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The Americas Journal of Plant Science and Biotechnology

Volume 5 Special Issue 2 2011
Plant science and biotechnology in North America: Focus on Canada III

AmJPSB
ISBN 978-4-903313-85-6

How to reference: Lyzenga WJ, Stone SL (2011) Protein Ubiquitination: An Emerging Theme in Plant Abiotic Stress Tolerance. In: Al-Mughrabi K (Ed) Plant science and biotechnology in North America: Focus on Canada III. The Americas Journal of Plant Science and Biotechnology 5 (Special Issue 2), 1-11


Guest Editor

Khalil Al-Mughrabi

Potato Development Centre, New Brunswick Department of Agriculture and Aquaculture, Canada

www.gnb.ca/0029/10/0029100001-e.asp


CONTENTS AND ABSTRACTS

Wendy J. Lyzenga, Sophia L. Stone (Canada) Protein Ubiquitination: An Emerging Theme in Plant Abiotic Stress Tolerance (pp 1-11)

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ABSTRACT

Invited Review: The ubiquitin proteasome system (UPS) effectively and efficiently controls the abundance of regulatory proteins, removes abnormal proteins and regulates the activity of signalling proteins. This allows for control of regulatory networks and adaptation to external stimuli. Plants utilize the UPS to alter their proteome, to modulate cellular activity and thus cope with unfavourable growth conditions. Recent studies demonstrated that the UPS plays a critical role in abiotic stress tolerance. Using the model research plant Arabidopsis thaliana, E3 ubiquitin ligases, the substrate-recruiting component of the ubiquitination pathway, have been identified as regulators of salinity, cold, heat and drought stress tolerance. E3 ubiquitin ligases also play a central role in regulating the signalling pathway initiated by the stress phytohormone abscisic acid. These studies establish a direct link between ubiquitination and plant response to environmental stresses. This work has been extended to other model plants and provides a strategy for enhancing plant stress tolerance utilizing the regulatory enzymes of the UPS. This review focuses on the recent progress in understanding the role of the UPS in abiotic stress tolerance and discusses strategies for improving stress tolerance by targeting E3 ubiquitin ligases.

 

Teresa de Kievit, Bee Hameeda, Carrie Selin, W. G. Dilantha Fernando (Canada) Using Molecular Techniques to Understand and Enhance Biological Control by Pseudomonas spp. (pp 12-19)

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ABSTRACT

Invited Review: The health and environmental impact of agrochemicals make alternative methods of disease control more attractive for sustainable crop production. Biocontrol strains of bacteria that are able to inhibit plant pathogenic fungi and suppress plant diseases represent one of the most promising alternatives. Various mechanisms of biological control have been recognized including effective root colonization, production of AF metabolites, interference with fungal pathogenic factors, and elicitation of induced systemic resistance in the plant. These mechanisms were initially demonstrated through microbiological and/or biochemical techniques. The advent of molecular techniques to study the genetic basis of biological control has shed light on genes responsible for production of antibiotics and degradative enzymes. Through inactivation, overexpression, and analysis of gene expression patterns, their role in biocontrol has been more clearly defined. In this review we describe the work done in Canada, using molecular techniques, to understand biological control in Pseudomonas chlororaphis PA23. The end goal of this research is to develop more reliable products that demonstrate enhanced performance in the field.

 

Manjula S. Bandara, Ee L. Lee, James E. Thomas (Canada) Gotu Kola (Centella asiatica L.): An Under-utilized Herb (pp 20-31)

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ABSTRACT

Invited Review: The short growing season and harsh climate found in many parts of Canada necessitates development of both field and greenhouse-based plant production. Gotu kola (Centella asiatica L. Urban) is a member of the Apiaceae family, which is characterized by its constantly growing roots, and long copper-coloured stolons (runners) with long internodes and roots at the base of each node. Also known as Indian pennywort, it is a perennial creeping plant native to India, China, Japan, North Africa and Sri Lanka. Gotu kola has been used as a therapeutic herb in India, China and Indonesia for thousands of years. Its ability to heal wounds, to improve mental complications and to treat skin lesions are the main reasons for its wide spread use in those countries. In the western world, the crop is becoming popular due its ability to boost mental acuity and improve circulation. Growth of gotu kola on the Canadian Prairies has met with limited success and potential for field production of the crop is slim due to unfavourable growing conditions. It appears that annual in vitro production of the plant through tissue culture and clonal propagation in the greenhouse is necessary prior to transfer of the plant to the field. Alternatively, continuous propagation of gotu kola as an herb grown under greenhouse conditions appears to show considerable promise. The plant can successfully be grown in combined culture with fish in a closed recirculation aquaponic system that appears competitive with most highly productive commercial greenhouse ventures.

 

James E. Thomas, Manjula Bandara, Darcy Driedger, Ee L. Lee (Canada) Fenugreek in Western Canada (pp 32-44)

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ABSTRACT

Invited Review: Fenugreek (Trigonella foenum-graecum L.) is a self-pollinating, annual leguminous crop which is well suited to growth in cool and temperate growing regions with low to moderate rainfall, making it suitable for growth within the semi-arid regions of western Canada. Best known as a spice from India, it also has a long history of use as forage feed for livestock and as a medicinal plant that can be used for treatment of a variety of ailments ranging from diabetes, heart disease, and infections, to treatment of cancer. In recent years, laboratory studies and clinical trials have focused on fenugreek as a potential nutraceutical. These studies have shown that fenugreek plants possess immunomodulatory, hypocholesterolaemic, hypoglycaemic, gastro- and hepatoprotective and antioxidative properties. Pharmacological properties of fenugreek have been explored to identify a role for the plant in diabetes management and in cardiovascular health, indicating the presence of bioactive compounds in fenugreek, which may be responsible for its health benefits. Commercial production of fenugreek in western Canada dates back to 1990 when it was introduced for growth as a spice in Saskatchewan. Fenugreek cultivars developed for use in Canada include ‘AC Amber’, ‘CDC Quatro’, ‘CDC Canagreen’ and ‘CDC Canafen’ which were developed mainly for use as a spice or for use in functional food / nutraceutical extracts of the seed, and ‘AC Tristar’ which has been developed primarily for use as livestock forage. In this manuscript we look at some of the major biochemical constituents of fenugreek and the physiological effects of these compounds on animal systems. We also look at processing facilities in western Canada that are supporting development of new value-added products for the emerging Canadian functional food industry. New research directions being exploited to develop novel fenugreek varieties with potential for use both domestically and to compete in the international market place are examined.

 

Mohammad Khakbazan, Cliff Hamilton, Ramona Mohr, Cynthia Grant (Canada) Water and Nutrient Crop Sufficiency Models for Potato, Wheat, Canola, Oats, Alfalfa, and Corn (pp 45-60)

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ABSTRACT

Invited Review: Crop water and nutrient efficiency is very important for optimal economic and environmental productivity. Functional models relating crop yields to water and nutrient requirements are integral to many modeling studies forecasting climate change impacts on crop production and environmental footprints. The objective of this paper was to collect data, and identify or develop statistical models relating water and nutrient requirements to yield for some major crops grown in western Canada through a review of studies conducted in the Great Plains. Statistical models developed to predict water, nitrogen, and phosphorus rates for potato, wheat, canola, oats, alfalfa, and corns were reviewed and compared in terms of optimal yield achievements. Water and nutrient requirements depend on crop species, and varies among regions and models. Based on statistical models reviewed or developed in this study, the optimal growing season water requirement for wheat, oats, canola, alfalfa, and corn was 350, 450, 350, 500-600, and 425 mm, respectively. Average water use of potato for Manitoba was in the range of 375 to 400 mm but could go as high as 696 mm. Optimal nitrogen sufficiency for potato was reported to be 200 kg N ha-1. Nitrogen requirements for wheat, oats, canola, alfalfa, and corn were 105, 100-110, 150-220, 0 or 35-55, and 160 kg N ha-1, respectively. Optimal phosphorus sufficiency for potato was reported to be about 50 kg P ha-1 for Manitoba. Phosphorus sufficiency for wheat, oats, canola, alfalfa, and corn were about 15-50, 25-29, 26-36, 36-60, and 33-64 kg P ha-1.

 

Pervaiz A. Abbasi (Canada) Exploiting and Understanding Disease Suppressing Effects of Fish Emulsion for Soil-borne and Foliar Diseases (pp 61-68)

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ABSTRACT

Invited Review: Organic soil amendments, such as fish emulsion (FE), provide nutrients to crops, alter the biological, chemical, and physical properties of soil, and can suppress plant diseases. FE is a liquid fertilizer used primarily for crop production, but we recently found that FE can also act as a disease management product. As a pre-plant soil amendment, FE provided suppression of seedling damping-off of radish and cucumber under growth room conditions. The damping-off protection increased with the length of incubation of FE in the substrate suggesting that disease control was biologically-based. Microbial activity was also enhanced in the FE-amended soils or substrate. Under micro-plot and field conditions, FE as a pre-plant soil amendment to various soils from commercial potato fields with low to high scab levels also reduced potato scab severity in some soils and increased tuber yield in most soils. In the greenhouse trials, FE added to a sandy-loam soil protected eggplants from verticillium wilt and increased plant biomass. Foliar sprays of diluted FE solutions reduced bacterial spot severity on tomatoes and peppers and increased fruit yield. In the laboratory tests, FE reduced the viability of Verticillium dahliae microsclerotia within 1 day after incorporation in a sandy-loam soil indicating that FE contains toxic substances. We detected high quantities of organic acids including some known toxicants such as acetic and formic acids in the FE samples. A mixture of these organic acids at the proportions found in FE provided pathogen or disease suppression depending on the soil and substrate. FE is an excellent model system for development of an organic amendment as fertilizer with disease suppressing effects.

 

Jaimie Schnell, Philip Macdonald, Brian Miki (Canada) Understanding Plants Modified by Transgenesis Using High-Throughput Profiling Technologies and the Relevance for their Regulation in Canada (pp 69-75)

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ABSTRACT

Invited Mini-Review: Unintended effects can occur in transgenic plants through interactions between genetic elements at the site of insertion or through interactions between the introduced gene and endogenous plant processes. High through-put profiling technologies have been applied to identify unintended effects in transgenic plants and have provided insight into their nature and extent. These studies have revealed that the process of transgenesis is not universally disruptive to plants and does not necessarily produce unintended effects. In contrast, there is often significant variability in the profiles of plants that have been developed using conventional breeding techniques, suggesting that transgenesis is no more likely to produce unintended effects than these other breeding approaches. The nature of the transgene is likely to be the most important factor that determines the extent of unintended effects that occur in transgenic plants, although there is some evidence that even genes that alter transcriptional networks may not introduce unintended effects. These observations support Canada’s unique regulatory approach, which is based on the presence of a novel trait as opposed to the process of transgenesis. This greater understanding of unintended effects in transgenic plants can also help further shape the regulatory system by guiding the allocation of resources to those transgenic plants that represent the greatest risk.

 

Germán Avila-Sakar, Avra S. Laarakker (Canada) The Shape of the Curve of Tolerance to Herbivory (pp 76-82)

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ABSTRACT

Original Research Paper: Perhaps the most questioned aspect of defoliation experiments that fail to detect negative effects of damage is whether the amount of tissue removed was appropriate. Despite this implicit acknowledgment that low levels of damage may not cause a detectable change in plant fitness, many studies of plant-herbivore interactions assume that plant fitness decreases with damage following a simple linear relation. However, the (apparently accepted) absence of a fitness effect of herbivory at low levels of damage implies that the reduction in fitness either starts at a damage threshold greater than zero (a truncated fitness function), or follows a convex (inverted J-shaped), curvilinear function. The possibility of a convex tolerance function is highly relevant to herbivory studies because it modifies the expectation that damage should invariably cause a decrease in fitness, and opens the possibility that damage could have positive or null effects on plant fitness depending on the exact shape of the function for a particular plant-herbivore system. Here, we expand on a previously published model to show that the tolerance function is more likely to be curvilinear because of the way in which the relative growth rate changes with damage. Finally, we argue that a convex tolerance function would favour the evolutionary stability of a mixed defence system, characterized by simultaneous allocation of resources to resistance and tolerance traits.

 

Julia Reekie, Eric Specht, Kathryn Carter, Margaret Appleby, Hannah Fraser, Ken Wilson, Lindsay Pink (Canada) Optimizing the Delivery of GF-120 NF Naturalyte Fruit Fly Bait to Control Apple Maggot in Organic Orchards (pp 83-87)

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ABSTRACT

Original Research Paper: The apple maggot (Rhagoletis pomonella) is a key pest of apples in eastern Canada and the United States causing fruit damage and significant economic losses. Research was conducted to optimize the delivery of a newly registered product, GF-120 NF Naturalyte Fruit Fly Bait (GF-120; active ingredient: spinosad) to control apple maggots in organic orchards. The effectiveness of applying GF-120 at two application intervals (7- and 14-day) and the potential of using perimeter sprays and alternate row spraying to control apple maggots were tested in apple orchards. The goal is to achieve acceptable level of pest control by using the minimum amount of control product. In a separate trial, application methods were refined for the maximum distribution of GF-120 within tree canopies and to prune fully grown, 45-year old ‘McIntosh’ large-sized trees for better penetration of GF-120 into inner tree canopies. Results showed that GF-120 should be applied every 7-10 days following label recommendations to adequately control apple maggots in orchards with severe pest pressure and resident infestations. If the apple maggot is not a resident pest, it is possible to apply spray to alternate tree rows or only to the perimeter of the orchard to control pest invasions. In orchards consisting of very large trees with dense foliage, uniform distribution and good penetration of GF-120 into tree canopies are extremely important to attain effective apple maggot control.

 

Chrystel Y. Olivier, Ginette Séguin-Swartz, Brian Galka, Owen O. Olfert (Canada) Aster Yellows in Leafhoppers and Field Crops in Saskatchewan, Canada, 2001–2008 (pp 88-94)

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ABSTRACT

Original Research Paper: Leafhopper populations were sampled in canola and cereal crops over an eight year period at seven locations in Saskatchewan, Canada. Aster yellows (AY) disease incidence was determined at the same locations in canola in 2001–2008 and in cereals in 2005–2008. Over 20 leafhopper species tested positive for the presence of AY phytoplasma DNA at least once in the course of the study. Overall, the six-spotted aster leafhopper Macrosteles quadrilineatus was the most abundant species and had the highest infection rate. Most insects were infected with AY phytoplasma strain 16SrI-A; strain 16SrI-B was also detected. Macrosteles quadrilineatus was most abundant in barley and wheat fields. The AY phytoplasma vector Amplicephalus inimicus and leafhoppers belonging to the genus Psammotettix were found mostly in cereal crops and were infected with AY phytoplasma strain 16SrI-A or -B; strain 16SrI-C was also identified in A. inimicus. Twelve new potential AY phytoplasma vectors were identified. Strains 16SrI-A and -B were detected in tissue and seed of canola, barley and wheat. Strains 16SrI-A, -B, and -C were detected in oats. Strains 16SrI-A and -B were also detected in other crops, including chickpea, dill, caraway, coriander, and echinacea, and in weedy species, including goldenrod, dandelion, wild mustard, and stinkweed. The study confirmed that visual assessment of AY incidence in crops underestimates the number of plants infected with the AY phytoplasma.

 

Steve Haber, Jeannie Gilbert (Canada), Dallas L. Seifers (USA), André Comeau (Canada) Epigenetics Serves Genetics: Fusarium Head Blight (FHB) Resistance in Elite Wheat Germplasm (pp 95-100)

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ABSTRACT

Original Research Paper: Current gene introgression-based approaches have made only modest progress toward the goal of developing Canadian wheat cultivars with strong resistance to Fusarium head blight (FHB). Re-examining comparisons of gene induction in resistant and susceptible near-isogenic lines of ‘Sumai 3’, a well-established source of FHB resistance, suggested that resistance was conditioned by effective expression of gene alleles already present in both resistant and susceptible lines. Our alternative approach, based on modifying expression of existing gene alleles, rather than introgressing new ones, aims to preserve the valuable traits accumulated over time by breeders while changing the small number of traits needing improvement. Starting from a single seed of the doubled haploid Canadian wheat cultivar, ‘McKenzie’, successive generations of selfed lines inoculated with Wheat streak mosaic virus (WSMV) evolved resistance to WSMV infection that became genetically fixed with repeated rounds of selection. Some of these lines also evolved improved FHB resistance which has proved stable in three years of testing. Improved resistance to leaf spots, while not specifically selected for, was also recorded in one family of lines, suggesting the versatility of such approaches to crop improvement. In a preliminary agronomic trial conducted in the absence of deliberately applied disease pressure, the evolved line with the best apparent combination of new traits confirmed its promise by equalling or surpassing its ‘McKenzie’ progenitor in the parameters that define the cultivar class. To honour the Scottish philosopher who prepared the ground for evolutionary thinking, we provisionally name this line Hume.

 

Wei-Chin Lin, Glenn S. Block, David L. Ehret (Canada) The Effect of H2O2 Application during Production on Greenhouse Pepper Shelf Life (pp 101-104)

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ABSTRACT

Original Research Paper: Greenhouse-grown sweet peppers (Capsicum annuum L.) are commercially harvested at full color and stored at 10°C or above to avoid chilling injury. This study was undertaken to determine whether a H2O2 pre-treatment during production could reduce postharvest loss due to storage decay. Pepper fruit were stored at 2.5, 5, 7.5 or 10°C for 28 days, and then transferred to 21°C for an additional three days. Each fruit was visually inspected every three to four days during storage. When a fruit showed signs of incipient decay, the days elapsed between that day and the date of harvest was recorded as the shelf life. There were two experiments. In Experiment 1, a one-time application of 500 ppm H2O2 was imposed over 2~3 days in each of three production seasons (early, mid- and late). Shelf life was determined for three weekly harvests in each of three seasons. Effects of H2O2 were apparent through interactions with other factors. The H2O2-treated fruit had longer shelf life than control fruit when they were stored at 2.5°C or 5°C, depending on production season and on the number of weeks following H2O2 application. In Experiment 2, a single application of H2O2 for 5 days was followed by three weekly harvests. H2O2 prolonged the shelf life as a main effect. Our results indicated that pre-harvest application of 500 ppm H2O2 potentially prolonged the shelf life of greenhouse peppers either as a main effect or through interaction with other factors (i.e. under different specific experimental conditions). A single application of H2O2 seemed to be adequate for up to three weeks.

 

Christophe M. Herbinger, Kristian Gordos, Heather Allen (Canada) Tetranucleotide and Dinucleotide Microsatellite Markers for Red Spruce (Picea rubens) (pp 105-111)

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ABSTRACT

Original Research Paper: Three library enrichment protocols were used to develop tetra-and dinucleotide microsatellite markers for red spruce (Picea rubens). Two enrichment methods based on a single round of magnetic beads-based subtractive hybridization showed limited success. A third method with two successive rounds of subtractive hybridization had a high enrichment success but was found to increase the rate of redundancy and chimerical sequences among the clone sequences. Several single locus tetra- and dinucleotide markers were discovered and can be useful in mapping studies. All newly developed markers except one were characterized by a high frequency of null alleles. One new and one previously described microsatellite marker were identified as informative, reliable and characterized by a low null allele frequency, and were suitable for paternity/parentage and population genetic analyses in red spruce.

 

Sandra Babin, Karthikeyan Narayanan, Agnes Murphy, Hielke De Jong, Gefu Wang-Pruski (Canada) Identification of the Gene Encoding Cinnamic Acid 4-Hydroxylase and its Function to After-Cooking Darkening in Potatoes (pp 112-121)

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ABSTRACT

Original Research Paper: After-cooking darkening (ACD) is a gray-black discoloration of the potato tuber, formed after cooking by the oxidation of an iron-chlorogenic acid complex. The trait has a negative impact on the processing quality of both fresh and processed products. Currently, the French fry industry uses preventative chemicals to control its severity. Cinnamic acid 4-hydroxylase (C4H) is an essential enzyme for the biosynthesis of chlorogenic acid and therefore has a key function in the ACD mechanism. Previously, the c4h gene or its expression profile had not been characterized in potatoes. In this study, the full-length c4h gene was cloned and sequenced from both genomic DNA and cDNA of ‘Russet Burbank’ tuber tissue by PCR and 5′ and 3′ RACE. The gene expression of c4h was examined by Northern hybridization in selected diploid clones known for both low and high degrees of ACD, and in cultivars used in commercial French fry production. Gene expression analyses indicated that there was no significant difference in the expression of c4h between the commercial cultivars ‘Russet Burbank’ and ‘Russet Norkotah’, which showed a similar degree of ACD severity in the samples produced in the season. In contrast, the level of the c4h transcript was significantly higher in the diploid clones with severe ACD and lower in the diploid clones with resistance to ACD. These results correlated with the levels of ACD in these tuber samples. The results suggest a significant relationship between the levels of c4h gene expression and the degree of ACD in potato tubers. The gene can be used to design a DNA marker for guiding breeding of ACD-resistant cultivars.

 

Krishan Kumar, Kequan Xi, Thomas Kelly Turkington, Jennifer Zantinge, Andy Tekauz, James Henry Helm, Jalpa Prasad Tewari (Canada) Evaluation of in Vitro Ground Leaf and Grain Assays to Screen Barley for Resistance to Fusarium Head Blight (pp 122-128)

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ABSTRACT

Original Research Paper: Ground leaf from the greenhouse grown plants and grain harvested from field were used in in vitro assays to evaluate barley (Hordeum vulgare L.) germplasm for resistance or tolerance to Fusarium head blight (FHB) incited by Fusarium graminearum Schwabe and F. culmorum (W.G. Smith) Sacc. On media incorporating ground leaf tissue of eight barley genotypes, F. graminearum displayed significantly larger colonies on medium made from susceptible ‘AC Lacombe’ and ‘Stetson’ barley compared to resistant ‘Chevron’ and I92130. Macroconidial production was significantly reduced on ‘Chevron’-based ground leaf tissue medium. In another test including ten barley genotypes, fungal colonies were larger on medium that contained ground grain from susceptible ‘AC Lacombe’ and ‘Stander’ barley compared to ground grain from resistant Penco/Chevron, ‘Seebe’ and I92130; ground grain from other barley cultivars or germplasm supported intermediate fungal growth. Similar results using ground grain from susceptible and resistant lines were obtained with 15 additional breeding lines. The results were repeatable as evidenced by a significant correlation (r = 0.87, P < 0.05) between tests. Ground grain medium prepared from resistant barley germplasm resulted in reduced sporulation by F. graminearum compared to that measured using susceptible cultivars. Both the in vitro leaf tissue and ground grain assays resulted in a similar ranking for fungal colony diameter. Fungal growth using the ground leaf or ground grain assay was correlated with FHB field reactions for a small number of barley lines (r = 0.69, P < 0.05; r = 0.56, P < 0.05), but was not correlated with field FHB reactions that involved a larger number of genotypes. The significance of the two in vitro assays is discussed in relation to screening for FHB resistance.

 

Jichong Zhang (Canada/China), Tim Xing (Canada), Gongshe Liu (China), Qiang Liu, Benoit Bizimungu, Yves Leclerc, Xiu-Qing Li (Canada) Starch Granule Sizes of Surface and Inside Tissues of Potato Strips after Deep-Freezing Storage (pp 129-131)

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ABSTRACT

Short Comunication: It is a common practice in plant research that fresh plant samples are stored in -80°C after rapid freezing in liquid nitrogen. However, the effect of this process on plant tissues is unclear. Most plant tissues have starch granules. We conducted microscopic observation of starch granules from both the surface and inside of potato tuber strips of the cultivar ‘Shepody’ one hour as well as 5-years storage at -80°C after the liquid nitrogen deep-freezing. The starch granule shape is similar before and after the two storage durations. After one hour storage, the starch granule length showed no changes. However after the long-term storage, the surface ones were significantly shorter than those from the inside tissues of the strips. The mean length of all the granules was 24 and 28 µm, respectively, for starches on the surface and inside, while the mean length of the 10% largest starch granules was 45 and 57 µm, respectively. The reduction in length of the surface starch granules is likely due to potential water evaporation inside the closed plastic tubes. The results indicate that native fresh potato starch can reduce its granule size under certain conditions. This finding might open approaches to adjust starch-related oil absorption during frying of frozen potato products.

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