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.     

Anatomical evidence for the existence of roots on potato tubers and stolons

Roots on potato tubers and stolons displayed the normal root anatomy which consisted of a central vascular cylinder surrounded by endodermis with Casparian strips, the cortex and epidermis. Tuber roots appear to initiate from the parenchyma cells adjacent to the vascular tissue. Shoot tips were similar to normal apical meristems. These observations support our research demonstrating the growth of functional roots from potato tubers and stolons.     

Coastal Russet: A mid-season Russet-skinned potato cultivar

Coastal Russet (tested as B9596-2) is a clone with mid-season maturity that produces russet skin tubers that are long and slightly flattened. Tuber yields in the eastern portions of the United States have been considerably greater than for BelRus. Tubers are well-shaped, have shallow eyes, and are attractive in appearance. Tuber appearance and size make this cultivar very well suited for the tablestock market. It is not suitable for processing. Coastal Russet is highly resistant to tuber net necrosis caused by late current season infection with leafroll and is tolerant to common scab.     

The genetic basis for tuber greening in 24-chromosome potatoes

Greening of potato (Solarium tuberosum L.) tubers is often a problem in retail markets. An experiment was performed to study the mode of inheritance of tuber greening in 24-chromosome potatoes. Tuber greening was determined to be quantitatively inherited. Genetic and environmental variance components were calculated. Tuber greening inheritance is due to additive and epistatic effects. Epistatic effects accounted for 59% of the genetic variance. No dominance or maternal effects were observed. Narrow sense heritability was 0.27 and broad sense heritability was 0.66 after location, block, and genotype by environment interactions were removed. Broad sense heritability for tuber greening is large enough to permit effective selection against tuber greening in potato breeding programs when epistasis can be fixed.     

Reaction of potato tuber slices toPhytophthora infestans in relation to physiological age

Tuber resistance toPhytophthora infestans was studied in relation to physiological age in tubers of the cultivars Atzimba, Katahdin, Kennebec, and Sebago. Resistance to race1,2,3,4 was evaluated in freshly harvested tubers, and tubers stored at 5 C for up to 215 days. Atzimba tubers were highly resistant when freshly harvested but became increasingly susceptible as they aged physiologically. Tubers of the other three cultivars were susceptible when freshly harvested and also when aged. Further, 57 tuber selections from among 11 crosses initially gave resistant reactions. However, after storage for six months at 5 C, 26.3% of the selections remained resistant, 22.8% were moderately resistant, 31.6% moderately susceptible, and 19.3% fully susceptible.     

Pre and early post-emergence weed control with Paraquat in potatoes

Studies using Paraquat herbicide for early post-emergence control of broadleaved and grass weeds in Katahdin and Russet Burbank potatoes were conducted in Maine during four growing seasons. All rates and times of application of Paraquat gave good commercial control of grass and broadleaf weeds when compared to Premerge and Dowpon treatment as checks. Paraquat applied to Katahdins 2 weeks after ground crack reduced the yield of tubers but did not significantly affect specific gravity. Yield and specific gravity of Russet Burbank was reduced by Paraquat applied one and 2 weeks after ground crack. Paraquat can be used effectively for weed control in Katahdin up to one week after ground crack without crop damage. In Russet Burbank it appeared that application at ground crack was about as late as Paraquat could be applied without affecting yield or specific gravity of tubers.     

Factors affecting infection of potato tubers byAlternaria solani in Colorado

Potato tubers became infected byAlternaria solani at the time of harvest. Infection occurred only on wounded tubers irrespective of their depth in the soil. The presence of free moisture on unwounded tubers did not increase the incidence of infection, and immature unwounded tubers were not susceptible. Tuber infections may be reduced by allowing tubers to fully mature before harvest or possibly, by applying chemicals to the soil surface.     

Effets of soil potash treatment and storage temperature on blackspot bruise development in tubers of fourSolanum tuberosum cultivars

Plots of Russet Burbank, Nampa, Targhee, and A6371-2 received O, 250, and 500 lb of potash (K₂O/A as KC1 or K₂SO₄). Tubers were bruised following harvest. Potash treatment had no significant effect in reducing blackspot development when there was no yield response to K fertilization. On soil that tested low for K, potash treatment significantly reduced blackspot development for all four cultivars. Tuber subsamples were bruised after 6 mo in storage at either 1.7 or 10 C. Differences in blackspot bruise development between low and high K were maintained for those tubers stored at 10 C; differences were not maintained and little discoloration developed in tubers stored at 1.7 C, due perhaps to less enzyme activity and less substrate. The Nampa cultivar was significantly more resistant to blackspot than the other three cultivars.     

Shoot formation in potato tuber discs in tissue culture

Tuber discs of potato (Solanum tuberosum) growing on a modified Murashige and Skoog medium produced callus and embryoid bodies but failed to form shoots. However, if 0.4 ppm of 6-benzylaminopurine was added to the basal medium, shoots became visible seven weeks after inoculation.     

Bison,a new red-skinned potato variety

Bison, a new red potato, was introduced by North Dakota State University. This new red variety has smooth tuber type and bright red skin color. Bison yields somewhat less than Norland and Red Pontiac but the advantage of Bison over these two varieties is its uniformity and bright red color. Bison is about medium in total solids and makes chips comparable in color to Norchip but lighter in color than Kennebec. Bison is resistant to race 0 of the late blight organismPhytophthora infestans, but susceptible to race 1–4.     

Growing potato plants by the water culture technique

A water culture technique was developed for the study of the nutrient requirements of the potato plant. Tuber formation was avoided by pinching off the stolons as they developed and hence vegetative growth could be studied without the complication of abnormal tuber formation in the culture solution. The K deficiency symptoms obtained by this method were essentially the same as those observed for field grown plants.     

Potato leafroll virus purification and antiserum preparation for enzyme-linked immunosorbent assays

Potato leafroll virus (PLRV) was purified from potato foliage and stems with an average yield of 0.14 mg of PLRV/kg of potato. Modifications of an existing purification procedure are reported. Five low dosage (38-118 μg of PLRV) intravenous injections were used to produce a PLRV antiserum for use in enzyme-linked immunosorbent assays (ELISA) from tubers. PLRV was readily detected in ELISA testing of potato tubers and leaves and inPhysalis floridana Rybd. Non-specific reactions were low with all tissues. In parallel tests, a Canadian antiserum produced higher nonspecific reactions with tuber and leaf tissue. The results indicated that the use of low dosage-intravenous injections might be necessary methodology for producing PLRV antiserum for use in ELISA diagnostic tests with tuber tissue where high non-specific reactions have been reported.     

A rapid and simple method for determination of potato chloroplast DNA type

A procedure for restriction enzyme analysis of the potato chloroplast DNA (ctDNA) is described. The advantages of this method are: 1) rapid determination of ctDNA type, 2) no ultracentrifugation, and 3) low cost of analyses. This method makes it easy to distinguish the ctDNA types of wild and cultivated potato accessions.     

Vine pulling as a means of top killing potatoes

Vine pulling as a means of top killing potatoes was evaluated by measuring tuber discolouration, desiccation of stems and leaves, stems missed and rerooted, and tubers exposed during pulling. Tuber discolouration ratings determined for potatoes that had been top killed in mid-August by chemical desiccant, rotobeating or vine pulling, remained low during the four-year study except in 1978 with the chemical desiccant. Machine pulling evaluations indicated effective vine kill to be rated at 89–99% for leaves and 79–98% for stems with several cultivars of potatoes. A number of stems rerooted which reduced the vine kill ratings.     

Use of enzyme-linked immunosorbent assay to detect potato leafroll virus in field grown potato,cv. Russet Burbank

Use of enzyme-linked immunosorbent assay (ELISA) in detecting potato leafroll infections in field grown potato, cv. Russet Burbank, was studied from 1986 to 1988 at Rosemount, Minnesota. The objective was to determine relative reliability of current season foliage ELISA, tuber tissue ELISA, and tuber progeny foliage ELISA. Serological tests were most accurate when foliage of tuber progenies was tested. ELISA underestimated total leafroll infection when current season foliage from the inoculated plant was used, in those plants inoculated during late tuber bulking stage. Current season foliage ELISA tests using newly expanded terminal leaflets were more reliable than were tests using older leaflets. Leafroll infection was detected in the current season foliage and tuber progenies (tuber tissue as well as tuber progeny foliage) of some plants seven days after inoculation. Most current season foliage infections were detected by day 14–28 depending on year. Differences among years were most likely caused by variation in quality of virus source plants and numbers of vectors used in inoculation. ELISA tests on tuber tissue were almost as effective as ELISA tests on tuber progeny foliage in detecting potato leafroll 20 days after inoculation, but ELISA on tuber tissue substantially underestimated infection if plants were sampled earlier. Maximum percent tuber infection occurred 20 days or more after inoculation. Movement of the virus from the inoculated stem to other stems decreased with increased plant age at inoculation. Percent infected tubers declined with increased plant age at inoculation. Action thresholds developed for aphids in managing potato leafroll virus should take into account the temporal change in percent infected tubers.     

Updated listing of potato species names,abbreviations and taxonomic status

Tuber-bearingSolanum species described since 1753 are listed alphabetically. A three-letter abbreviation for numerous species not included in Simmonds (1963) are proposed. Some pertinent taxonomic notes are provided for all species names. The systems of classification proposed by S.M. Bukasov, D.S. Correll, J.G. Hawkes, and C.M. Ochoa have been used to determine the current taxonomic status of each species.     

Evaluation of thiabendazole and pentachloronitrobenzene for control of the Rhizoctonia disease complex on white potato (Solanum tuberosum L.)

Thiabendazole (TBZ) and pentachloronitrobenzene (PCNB) alone and in combination were laboratory, greenhouse, and field tested during a five-year period (1977-1982) for their effectiveness in reducing incidence and severity of damage caused byRhizoctonia solani to white potato (Solarium tuberosum). Growth ofR. solani on amended potato dextrose agar was prevented at 7 ppm TBZ and 80,000 ppm PCNB. Tuber-borne sclerotial germination and hyphal growth were prevented following seed treatment with 6,000 ppm TBZ, and severely inhibited by combination treatments of 12,500 or 50,000 ppm PCNB and 1,500 ppm TBZ. Seed treatments which provided the most effective field control ofR. solani were combinations of PCNB (50,000, 25,000 ppm) and TBZ (1,500 ppm), followed by TBZ alone (6,000 ppm) and PCNB alone at rates of 50,000 ppm or above.     

Influence of temperature and length of storage on resistance of potato to tuber rot induced byErwinia chrysanthemi

Tubers of 11 clones ofSolanum tuberosum subsp.andigena (andigena) and 12 cultivars ofS. tuberosum subsp.tuberosum (tuberosum) were inoculated with water suspensions (5.5 × 10⁴ 5.5 × 10⁵, 5.5 × 10⁶ CFU/ml) ofErwinia chrysanthemi. Tubers were inoculated immediately after harvest and after 6 and 16 wk of storage at 4 and 23°C. Tuber rot incidence in andigena and tuberosum increased as inoculum concentration increased. Based on tuber rot severity, clones of andigena were classified as resistant, intermediate, or susceptible and cultivars of tuberosum were classified as intermediate or susceptible. Rot severity increased in all tubers stored at 4°C and in tubers of tuberosum stored at 23°C; rot did not increase in tubers of andigena stored at 23°C. Electrolyte leakage (EL), total sugars (TS), reducing sugars (RS), non-reducing sugars (NRS) and dry matter (DM) were determined in non-inoculated tubers. There was a significant positive correlation between the rate of EL, concentration of RS and tuber rot in andigena and tuberosum. Tuber rot and DM were negatively correlated in tubers of andigena; but they were not correlated in tuberosum. Clones of andigena with low EL, TS, RS, and high DM were resistant to tuber rot, and the incidence of tuber rot in these clones was much less influenced by temperature and length of storage. The influence of temperature and length of storage on susceptibility toE. chrysanthemi may be explained by increased cell membrane permeability; increased leakage of accumulated sugars in potatoes stored at 4°C could favor bacterial proliferation resulting in more disease.     

Origin and inheritance of solarmarine glycoalkaloids in commercial potato cultivars

Tuber tissues of 123 commercial cultivars were tested for their ability to synthesize solamarine glycoalkaloids. Eleven cultivars including ‘Kennebec’ and ‘White Rose’ synthesized major concentrations of solamarines, ranging between 42 and 85% of total glycoalkaloid, when tuber slices were exposed to light during wound-healing. Tuber tissues of the other 112 cultivars did not synthesize solamarines, or they synthesized only trace concentrations of these unusual glycoalkaloids. Nine of the 11 solamarine-synthesizing cultivars have a common ancestor, USDA 96-56. This parental clone synthesizes major solamarine concentrations and it also carries the R₁ gene for late blight resistance that it inherited fromSolatium demissum. Results of solamarine analyses of foliage from 47 USDA 96-56 selfed progeny suggest that this parental clone is the source of a major gene(s) for solamarines present in 9 of the commercial cultivars. However, there appeared to be an alternative source of a gene(s) for solamarines because ‘White Rose’, with onlyS. tuberosum ancestors, also synthesized major solamarine concentrations. There was no association between the R₁ gene for late blight resistance and the ability to synthesize solamarines in 31 USDA 96-56 selfed progeny that were analyzed for both characters.