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.     

Tuber Resistance and Slow-Rotting Characteristics of Potato Clones Associated with the Solanaceae Coordinated Agricultural Project to the US-24 Clonal Lineage of <Emphasis Type="Italic">Phytophthora infestans</Emphasis>

Late blight, caused by Phytophthora infestans, is a devastating disease on potato worldwide and new lineages of the pathogen continue to develop in the U.S. Breeding for resistance is important for economic and environmental purposes. The Solanaceae Coordinated Agricultural Project (SolCAP) focuses on linking allelic variation in genes to valuable traits in elite cultivated potato germplasm. This research assessed the SolCAP diversity panel (206 clones in Washington and 213 clones in Wisconsin) for tuber resistance to the US-24 clonal lineage of P. infestans after potatoes were harvested from fields in Washington and Wisconsin in 2011. This is the first time this germplasm has been evaluated for tuber resistance to P. infestans using a non-intrusive zoospore inoculation technique. Clones with a percent incidence of 30% or less were considered resistant and only eight clones (Palisade Russet, AWN86514–2, MSL268-D, MSM171-A, MSM182–1, MSN230-1RY, Patagonia and Yukon Gem) were characterized as resistant at both locations. These clones have previously demonstrated high to moderate partial foliar resistance to isolates of P.infestans and therefore represent germplasm with both foliar and tuber resistance. Nine clones (AWN86514–2, F66041, MN 18747, MSM 182–1, MSN230-1RY, Modoc, Ama-Rosa, Patagonia and Purple Majesty), were characterized as slow-rotting at both locations with a mean percent internal rot of 75% or less after 33 days of storage. Two clones, MN 18747 and Modoc, are considered to have the highest risk of being a carrier for P. infestans of all the clones evaluated in the SolCAP collection. Not a single clone demonstrated complete tuber resistance to the US-24 strain at both locations.     

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.     

Protein,starch, and non-protein nitrogen accumulation in high protein hybrids and low protein cultivars

Tuber protein, starch, non-protein nitrogen and percent dry matter content were measured during tuber development of four Phureja-Tuberosum-Andigena hybrids and two Tuberosum cultivars. Percentages of starch and protein in the tuber dry matter were curvilinearly related to tuber size in all six clones. The amounts of starch and protein in a tuber were linear functions of tuber size. Rates of protein accumulation in some of the hybrids were higher than those of either cultivar. Starch accumulation rates were similar among all six clones. The high protein character of at least one of the hybrids was associated with starch containing storage tissue. Differences between high and low protein clones were mainly related to quantitative differences in the subunit composition of the protein. The ratio of non-protein nitrogen to protein N was similar among the six clones. Relationships between percent dry matter and starch content were not consistent among the six clones.     

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.     

Potato haploid performance in 2x × 4x crosses

Nineteen haploids (2n = 2x = 24) extracted from four tetraploids ofSolanum tuberosum (2n = 4x = 48) with high 2n egg frequencies and known mode of 2n egg formation were evaluated via 4x progeny from 2x × 4x crosses (haploid × cultivar) for total tuber yield, tuber appearance and tuber set. Ninety-eight, 4x families (15-20 genotypes each) were planted in the randomized complete block design with two replications at two locations. Analyses of variance were conducted for all haploids over three common testers, and each of the four groups of haploids individually over a variable number of testers. The performance of haploids, based on general combining ability effects, was consistent for all traits, when tested with either three or more testers. Diploid clones can be evaluated in 2x × 4x crosses using three unrelated adapted 4x testers. Nonorthogonal comparisons indicated no significant differences for all traits among four groups of haploids, and between modes of 2n egg formation. Significant variation within each group of haploids indicates that selection at the haploid level should be carried out among haploids from either the same or different cultivars. Superior haploids can be utilized in 2x × 4x and 2x × 2x breeding schemes to generate 4x clones.     

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.     

Elba: A late maturing,blight resistant potato variety

Elba is a high yielding cultivar which combines resistance to the golden nematode, foliar infection byPhytophthora infestans andAlternaria solani, andVerticillium wilt. Elba is a late maturing tablestock cultivar especially well adapted to organic soils. In small plots and on farmers’ fields it has demonstrated its worth in reducing the need for foliar fungicides to prevent blight.     

Some anatomical and physiological potato tuber characteristics and their relationship to hollow heart

The inception site of hollow heart (HH) and possible relationships between HH and physiological or anatomical characteristics of tubers were investigated. Scanning electron micrographs revealed cells at the site of HH inception were physically rather than enzymatically degraded. Transmission electron micrographs of tuber pith cells from non hollow (NH) tubers showed cell wall and cytoplasm width varied among cultivars but were not related to HH resistance. Water potential of NH tuber tissues at the pith, bud, center and stem end of 3 cultivars and one selection varying in resistance to HH was determined. Although the water potential gradually became less negative as tubers advanced in maturity, no differences were found in water potential between pith cells in various parts of tubers or among cultivars. Tuber pith cells increased in size concomitant with tuber growth. In all tubers pith cells were largest in the center and stem end and smallest in the bud end, but differences in mean pith cell size among cultivars were not related to HH susceptibility. However, within a cultivar the bud, center, and stem end pith cells of HH tubers were all smaller than the corresponding pith cells from similarly sized NH tubers.     

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.     

Genetic variation in a population of tetraploid potatoes: Tuber resistance to the tobacco flea beetle

Variation in resistance to tuber damage by the tobacco flea beetle,Epitrix hirtipennis (Melsheimer) was investigated for progeny from a group of parental clones from the USDA potato breeding program. Each of nine clones, used as males, was crossed with three different clones, and the family responses were measured in field tests (Lubbock, Texas, 1967 and 1968) by counting tuber pits made by the flea beetle larvae. Statistically significant differences among families were found. The differences were due mainly to the male parents, since the male variance component, σ _M ² (0.470±0.235), was larger than the variance component of females mated to the same male, σ _F(M) ² (0.080±0.057). Theoretically, each of these components contains one-fourth of the genetic additive variance, and therefore, should be nearly equal if digenic, trigenic, and quadrigenic effects are small (and if no maternal effects are present). Apparently the male and female parents did not, in relation to the frequency of alleles controlling response to the flea beetle, represent the same genetic population. Heritability on an individual basis, calculated with 4 σ _M ² as numerator, equals 0.64±0.36; and at a 10% selection level the genetic advance value predicted for individual selection equals 1.896 SD units. If 100 males were crossed to one female each, and 20 progeny per family tested in 10 replicates, the genetic advance value predicted for selecting the best 10 males on the basis of their family performance equals 0.976 SD units. Thus individual or phenotypic selection appears to be more effective than selection based on half-sib progeny tests.     

A rapid method for determining blackspot susceptibility of potato clones

Two methods of determining susceptibility of potato clones to blackspot were compared: (1) bruising by weight dropping and (2) bruising by abrasive peeling. A highly significant positive correlation was obtained between the intensity of enzymatic discoloration following abrasive peeling and the amount of blackspot that developed by weight dropping (r=0.93). Abrasive peeling was more rapid than the weight-dropping method. Tuber samples were abraded 30 sec and the amount of enzymatic discoloration evaluated after 24 hr. The need for individually bruising and hand peeling of tubers was eliminated with this method. Because of the rapidity of the abrasive peeling method, it can be used effectively in potato breeding programs to screen large numbers of clones for blackspot susceptibility. Results indicate that tuber maturity affects enzymatic discoloration and blackspot susceptibility. Immature tubers, dug while the vines are still green, are more resistant to blackspot than mature tubers. Tuber maturity therefore must be considered when screening clones for susceptibility to blackspot.     

Variability in the concentration of three heat stable proteinase inhibitor proteins in potato tubers

The variability of three well characterized proteinase inhibitors, Inhibitor I, molecular weight 39,000, Inhibitor II, molecular weight 21,000, and Carboxypeptidase Inhibitor, molecular weight 4,100, were determined in apical cortical tissues of individual potato tubers of the Russet Burbank variety. The three inhibitors varied within ± 20% among sixty-five tubers and cumulatively represented about 7% of the total soluble proteins. The inhibitors were highly variable among tubers of 106 clones from randomly chosen varieties. Inhibitor I varied about twelve-fold (60 to 745 μg/ml juice), and Inhibitor II varied about seven-fold (158 to 1,025 μg/ml juice). Carboxypeptidase Inhibitor varied from as low as zero (seven varieties) to over 850 μg/ml tuber juice. With 80 tubers from fourteen varieties of potatoes, a positivecorrelation was found between the concentrations of Inhibitor I and Inhibitor II and total soluble protein. Carboxypeptidase Inhibitor did not correlate well with total soluble protein. The positive correlations of Inhibitors I and II (a correlation coefficient of 0.70) with total soluble protein indicated that the proteinase inhibitors may be excellent markers for genetic studies for selecting high protein potato tuber varieties.     

Influence of slit plastic mulches and nitrogen fertilization rates on potato yield and quality

Clear and black slit plastic mulches had little effect on tuber yields when compared with unmulched controls during two growing seasons. Mulching films significantly increased the incidence of pinkeye, caused byPseudomonas spp. and varius types of soft rot in 1974 but not in 1975. The incidence of tuber greening was higher than normal both years due to inability to hill with mulch films in place. Under these conditions, black plastic reduced the incidence of greening. Significant yield responses were observed for an increase in nitrogen fertilization rate from 100 (45.36 kg) to 140 (63.5 kg) but not from 140 to 180 1b, (81.65 kg) N/A. Plastic mulches did not affect the nitrogen response. Higher post-harvest inorganic soil nitrogen levels were found under both mulches compared with unmulched controls.     

Yield-evapotranspiration relationships and seasonal crop coefficients for frequently irrigated potatoes

‘Russet Burbank’ potatoes (Solarium tuberosum L.) were subjected to various levels of water application during the growing season. Water applied, rainfall, and soil water changes were measured at weekly intervals. Tuber yield and quality increased as water consumption increased from 300 mm to 650 mm. Evapotranspiration (ET) increased rapidly from plant emergence until early tuber bulking and declined gradually as plants matured. Comparing ET with pan evaporation provided coefficients (K) which changed in response to crop growth stages. K increased from 0.3 at emergence to over 0.8 during maximum leaf area and declined with crop maturity. The relationship between K and crop growth stage can be used with confidence in scheduling irrigation of potatoes in north central Oregon.     

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.     

A Study of the relationship of late blight resistance to glycoalkaloid content in fifteen potato clones

Tuber glycoalkaloid (TGA) content, leaf glycoalkaloid (LGA) content, and the level of multigenic resistance to late blight were determined for 15 potato clones. There was no association between the level of blight resistance and the TGA or LGA contents in these clones. However, TGA and LGA contents were highly correlated. The genotypic correlation coefficient between TGA and LGA contents for the 15 clones was 0.82 (SE = 0.115). TGA contents from blight-infected plants were not significantly higher than TGA contents from healthy (fungicide-protected) plants. The results indicate that breeders should be able to select for multigenic late blight resistance withohut increasing TGA contents of clones in their breeding programs.     

Breeding behavior of resistance to green peach aphid in tuber-bearing Solanum germplasm

Fifty-seven tuber-bearingSolanum progenies including species and interspecific hybrid derivatives were evaluated for resistance to green peach aphid (GPA),Myzus persicae (Sulzer), using an excised leaflet test. The progenies segregated for resistance and most contained some highly resistant clones. Resistance appeared to be partially dominant and genotype-environment interaction was low. Heritability estimates of 50–60 percent were obtained from both diploid and tetraploid populations.