefits from sudangrass green manures beyond the effects of Verticillium suppression became further evident following a greenhouse study that involved field soil and sudangrass that had been grown in the same field. This study corroborated both field experiments by showing increased yields with green manures of sudangrass that approximated 5.5 t ha-1 dry wt. As with the field studies, these yield benefits also extended beyond the effects of Verticillium suppression and were closely associated with significant increases ofFusarium equiseti, F. oxysporum, andF. solani. Throughout all studies, sudangrass green manures significantly increased microbial activities with increased populations ofFusarium spp. and increased concentrations in soil of mineralizable N, organic P, K, Mn, along with the percent soil organic matter -all factors that could have contributed to significant increases of yield and quality.

Rate and timing of nitrogen fertilization of Russet Burbank potato: Nitrogen use efficiency

This study evaluated rate and timing of N fertilization effects on the N use efficiency characteristics of rain-fed Russet Burbank potato. Trials conducted in 1999–2001 included different rates of fertili zer N (0–160 kg N ha-1 in 1999 and 0–200 kg N ha-1 in 2000 and 2001) applied either at planting according to normal grower practice, or at hilling, the latest time that granular fertilizer can practically be applied. Whole-plant dry matter and N accumulation were determined at topkill. Soil inorganic N content was measured to 30-cm depth at planting and at tuber harvest. Soil N supply (plant N accumulation plus soil inorganic N content at harvest with no fertilizer N applied) varied from 77 to 146 kg N ha-1 depending on the year. Crop N supply (soil N supply plus fertilizer N applied) was a better predictor of plant N accumulation than fertilizer N rate, and was used to remove the confounding effect of variation in soil N supply when making among-year comparisons for N use efficiency characteristics. Nitrogen uptake efficiency (NUpE; plant N accumulation/crop N supply) decreased with increasing rates of N applied at hilling N rate in 1999, which was a dry year, but was not influenced by at-hilling N rate in 2000 and 2001, or by at-planting N rate in any year. Nitrogen use efficiency (NUE; dry matter accumulation/crop N supply) and N utilization efficiency (NUtE; dry matter accumulation/plant N accumulation) decreased curvilinearly with increasing crop N supply in each year. Similar relationships between NUE and crop N supply, and between NUtE and plant N accumulation, among the 3 yr of the study suggest that these relationships are largely independent of seasonal climatic variation, and are primarily genetically controlled. Timing of N fertilization had no effect on any N use efficiency parameter, with the exception of reduced NUpE associated with split N application in 1999. This suggests that under rain-fed potato production in Atlantic Canada, timing of N fertilization has no significant effect on N use efficiency of Russet Burbank potato in years of adequate soil moisture, but NUpE may be decreased by split application of N in dry years. Key words: Solanum tuberosum, soil inorganic N, apparent fertilizer N recovery

Rate and timing of nitrogen fertilization of Russet Burbank potato: Yield and processing quality

Split fertilizer N application is thought to improve fertilizer N use efficiency of potato, primarily by reducing NO3 leaching losses. This study evaluated the effects of the rate and timing of N fertilization on yield and processing quality of Russet Burbank potato under rain-fed production. Trials conducted in 1999–2001 included different fertilizer N rates (0–160 kg N ha-1 in 1999 and 0–200 kg N ha-1 in 2000 and 2001) applied either at planting according to normal grower practice, or at hilling, the latest time that granular fertilizer can practically be applied. Tuber total and marketable yield, size distribution, specific gravity, fry colour and tuber concentrations of NO3, sucrose and glucose were measured. Increasing rates of N fertilization increased tuber yield and tuber size, increased tuber NO3 concentration and decreased tuber specific gravity, but had little effect on tuber sugar concentrations or fry colour. Season-to-season variations in total tuber yield responses to N fertilization rate were attributed primarily to variation in soil N supply. Timing of N application had little effect on tuber yield, size distribution or processing quality under adequate soil moisture conditions. However, under dry soil conditions, split N application reduced tuber yield and tuber size. Key words: Solanum tuberosum, tuber specific gravity, tuber nitrate concentration, fry colour

Interaction of spatially separated Pratylenchus penetrans and Verticillium dahliae on potato measured by impaired photosynthesis

Experiments were conducted under growth‐chamber conditions to determine if Pratylenchus penetrans systemically alters light use efficiency (LUE) of Russet Burbank potato infected by Verticillium dahliae. Pathogen separation was achieved by inoculating potato roots with the nematode prior to injecting fungal conidia into the stem vasculature. Treatments were P. penetrans alone, V. dahliae alone, nematode and fungus together, and a no‐pathogen control. Gas exchange was repeatedly and nondestructively measured on the fifth‐youngest leaf with a Li‐Cor LI‐6200 portable photosynthesis system. By 16 and 20 days after stem injection with the fungus, LUE was synergistically impaired in jointly infected plants. Transpiration in plants infected with both pathogens was significantly reduced. However, the combined effect of nematode and fungus was synergistic in one experiment and additive in the other. Stems were destructively harvested when LUE was synergistically impaired. Coinfected potato plants contained more colony‐forming units (CFU) of V. dahliae in stem sap than those infected by the fungus alone in one experiment. Evidence is provided that infection of Russet Burbank roots by P. penetrans systemically affects disease physiology associated with stem vascular infection by V. dahliae. The findings indicate that the role of the nematode in the fungus/host interaction is more than simply to facilitate extravascular and/or vascular entry of the fungus into potato roots.

Tillage and seed-sprouting strategies to improve potato yield and quality in short season climates

Management practices that accelerate crop development and allow earlier harvest would be beneficial in short-season potato (Solanum tuberosum L.) production areas. Yield and quality of the potato cultivar ‘Russet Burbank’ were evaluated in a 2-yr study in northern Maine to determine effects of soil tillage and seedsprouting treatments designed to dry soil early in the spring and hasten seed emergence. The tillage treatments, consisting of fall raised bed (RB), fall ridge till (RT), and spring chisel plow (CH), were tested in combination with green-sprouted and non-sprouted seed tubers on a Caribou gravelly loam (coarse-loamy, mixed, frigid,Typic Haplorthod). Plants from green-sprouted seed emerged earlier than from non-sprouted seed tubers (87%-96% vs 21%-37%, respectively, at 18 days after planting [DAP] in 2000; and 73%-88% vs 18%-23%, respectively, at 20 DAP in 2001). Green-sprouted seed tubers in RB yielded 4.6 to 5.9 T ha-1 more than nonsprouted seed tubers in RB. However, non-sprouted seed tubers yielded higher than green-sprouted seed tubers in RT by 2.9 to 4.2 T ha-1 and in CH by 1.1 to 4.1 T ha-1. Similarly, green-sprouted seed tubers in RB and nonsprouted seed tubers in RT and CH produced higher marketable yield, greater tuber length, and greater tuber diameter than the corresponding seed-sprouting treatment. In the comparatively wetter year (2000), the use of green-sprouted seed tubers in RB significantly increased total and marketable yields, and produced longer and larger tubers than all other treatments. However, in 2001 (relatively dry year), yield and quality from green-sprouted seed tubers in RB did not differ from non-sprouted seed in RT or CH. Green-sprouted seed produced fewer sunburned and rotten tubers, but more misshapen tubers than non-sprouted seed in RB tillage. The technique of producing Russet Burbank potatoes in raised beds is a promising system in regions with short growing seasons for enhancing early soil drainage during spring and improving soil water retention during critical periods of crop growth and development.

CIPC and 2,6-DIPN sprout suppression of stored potatoes

A five-year storage season study using small-scale bins was undertaken to determine the effectiveness of 2,6-diisopropylnaphthlene (2,6-DIPN) in combination with isopropyl-N-(3-chlorophenyl)carbamate (CIPC) for sprout suppression of stored potatoes (Solanum tuberosum L.). The study environment simulated a commercial operation and the storage bins held up to 4,500 kg of tubers. Russet Burbank potatoes were tested for four storage seasons, and for one season the bin space was split between Ranger Russet and Snowden potatoes. Sprout suppression was measured as percent acceptable for fresh pack (%AFP), defined as sprouts ≤3 mm in length. When 2,6-DIPN was used alone at 8.3 mg kg-1 fw, it only provided short-term sprout suppression. Sprout suppression responses for the two chemicals were similar for Russet Burbank, Snowden and Ranger Russet. When 2,6-DIPN was used in combination with CIPC, a significant increase in sprout suppression was observed. In addition, when the two chemicals were used in combination, the amount of CIPC could be reduced by as much as 50% while still maintaining equal or better sprout suppression as compared to CIPC alone. For overall long-term sprout suppression, the best treatment was a combination of CIPC and 2,6-DIPN, each at 16.6 mg kg-1.

Enhancement of the primary flavor compound methional in potato by increasing the level of soluble methionine.

The primary flavor compound in potato, methional, is synthesized from methionine by the Strecker degradation reaction. A major problem associated with potato processing is the loss of methional. Methional or its precursor, methionine, is not added back during potato processing due to high costs of production. A novel approach to enhance the methional level in processed potato would be to increase the production of its precursor, soluble methionine (Met). Cystathionine gamma-synthase (CGS) is a key enzyme regulating methionine biosynthesis in plants. To increase the level of soluble methionine in potato, Arabidopsis thaliana CGS cDNA was introduced under transcriptional control of the cauliflower mosaic virus 35S promoter into Russet Burbank potato by Agrobacterium-mediated transformation. Ten different transgenic potato lines (CGS1-10) were analyzed. Immunoblot analysis demonstrated that Arabidopsis CGS is expressed in the leaves, tubers, and roots of transgenic potato plants. CGS enzymatic activity was higher in the leaves and roots of the transgenic potato lines compared to the wild-type potato. Methionine levels in the leaves, roots and tubers of transgenic potato lines were enhanced as high as 6-fold compared to those in wild type potato plants. The methional level in baked tubers of field-grown transgenic potato lines was increased between 2.4- and 4.4-fold in lines CGS1, CGS2, and CGS4. The increase observed in methional levels correlated with the soluble methionine level in the tubers from the same lines measured before processing. These results provide the first evidence that the methional level can be enhanced in processed potatoes by increasing the production of its precursor, methionine.

Postharvest Biological Control of Potato Sprouting by Fusarium Dry Rot Suppressive Bacteria

Chemical sprout inhibitors are applied to over 50% of the potato harvest to extend storage time. In the U.S.A., CIPC (1-methylethyl-3-chlorophenylcarbamate) is the only synthetic chemical registered for postharvest sprout control of stored potatoes, and it is the most widely used sprout inhibitor world-wide. Due to environmental and health safety concerns, the use of CIPC has become more restricted, and alternative sprout control methods are sought. Six bacteria strains, exhibiting superior dry rot suppressiveness in previous research, were grown in two different liquid culture media and sprayed on Russet Burbank potatoes. In growth chamber and pilot experiments repeated at two storage sites in two successive years, all six isolates demonstrated significant sprout control capabilities when applied after growth on at least one of the culture media supplied. Of the six strains tested, Pseudomonas fluorescens bv.V S11:P:12 and two strains of Enterobacter sp., S11:T:07 and S11:P:08, exhibited highest relative performance levels with sprout control being statistically similar to that of 16.6 ppm CIPC thermal fog after 4-5 months storage.

Comparative effects of cut and treated seed tubers vs untreated whole seed tubers on seed decay, Rhizoctonia stem canker, growth, and yield of Russet Burbank Potatoes

Whole seed tubers have been reported to have performance advantages over seed tubers that have been cut, even if the cut tuber pieces are treated with a fungicide dust. For this study, whole seed tubers were compared to cut seedpieces and to cut seedpieces treated with four different commercial fungicide dusts for five consecutive seasons. A new field generation 3 Russet Burbank seed lot was used for each of the five years of this study. Both whole tubers and cut seedpieces were inoculated withFusarium spp., and the seedpieces were then treated with a fungicide dust. Inoculated and uninoculated untreated controls were also included. Emergence,Fusarium seed decay,Rhizoctonia stem canker, stem numbers, and vigor, as well as yield and grade data were obtained.Rhizoctonia stem canker in stems grown from whole seed tubers was significantly higher than in stems from seedpieces receiving fungicide treatment in several of the study years. Predicting whole seed tuber performance is difficult because performance varies more from year to year than performance of cut and treated seedpieces. Yield performance of whole seed tubers was not significantly better than cut and fungicide-treated seedpieces in any experimental year, and yield of large (over 280 g) tubers was significantly less than that recorded for two of the treatments when data from all five years were combined. This study demonstrated that untreated whole seed did not outperform cut and treated seedpieces for vigor, stem numbers, disease ratings, or yield in small plot comparisons for five consecutive seasons.

Effect of storage period, cultivar and two growing locations on the processing quality of french fried potatoes

The source of raw potato tubers and the tubers’ duration of storage have a significant effect on color and texture of french fries. Controlling these variations is crucial to ensuring a consistent, high-quality end product. Russet Burbank and Shepody potatoes grown at two sites in Manitoba, Canada were stored for 9 and 11 months in 1994, and for 1 and 3 months in 1995, to determine the effects of short-term storage period, cultivar, and two tuber-growing locations on fry color and texture. French fry texture was measured by a puncture test, and peak force and peak deformation used as indices of textural quality. Large peak forces and deformations were assumed to be indicative of improved textural quality. Hunterlab L (lightness) value was used to determine fry color, higher values being associated with improved color quality. Fries processed from 11-month-old tubers had improved color and textural quality compared to those processed from 9-month-old tubers. Fries processed after 3 months tuber storage were darker in color but firmer in texture than fries processed from tubers after 1 month of storage. Differences in texture and color between the two cultivars were more evident with prolonged storage; fries processed from Russet Burbank potatoes were superior in texture and lighter in color than fries made from Shepody potatoes. With respect to site, fries processed from potatoes grown at Portage had better texture but darker color than those processed from Carberry potatoes. It was postulated that the calcium content of the soils may be responsible for both these results.

Control of polyphenol oxidase in whole potatoes by low temperature blanching

Russet Burbank potatoes can be blanched up to 60 min at 50 °C without any loss in firmness and without appearance of browning on their peels, eyes or infected areas. Low temperature blanching (LTB) for 45 min did not cause a significant reduction in crude polyphenol oxidase (PPO) activity (12%). However, when heating time was extended to 60 min, the activity and specific activity of the enzyme were reduced by 27–45% and 22–43% respectively. The remaining enzyme extracted from heated potatoes was partially purified 3.3–3.75-fold by 0–95% ammonium sulphate precipitation and dialysis, and its kinetic parameters were determined. The comparison of the kinetic parameters of PPO in control (Km=10.3 mM and Vmax/Km=0.15) and in 60 min heated potatoes (Km=13 mM and Vmax/Km=0.054) indicated the reduced affinity of the remaining enzyme to its substrate. Thus, LTB at 50 °C for 60 min not only inactivated part of the PPO activity but also reduced the kinetic capacity of remaining enzyme. Extending heating time to 75 min caused the appearance of slight browning on the peels and eyes of potatoes and reduced their firmness. The observed browning was due to the sharp drop in the Km that caused the activation of the PPO. Heating at 50 °C did not affect lipoxygenase activity, but the Km of the enzyme dropped from 0.4 to 0.15 mM and the enzyme became kinetically more reactive at low substrate concentrations. Covalently bound pectin methylesterase considerably activated (38%) by heating and this caused the drop of pH in potato tissues.

Comparison of sensory differences of stored Russet Burbank potatoes treated with CIPC and alternative sprout inhibitors

The sensory properties of Russet Burbank potatoes treated with three naturally occurring volatile compounds, as alternatives to CIPC for sprout inhibition, were evaluated. Potatoes from the 1995 and 1996 crop years were treated with salicylaldehyde, 1,8-cineole, 1,4-dimethylnaphthalene, or CIPC prior to dormancy break during storage and stored for up to 16 wk. Sensory differences between potatoes treated with alternative sprout inhibitors and CIPC-treated or untreated potatoes and inhibitor concentration were determined at 2-wk intervals. Potatoes treated with 1,8-cineole or salicylaldehyde, but not 1,4-dimethylnaphthalene, were significantly different from the untreated potatoes or potatoes treated with CIPC. Sensory detection threshold levels for the alternative inhibitors were measured in a model potato system. The residual levels of the sprout inhibitors were within the detection threshold range for 1,8-cineole (0.02–0.04 ppm), but not for salicylaldehyde (0.0–0.10 ppm) or 1,4-dimethylnaphthalene (0.80–1.40 ppm). The presence of the residual sprout inhibitors and/or the influence of sprout inhibitors on potato metabolism during storage contributed to observed differences in sensory quality of stored potatoes.

Control of enzymatic browning in potato (Solanum tuberosum L.) by sense and antisense RNA from tomato polyphenol oxidase.

Polyphenol oxidase (PPO) activity of Russet Burbank potato was inhibited by sense and antisense PPO RNAs expressed from a tomato PPO cDNA under the control of the 35S promoter from the cauliflower mosaic virus. Transgenic Russet Burbank potato plants from 37 different lines were grown in the field. PPO activity and the level of enzymatic browning were measured in the tubers harvested from the field. Of the tubers from 28 transgenic lines that were sampled, tubers from 5 lines exhibited reduced browning. The level of PPO activity correlated with the reduction in enzymatic browning in these lines. These results indicate that expression of tomato PPO RNA in sense or antisense orientation inhibits PPO activity and enzymatic browning in the major commercial potato cultivar. Expression of tomato PPO RNA in sense orientation led to the greatest decrease in PPO activity and enzymatic browning, possibly due to cosuppression. These results suggest that expression of closely related heterologous genes can be used to prevent enzymatic browning in a wide variety of food crops without the application of various food additives.

NewLeaf Plus® Russet Burbank potatoes: replicase-mediated resistance to potato leafroll virus

Potato leafroll poleovirus and the Colorado potato beetle (Leptinotarsa decemlineata (Say)) are major pests of potato in the USA. The US Department of Agriculture estimates that over 50% of annual insecticide use on potato is applied to control the Colorado potato beetle and aphids that transmit potato leafroll virus (PLRV). To address this issue, Russet Burbank potatoes have been genetically modified for a high level of resistance to infection and the resulting disease symptoms caused by PLRV and to feeding damage caused by the Colorado potato beetle. This resistance was achieved by the expression of the unmodified full-length replicase gene of PLRV and the cry3A insect control protein gene from Bacillus thuringiensis var. tenebrionis. Plant expression constructs containing various modifications of the PLRV replicase gene were produced during the development of this product. The genes in these constructs were a full-length unmodified replicase (open reading frame 2a/2b), an antisense orientation of the full-length cDNA, an open reading frame 1 translation of the full-length gene, and a gene truncation containing the 3′ sense coding portion of the replicase gene. Growth chamber experiments demonstrated that transformation of plants with the full-length and 3′ sense coding constructs substantially protected these potato plants from infection and disease symptoms caused by PLRV. The Russet Burbank potato expressing the full-length PLV replicase gene and the cry3A gene is a new potato product from NatureMark called NewLeaf Plus®.

Influence of early-season nitrogen application pattern on impact sensitivity in Russet Burbank potato tubers

As part of an effort to assess the influence of cultural practices on bruising in potato tubers, this work was a preliminary study to determine whether the pattern of early-season nitrogen fertilizer application influences impact sensitivity (bruise threshold and bruise resistance) in Russet Burbank tubers. Tissue sample impact failure stress, strain, and shock wave speed, and whole-tuber bruise energy and bruise volume were measured on tubers from two soils and three early-season nitrogen fertilizer application patterns. Results showed that fertilizer pattern significantly influenced bruise threshold in the higher-permeability soil and bruise resistance in both soils. The worst fertilizer treatment resulted in bruises nearly twice the size of those in the other two treatments. The split 56 kg/ha preplant and 56 kg/ha postplant nitrogen treatment gave significantly higher bruise threshold in the higher permeability soil and highest bruise resistance in both soils (higher is better). Fertilizer treatment effects were less pronounced in the lower permeability soil, with no significant effect on bruise threshold in that soil.

Compositional and enzymatic changes associated with the sugar-end defect in Russet Burbank potatoes

This study was initiated to determine the starchsugar composition and the activities of relevant enzymes of carbohydrate metabolism in Russet Burbank (cv.) potatoes exhibiting the sugar-end defect. The frequency of sugar-end tubers was increased by applying a single, transient, moisture-deficit stress period following tuberization. The following properties were unique to sugar-end tubers compared to normal tuber tissue. (1) Starch and total solids decreased markedly while glucose content increased 15-fold, (2) The concentration of Suc was markedly lower, (3) Pi was slightly but significantly increased, (4) The activities of UGPase and Susy decreased nearly 3 and 2-fold, respectively, (5) The activity of AGPase decreased 50%, (6) The ratio of STPLase to AGPase shifted over 3-fold in favor of starch mobilization, (7) Basal AcInv activity (assayed in the presence of inhibitor) increased 7-fold during storage, (8) Tuber Glc concentration showed a better correlation to basal Aclnv activity than to total Aclnv activity (inhibitor destroyed), (9) Kinetic analysis suggested that the level and/or effectiveness of the Aclnv inhibitor was decreased in the sugar-end tuber tissue. These results are discussed in relation to metabolic changes which occur in converting a starch storing tuber to one primarily involved with starch mobilization.