Small Tubers Research Articles

EFFECT OF FOLIAR SPRAYS WITH NUTRIENT SOLUTION AND SEED SIZE ON THE STORABILITY OF POTATO TUBERS DESIREE CV.

This study was conducted in the field and cold storage unit, Department of Horticulture, College of Agriculture, University of Baghdad, during Autumn 2004 and spring 2005, two sizes (20-35) mm and (40-55) mm were used, the types of nutrient solution (grow more, grow plus, king life) were sprayed twice, the first after 45 days from planting and the second after 21 days from the first sprays. After the harvest, curing was done and the potatoes tubers were kept in bags with 5 kgs for the experimental unit with 3 replicate, CRD were used. All the treatments were stored at 4 + 2 o C for 3 months. Reconditioning were used for the potatoes taken from the cold store. The experimental results shows that no significant differences due to the seed sizes in the percentage of weight loss in the first season, while the smaller seed size enhanced the weight loss up to 4.88% as compared with the large tuber seeds which reduced it to 3.99 %. Spraying with grow more increased the percentage of weight loss up to 4.42% as compared with spraying with grow plus which reduced this percentage to 3.66% for the first season. In the second season, spraying with king life increased this percentage up to 5.97% as compared with spraying with grow more which reduced this percentage to 3.41% at the end of store period. There is no significant differences due to tuber seed size and type of nutrient solutions used in this study on the percentage of decay. There is no significant differences due to the tuber sizes used in this study in the number of sprouted eyes in the first season. The small size tubers increased this percentage up to 61.1% in the second season as compared with large size tuber which reduced this percentage to 57.1 %. The control treatment significantly increased the percentage of sprouted eyes up to 46.9 % as compared with the treatment with grow plus while reduced this percentage to 37.7 % in the first season, while in the second season treatment with grow more increased the percentage up to 69.2 % as compared with control which cases a reduction of this percentage to 50.7 %.

Second Generation European Corn Borer Injury and Irish Potato Physiology, Yield, and Quality

European corn borer (ECB) [Ostrinia nubilalis (Hübner)] (Lepidoptera: Crambidae) is known to infest Irish potato (Solanum tuberosum L.) but only causes economic damage during the first generation in East Coast potato producing areas. However, in Nebraska, second generation ECB infest potato plants during the bulking period and may reduce yield and/or potato quality. Experiments were conducted in 2001, 2002, and 2003 to examine physiological and yield effects of second generation ECB injury to potato in Nebraska. Pike, Atlantic, and three Frito Lay proprietary varieties (FL1867, FL1879, and FL1833) were used. Experimental plots were infested with four ECB egg masses per plant to simulate ECB infestation by second‐generation larvae; controls received no egg masses. Photosynthetic rates, tuber weights, tuber size grades, solids, and fry quality were measured. Potato plants with ECB infestation had significantly reduced photosynthetic rates on ECB‐infested stems and on uninfested stems on the same plant when larvae were in the fifth instar. When insects were in the fourth instar, photosynthetic rates were reduced only on ECB‐infested stems. In 2001, ECB infestation reduced the average mass of large tubers and increased the amount of small tubers in FL1867 and FL1879. In 2002, significant yield reductions were not observed. Across both years, ECB‐infested plots produced fewer large (65‐ to 100‐mm diam.) tubers than control plots. Other tuber properties and chip qualities were unaffected. This study indicates that second generation ECB infestation of approximately 30% infested plants results in economic loss for some chipping varieties and affects tuber bulking. In contrast to east coast growers, Midwest potato farmers must be concerned with second generation ECB.

Swan foraging shapes spatial distribution of two submerged plants, favouring the preferred prey species

Compared to terrestrial environments, grazing intensity on belowground plant parts may be particularly strong in aquatic environments, which may have great effects on plant-community structure. We observed that the submerged macrophyte, Potamogeton pectinatus, which mainly reproduces with tubers, often grows at intermediate water depth and that P. perfoliatus, which mainly reproduces with rhizomes and turions, grows in either shallow or deep water. One mechanism behind this distributional pattern may be that swans prefer to feed on P. pectinatus tubers at intermediate water depths. We hypothesised that when swans feed on tubers in the sediment, P. perfoliatus rhizomes and turions may be damaged by the uprooting, whereas the small round tubers of P. pectinatus that escaped herbivory may be more tolerant to this bioturbation. In spring 2000, we transplanted P. perfoliatus rhizomes into a P. pectinatus stand and followed growth in plots protected and unprotected, respectively, from bird foraging. Although swan foraging reduced tuber biomass in unprotected plots, leading to lower P. pectinatus density in spring 2001, this species grew well both in protected and unprotected plots later that summer. In contrast, swan grazing had a dramatic negative effect on P. perfoliatus that persisted throughout the summer of 2001, with close to no plants in the unprotected plots and high densities in the protected plots. Our results demonstrate that herbivorous waterbirds may play a crucial role in the distribution and prevalence of specific plant species. Furthermore, since their grazing benefitted their preferred food source, the interaction between swans and P. pectinatus may be classified as ecologically mutualistic.

Grit Ingestion and Size-related Consumption of Tubers by Graylag Geese

In herbivorous birds the processing rate of food is constrained by gizzard capacity. To enhance digestive processes, many species ingest grit to grind the food. Grit ingestion, however, may further limit the capacity of the gizzard. Graylag Geese (Anser anser) wintering in SW Spain fed mainly on Alkali Bulrush (Scirpus maritimus) tubers, showing a preference for small tubers. This preference may be due to a faster disintegration of small tubers than larger ones inside the gizzard. As larger tubers are likely coarser than smaller tubers, more grit would be necessary to process larger tubers. However, the ingestion of more grit to grind large tubers would be at the expense of ingesting additional tubers because of gizzard capacity limitations. Under these circumstances, there may be an inverse relationship between tuber size and amount of grit ingested to optimize food ingestion. Indeed, we found such a relationship. Grit facilitated the disintegration of tubers. This suggests that relying on some amount of grit to facilitate the grinding of food should outweigh the loss of gizzard capacity to the amount of food ingested.

Effect of Perforated Film And Polypropylene Nonwoven Covering On The Marketable Value of Early Potato Yield

Effect of Perforated Film And Polypropylene Nonwoven Covering On The Marketable Value of Early Potato Yield The effect of cover material (perforated polyethylene film, polypropylene nonwoven) and date of its removal (2 and 3 weeks after plant emergence) on the marketable value of the yield of early potato cultivar (Aksamitka, Cykada) was investigated. Potatoes were harvested 60 and 75 days after planting, in the second and third decade of June. Plant vegetation forcing by covering resulted in an increase in the marketable tuber yield (diameter >30 mm) and improved marketable value due to a reduced share of small tubers, with the diameter of 31-40 mm, especially at a very early date of potato harvest. In potato cultivation for very early crop, the cover material had a greater effect on the tuber yield and its marketable value than the length of plant covering period. Perforated film was a better kind of cover than polypropylene nonwoven, especially in the year with cold spring. At the delayed date of potato harvest the marketable tuber yield depended, to a higher degree on the date of cover removal. Higher yield was obtained when the cover was removed 2 weeks after plant emergence.

Tuber development phenotypes in adapted and acclimated, drought-stressed Solanum tuberosum ssp. andigena have distinct expression profiles of genes associated with carbon metabolism

A drought screen identified accessions of Solanum tuberosum ssp. andigena that showed varying degrees of physiological acclimation or adaptation to repeated drought stress. The accessions also showed variable tuber phenotypes from small tubers that failed to develop in an accession that showed photosynthetic adaptation to normal tubers in an accession with a phenotype showing some degree of photosynthetic adaptation and acclimation. Using microarray data, we correlated the expression of genes associated with carbon metabolism with the tuber development phenotypes under drought. Genes associated with sucrose and starch metabolism showed responses consistent with starch deficiency in the adapted accession and normal starch deposition in the intermediate accession. Starch phosphorylase and glycogen bound starch synthase were induced in the adapted accession, which had abnormal tuber development. Genes associated with trehalose were induced in the intermediate accession with normal tuber development. Genes associated with respiration were also induced in the intermediate accession, and a pattern compatible with the existence of a 3PGA recovery pathway was revealed. Expression of thioredoxin genes also correlated with tuber development phenotypes under drought stress. The data suggest differential regulation of starch deposition in accessions of Andigena with different abilities to respond to drought stress.

Dynamics of soilborne Rhizoctonia solani in the presence of Trichoderma harzianum: effects on stem canker, black scurf and progeny tubers of potato

Stem canker and black scurf are diseases of potato caused by the fungus Rhizoctonia solani. Spatiotemporal experimentation and empirical modelling were applied for the first time to investigate the effect of antagonistic Trichoderma harzianum on the dynamics of soilborne R. solani on individual potato plants. Trichoderma harzianum reduced the severity of symptoms, expressed as ‘rhizoctonia stem lesion index’ (RSI), during the first 7 days post‐inoculation when the inoculum of R. solani was placed at certain distances (30–60 mm) from the host. For example, with inoculum at 40 mm from the host, RSI was 6 and 40 with and without T. harzianum, respectively. At later observation times, the antagonistic effect was overcome. Trichoderma harzianum reduced the severity of black scurf on progeny tubers. Furthermore, the mean number of progeny tubers per potato plant was reduced by the biocontrol treatment (means of 6·5 ± 1·1 and 9·9 ± 2·7 tubers per plant with and without T. harzianum, respectively), as was the proportion of small (0·1–20·0 g) tubers (48% and 66% with and without T. harzianum, respectively). Additionally, there were fewer malformed and green‐coloured tubers in pots treated with T. harzianum than in those without T. harzianum.

Detection of subtle structural abnormality in tuberous sclerosis using MEG guided post-image processing

Abstract The present study aimed to investigate whether magnetoencephalography (MEG) information could result in the detection of subtle anatomical abnormalities at re-review of conventional magnetic resonance imaging (MRI) by a new MEG guided post-image processing technology. Eight paediatric patients with tuberous sclerosis complex (TSC) confirmed by clinical and neuroimaging findings were retrospectively studied. MEG data were recorded using a whole-cortex CTF OMEGA system. Irritable zones were localized using synthetic aperture magnetometry (SAM). A new MEG guided post-image processing technology was employed to identify the “small tubers” found only by SAM. MRI detected 42 tubers for the 8 patients. SAM found 51 irritable zones, and 31 out of the 51 zones were around tubers (31/42, 74%). Among 20 of the 51 zones, which did not have corresponding MRI tubers, we detected 14 subtle lesions in total; 9 of 14 were found in low frequency band (1–35 Hz); 5 of 14 were found in high frequency band (35–60 Hz and 60–120 Hz). SAM appeared to offer more detection of irritable zones and beneficial frequency descriptions. The majority of these irritable zones detected only by SAM were indicated to be small tubers by MEG guided post-image processing technology. This technology might be a powerful tool in the detection of subtle structural abnormalities.

Evaluation of somatic hybrids of potato with Solanum stenotomum after a long-term in vitro conservation

Somatic hybrids of potato with a cultivated relative, Solanum stenotomum also called Solanum tuberosum Stenotomum group, were evaluated for their physiological and agronomical characteristics as well as the stability of the introgressed resistance to bacterial wilt, caused by Ralstonia solanacearum, after a long-term in vitro conservation for more than 5 years. Analysis of photosynthesis showed that the PEPC/Rubisco ratio remained lower than 0.5 for all vitroplants of potato and the somatic hybrids, except for the relative species. This indicates that the carbon metabolism is heterotrophic (ratio > 1) for S. stenotomum, and autotrophic for potato and the somatic hybrids (ratio < 1). In both in vitro and greenhouse conditions, potato and the somatic hybrids produced few bigger tubers, while many small tubers were obtained from the relative. The hybrid tubers were morphologically intermediate. The starch content of hybrid tubers was much lower than that of potato, but similar to that of the relative species. Interestingly, the level of bacterial resistance, introgressed from S. stenotomum into potato, was shown to be very stable and remained as high as that of the relative after a long-term period of in vitro conservation.

Yield Response of Indeterminate Potato (Solanum tuberosum L.) to Simulated Insect Defoliation

Yield response to insect defoliation is primarily a function of light interception. A series of leaf removal experiments were conducted on an indeterminate chipping variety of Irish potato, Solanum tuberosum L., to simulate late‐season insect defoliation injuries. Leaf removal was conducted following a computer simulation model for growing insect populations. Across 2 yr, 50 to 75% of the canopy leaf area was removed during a 10‐d period. In 2001, 75% leaf removal resulted in a 14% yield loss (in total potato weight) while in 2002, 50% defoliation resulted in 15% yield loss and 75% leaf removal resulted in 22% yield loss. In addition to yield differences, high defoliation reduced number and weight of large (65–100 mm diam.) tubers and increased the number of small tubers (47–64 mm diam.). Yield loss was significant when defoliated canopies remained below a leaf area index (LAI) of 4.0. Percentage light interception was a better predictor of potato yield than was percentage defoliation. These data are consistent with the light interception hypothesis and show that remaining leaf area is a better predictor of yield potential than percentage defoliation. Thus, treatment decisions based on light interception and LAIs rather than estimates of percentage defoliation should be applicable to indeterminate varieties of potato.

Growth-room and field studies with seed tubers treated with ethylene and 1-methylcyclopropene (1-MCP) during storage

Based on ethylene management in potato storage, we hypothesized that the applied treatments would modify number of sprouts per seed tuber. Thus, in combination with in-row spacing (closer for seed, wider for processing) in the field treatments will give either (1) a high number of small tubers destined for seed use, or (2) a relatively smaller number of large, uniform tubers suitable for processing. A three-year study (2001–2003), conducted with two french fry processing cultivars, Russet Burbank (RB) and Shepody (SH), aimed at the development of a novel modified atmosphere seed tuber storage treatment. Seed tubers were stored at 4 C from October to May of each year in a cold room under five modified atmospheric regimes: (1) air ventilation only (Control); (2) 4 µl L−1 ethylene applied continuously beginning in November and (3) beginning in February; (4) 1 µ1 L−1 MCP (1-methylcyclopropene) applied as a gas for 48 h only in early December followed by continuous 4 µl L−1 ethylene and (5) MCP alone applied as above. Each year, once a month (mid-January until end of April), a number of seed tubers was taken from each storage treatment, planted to pots and grown for 4 wk in a growth-room. In these studies, shoot emergence from the ethylene-treated seeds of both cultivars occurred significantly earlier, giving higher number of stems per tuber and stolons per stem than Control and MCP treatments. Moreover, the time to emergence after planting decreased with the increased length of storage. Field studies that were conducted from the end of May (planting) until October each year, produced similar trends (although not significant atP≤0.05) and resulted in a higher number of tubers per stem. In RB at the closer in row spacing (30 cm) used for seed production, ethylene enhanced yield of smaller tubers in the 30- to 115-g and 115- to 300-g categories. The ethylene storage treatments also increased tuber number per plant, but not the total mass of harvested potatoes. The MCP treatment, in combination with the wider in-row spacing (40 cm) used for the production of processing tubers, significantly increased the percentage of large tubers (>300 g). In SH, contrary to RB, the ethylene treatments did not alter tuber size distribution and the application of MCP reduced tuber size rather than increasing it. Results from this study suggest that both ethylene and MCP can be used in seed potato storage to influence the tuber size distribution of the crop from that seed.

Selection Criteria for Potato Tubers To Minimize Acrylamide Formation during Frying

A number of parameters linked to the selection of potato tubers were evaluated with regard to their potential to influence acrylamide formation in French fries. The formation of acrylamide, which is a potential human carcinogen, can be minimized for a big extent by the selection of an appropriate tuber. This study focused on the following selection criteria: variety as influenced by storage time and soil type, underwater weight, and tuber size. A total of 16 varieties were compared, concerning their potential for acrylamide formation. From that survey, certain varieties, such as Tebina and Quincy, could be appointed as unsuitable for frying. The differences in the potential of acrylamide formation between the varieties could mainly be explained by the reducing sugar content of the potato (R2 = 0.82, n = 96). The investigated type of soil and storage time at 8 degrees C appeared to have a minor influence on the acrylamide formation during frying. On the other hand, the tuber size of the potato did contribute in a significant manner to the acrylamide formation. Smaller tubers were more susceptible to acrylamide formation and should be avoided in the frying process. The last selection parameter, the underwater weight, appeared to be of minor importance in the acrylamide formation. On the basis of these simple selection criteria, it is possible to make a first screening of potatoes to reduce the acrylamide formation during frying.

Novel Mutation in the TSC2 Gene Associated with Prenatally Diagnosed Cardiac Rhabdomyomas and Cerebral Tuberous Sclerosis

Cardiac rhabdomyomas are prenatal echocardiographic markers for tuberous sclerosis complex (TSC). TSC is caused by mutations in the genes TSC1 and TSC2. We report a 28-year-old, gravida 5, para 2, woman with an uncomplicated pregnancy until prenatal ultrasound at 34 weeks' gestation revealed fetal cardiac tumors. Ultrafast magnetic resonance imaging (MRI) at 36 weeks' gestation showed cardiac rhabdomyomas and small subependymal tubers. At 39 weeks' gestation, a 2,262 g female infant was delivered uneventfully. Postnatal echocardiography confirmed cardiac rhabdomyomas and MRI verified small cerebral subependymal tubers. Mutational analysis of TSC1 and TSC2 genes using denaturing high-performance liquid chromatography and direct sequencing of the genes was performed and revealed that the parents had wildtype DNA, while the proband was heterozygous for a novel de novo nonsense mutation, c.4830G >A, in exon 36 of the TSC2 gene, resulting in a change of codon 1610 TGG (tryptophan) to TGA (stop codon). The mutation predicted a W1610X premature termination of the tuberin protein. These findings support an association between a TSC2 de novo nonsense mutation and prenatally detected cardiac rhabdomyomas and cerebral tuberous sclerosis. Familial molecular analysis of TSC1 and TSC2 in cases with prenatally diagnosed cardiac rhabdomyomas and cerebral tuberous sclerosis lesions is helpful in prenatal diagnosis and genetic counseling.

Manipulating Stem Number, Tuber Set, and Yield Relationships for Northern‐ and Southern‐Grown Potato Seed Lots

The ability to predict tuber set and size development for a particular lot of seed potatoes (Solanum tuberosum L) would facilitate the development of techniques for optimizing tuber grade. Toward this goal, stem number, tuber set, yield, and grade relationships were manipulated and modeled for northern‐ (Alberta, Canada) and southern‐grown (Montana and Washington) Ranger Russet and Russet Burbank seed potatoes. Seed‐tubers with a range in apical dominance were produced by varying the temperature (aging) at the beginning of a 200‐d storage period. Seed source affected stem numbers, tuber set, and size, with southern seed producing more but smaller tubers than northern seed; however, seed source had no effect on total and U.S. No. 1 tuber yields. Tuber set and size distributions were highly correlated with stem numbers, the latter increasing substantially when storage degree days were held constant but temperature was increased. Changes in tuber size distribution with increasing stems occurred with relatively little effect on total, U.S. No. 1, and marketable tuber yields. Therefore, in a long growing season area like the Columbia Basin, adding heat units to seed at the beginning of storage effectively alters tuber size distribution. The differential behavior of these seed sources, along with the ability to predict tuber set and size from mainstem numbers, provides an opportunity to adjust agronomic practices to optimize yield for specific markets.

Putrescine N-methyltransferase in Solanum tuberosum L., a calystegine-forming plant

Putrescine N-methyltransferase (PMT, EC 2.1.1.53) catalyses the first specific step in the biosynthesis of tropane and nicotine alkaloids. Potato (Solanum tuberosum L.) contains neither nicotine nor the medicinal tropane alkaloids hyoscyamine or scopolamine, but calystegines. They are nortropane alkaloids with glycosidase inhibitory activity. Based on the assumption of calystegine formation by the tropane alkaloid pathway, PMT genes and enzymes were investigated in potato. Sprouting tubers contained both N-methylputrescine and PMT activity. Two cDNA clones coding for PMTs were obtained together with a cDNA clone for spermidine synthase (SPDS, EC 2.5.1.16). The pmt sequences resemble those from Nicotiana tabacum (85% identity) and those from tropane alkaloid plants, Atropa belladonna (80% identity) and Hyoscyamus niger (79% identity). They are less similar to SPDS of S. tuberosum (66% identity). Expression of pmt1 and spds cDNA in Escherichia coli yielded active enzymes, while pmt2 expression resulted in insoluble protein. Chimera proteins obtained by fusion of fragments of S. tuberosum pmt2 and H. niger pmt were active as PMT, if the initial part of pmt2 was used, indicating that a mutation in the terminal part of the gene caused insolubility of the enzyme. PMT1 was purified after expression in E. coli and proved to be an active N-methyltransferase without SPDS activity. The enzyme was specific for putrescine (K (M) 250 microM) and inhibited by n-butylamine and cadaverine. While spds was transcribed in all plant organs, pmt transcripts were found in small tuber sprouts only. The results confirm that in potato genes and enzymes specific for the tropane alkaloid metabolism are expressed and active.

Advantages of Wild Diploid Solanum Species Over Cultivated Diploid Relatives in Potato Breeding Programs

For breeding programs of the tetraploid potato (Solanum tuberosum), both wild and cultivated diploid relatives are valuable sources of genetic diversity. While both types of germplasm are used in breeding programs, there are several advantages to using wild relatives. Diploid relatives are typically crossed with haploids (2n = 2x = 24) from tetraploid S. tuberosum to improve daylength adaptation. Most haploids are male sterile, so they are typically used as female parents. Cultivated diploids, such as members of the Phureja Group, produce male sterile hybrids when crossed as females to haploids; wild relatives, such as S. tarijense, often produce male fertile hybrids. Tuber yield following crosses of haploids to cultivated or wild relatives is often high. However, cultivated relatives generally produce hybrids with a high set of small tubers; hybrids from wild relatives are variable, but many are similar to cultivars in tuber size and set. While tubers of hybrids from cultivated relatives are typically rough, with deep eyes and raised internodes, those from wild relatives are often smooth. Tuber dormancy in hybrids with cultivated relatives is generally short, while that in hybrids with wild species is longer, allowing for storage over winter. Finally, resistance to several major diseases and stresses has been found in wild species and their hybrids with S. tuberosum haploids. The desirable traits in hybrids are transmitted to tetraploids via unilateral sexual polyploidization (4x × 2x or 2x × 4x crosses in which the diploid parent produces 2n gametes). Wild Solanum species are recommended for use in potato breeding programs as sources of genetic diversity that can be adapted easily following hybridization with S. tuberosum haploids.

THE INFLUENCE OF GIBBERELLIC ACID ON GROWTH AND FLOWERING OF SOME ZANTEDESCHIA CULTIVARS GROWN OUTDOORS

The research was carried on rather small tubers (55-60 g) of four Zantedeschia cultivars: ‘Black Magic’, ‘Pink Persuasion’, ‘Cameo’ and ‘Florex Gold’. The aim of the experiment was the evaluation of gibberellic acid (GA3) treatment, tuber dips in 0, 50 and 100 mg L -1 GA3 solutions before planting. Plants were grown outdoors, in containers during summer months, from June to October. The GA3 application generally delayed Zantedeschia flowering, however, the reaction of cultivars were different. The earliest flowering was observed on the cultivar ‘Florex Gold’, 54 days, then ‘Black Magic’ and ‘Pink Persuasion’, 58 days. The latest flowering was ‘Cameo’, after 63 days. As expected GA3 application increased flower yield in all varieties by 2-3 times. The highest yield was obtained on ‘Florex Gold’ and ‘Pink Persuasion’, 5-6 flowers/tuber. The cultivars ‘Cameo’ and ‘Black Magic’ gave 3-4 flowers/tuber. The GA3 application did not affect the flower weight. Fresh weight of tubers, lifted after flowering, of cultivars with shorter flowers as ‘Florex Gold’ and ‘Pink Persuasion’ decreased, and increased in cultivars with long, big flowers (‘Black Magic’ and ‘Cameo’).

Head-bobbing behavior in foraging whooping cranes favors visual fixation

Many species of birds move their heads forward through a series of successive, fixed positions when walking. This unique ‘head-bobbing’ behavior stabilizes visual fields during body movement, preventing motion blur of the retinal image [1–3]. Gaze stabilization could be required for successful visual search, particularly for moving objects [4], but the time available for stabilization varies with walking speed. No direct evidence has been published showing that birds favor the stabilization phase while foraging either for moving or immobile food.

Responses of potato cultivars to the common scab pathogens, Streptomyces scabies and S. turgidiscabies

SummaryA glasshouse experiment was conducted to study the responses to Streptomyces scabies and S. turgidiscabies in potato cultivars Bellona, Matilda and Sabina (Solanum tuberosum). Potatoes were grown in a peat‐sand mixture inoculated with one of the two strains of either S. scabies or S. turgidiscabies. Logit models were used to analyse the data on disease incidence and severity, whereas the data on emergence and yield were tested by analysis of variance. S. turgidiscabies, a recently described potato pathogen in Finland, possessed a high ability to cause superficial, raised and pitted lesions on all three cultivars tested. Symptoms induced by S. turgidiscabies were similar to those of S. scabies, regardless of the cultivar, which suggests that the two causal organisms of common scab cannot be distinguished based on symptoms. Infection by S. turgidiscabies and S. scabies delayed emergence, had the tendency to decrease the yield, and increased the proportion of small tubers in the yield, regardless of the potato cultivar. Differences in the levels of resistance to common scab were evident between potato cultivars, since cvs. Matilda and Bellona showed higher disease incidence and more severe scab symptoms than cv. Sabina.

Impact properties, phase structure, compatibility, and fracture morphology of polyamide‐1010/thermoplastic poly(ester urethane) elastomer blends

AbstractBlends of polyamide‐1010 (PA1010) and a thermoplastic poly(ester urethane) elastomer (TPU) were prepared by melt extrusion. The impact properties, phase structure, compatibility, and fracture morphology under impact were investigated for PA1010/TPU blends. The results indicated that TPU enhanced the impact strength of PA1010, and the best impact modification effect of the blends was obtained with 20 wt % TPU. The phase structure was investigated with scanning electron microscopy, and the compatibility was investigated with dynamic mechanical analysis and small‐angle X‐ray scattering. The study of the fracture morphology of PA1010/TPU blends indicated that the fracture surface of the blends had special features, consisting of many fibrillar elastomer particles and a conglutination–multilayer structure, as well as many small tubers on this structure. These fracture phenomena could not be found on the fracture surface of pure PA1010. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1177–1185, 2005