Anatomy and compositional variations within potatoes. IV. Total solids distribution in different cultivars

Distribution of cortical, perimedullary, and pith tissues and total solids content were determined on both a fresh and a dry weight basis for six potato cultivars grown concurrently in three locations in California. At one location, tubers harvested 80 days from planting were 1.0 to 2.5% lower in total solids than tubers harvested at later dates. The high solids cortical tissues ranged from 39 to 51% of whole tubers on a dry basis, and the amount appeared to be related to tuber shape. White Rose and Red LaSoda showed greater difference in per cent total solids between cortical and perimedullary tissues than did Kennebec, Lenape,³ Norchip, and Russet Burbank. The high total solids of the cortical tissues is particularly significant to processing losses. Any method of peeling that removes one half the linear depth of the cortical tissues can result in a loss of 25% or more of total tuber solids, depending upon cultivar and tuber shape. Tuber development and distribution of total solids and other components were previously described for Red Pontiac, Russet Burbank, and White Rose tubers obtained from the retail market (6,9,10,11). It was particularly noted that the high-solids cortical tissues, although averaging only about 6mm in depth, comprised between 40 and 50% of both fresh and dry tuber weights (6,11). Because this sort of distribution of solids is especially significant to peeling loss, possible differences in solids among cultivars and at different harvest dates were investigated.     

Observations on the structure and osmotic potentials of parenchyma associated with the internal phloem of potato tubers

The structure and osmotic potentials of parenchyma cells associated with internal phloem of growing, dormant, and sprouting potato tubers (Solanum tuberosum L. cv. Irish Cobbler) were studied. Companion cells, specialized parenchyma cells, and storage parenchyma cells were recognizable by differences in structural characteristics. Companion cells were usually densely cytoplasmic with numerous large mitochondria and plastids with little or no starch. The specialized parenchyma cells which surrounded groups of sieve tubes and companion cells had numerous vacuoles of various size, small mitochondria, plastids with very little or no starch, and protein inclusions. Storage parenchyma cells had amyloplasts with very large starch grains, a large central vacuole with osmiophilic inclusions, and few organelles in a peripheral cytoplasm. The osmotic potentials of specialized parenchyma cells and storage parenchyma cells were similar and did not vary regardless of whether the tubers were growing, dormant, or sprouting.     

Anatomy and compositional variation within potatoes II. Phenolics,enzymes and other minor components

Minor components, including principal phenolics and certain enzymes, are distributed within the potato tuber according to patterns that are significant to many practical problems in the growing, handling, and utilization of potatoes. Chlorogenic acid is much more concentrated in outer than in inner tissue zones; is also highly concentrated in the phloem and phloem parenchyma tissues of both cortex and perimedullary zone. Tyrosine is generally distributed but is more concentrated in the stem end than in the bud end of the tuber and probably is also more concentrated in central than in outer tissues. Results of histochemical tests on distribution of these phenolics agree in general with quantitative analytical results. Phenolases and peroxidase also show characteristic patterns of distribution. Peroxidase affects tissue differentiation and specialization and shows strong histochemical relationship with cell-wall specializations. Phenolases show association with distributions of phenolic substrates and usually are associated with cell contents. Distribution patterns are reviewed for other minor constituents, such as, iron, copper, ascorbic acid, thiamine and solanin.     

Influence of Colorado potato beetle sample counts and plant defoliation on potato tuber production

Field experiments were designed to subject Superior potato plants to various levels of defoliation by the Colorado potato beetle (CPB)Leptinotarsa decemlineata (Say), Coleoptera: Chrysomelidae. Defoliation occurred during each of five consecutive plant growth periods and CPB population, plant leaf area, and tuber weight data were recorded for each period. A visual defoliation rating scheme provided an accurate estimate of actual potato plant leaf area of defoliated plants. Data generated from regression analysis demonstrated a significant dependence of leaf area on CPB numbers per plant during some plant growth periods, but numbers of CPB accounted for very little of the total variation in tuber weight. Plant leaf area was the most important independent variable in the tuber weight regression model.     

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.     

Inheritance of tuber traits from phureja in diploid phureja - Tuberosum hybrids

Heterosis and combining ability for tuber number, average tuber weight, and total yield were evaluated in Phureja - haploid Tuberosum diploid hybrids. Heterosis estimates suggest dominance for high tuber number and low average tuber weight in Phureja. Total yield of the hybrid population exceeded the high parent. The higher-yielding segment of hybrids had a significantly higher number of smaller tubers per plant. Breeding value could be improved by attaining high yield with a lower number of larger tubers per plant. General combining ability was the only significant source of variation for tuber number and average tuber weight indicating high heritability. Phenotypic recurrent selection should be an effective approach to manipulating these traits. General and specific combining ability were significant for total yield. Full exploitation of genetic variance for yield will require test-crossing.     

Heritability of Yield Components Under Irrigated and Drought Conditions in Andigenum Potatoes

Drought is one of the major abiotic factors that affect potato production in the tropics and sub-tropics. Molecular plant breeding offers promising opportunities for developing drought tolerant cultivars, but genetic gains to be achieved through breeding depends strongly on the genetic variance and heritability of traits used in the selection process. In the present study, genetic variance and heritability of tuber yield and its components were estimated in the native potato cultivar group Andigenum, expected to include promising drought tolerant progenitors. Twenty-seven full sib families obtained from crossing 18 parents arranged in 3 mating sets were grown under irrigated and terminal drought conditions. Heritability for tuber yield, estimated from female to male variance components was 0.68 and 0.41, respectively, in the irrigated treatment, and only 0.18 and 0.06 under drought conditions. Tuber number was highly significantly correlated to tuber yield but the heritability of this trait (estimated both from female to male variance) was lower than yield heritability and its non-additive genetic variance was higher than its additive genetic variance, particularly when estimated from the female variance component. Heritability of average weight per tuber estimated for male variance component was very high under both irrigated and drought conditions. Its additive genetic variance was much higher than its non-additive genetic variance. However, average weight per tuber correlated to tuber yield within parents but not within families. These results indicate that selection for increased tuber yield under drought conditions in the Andigenum cultivar group may be slow due to its low heritability and high value of non-additive genetic variance. They also suggest that yield components may not be useful as indirect selection criterion for yield, because of their low heritability and/or poor association with yield. The identification of drought tolerance related traits with high heritability and closely associated to tuber yield under drought is consequently required to improve adaptation of potato to drought-prone conditions and efficient utilization of Andigenum potatoes for this purpose.     

A reevaluation of bromoethane in comparison to rindite for the post-harvest detection of potato virus Y in tubers by ELISA

A reevaluation of breaking tuber dormancy with bromoethane to increase the concentration of potato virus Y in the tuber revealed a positive response, by ELISA testing, to the treatment. The degree of response increased with the maturity of the tuber. Response to treatment with rindite was generally stronger, although differences were slight.     

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.     

Daniel-Navan: A white-skinned,medium-late potato cultivar suitable for regions with a hot climate

Daniel-Navan is a new potato cultivar suitable for the spring crop (between February and July) in the Negev region of Israel, and having a high yielding potential with excellent tuber appearance. The cultivar is resistant to heat stress, Verticillium wilt (V. dahliae) and early blight (Alternaria solani). Tubers of Daniel-Navan are oval, white-skinned, with creamy-white flesh, free of deformities, and growth cracks. It has a high dry matter content (22.7%) and boils and bakes well. The marketable yield of Daniel-Navan obtained at maturity consistently surpasses that of Desiree, the control. Daniel-Navan is a main crop cultivar bred and selected by the Horticultural and Plant Breeding Station, Northern Ireland, and the Agricultural Research Organization, Gilat Experiment Station, Israel. Owing to its high yielding performance and tuber quality, this cultivar could be suitable for use in regions with a hot climate.     

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.     

Albinism of potato spindle tuber viroid-infected Rutgers tomato in continuous light

Potato spindle tuber viroid (PSTV) caused albinism in the new growth of Rutgers tomato under continuous light. The albinism response was obtained with 4 isolates causing severe symptoms in tomato and with 1 mild isolate which is normally symptomless. Rutgers tomato inoculated with the 4 severe strains of PSTV developed typical ‘bunchy top’ symptoms in 12 to 16-hr day lengths. Symptoms developed slower and much less distinctly on plants incubated in 6-hr days. New growth in PSTV-infected plants was green in short days (12-hr illumination) and chlorotic to white in continuous light. Infectivities of extracts from white portions of plants were from 3 to 10 times greater than those from green portions of infected plants. Albino symptoms also developed in other tomato varieties when inoculated with PSTV and kept under continuous light. Albinism was most pronounced under continuous light at 30°C, somewhat less intense at 24°, and at 16°, new growth of infected leaves and stems remained green. Albinism did not develop in otherSolanum species which are symptomless hosts of PSTV nor in seedling potato plants grown in continuous light.     

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.     

Variability for photoperiodic reaction among diploid and tetraploid potato clones from three taxonomic groups

The photoperiodic behaviour of 18 potato clones from three taxonomic groups (Andigena, Phureja, and Tuberosum diploid and tetraploid) was studied under controlled environments. Day lengths of 11, 13, 15, and 17 hours were provided with all other environmental conditions common. Six characters were studied: tuber formation, stem height, haulm weight, tuber number, tuber weight, and tuberization efficiency (tuber weight/haulm weight). All clones showed well defined critical daylength values at which tuberization was either absent or irregular. A wide variability for critical day length was observed among clones, the higher values corresponding to Tuberosum tetraploid and the lower values to the Phureja group. Stem height and haulm weight increased as photoperiod increased. Tuber number remained practically the same for all groups but Phureja which showed an inverse relationship. Tuber weight decreased as daylength increased for the groups Andigena, Phureja, and Tuberosum diploid which on the average showed a short day reaction for tuber yield. Tuberosum tetraploid did not show any significant change, behaving as a day neutral type. Tuberization efficiency was, in general, decreased as daylength increased suggesting a short day behaviour for all groups. A regression analysis of tuber yield and tuberization efficiency on photoperiod indicated that, in general, tetraploid genotypes were less sensitive to drastic increases in daylength than diploids.     

Harvesting potatoes with minimum damage

Temperature, tuber condition and harvester operation must be considered if potatoes are to be harvested with minimum damage. In general, total damage increased as temperature decreased; however, the type of damage resulting from impact was influenced by temperature and tuber condition. The data indicate that a tuber turgidity level occurs wherein total damage susceptibility level is minimal for a given tuber temperature and that the proper tuber turgidity level changes as temperature changes. A tuber hydration level which produces little damage when bruised at a flesh temperature of 65–70 F results in severe damage (shatter bruise) when subjected to the same force at 45–50 F. Conversely, a hydration level which results in severe blackspot at 65–70 F may result in slight to moderate total damage when subjected to the same impact at 50–55 F. Data from several commercial harvester studies indicate that damage may increase rather than decrease with a reduction of harvester speed. The ratio of chain speeds to forward speed was found to be more important than forward speed alone. The optimum ratios varied and were dependent on potato yield. Theoretical ratios based on the volume of tubers at different yield levels and harvester chain capacities were calculated and compared with actual ratios of commercial harvest operation. Harvesters operated with chain speed to forward speed ratios near the theoretical ratios resulted in low tuber damage (25%) with forward speed ranges of 1.60 to 3.25 mph. Harvesters operating with ratios differing considerably from theoretical ratios resulted in a high level of damage (66%). The catechol test identified shatter bruise damage which ruptured the skin, but did not detect internal blackspot. Therefore, the catechol test should be used with discretion when attempting to determine the total damage level. Lye peeling and abrasive peeling identified both blackspot and severe shatter bruise damage and should be used when determining harvester operation speeds when both types of damage occur.     

Calcium and magnesium distribution in potato tubers

The calcium present in the potato tuber is partially extractable by water and by dilute HCl. Either of these procedures may show higher calcium content than dry-ashing. A degree of fractionation of calcium can be obtained by extraction by 1N HCl, first at room temperature and then at 70 C. Wet-ashing yielded consistently higher results for calcium than dry ashing. Analysis for calcium and magnesium in potato pith and cortex were made by wet-ashing following total sampling. The cortex of the tuber was found to contain about half of the weight but from 2/3 to 4/5 of the tuber calcium. Cortex as used here indicates the tissue exterior to the vascular ring. Magnesium was distributed evenly on a tissue weight basis. Kennebec tubers grown in three different states differed substantially in calcium content but not in magnesium content. This difference was especially pronounced in the cortex. Dividing the pith into inner and outer regions revealed that calcium levels were nearly the same throughout the pith.     

Accumulation of dry matter and N,P, K,by Russet Burbank,Oromonte and Red McClure potatoes

Potato plants of Russet Burbank, Oromonte and Red McClure varieties were studied in the San Luis Valley of Colorado to determine their dry matter and nutrient accumulation. The following observations were made in the 1967 growing season.

1. Growth patterns for the three varieties were similar, but average growth rate of Oromonte and Red McClure was higher than that of Russet Burbank.
2. Top growth reached its peak in 61, 55, and 50 days after emergence for Russet Burbank, Oromonte and Red McClure, respectively.
3. In the 3 weeks before killing forst, tuber growth equalled 50% of maximum tuber dry weight for Russet Burbank and about 61% for Oromonte and Red McClure.
4. Total N uptake with a yield of 300 cwt per acre was about 127 lb for each variety, assuming a linear relationship between tuber yield and nitrogen uptake. The tubers contained about 71% of the total N uptake.
5. Total P uptake with a yield of 300 cwt per acre was about 16 1b for each variety, assuming a linear relationship between tuber yield and P uptake. The tubers contained about 83% of total P uptake.
6. Total K uptake with a yield of 300 cwt per acre was 132, 187, and 147 lb (not significantly different) for Russet Burbank, Oromonte and Red McClure, respectively, assuming a linear relationship between tuber yield and K uptake. The Russet Burbank tubers contained 63% of the total K uptake and Oromonte and Red McClure about 52%.
7. Tuber dry matter per cent increased during the season until 2 weeks before a killing frost (65 to 69 days after emergence). At harvest, the dry matter approximated 21% for the varieties studied.

     

Parenchyma cell growth in potato tubers I. Different tuber regions

Enlargement rates of starch-storage parenchyma cells during growth of Kennebec and Russet Burbank potato cultivars were determined for cortical, perimedullary, and pith tissuues of bud ends, midsections, and stem ends of tubers. Average volumetric size of parenchyma cells increased 7 to 18x during growth of Russet Burbank tubers, with the greatest increases occurring in cortical and perimedullary cells of bud ends and midsections, and the least in stem ends and pith tissues. In Kennebec tubers parenchyma cells in both stem end and midsection increased only 5 to 8 x, whereas increases in bud ends ranged from 8 to 20 times. Cell enlargement to tuber enlargement ratios appproached unity early in growth of Russet Burbank tubers. As tubers increased beyond the 45 g size, cell enlargement and tuber enlargement rates were essentially equal. Calculations of cells per unit tissue volume agreed with ratio determinations. The timing of such unity appeared to be delayed in Kennebec tubers, and was not quite as pronounced as in Russet Burbank tubers. This may have been due to differences in growth rates of individual tubers in response to cultural conditions. In general, cells of harvestmature Kennebec tubers were about 60% as large as similar cells of Russet Burbank tubers.     

Subcellular localisation of calcium in potato tubers

Summary Deposits, believed to contain calcium, were located in different cells of the potato tuber after using an antimonate procedure. In the starch-storage parenchyma of the medulla and cortex antimonate deposits were abundant within vacuoles, on the tonoplast, and to a lesser extent in cell walls. Phloem tissues contained a high concentration of deposits, mainly within companion cells and phloem parenchyma, consistent sites of deposition being mitochondria, plastids and tonoplasts. Deposits were abundant within vacuoles of cells of the xylem parenchyma. Within vessel elements deposits were limited to the surface of secondary wall thickenings. Antimonate deposits associated with the middle lamella of xylem parenchyma were rarely found. The results are discussed in relation to previous findings for potato tubers and for higher plant cells in general.