Mechanical and rheological properties of calcium carbonate-filled ethylene propylene diene elastomer reinforced by metallic acrylate salt

High performance ethylene propylene diene methylene elastomer (EPDM)/calcium carbonate (CaCO₃)/aluminum triacrylate (ALTA) hybrids have been prepared by a melt compounding process. The mechanical properties of the peroxide cured EPDM/CaCO₃/ALTA vulcanizates were investigated by tensile, hardness, resilience, abrasion and fatigue life tests. The results showed that the ALTA can greatly improve the modulus at 100 %, tensile strength, abrasion resistance and fatigue life of the EPDM/CaCO₃/ALTA vulcanizates, while retaining their high elongation at break. ALTA as a reactive filler had accelerating effect on the vulcanization reaction of and increased the crosslink density of the EPDM/CaCO₃ composites. This phenomenon is due to increasing the ionic bonds arise from both homo-polymerization of ALTA and graft co-polymerization of it onto the EPDM. Scanning electron microscopy (SEM) revealed the presence of ALTA causes to the roughness of the fracture surface of CaCO₃-filled EPDM compounds demonstrating high interaction between the fillers and EPDM improved by introduction of ALTA. Dynamic mechanical analysis revealed that the glass transition temperature (T _g ) and dissipation peak (tan δ) of EPDM composites decreases with increasing ALTA content. Decrease in tan δ value and inward shifting of T _g were related to improved interaction of filler and EPDM.     

Protein in potato flakes: Evaluation by the meadow vole (Microtus pennsylvanicus)

Th protein content of six potato cultivars, Russet Burbank and the numerically designated 58, 709, 711–3, 321–65 and 322–6, ranged from 5.5 to 8.7 g per 100 g. Similar results were obtained by both Kjeldahl and Biuret procedures. Amino acid analyses with a Beckman model 120C showed methionine to be the low level amino acid. Glutamic and aspartic acids were in higher amounts than the essential amino acids. The Chemical Score was similar to data of bio-assays by the meadow vole,Microtus pennsylvanicus. Cultivar 58 produced the greatest weight gain, but was only significantly higher than cultivars 709 and 711–3. Both weight gains and digestibility were increased by the inclusion of methionine in the diet.     

Improved procedures for the isolation and culture of protoplasts fromSolanum etuberosum

An efficient and convenient procedure for the isolation of protoplasts fromSolanum etuberosum is described. Excised leaves of plants grownin vitro were preconditioned for 3 days in the dark at 4 C. A 16 h enzyme digestion followed with purification by flotation in Babcock bottles produced a mean yield of 12.5 × 10⁶ protoplasts/g fresh weight. Protoplast viability as judged by morphology at the time of isolation was 89%. Liquid preculture for 1 day at 1 × 10⁶ protoplasts/ml was used prior to plating at 1 × 10⁵ protoplasts/ml and gave a mean survival of protoplasts of 43% after 8 days in culture.     

Redsen: A new bright red-skinned potato cultivar

Redsen is a smooth, round, bright red-skinned potato cultivar with medium to high yield potential. It has resistance to race 0 of late blight (Phytophthora infestons) and is moderately resistant to some strains of silver scurf (Helminthosporium solanum) and common scab (Streptomyces scabies). The red color resists fading during storage and Redsen retains excellent marketability during storage.     

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.     

Fungi associated with Collembola and mites isolated from scabby potatoes

Collembola and mites from the lesions of tubers infected with the acid scab organism were tested for the presence of fungal potato pathogens.Streptomyces spp. were found on and in the bodies of these arthropods.Verticillium albo-atrum was present on the external surface and in the body of the Collembola. Various other soil-inhabiting fungi which are not known to be potato pathogens and which were found on and in the bodies of these arthropods are noted.     

Comparison of latex agglutination,enzyme-linked immunosorbent assay,and indicator plants for detection of potato viruses S and X in potatoes

Potato virus S (PVS) was consistently detected by the enzyme-linked immunosorbent assay (ELISA) and the latex agglutination test (LAT) at dilutions (PVS sap: healthy sap) of 1:499 and 1:19, respectively. Mechanical inoculation ofNicotiana debneyi gave variable results with detection possible 38% of the time at dilutions of 1:499. Potato virus X (PVX) was consistently detected by ELISA and LAT at dilutions (PVX sap: healthy sap) of 1:199 and 1:49, respectively. Mechanical inoculation ofGomphrena globosa with PVX resulted in consistent detection of the virus at a dilution of 1:499.     

S-methyl-L-cysteine content of various legume meals

Total nitrogen, total sulphur and S-methyl-L-cysteine content of seed meals ofPhaseolus vulgaris, Vigna aureus, Vigna unguiculata, Phaseolus lunatus, Pisum sativum, Cajanus cajan, Vicia faba major,Vicia faba minor,Glycine max, Lupinus albus andSphenostylis stenocarpa, have been determined. The nutritional significance of the presence of S-methyl-L-cysteine is discussed, together with the role that this amino acid may play in interfering with the determination of methionine by cleavage with cyanogen bromide and subsequent gas-chromatographic identification of methyl thiocyanate.     

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.     

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.     

Molecular Analysis of Phytophthora infestans (Mont.) de Bary from Chapingo,Mexico. Phylogeographic Referential

An Andean origin of Phytophthora infestans was originally based on written records, and recently inferred from mitochondrial and nuclear gene genealogies, which emphasize a common South American origin of the European isolates, and absence of the I-b haplotype in Mexico (recently identified in Tlaxcala, Mexico). In order to compare such results, we sequenced the nuclear genes β-tubulin, Ras, and Intron Ras, and rDNA ITS regions in 24 P. infestans genotypes isolated, identified, and selected, during three crop growing cycles in Chapingo, Mexico. The pathogen showed homology and 100 % sequence similarities to the ones reported for the Andes and Europe β-tubulin, Ras, and Intron Ras genes. Results for the ITS region were inconclusive. The molecular oomycete similarities from the three geographical regions (South America, Europe, and Mexico), and the Mexican genotypes characteristics reported in the species supports the hypothesis of the location of P. infestans diversity and a center of dispersal in the central highlands of Mexico.     

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.     

Allergenicity Assessment of Genetically-modified Tobacco Expressing Salt Tolerance cbl Gene

It is mandatory to assess the allergenic potential of genetically modified (GM) crops before their commercialization. Recently, a transgene [Calcineurin B-like (CBL) protein] has been introduced into tobacco plant to make the crop salt resistance. Therefore, it was felt necessary to assess the allergenic potential of the cbl gene product, which was introduced and expressed in Nicotiana tabacum (tobacco) plant and compared the allergenic effects with the wild-type (WT) counterpart. Bioinformatic analysis revealed that there was no significant sequence homology with known allergens. Also, no difference between the protein digestibility profiles of GM and WT tobacco was found. Rapid digestion of CBL protein (Mol Wt 35 kDa) by simulated gastric fluid (SGF) indicated reduced chances of this protein to induce allergenicity. In addition, BALB/c mice sensitized by intraperitoneal administration of WT and GM tobacco protein showed comparable levels of clinical score, specific IgE, IgG1, histamine level, similar effect on different organs as well as IgE binding proteins. These findings indicate that insertion of cbl gene in tobacco did not cause any additional allergic risk to consumer and the GM and native tobacco proteins behave similarly in both in vitro and in vivo situations even after genetic modification.     

The extraction and partial purification of a rhamnosidase from Colorado potato beetle larvae (Leptinotarsa decemlineata (Say))

An enzyme which hydrolyzed a terminal rhamnose moiety from α-chaconine was extracted and partially purified from Colorado potato beetle (CPB) (Leptinotarsa decemlineata) larvae. This ammonium sulfate precipitated enzyme fraction resulted in nearly 97% metabolism of α-chaconine after a 144 hour incubation period at 42 C as determined by high performance liquid Chromatographic (HPLC) analysis. Approximately 81% of the metabolized α-chaconine was detected asβ ₂-chaconine. The isolated enzyme fraction from CPB larvae exhibited no metabolism of α-solanine. Metabolism was also followed over time by thin layer chromatography (tlc).     

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.     

Purification of potato virus A and its detection in potato by enzyme-linked immunosorbent assay (ELISA)

Potato virus A (PVA) was purified fromNicandra physaloides by a simple method that omitted organic solvent clarification and consisted of differential centrifugation followed by equilibrium centrifugation in CsCl. An antiserum was produced that specifically detected PVA in potato leaf sap using either the SDS-agar test or enzyme-linked immunosorbent assay (ELISA). No heterlogous reaction of the antiserum with potato virus Y was detected. Purified PVA was highly infectious; it had an A 258/280 nm absorbance ratio of 1.28. The particles had a normal intact appearance in the electron microscope. Detection of PVA in potato sprouts and foliage by ELISA was compared with the local lesion assay onPhysalis angulata L. plants. ELISA was superior over an indicator plant test when sprout tissue was used. PVA antiserum reacted similarly with mild and crinkle isolates.     

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.     

Effect of storage temperature and extraction methods on dormancy and germination of true potato seed

Seed treatments, methods of extraction and storage temperature were examined for effects on viability and dormancy of true potato seed. Dormancy of 4x?2x (S. tuberosum ×S. phureja) hybrids was eliminated after 7 months at room temperature and after 10 months at 4 C. However, data on the velocity and uniformity of germination (coefficient of velocity) revealed the presence of a residual dormancy that persists for nearly two years in seeds stored at 4 C, but which is largely eliminated after one year in seeds stored at room temperature. Seed viability was not affected by blender extraction, although seed extracted by hand gave a significantly lower initial coefficient of velocity (CGV). Application of gibberellic acid (GA, 1000 ppm) as a 24-hour soak to freshly extracted seed eliminates dormancy as effectively as GA applied during germination, and produces no deleterious effects on seed viability up to two years in storage. There were genotypic differences for seed dormancy within the tetraploid and diploid groups examined. SeveralS. tuberosum cultivars displayed a dormancy effect (lower CGV’s) in fresh seed that was not completely eliminated by GA, but which declines over time in storage.     

Rapid extraction and solubilization of potato starch with Dimethylsulfoxide

Dimethyl sulfoxide (DMSO) solubilization of starch from lyophilized potato tissue is equally quantitative and more convenient than solubilization in dilute alkali, especially when analysis of a large number of samples is necessary. Starch extraction with DMSO decreases the handling time of each sample by eliminating sonication, filtration, and centrifugation steps required by the NaOH solubilization technique.