Inheritance of potato chip color at the 24-chromosome level

Potato chip color is an important trait in determining quality and acceptability of cultivars for processing. Therefore, the genetics of potato chip color is important in varietal breeding. The use of 2xS. tuberosum Group Tuberosum haploid × 2x wild species hybrids provides disomic inheritance for genetic analysis of chip color. Two hundred forty haploid-species hybrids representing crosses between 15 haploids and 10 species were evaluated for potato chip color after 21 days reconditioning (18 to 20C) following 6 months at 4C. Phenotypic variation for chip color was found among the haploid-species hybrids. Crosses between good, medium, and poor performing clones were made in all combinations and 136 families were obtained. Progeny were evaluated for reversion resistance (chipping direct from 10C storage) and reconditioning (chipping from 4C after tuber warming) chip color. Variation for chip color was found among the progeny for each trait. Significant correlations between reversion resistance and reconditioning were found. Yet, the use of at least two chip tests (one for reversion resistance and one for reconditioning) is more informative than the use of one test and subsequent predictions made, regarding the other trait. A three locus hypothesis for both reversion resistance and reconditioning is proposed for the inheritance of each trait. One dominant allele at each of the three loci is necessary for good chipping. One or two loci may be common to both characteristics. Good chipping 2x hybrids that produce 2n pollen can be used to transfer this trait to the 4x level through use of 4x × 2x crosses.     

RBM134: A mutant of Russet Burbank susceptible to blackspot bruise

A radiation induced mutant of Russet Burbank was recovered that is more susceptible to blackspot bruise than the original cultivar. The mutant was evaluated and characterized for several agronomic and biochemical traits. Compared to Russet Burbank the mutant had slightly lower tuber yield, smaller average tuber weight, a higher number of tubers per plant, higher percent tuber dry matter, similar total tuber dry matter yield, lower tuber protein and higher free tyrosine content. Vine growth and appearance was indistinguishable from Russet Burbank. This mutant should provide an excellent tool for better understanding the tuber characteristics contributing to blackspot bruising in potatoes.     

Techniques for detecting and measuring developmental and maturational changes in tuber native periderm

We developed a technique to quantitate native periderm permeability during tuber growth and maturation by porometrically determining vapor conductances. We also describe a simple, inexpensive means of determining the corresponding weight per unit area of suberized phellem cells (skin) in native periderm during tuber growth and maturation as a means of assessing the developmental status of native periderm. The porometric technique is very sensitive and rapid. Porometrically derived vapor conductances of mature native periderms were measured without difficulty, and native periderms were found to release ~0.005 moles of water vapor/meter² native periderm surface/sec. into a dry test atmosphere. Immature native periderm released up to 28 times more water vapor than mature periderm even though the phellem cells were histochemically determined to possess both major components of suberin. We demonstrated use of the porometric technique by determining maturational changes in periderm permeability of growing/immature tubers and mature tubers at harvest. The technique revealed that the native periderm of Russet Burbank tubers was more permeable and had the potential to lose more water vapor, until becoming permeably mature, than Norchip or Norland tubers harvested on the same dates. The dry weight of the skin (phellem tissue) of native periderm (mg/ cm²) for all three cultivars increased during tuber growth, but plateaued to a relatively constant level, or slightly declined, while plants were still alive during the latter period of tuber growth. During this period, periderm vameable conductances were undergoing substantial declines. Comparison of skin dry weights of immature tubers indicated that stem end regions of tubers were developmentally ahead of equatorial and bud end regions; this difference decreased as the tubers matured at harvest time and was less apparent with some cultivars.     

Nitrogen and potassium fertilization of potatoes: Sugars and starch

Considerable evidence exists that both N and K influence potato (Solanum tuberosum L.) yields and quality. The impact of nutrients on tuber quality parameters under field conditions should be identified so optimum management practices can be utilized. We evaluated the N and K fertilization by K-sources effects on concentrations of nutrients, reducing sugars, sucrose and starch in the stem and apical tuber ends from two irrigated field experiments with the Russet Burbank cultivar. Nitrogen rates of 0,112, 224 or 336 kg ha^?1 were combined with selected K rates of 0, 112, 224 or 448 kg ha^?1 as either KCl or K₂SO₄ arranged as an incomplete factorial. A multiple linear regression model was fit to the data and used to predict the response surface for a complete factorial for each K-source. Nitrogen applications increased or decreased reducing sugars in the apical and stem ends, respectively. Potassium decreased reducing sugars in both tuber ends. Sucrose was higher in the apical end than in the stem end but was not appreciably affected by fertilizer treatment. Nitrogen and potassium applications reduced dry matter and starch concentrations in both tuber ends. Potassium had a smaller effect on the apical end when starch was expressed on a dry weight basis, indicating that increased water content was a factor in the K effect. Both N and K concentrations in the tuber ends were negatively related to starch concentrations, but the relationship was different for the apical and stem ends. Tuber Cl concentration indirectly affected starch concentrations in the stem end when KCL was applied. The K fertilization effect on specific gravity depended upon the K concentration in the harvested tuber and was independent of K fertilizer source. These data illustrate the effects of preplant N and K fertilization rates on final tuber quality parameters. Additional studies are needed to further define the effects of nutrient concentrations at different plant growth stages.     

Genetic relationships of Japanese potato cultivars assessed by RAPD analysis

Seventy-three breeding lines and cultivars, which included all Japanese cultivars, were assessed by random amplified polymorphic DNA (RAPD) analysis. Thirty-one of 40 decamer primers revealed 84 scorable RAPDs. Using these RAPDs, 67 of 73 cultivars were distinguished from each other. One of the cultivars released as a protoclonal variant was able to distinguish from the parent by increasing the number of primers surveyed. Based on the number of different RAPDs between each pair of accessions, cluster analysis was performed to exploit genetic diversity in Japanese cultivars. Closely related cultivars deduced from their pedigrees were clustered closely, indicating that similarities based on the presence vs. absence of RAPDs were reflections of genetic similarities. Old Japanese cultivars, as suggested by their similarity of chloroplast DNA toS. tuberosum ssp.andigena, were indeed clustered with ssp.andigena accessions, supporting these were relic cultivars of early European potatoes. The present study suggests that Japanese potatoes are an interesting mass of genetic diversity including North American, European, and Andean germplasms and relic potatoes.     

TerraRossa: A Mid-Season Specialty Potato with Red Flesh and Skin and Resistance to Common Scab and Golden Cyst Nematode

TerraRossa (POR01PG20–12) is a mid-season specialty potato, released by Oregon State University, and is a product of the Northwest Potato Variety (Tri-State) Development Program. This cultivar is unique among commercially available potato cultivars in that plants produce small- to medium-sized smooth, oblong- to long-shaped tubers with red skin and red flesh. Total tuber yields of TerraRossa are similar to Dark Red Norland and less than Red La Soda. Average tuber size (136 g) is less than both of the comparison cultivars, reflecting inherent differences in tuber size distribution. TerraRossa tubers have total antioxidant levels higher than traditional white fresh varieties and comparable to the All Blue purple potato, known for its high antioxidant levels. Sensory evaluations of TerraRossa tubers indicated that it has good culinary attributes following boiling, baking, and microwaving. Potato chips made from TerraRossa tubers retained their unique red color, which represents a novelty in the chipping industry. TerraRossa could be a good candidate for the organic sector due to its tolerance to common scab (Streptomyces scabies) and tuber late blight (Phytophthora infestans) and its resistance to golden cyst nematode (Globodera rostochiensis). Due to its high yields, high chipping quality, good culinary properties, high antioxidant content and disease resistance, TerraRossa is a good candidate for opening new specialty type markets, adding diversity to the marketplace.     

Diploid potato germplasm derived from wild and land race genetic resources

Diploid cultivated species, haploids derived from tetraploid cultivars, and their wildSolanum relatives were used to generate various diploid potato genetic stocks. These stocks have significant value in potato breeding because: 1) genetic diversity in the potato population can be kept variable with the diploid germplasm which confers genetic variation from wild and cultivated species; 2) crossability of this diploid germplasm is facilitated by the function of 2n gametes; and 3) high levels of pest resistances originating from the process of introgression of the wild and cultivated genetic resources can be used to improve the tetraploid cultivated potato genepool.     

Yield development in potatoes as influenced by cultivar and the timing and level of nitrogen fertilization

Path-coefficient analysis based on an ontogenetic model was used to study the relationships between tuber yield and yield components as influenced by cultivar and nitrogen fertilization. Four experiments were carried out from 1987 to 1989 in Granada, southern Spain. Two of these experiments used six potato cultivars with a single N rate, while the other two experiments used one cultivar and nine levels of N, split between planting and top-dressing. Variation in tuber yield between cultivars resulted mainly from differences in stem number per m² followed by tubers per stem and, to a lesser extent, average tuber weight. In N experiments, however, average tuber weight was the only yield component that showed a significant direct effect on yield, while the number of stems per m² and tubers per stem had negligible direct effects. In addition, the ontogenetic model used indicated compensatory mechanisms during the formation of the three yield components in the potato, which resulted stronger in the N experiments.     

Yield and relationships among tuber size,sucrose and chip color in six potato cultivars on various harvest dates

Cultivars were harvested biweekly for yield, weekly for sucrose determinations, and stored for chipping. At the last harvest Crystal was highest in total and marketable yield. Specific gravity was higher in Lemhi, Russet Burbank, and Norchip than in Kennebec, Crystal and Dakchip. Storage tests showed Norchip had superior chipping color to other cultivars. Dakchip had better color after short rather than after long-term storage, while the opposite was true for Kennebec and Russet Burbank. Lemhi and Crystal were marginal in color throughout storage. Sucrose (mg sucrose/g fresh tuber) expressed as a sucrose rating (SR) ranged from 1.2 to 11.9 among the various cultivars and harvest dates. Correlation between SR’s and tuber size within cultivars ranged from ?.91 to ?.97. Variability in sucrose content of immature tubers explained 70% of the variability in chip color among cultivars after storage from four to six months. Sucrose levels may be used to predict relative chipping quality of various cultivars after moderate to long-term storage if measured during early tuber development when differences in sucrose concentration are greatest among cultivars.     

Potato genetic resources: Sources of resistance and systematics

The major potato of commerce,Solanum tuberosum L., is the fourth most important food crop in the world after rice, wheat and corn. Fortunately, the potato has many primitive cultivars and wild species relatives useful to reduce our reliance on chemical controls. These include resistances against diseases, pests, and traits for useful agronomic characters such as yield, specific gravity, chipping qualities, and suppression of enzymatic browning. This paper summarizes some of these qualities, and provides an overview of germplasm availability and taxonomy of the wild species. The major potato of commerce,Solanum tuberosum L., is the fourth most important food crop in the world after rice, wheat and maize. It is grown in more countries than any other crop but maize, and forms the staple crop of many societies. Over 280 million metric tons were grown worldwide in 1989, with Eastern Europe growing 46%, Asia 22%, Western Europe 17%, North America 7%, Latin America 5%, and Africa 3% (2). It is the leading vegetable crop in acreage and farm value in the United States, with 1.2 million acres planted in 1991, with a value of sales almost two and one-half billion dollars (53).Solanum tuberosum is one species of a group of seven cultivated and 216 additional tuber-bearing, and nine non-tuber-bearing wild relatives, all classified by Hawkes (41) in the genusSolanum, sectionPetota Dumort The purposes of this paper are threefold: 1) to provide examples of the proven and potential utility of wild and cultivated landrace members of sect.Petota for reducing our reliance on chemical controls for many pests and diseases that affect commercial cultivars, 2) to provide an overview of the status of germplasm availability of these species, and 3) to highlight the benefits for continuing germplasm collections and systematic studies of the group.     

An approach to field screening potato genotypes for potato leaf roll virus resistance

Eight potato cultivars and two advanced breeder selections were assessed for field resistance to the potato leaf roll virus (PLRV) following field exposures in which PLRV-infected Russet Burbank plants were used as inoculum sources within treatments. This screening protocol provided consistent PLRV resistance ratings despite year-to-year variation in PLRV pressure. Secondary disease incidence based on enzyme-linked immunosorbent assay (ELISA) of foliage from tuber progeny ranged from 0–87% in 1990 and 0–67% in 1991, and was consistent with reported PLRV resistance ratings for eight of ten genotypes. Agreement between visual assessment and ELISA on plants from harvested tubers was 94% in 1990 and 83% in 1991, for all genotypes. However, agreement data were inconsistent from year-to-year, with the exception of three genotypes. In both years, current season infection, based on ELISA of foliage, was detected in less than two percent of the plants and, was inadequate as a measure of secondary PLRV incidence. Green peach aphid (GPA) populations did not differ among genotypes at sampling times during the season, but the PLRV concentration in GPA colonizing Russet Burbank plots was significantly higher than in GPA colonizing any other genotype.     

AC Ptarmigan: An early maturing potato cultivar with good chipping and fresh market quality

AC Ptarmigan is an early maturing, buff skin, cream flesh potato cultivar which has good, stable chip quality and can be processed directly from the field. The cultivar has uniform attractive tubers with shallow eyes. It is moderately resistant to common scab, early blight, potato virus Y and potato leafroll virus. It is susceptible to late blight and shows clear field symptoms when infected with bacterial ring rot.     

Goldrush: A new high quality russet-skinned potato cultivar

On March 1, 1992, the North Dakota Agricultural Experiment Station announced the release of a new russet potato cultivar named Goldrush. Goldrush is an oblong, smooth, russet-skinned potato cultivar that has very white flesh, good culinary quality, resistance to hollow heart and is adapted for both the fresh and processing market.     

Snowchip: A high yielding potato variety for Alaskan growers and processors

Breeding ad selecting potatoes in Alaska to develop a variety that could be depended upon to process into light-colored chips has resulted in the naming and release of Snowchip. It is a selection from the cross Stately × Ontario. The oval, uniform, light buff, shallow-eyed tubers are suitable for either fresh market or chipping. Dry matter content of Snowchip, over a three-year period, expressed as specific gravity significantly exceeded Kennebec, Alaska 114 and Green Mountain. The rest period of this cultivar is short as is its paternal parent Ontario. However, Snowchip keeps well in storage at 38°F or cooler. Light-colored chips have been made conventionally from the 1971, 1972 and 1973 potato crops.     

Comparison of the effectiveness of different methods of screening for bacterial soft rot resistance of potato tubers

Tubers from eight potato cultivars (cvs) grown at two different locations in Wisconsin were tested for bacterial soft rot resistance using different inoculation techniques. The procedures included 1) point inoculations of tubers with different inoculum levels followed by incubation in ambient or low oxygen condtions, 2) inoculation of mechanically bruised tubers followed by incubation in a mist chamber, and 3) a standard slice inoculation method. The point titration test followed by incubation in dew chamber and the mist chamber-bruise test showed similar patterns of resistance for cultivars that were used in these experiments. These two methods are considered to be effective for screening potato tubers for bacterial soft rot resistance. Point titration methods are very useful if only limited numbers of tubers are available. The mist chamber-bruise test is simpler than the other procedures; however, to obtain reproducible results large numbers of tubers are required. Because of the great variability of the results obtained in inoculation of slices, the reliability of this approach can be questioned as a standardized method for evaluation of resistance. Tubers of somatic hybrids ofS. brevidens andS. tuberosum and their sexual progeny were significantly more resistant to bacterial soft rot than tubers of moderately resistant cultivars when evaluated by each of the assay procedures.     

Development and production of monoclonal antibodies for the measurement of solanidine potato glycoalkaloids

Although it is generally acknowledged solanidine glycoalkaloids found in domestic potato cultivars are of sufficient toxicity to require testing prior to the release of new varieties, the widespread use of one of the most promising analysis techniques, immunoassays, is hampered by the variability of polyclonal antibody that has been developed for these analyses. We report the development of a uniform monoclonal antibody (mouse IgG1) that binds to solanidine and demissidine alkaloids for use in immunoassays. The monoclonal producing hybridoma developed is sufficiently resilient to produce the antibody in protein free media, from which very pure antibody could be isolated by simple ammonium sulfate precipitation. The purified antibody can be freeze-dried for storage and performs well in immunoassays with very low background absorbances. The monoclonal antibody was used in the optimized immunoassay at a concentration of 200 ng/mL with only 10 ng/mL concentration required for detectable signals (titer). From half absorbance levels (I₅₀ values) the antibody detected α-solanine the best (0.021 μM) while α-chaconine, demissidine and solanidine were detected at levels of 0.043, 0.092 and 0.103 μM, respectively.     

Use of seedling tubers from TPS in southern Italy

The TPS seedling tuber technique can be successfully adopted in developing as well as in developed countries as a standard agronomic system for potato production. Experimental work has been started in order to select the best parental lines and to evaluate the appropriate breeding schemes for the use of this technique in southern Italy. During 1989 48 true potato seed (TPS) families with different genetic backgrounds were tested for seedling tuber production and they produced a good yield. The seedling tuber families were tested for tuber production during 1990 by subdividing them in two size classes: 25mm-35mm and 35mm-45mm. The highest yield was attained by 4X x 2X families and the analysis of variance indicated significant differences with regard to tuber size and TPS families for both total and marketable tuber yield. This technique has significant potential for providing tubers for both the fall and winter crop in Italy.     

Eradication of potato wart disease from Maryland

Potato wart disease, caused bySynchytrium endobioticum (Schilb.) Perc., is a disease of quarantine significance due to the production of persistent resting spores and lack of effective chemical control measures. The disease was present in limited areas of Pennsylvania, Maryland and West Virginia in 1918–1920 and was thought to have been eradicated by 1974. A recent survey in Maryland to verify eradication in that state had revealed the presence of resting spores of the fungus in one home garden in Allegany County. A subsequent delimiting soil sample survey was conducted in and around the old quarantine area in Allegany County. None of the soil samples from 176 home gardens surveyed were positive forS. endobioticum resting spores. Bioassays with susceptible potato cultivars were conducted for five consecutive years at the site from which spores had been recovered. During three of the five years, environmental conditions did not preclude development of disease, yet no symptoms were obtained. According to the USDA APHIS guidelines for eradication of potato wart disease, the spores at the Allegany County, Maryland site are declared nonviable and Maryland is considered to be free of the potato wart pathogen.     

Evaluation of on-farm irrigation scheduling methods for potatoes

The neutron probe, infrared thermometry and crop water stress index (CWSI), and a computer-assisted irrigation scheduling method were evaluated in terms of their effect on tuber yield, tuber quality, and water use. The experiment was conducted during 1990 and 1991 near Othello, central Washington, using Russet Burbank potatoes grown in a silt loam soil. Irrigation treatments did not commence until after tuber initiation. In general, no differences in total number of tubers and total tuber yield resulted from the different scheduling methods. However, the canopy temperature method showed reduction in the yield of number one tubers in 1990. The least total irrigation water was applied during the growing season with the neutron probe method. Using CWSI values above 0.5 to 1.0 (scale 0 to 10) for two consecutive days as a threshold to schedule irrigations appeared to be adequate for potatoes grown in silt loam soils. However, shortcomings of infrared thermometry suggested that this method may not be practical for scheduling irrigation of potatoes.