Effect of whole seed tuber size and pre-plant storage conditions on yield and tuber size distribution of Russet Burbank

Field experiments were conducted in 1995, 1996, and 1997 at Agriculture and Agri-Food Canada’s Harrington Research Farm to assess the effect of whole seed tuber size and pre-plant seed storage conditions on processing yield (> 51 mm dia.) of potato (Solanum tuberosum L. cv Russet Burbank). Following commercial storage, seed tubers were stored at 4.4 C then subjected to one of three pre-plant treatments: (1) planted directly from storage, (2) held at 10 C for 3 wk before planting, or (3) green-sprouted for 3 wk before planting. Five sizes of whole seed were used (28, 42, 56, 70, and 84 g) with a variable size cut seed treatment added for comparison. Plots were harvested 138,134, and 131 days after planting in 1995, 1996, and 1997, respectively. Cut seed produced a higher yield of tubers > 51 mm diameter in comparison to all whole tuber seed sizes, with the exception of the 28 and 56 g sizes. In terms of total yield, the 28and 42-g whole seed tubers yielded significantly less than all other seed sizes examined. Warming or greensprouting seed tubers prior to planting did not increase tuber yield. The larger whole seed tuber sizes tended to result in greater numbers of stems and tubers per plant. To maximize marketable yield of Russet Burbank planted from whole seed tubers, it is recommended that the seed be between 28 and 42 g in size. Accepted for publication 25 May 2004.     

Tuber growth and biomass partitioning of two potato cultivars grown under different n fertilization rates with and without irrigation

Nitrogen and water deficiencies are known to affect potato yield, but much less is known of their effect on tuber growth and biomass partitioning. The objective of this on-farm study conducted at two sites in each of three years, 1995 to 1997, was to determine the effects of supplemental irrigation and N fertilization rates on tuber growth and biomass partitioning of the cultivars Shepody and Russet Burbank. The N fertilization rates were 0,100, and 250 kg N ha^-1in 1995, and 0, 50,100, and 250 kg N ha_?1 in 1996 and 1997. The highest bulking rate observed in our study (7.3 g fresh tubers m^-2 °C^-1) can be considered near the potential bulking rate in New Brunswick. The water deficit in the absence of supplemental irrigation reduced this potential bulking rate by as much as 40%, but this reduction was much less at five of six sites and negligible at two of six sites. Nitrogen deficiency reduced the bulking rate at two of six sites. This negative effect of N deficiency on bulking rate was greater with irrigation than without irrigation at two of six sites; the tuber bulking rate with irrigation was reduced by as much as 50% with no N applied at one site. Shepody had a greater bulking rate than Russet Burbank. The tuber bulking of Russet Burbank, however, started earlier and lasted longer than that of Shepody. Water and N deficiencies increased biomass partitioning to tubers and large roots. Shepody partitioned a greater proportion of its biomass to large roots and had a greater root biomass than Russet Burbank. Our results demonstrate the ability of potatoes to modify biomass partitioning when grown under water and/or N stresses. As a result of this compensation, the reduction in tuber yield due to limited N and water stresses is minimized.     

Nitrogen Response of French Fry and Chip Cultivars Selected for Low Tuber Reducing Sugars

New cultivars ‘Alpine Russet’, ‘Dakota Trailblazer’ and ‘Ivory Crisp’ have lower tuber reducing sugars and acrylamide-forming potential. Adoption of new cultivars by growers requires information about their responses to agronomic factors such as nitrogen (N) fertilizer. The objective of this study was to determine the effect of N rate on yield and quality of new cultivars relative to conventional cultivars ‘Russet Burbank’ and ‘Snowden’. The experiment was conducted over two years as a randomized complete block design replicated four times with five N rates and five cultivars. The new cultivars had comparable or higher marketable yields, and a higher percentage of large tubers (greater than170 g) than the standard cultivars. Total and marketable yields responded quadratically to N and optimized at 231 kg ha^?1 in 2011 and 319 kg ha^?1 in 2012 for all cultivars. ‘Dakota Trailblazer’ had high hollow heart incidence (greater than 10% at N rates above 125 kg ha^?1), and excessively high specific gravity, making it undesirable for processing but with potential to be a parent in a breeding program. ‘Alpine Russet’ and ‘Ivory Crisp’ had specific gravity suitable for commercial processing, and low hollow heart incidence at all N rates. Critical petiole nitrate-N concentrations 50 and 70 days after planting for all cultivars were greater in 2012 than in 2011, suggesting that interpretation of critical values can be affected by growing conditions.     

Effect of short- and long-term exposure of seed tubers to low temperatures on the growth and yield of five potato cultivars

Trials were conducted in Alberta with Norchip, Norland, and Russet Burbank and in Ontario with Kennebec, Russet Burbank, Norchip, and Superior tubers to determine their response to short-term exposure to air temperatures of 0, ?1, and ?5 C and to long-term exposure to ?1, 0, 1,2, and 3 C. Exposure of seed tubers to ?1 C from 6 hours to 5 days did not affect growth characteristics or tuber yield of any of the five cultivars studied. Long-term (October–May) exposure to ?1 C in one study severely reduced emergence and tuber yield of Norchip (P<0.05). While the marketable yield of Russet Burbank was also reduced (P<0.05) by this treatment, Norland was not affected. Tubers of all cultivars exposed to air temperatures of ?3 or ?5 C for longer than 24 hours were severely injured and were not planted in the field trials at either location. In Alberta exposure of seed tubers of Norchip, Norland, and Russet Burbank to ?5 C for 6 and 12 hours caused a reduction (not significant) in yield. In Ontario, long-term storage at 1, 2, and 3 C and in combination with short-term (2 weeks) exposure to 0 or 10 C had no effect on growth or marketable yield of Norchip, Russet Burbank, Superior, and Kennebec seed tubers.     

1,4-Dimethylnaphthalene treatment of seed potatoes affects tuber size distribution

1,4-DMN is a relatively new sprout inhibitor for use on maincrop and seed potatoes. Despite its registration as a “dormancy enhancer” for seed, relatively little is known about its effects on plant establishment and productivity. The main objective of this study was to evaluate the effects of 1,4-DMN on the productivity of seed potatoes. ‘Umatilla Russet’ (UR), ‘Ranger Russet’ (RR), and ‘Russet Burbank’ (RB) seed tubers were stored at 4, 7, and 9 C over three seasons to create 80-, 554- and 642-degree-day seed, and 1,4-DMN was applied to maintain dormancy several times during each season. 1,4-DMN residue levels at the end of storage were lower in seed aged at higher temperatures. Multiple applications of 1,4-DMN at higher-than-label rates were necessary to effectively inhibit sprouting of seed of all cultivars stored above 4 C. In field trials, depending on cultivar and year, 1,4-DMN either delayed plant emergence slightly or had no effect. 1,4-DMN increased stem numbers from RB and UR seed, but not from RR seed. 1,4-DMN reduced total tuber yields by 3.2 to 5.6 t ha^?1 (5% to 9%), and U.S. No. 1 tuber yields by 4.8 to 7.8 t ha^?1 (8% to 15%) in all cultivars, regardless of seed tuber age. 1,4-DMN also reduced the average tuber weight for all three cultivars and shifted the size distribution from larger (> 284 g) to smaller tubers. 1,4-DMN reduced the respective yields of > 397-g, 340-to 397-g, and 284-to 340-g tubers by 43%, 19%, and 18% for RR seed, 31%, 14%, and 11% for RB seed, and 40%, 47%, and 27% for UR seed. Conversely, depending on cultivar, yields of smaller tubers (≤170 g) were 11% to 38% higher from 1,4-DMN-treated seed. The shift in tuber size distribution for RR was accompanied by a 1,4-DMN-induced increase in tuber number per plant and per hectare. However, no such effects on tuber set occurred in RB and UR. Moreover, in most cases, the 1,4-DMN effects on yield and tuber size distribution were independent of seed age. Since the 1,4-DMN-induced shifts in tuber size distribution were greater than the reductions in total and U.S. No. 1 yields, 1,4-DMN may be a suitable treatment to reduce average tuber size and increase yield and uniformity of specific size classes of tubers to more closely match market requirements.     

Response of russet norkotah clonal selections to nitrogen fertilization

The low vine vigor and high N requirement of Russet Norkotah may lead to N loss and groundwater contamination on coarse-textured soils. Recent clonal selections from Texas have produced strains that have larger and stronger vines, which may alter N requirements. This twoyear study examined the N use efficiency (NUE), yield, and quality of Russet Norkotah strain selections fertilized with different N levels on a Hubbard loamy sand in central Minnesota. The selections, Texas Norkotah Strain (TXNS) 112, TXNS 223, and TXNS 278 were grown with standard Russet Norkotah under irrigated conditions and received total N levels of 28, 112, 224, or 336 kg ha^-1. Total, marketable, and large (>340 g) tuber yields increased linearly (P>0.05) with rate of N application in 1998 but not in 1997. The genotype main effect was not significant for any of the tuber yield parameters measured based on fresh weight. Vine, tuber, and total dry biomass yields were 116%, 5.8%, and 13.2%, respectively, higher with the selections than Russet Norkotah. Harvest index (HI), or the proportion of total dry matter partitioned to tubers, was 7% greater for Russet Norkotah than the TXNS selections, reflecting the larger vine growth of the selections. The selections accumulated significantly higher N in the vines (0.113 kg kg^-1 N) than the standard clone (0.053 kg kg^-1 N) as N rate increased from 28 to 336 kg ha^-1, and the difference between the selections and the standard clone was larger at higher N rates than at lower N rates. Russet Norkotah partitioned 10% more N to tubers than did the TXNS selections, reflecting the difference in HI between the standard cultivar and its clones. Nitrogen recovered from fertilizer N applied in addition to the 28 kg ha^-1 starter N (NUE₂₈) averaged 36% and varied little with genotype, N rate, or cropping year. Biomass accumulation from similar N additions (AUE), however, was significantly higher for the selections than Russet Norkotah at 112 kg N ha^-1 in 1997 only. At low N rate (112 kg ha^-1), the selections had higher physiological use efficiency (PUE₂₈) (mean 45.9 g g¹) than Russet Norkotah (25.9 g g¹). Results from this study demonstrate that, although N recovery was similar for the four genotypes, the Texas Norkotah strains produced greater biomass than Russet Norkotah per kg N applied at low rate in 1997 and per kg of fertilizer N absorbed by the plant in both years. However, under the conditions of this study, higher biomass of the selections did not translate into a marketable yield advantage over the standard cultivar.     

Estimating potato yield responses from chemical control of early blight in Minnesota

The effect of early blight on tuber yield of two potato (Solanum tuberosum L.) cultivars (Russet Burbank and Norland) was evaluated using number and timing of applications of three chemicals to generate different disease epidemics in 1981 and 1982. Under the non-irrigated farming conditions in Minnesota, there were no significant differences among captafol, triphenyltin hydroxide and maneb-Zn in blight control to increase yield. Of the five spray schedules tested, a 7–10 day spray schedule initiated when blight severity exceeded 0.01%, and a 7–10 day schedule initiated when blight was found above the lower third of the plant, generally gave significant, positive yield responses with all three chemicals. At Rosemount in 1982, the greatest yield increases (relative to unsprayed) obtained were 34.9% and 48.6% in total tuber yields for Norland and Russet Burbank, respectively. At Rosemount in 1982, the highest yield increases (relative to unsprayed) obtained were 92.2% and 56.6% in total tuber yields for Norland and Russet Burbank respectively. At Grand Forks in 1981, the highest yield increases were 126.8% and 34.6% in total tuber yields for Norland and Russet Burbank respectively. Across all three experiments, maximum yield losses (percentage of [[yield of ‘healthy’—yield of unsprayed check]/yield of ‘healthy’’]) were 58.4% (US #1 tubers) and 55.9% (total tubers) for cv. Norland and 34.4% (US #1 tubers) and 36.2% (total tubers) for cv. Russet Burbank.     

Effect of two plant growth regulators on the yield and quality of russet burbank potatoes

Summary Foliar applications of ethephon (ETH) 300 g a.i. ha⁻¹; chlormequat chloride (CCC) 920 g a.i. ha⁻¹, with a second application of 230 g a.i. ha⁻¹ approximately 2 weeks later; and a mixture of the two (ETH/CCC) 156 g a.i. ethephon and 299 g a.i. chlormequat chloride ha⁻¹ were made to field-grown Russet Burbank potatoes in 1986, 1987 and 1989. All the treatments increased the number of tubers set and reduced the average tuber weight compared to the control resulting in a reduction in premium and marketable tubers, and an increase in small tubers. Differences were greatest for ETH and least for CCC. ETH and ETH/CCC decreased the specific gravity, increased the incidence of deformities, and decreased the incidence of tubers with hollow heart. The growth regulators did not affect fry colour.     

Western russet: A new potato variety with excellent fresh market and frozen-fried processing quality and field resistance to common scab and PVYo

Western Russet, designated experimentally as A7961-1, and resulting from the cross A68113-4 x Bel-Rus, was released in 2004 by the USDA/ARS and the agricultural experiment stations of Idaho, Oregon, and Washington. The foliage of Western Russet is spreading, with medium-sized olive-green leaves and abundant white flowers. The tubers are tan, with medium russet skin, oblong shape, a slightly prominent eyebrow, white flesh, and distinctly visible pith. Western Russet was compared with Russet Burbank in trials across the Pacific Northwest for yield, quality, and disease response. In general, Western Russet produced lower total yields than Russet Burbank, but on average and depending on location, similar U.S. No. 1 yields. When observed for defect problems, Western Russet exhibited resistance to second growth, growth cracks, shatter bruise, stem-end discoloration, and heat necrosis, moderate resistance to hollow heart, and moderate susceptibility to blackspot bruise. In product quality tests, Western Russet was rated similar to Russet Burbank for french fry and dehydrated potato flake quality and slightly inferior for baked potato quality. In replicated evaluations, Western Russet was found to have good field resistance to common scab and PVY^o, and moderate resistance to verticillium wilt and tuber net necrosis caused by PLRV. It demonstrated susceptibility to late blight, foliar PLRV, dry rot, soft rot, and tuber early blight. Biochemical analysis of Western Russet tubers showed markedly higher vitamin C content than those of Russet Burbank. Tuber glycoalkaloid concentration in tubers produced in a 1988 trial was 1.0 mg 100 g^?1.     

Short-Term exposure to low temperature in the fall affects field performance of seed tubers

Field trials were conducted in Alberta and Ontario with Norchip, Norland, Russet Burbank, Sangre and Superior potato cultivars to determine response to short-term exposure of seed tubers to below freezing temperatures in the fall. Exposure of the dormant seed tubers to ?-1 C for up to 48 hours did not affect the yield or growth characteristics of the cultivars. However exposure of seed tubers to ?-5 C temperatures for 6 or 12 hours caused marked (P < 0.05) reductions in marketable yield, marketable tuber number, maturity and vine size. Exposure to ?-5 C for periods longer than 12 hours resulted in severe freezing damage and subsequent decay of most of the tubers.     

Population density studies with Russet Burbank II. The effect of fertilization and plant density on growth,development and yield

The response of Russet Burbank grown at five plant densities (4.0 to 11.1 × 10⁴ plants ha^?1), to level of fertilization was studied in field experiments at Guelph, Canada in the 1972 and 1973 growing seasons. Growth analysis techniques were used to establish growth patterns of Russet Burbank at three of the above plant densities (4.0,6.3 and 11.1 × 10⁴plants ha^?1), while the effect on root development of rate of fertilization was observed in controlled environments. In both seasons total tuber yield was not influenced by plant density, while marketable yield showed a negative response to increased density. The interaction between plant density and level of fertilization did not approach significance in either season. Due to greater axillary branching at the lower plant densities, leaf area index and photosynthetically active radiation measured at two levels in the canopy, were similar at all densities. Fertilizer levels used in the field showed no negative effect on root growth in experiments conducted in controlled environments. Marked variation in the number of mainstems and thus the number of tubers produced per plant between seasons indicated the importance of using the mainstem as the basic population unit.     

Century Russet: A high-yielding fresh market cultivar with verticillium resistance

Century Russet, a high-yielding, late-maturing variety suitable for fresh tablestock use, was jointly released in 1995 by Agricultural Experiment Stations in Oregon, Idaho, Washington, Colorado, California, and Texas and the USDA Agricultural Research Service. Extremely high yields have been observed for Century Russet in variety trials conducted in Oregon and throughout the western United States under a wide range of soil and climatic conditions. Century Russet produced 40 percent higher marketable yields than Russet Burbank and 67 percent higher marketable yields than Russet Norkotah in 11 regional trials conducted over a three-year period in sevenwestern states. Uniform tuber shape, high yields of count carton sizes, and attractive tuber appearance make Century Russet well suited for the fresh market industry. It is not recommended for chipping or processing into frozen products because of low solids and dark fry color. Century Russet is highly resistant toVerticillium wilt and consistently develops less hollow heart, brown center, and other internal defects than Russet Burbank. It requires more time between vine kill and harvest than Russet Burbank for adequate tuber maturity and skin set. Bruised Century Russet tubers are susceptible to early blight andFusarium infection.     

Effect of seed piece size on performance of three potato varieties in the Klamath Basin of Oregon

A survey of cut seed lots from Klamath Basin commercial potato operations showed poor uniformity of seed piece size and numerous undersize seed pieces in most of the 18 seed lots examined over two years. Experiments were conducted in 1995, 1996, and 1997 to evaluate effects of seed piece size on the performance of Russet Burbank, Russet Norkotah, and Century Russet cultivars. Weighed seed tubers were cut into four pieces to obtain seed piece sizes of 21, 35, 50, 64, and 78 g (+/-2 g). Seed pieces less than 50 g resulted in delayed emergence and reduced stem numbers in all varieties. Effects of seed piece size on yield and tuber size distribution were greatest for Century Russet and least for Russet Norkotah, but were significant for all varieties over the three-year study. Increasing seed piece size increased yield of U.S. No.1 and total yield, while reducing tuber size. An economic analysis, based on crop values for fresh market use and seed costs, found optimum seed piece sizes of 64 g for Russet Burbank and Century Russet and 50 g for Russet Norkotah.     

Nitrogen fertilization of irrigated Russet potatoes in southcentral Alaska

Allagash Russet, BelRus, Frontier Russet, HiLite Russet, Russet Norkotah and Russet Burbank were evaluated with preplant N fertilizer levels of 0, 67, 134, 201, and 201 kg N/ha in a split application on a Knik silt loam in 1990 and 1991 near Palmer, Alaska. BelRus and Russet Norkotah yielded less marketable tubers than the other cultivars and Russet Burbank performed well under warm, dry 1990 conditions and poorly when conditions were cool and wet (1991). Allagash, HiLite and Frontier Russets were consistent producers with marketable tuber yields averaging 35.4, 32.3, and 32.2 t/ha, respectively. Marketable tuber yield was maximized with approximately 175 kg total N/ha (residual soil plus applied) and approached 43 t/ha in 1990. Splitting the N application had no significant effect on tuber yield. Newly released russets appear promising for commercial Alaska producers.     

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.     

Manipulation of microtubers for direct field utilization in seed production

A two-year field study was conducted to determine the effects of jasmonic acid (JA), light (duringin vitro explant production andin vitro tuberization phases), and dormancy-breaking treatment on performance of microtubers in the production of seed tubers (pre-elite) in five potato cultivars. Microtubers were produced under short day (8-h) conditions and in darkness, from stock plantlets pre-treated with JA and untreated, and on tuberization media with or without JA. Microtuber performance was compared to invitro plantlets transplanted directly to the field. Yields of tubers from microtubers were 30% to 40% of those from plantlets. Microtubers of cultivars Amisk and Russet Burbank produced the highest yields of pre-elite tubers. Atlantic microtubers performed poorly in the field. JA pre-treatment of stock plantlets, prior toin vitro tuberization, enhanced seeds tuber production from microtubers in Russet Burbank and lowered in Shepody. JA presence in media duringin vitro tuberization significantly lowered production of tubers while exposure to 8-h light resulted in microtubers performing significantly better in the field than microtubers produced in the dark. Dormancy release was the key factor influencing microtuber performance. Unlike greenhouse studies, gibberellic acid (GA₃) was more effective than Rindite. A further refinement of the production and handling methods is required before microtubers can be recommended for field production of seed tubers.     

Yield response of two potato culivars to supplemental irrigation and N fertilization in New Brunswick

Nitrogen and water are important factors influencing potato production, and crop response to these two factors may vary with cultivars. The yield response of two potato cultivars (Russet Burbank and Shepody) to six rates of N fertilization (0-250 kg N ha^-1) with and without supplemental irrigation was studied at four onfarm sites in each of three years, 1995 to 1997, in the upper St-John River Valley of New Brunswick, Canada. On average, irrigation increased total yield from 31.9t ha^-1 without irrigation to 38.41 ha^-1 with irrigation and marketable yield from 25.61 ha^-1 without irrigation to 30.71 ha^-1 with irrigation. Potato yields were increased by irrigation at nine out of the 12 sites, and the irrigation response was similar for both cultivars. Nitrogen fertilization significantly increased both total and marketable yields at all sites except one. The yield response to N fertilization was greater with irrigation. The N fertilization rate (Nmax) required to reach maximum total and marketable yield, however, was similar with and without irrigation. A large variation in Nmax was observed among sites. With irrigation Nmax varied between 158 and 233 kgN ha^-1 for total yield, and between 151 and 250 kg N ha^-1 for marketable yield. There was no interaction between N fertilization and potato cultivar for both total and marketable yields. The two cultivars had similar total yields (35 t ha^-1). Shepody, however, had a greater marketable yield (28.9 t ha^-1) than Russet Burbank (27.4 t ha^-1). Our results indicate that the response to two of the most significant factors of potato production, irrigation and N fertilization, varies greatly with sites and climatic conditions, and that field specific recommendations are required for the optimum management of N and irrigation.     

Teton Russet: An Early-Maturing,Dual-Purpose Potato Cultivar Having Higher Protein and Vitamin C Content,Low Asparagine,and Resistances to Common Scab and Fusarium Dry Rot

Teton Russet is an early-maturing, medium-russeted, potato cultivar with high merit for both fresh-pack and processing. In early harvest trials in the Pacific Northwest, Teton Russet had total yields similar to Russet Norkotah, and higher than Ranger Russet and Russet Burbank. Marketable yield of Teton Russet in the early harvest trials was also comparable to or higher than Russet Norkotah in Washington and Oregon, and higher than Ranger Russet and Russet Burbank at these sites, as well as in Idaho. In full-season trials, while total yield of the earlier-maturing Teton Russet tended to be lower than Ranger Russet and Russet Burbank, marketable yield was generally higher than Russet Burbank across the majority of sites due to its higher percentage of U.S. No. 1 tubers. Teton Russet is suitable for processing, with acceptable fry color following up to 8 months of storage at 8.9 °C. Uniformity of fry color was also very consistent. Teton Russet has shown lower levels of the amino acid asparagine relative to Ranger Russet and Russet Burbank which may contribute to lower acrylamide levels in French fries and other processed potato products. Teton Russet is notable for having resistance to common scab (Streptomyces spp.) and Fusarium dry rot, and is moderately resistant to tuber net necrosis. Analyses have also shown Teton Russet to have significantly higher protein levels than Russet Norkotah, Ranger Russet, and Russet Burbank, as well as higher vitamin C content than Russet Norkotah and Russet Burbank. Teton Russet was released in 2011 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon, and Washington, and is a product of the Pacific Northwest Potato Variety (Tri-State) Development Program.     

Effect of the ring rot pathogen and latent potato viruses on ring rot symptoms and yield of potatoes

The ring rot bacterium,Corynebacterium sepedonicum (Spieck. and Kotth.) Skapt. and Burkh., and latent potato viruses (potato virus S and potato virus X) were investigated for their effect on ring rot symptom development on potato plants in the greenhouse and on symptom development and yield of potatoes in the field. Both virus-free (VF) and virus-infected (VI) Red Pontiac stem cuttings root-inoculated with ring rot bacteria in the greenhouse developed typical (T) ring rot symptoms, and symptom severity did not differ between VF and VI plants. In a field study, both VF and VI Russet Burbank seed pieces knife-inoculated with ring rot bacteria produced plants with atypical (A) and T ring rot symptoms as well as a combination of both types. The data suggest that more A than T symptoms develop on VI plants and more T than A symptoms develop on VF plants. Combined infection with the ring rot pathogen and the latent potato viruses resulted in greater yield losses of total and marketable Russet Burbank tubers than infection with the bacterial or viral pathogens alone.     

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.