Single Potato Research Articles

StCDF1: A 'jack of all trades' clock output with a central role in regulating potato nitrate reduction activity.

Transcription factors of the CYCLING DOF FACTOR (CDF) family activate in potato the SP6A FT tuberization signal in leaves. In modern cultivars, truncated StCDF1.2 alleles override strict SD control by stabilizing the StCDF1 protein, which leads to StCOL1 suppression and impaired activation of the antagonic SP5G paralog. By using DAP-seq and RNA-seq studies, we here show that StCDF1 not only acts as an upstream regulator of the day length pathway but also directly regulates several N assimilation and transport genes. StCDF1 directly represses expression of NITRATE REDUCTASE (NR/NIA), which catalyses the first reduction step in nitrate assimilation, and is encoded by a single potato locus. StCDF1 knock-down lines performed better in N-limiting conditions, and this phenotype correlated with derepressed StNR expression. Also, deletion of the StNR DAP-seq region abolished repression by StCDF1, while it did not affect NLP7-dependent activation of the StNR promoter. We identified multiple nucleotide polymorphisms in the DAP-seq region in potato cultivars with early StCDF1 alleles, suggesting that this genetic variation was selected as compensatory mechanism to the negative impact of StCDF1 stabilization. Thereby, directed modification of the StCDF1-recognition elements emerges as a promising strategy to enhance limiting StNR activity in potato.

Mechanized No-Tillage Planting with Maize Straw Mulching Improves Potato Yield and Water Use Efficiency in Arid Regions of Northwest China

To explore the yield-increasing mechanism of mechanized potato planting with corn straw mulching, a two-year (2021 and 2022) field experiment was conducted to study the effects of mechanized no-tillage with straw mulching on potato yield and water use efficiency. This experiment included mechanized no-tillage potato planting with corn straw mulch covering (JG), plastic film mulching (HM), and open flat planting (CK). The results showed that mechanical no-tillage with straw mulching significantly affected soil water content in the 0–100 cm soil layer, yield, and water use efficiency (p < 0.05). There was no significant difference in yield between JG and HM, but it was significantly higher than that of CK. The yield of JG was 3.09~12.27% higher than that of CK. The yield increase was mainly achieved by increasing the potato weight per plant (0.697~0.862 **) and the average single potato weight (0.048~0.631). The tuber weight per plant was positively correlated with the plant height at the seedling stage (0.03~0.92 **) and positively correlated with the dry weight of stems and leaves at the tuber expansion stage and starch accumulation stage (0.74 **~0.95 **). It was negatively correlated with the number of branches at the tuber formation stage (−0.33~−0.88 **). Compared with CK, JG could significantly improve the water use efficiency of potatoes and reduce water consumption during the whole growth period of crops. In 2021, JG was 6.5% higher than CK, and HM was 6.88% lower than CK. In 2022, JG and HM increased water use efficiency by 26.17% and 14.50% compared with CK. When HM is applied in heavy soil areas, soil compaction can easily occur, which affects seedling emergence and reduces yield. At the same time, JG has strong adaptability to soil types and good yield stability. It can be seen that JG is a green and efficient mechanized potato cultivation technology suitable for dry farming areas.

Morpho-physiological responses of potato cultivars under weed competition

Morpho-physiological responses of potato cultivars under weed competition

Effect of N Fertilizer Dosage and Base/Topdressing Ratio on Potato Growth Characteristics and Yield

Nitrogen fertilizer is an important kinetic energy for potato production. To study the effect of nitrogen(N) fertilizer application and the topdressing ratio on potato growth and yield, different N application levels: N75 (75 kg ha−1), N150 (150 kg ha−1), N225 (225 kg ha−1) and different N fertilizer base/topdressing ratios: T1 (2:8), T2 (5:5), T3 (8:2), and T4 (10:0) were used to find the best N fertilizer operation. The results showed that higher yields can be obtained when 120–180 kg ha−1 N was applied under the base/topdressing ratio of 8:2 in silt loam (sand–silt–clay: 29-50-21). The base N fertilizer dosage largely determined the root morphology, while topdressing fertilizer mainly affected the leaf photosystem, however, rhizosphere topdressing at the early stages of bud emergence did not immediately affect the leaf soluble protein and the sugar content. Topdressing N increased the tuber crude protein and ascorbic acid content to some extent, but had weak effect on the amylose/amylopectin ratio, for the starch content was mainly influenced by total N application. When base N fertilizer was low, it could be compensated by applying fertilizer during flowering, though when the amount of base fertilizer was sufficient, topdressing would cause a decrease in the average single potato weight and an increase in potato sets per plant, thereby reducing the commercial potato rate. Overall, adopting a suitable base/topdressing ratio can promote plant growth and improve tuber quality and yield. However, the relationship between the specific application amount and the ratio under different soil texture conditions needs further study.

Does intercropping patterns of potato and safflower affect the density of Leptinotarsa decemlineata (Say), predators, and the yield of crops?

The impact of three intercrop patterns of potato (P), Solanum tuberosumL., and safflower (S), Carthamus tinctoriusL.: 4P:2S, 4P:4S, and 4P:8S (row ratios) along with single crops were examined on densities of the Colorado potato beetle (CPB),Leptinotarsa decemlineata(Say), biodiversity of predators, and yield profits over the growing season of potatoes in a randomized complete block design in 2019 and 2020 in Iran. The significant reduction in the densities of CPB (adults, eggs, and larvae) was seen in intercrops compared with single potato in either year. Accordingly, the damage index was decreased in intercrops than in single potato. Furthermore, intercrops resulted in an enhancement in the abundance of most predatory species of CPB, the Shannon diversity index (H΄), and the Pielou's evenness index (J'), especially in 4P:4S and 4P:8S than single potato. The values of R2 between the densities of CPB and the main predators were low (0.01 ≤ R2 ≤ 0.19) in June, whereas R2 values were significantly enhanced in July (0.13 ≤ R2 ≤ 0.71) and August (0.46 ≤ R2 ≤ 0.97). All intercrops delivered extra yield benefit compared with the single crops (LER ≥ 1.20 in 2019 and ≥ 1.18 in 2020). Our results disclosed that all intercrops, especially 4P:4S and 4P:8S could exercise in the controlling ofL. decemlineatain potato fields.

Verification of water-use efficiency estimates via carbon isotope discrimination in potato under varying nutrient statuses and CO2 conditions.

Elevated CO2 (eCO2 ) has the potential to increase plant biomass while decreasing water demand due to enhanced water-use efficiency (WUE), which interacts with nutritional status. Carbon isotope discrimination (Δ13 C) has been shown to be a valid proxy for estimating WUE; however, its validity is uncertain for plants in an environment where the interaction between CO2 and nutrition strongly affects WUE. Using a single potato cultivar (Irish Cobbler), we examined its validity through three independent trials with varying levels of P, N, or K (Trial P, N, and K, respectively) in growth chambers at two CO2 concentrations. WUE at the plant level varied with CO2 conditions and nutrient supply rates. Plant biomass was positively regressed against WUE in Trials P and K, and water use in Trial N. WUE was negatively regressed against Δ13 C across various nutrient supply rates within each CO2 environment. However, the relationship between WUE and Δ13 C was altered with CO2 enrichment by elevating the intercept along the y-axis (WUE) without affecting the slope, implying the involvement of isotopic discrimination in respiration or photorespiration. These results suggest that Δ13 C can be used to estimate WUE across various nutrient statuses, not only at the current CO2 but also at eCO2 when the comparisons are made within each CO2 condition.

'Candidatus Liberibacter' Pathosystems at the Forefront of Agricultural and Biological Research Challenges.

'Candidatus Liberibacter' Pathosystems at the Forefront of Agricultural and Biological Research Challenges.

In vitro reproduction of Pratylenchus neglectus on carrot discs and investigation of its interaction with Meloidogyne hispanica on potato

Root-lesion nematodes, Pratylenchus spp., and root-knot nematodes, Meloidogyne spp., can occur concomitantly in potato fields and the interactions between the two groups of plant parasitic nematodes (PPN) may represent a threat to the potato crop. The in vitro reproductive fitness of 3 Portuguese isolates of P. neglectus isolated from potato fields was assessed using monoxenic carrot disc cultures inoculated with 10 females and maintained at 25 °C. The three isolates were able to reproduce at 56 days after inoculation (DAI) and the final population densities were significantly increased at 84 DAI. The P. neglectus isolate with the best reproductive ability was further selected and the concomitant effects of P. neglectus and M. hispanica were investigated in a pot trial using potato (Solanum tuberosum L.) cv. Agria as host. Single potato sprouts were inoculated with 250, 500, 750 and 1000 of either P. neglectus mixed stages/M. hispanica second-stage juveniles, or a combination of both nematodes. At 60 DAI, nematodes were extracted from roots and soil, the final population densities determined, for both nematode species, and the reproductive factor calculated. The experiment was run twice. The results suggest an additive effect of M. hispanica on P. neglectus reproduction, although future tests are still needed to confirm the possibility of an increase of P. neglectus population densities for the next crop, when both nematodes are inoculated concomitantly. The information obtained reinforces the need for a careful monitoring of these two PPN species in potato crops.

Assessment and evaluation of different treatment schedules againstplant and tuber damage caused by soil pests on potato

Bio-efficacy of various treatment schedules, viz T1 (phorate + chlorpyriphos + imidacloprid + cartap hydrochloride), T2 (imidacloprid + acephate + chlorpyriphos + cypermethrin), T3 (phorate + chlorpyriphos + azadirachtin + Bacillus thuringiensis var. Kurstaki), T4 (Bacillus thuringiensis var. Kurstaki + azadirachtin ), T5 (phorate + imidacloprid + chlorpyriphos + cypermethrin), T6 (phorate + azadirachtin + Bacillus thuringiensis var. Kurstaki) and T7 (control) were evaluated against Agrotis ipsilon (Hufner) and mole cricket, Gryllotalpa africana, P.de. Beau. in single potato variety, Kufi Chandramukhi during rabi season of two potato-growing years in 2013-2014 and 2014-2015 from November to February. The percentage of plant (shoot) damage was found low in T1 (5.82 – 5.87%), than by T3 (6.12 – 6.49%), T2 (6.86 – 6.92%), T5 (7.31 – 7.62%), T6 (8.21 – 8.81%), T4 (8.61 – 9.32%) and T7 (10.70 – 11.13%) respectively. Similarly percentage of tuber damage of potato was noted highest in T7 (34.29 – 43.90 %) and it was lowest in T2 (13.15–15.66 %). Maximum marketable yield (t/ha) of potato tubers was obtained in T2 (26.28–26.80 t/ha), which was succeeded by T1 (26.19 – 26.92 t/ha) than other treatments and it was recorded minimum in control T7 (11.17–12.69 t/ha). Maximum cost-benefit ratio (CBR) was recorded in T5 (1:2.03 – 1:2.04) while it was found minimum in T6 (1:1.11 – 1:1.17). Among the different treatment schedules T5 and T2 were most effective in increasing marketable yield of potato tubers and reduction of soil pest incidence over control T7 and also over other treatments.

RNA-Seq analysis of resistant and susceptible potato varieties during the early stages of potato virus Y infection.

BackgroundPotato virus Y (PVY) is one of the most important plant viruses affecting potato production. The interactions between potato and PVY are complex and the outcome of the interactions depends on the potato genotype, the PVY strain, and the environmental conditions. A potato cultivar can induce resistance to a specific PVY strain, yet be susceptible to another. How a single potato cultivar responds to PVY in both compatible and incompatible interactions is not clear.ResultsIn this study, we used RNA-sequencing (RNA-Seq) to investigate and compare the transcriptional changes in leaves of potato upon inoculation with PVY. We used two potato varieties: Premier Russet, which is resistant to the PVY strain O (PVYO) but susceptible to the strain NTN (PVYNTN), and Russet Burbank, which is susceptible to all PVY strains that have been tested. Leaves were inoculated with PVYO or PVYNTN, and samples were collected 4 and 10 h post inoculation (hpi). A larger number of differentially expressed (DE) genes were found in the compatible reactions compared to the incompatible reaction. For all treatments, the majority of DE genes were down-regulated at 4 hpi and up-regulated at 10 hpi. Gene Ontology enrichment analysis showed enrichment of the biological process GO term “Photosynthesis, light harvesting” specifically in PVYO-inoculated Premier Russet leaves, while the GO term “nucleosome assembly” was largely overrepresented in PVYNTN-inoculated Premier Russet leaves and PVYO-inoculated Russet Burbank leaves but not in PVYO-inoculated Premier Russet leaves. Fewer genes were DE over 4-fold in the incompatible reaction compared to the compatible reactions. Amongst these, five genes were DE only in PVYO-inoculated Premier Russet leaves, and all five were down-regulated. These genes are predicted to encode for a putative ABC transporter, a MYC2 transcription factor, a VQ-motif containing protein, a non-specific lipid-transfer protein, and a xyloglucan endotransglucosylase-hydroxylase.ConclusionsOur results show that the incompatible and compatible reactions in Premier Russet shared more similarities, in particular during the initial response, than the compatible reactions in the two different hosts. Our results identify potential key processes and genes that determine the fate of the reaction, compatible or incompatible, between PVY and its host.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1666-2) contains supplementary material, which is available to authorized users.

First Report of Dickeya dianthicola Causing Blackleg on Potato (Solanum tuberosum) in Bulgaria.

Potato (Solanum tuberosum) is an important and widespread crop in Bulgaria. A new disease was observed on a single potato plot (Plovdiv region) without a history of potato cultivation in the spring of 2011. Initially, single lower leaves wilted on recently emerged plants (approx. 15% incidence) with subsequent desiccation of the leaf margins. The wilting progressed over time and eventually the whole stem became desiccated. A blackleg-like necrosis was noticed at the stem base when symptomatic plants were uprooted. Most diseased stems remained green above ground but pith tissue was heavily macerated and some of the stems became hollow as the pith dried out. Mother tubers were partially or entirely macerated. In most cases, the decay was initiated from the stolon end. Bacterial strains were obtained from symptomatic stems and tubers by dilution plating on King's B medium. The strains produced indigoidin pigment and induced a hypersensitive response 24 h after infiltration into tobacco and Sedum hybridum leaves (2). The strains were identified as Dickeya spp. by the production of the PCR amplicon of the pectate lyase ADE gene cluster (3) and of the pectate lyase I gene (4). The partial sequence of the fliC PCR amplicon (1) of strain SB2589 (GenBank Accession No. KF442436) displayed 100% homology with four whole genome shotgun sequences of Dickeya dianthicola in GenBank. Pectinolytic activity was demonstrated by inoculation of surface disinfested potato tubers of cv. Kondor. Conical core tissue was removed at the apical end and 100 μl bacterial suspension (107 CFU in sterile 10 mM phosphate buffer) was deposited in the cavity. The cap was reattached to the tuber and immobilized by Parafilm. Positive control tubers were inoculated with D. dianthicola reference strain GBBC 2039 (LMG 25864) and negative control tubers were inoculated with sterile 10 mM phosphate buffer. All tubers were incubated for 48 h at 28°C under micro-aerobic conditions reducing the air pressure to 90 mb in a vacuum incubator. The D. dianthicola reference strain and Bulgarian strains produced maceration of tuber tissue. Maceration was not observed in the negative control tubers. Potato plants cv. Kondor were grown from minitubers in sandy soil in plastic nursery containers. The plants were inoculated by root drenching (one application of cell suspension at 109 CFU/liter) when the stems were 15 to 20 cm high (tuber initiation stage). Plants were incubated at 25 to 28°C with regular watering. Wilting symptoms developed within 10 days of inoculation, followed by necrosis of the pith. Strains obtained from the inoculated stems were confirmed as D. dianthicola as described above. Based on the disease symptoms, the cultural, molecular, and pathological features of the strains, we conclude that the disease was caused by D. dianthicola and to our knowledge this is the first report of the pathogen on potato in Bulgaria. Furthermore, this incident warrants further surveys of pectinolytic bacteria causing blackleg-like symptoms in potato crops in Bulgaria.

Compost enhances plant resistance against the bacterial wilt pathogen Ralstonia solanacearum via up-regulation of ascorbate-glutathione redox cycle

The interactions between the pathogen Ralstonia solanacearum and potato Solanum tuberosum plants were studied to investigate the reactive oxygen species metabolic system and ascorbate (ASC)-glutathione (GSH) redox cycle in response to compost application. Single potato eyepieces were germinated and grown in pots containing sandy soil with or without compost at a rate of 7.5 g kg−1 soil. Non-compost- and compost-treated plants (CTP) were inoculated with R. solanacearum 25 days after planting and then analyzed after 10 days, unless otherwise stated. The present results revealed that pathogen infection caused a remarkable decrease in plant growth related parameters and productivity and an increase in disease incidence. However, under these conditions compost had substantially improved plant growth and decreased disease incidence and bacterial population. R. solanacearum resulted in significant enhancement in the activities of NADPH oxidase, lipoxygenase, the production rate of superoxide and hydroxyl radicals, levels of hydrogen peroxide, membrane lipid peroxidation, and protein oxidation indicating the induction of oxidative stress in potato roots. However, the pathogen-mediated enhancement in indices of oxidative stress was considerably decreased by compost application, which enhanced the activities of ascorbate peroxidase (APX, EC 1.11.1.11), monodehydroascorbate reductase (MDHAR, EC 1.6.5.4), dehydroascorbate reductase (DHAR, EC 1.8.5.1) and glutathione reductase (GR, EC 1.6.4.2) in infected potato plants, implying a better ROS-scavenging activity. Data also indicated that there were general increases in ASC and GSH content in infected compost treated plants, but non-compost treated ones significantly had lower levels of such redox metabolites. In addition, significantly higher ratios of ASC/DHA (dehydroascorbate) and GSH/GSSG (glutathione disulphide) were generally found in CTP than in non-compost treated-ones. The obtained results suggest that compost provides effective protection against the Ralstonia bacterial pathogen via up-regulation of the capacity of the ASC-GSH cycle and modulation of the cellular redox status, thereby eliminating ROS damage and sustaining membrane stability.

Different Reactions of Potato Varieties to Infection by Potato Leafroll Virus, and Associated Responses by its Vector, Myzus persicae (Sulzer)

Vector-dependent plant pathogens can alter their hosts such that vector behavior and pathogen spread are affected. For example, Potato leafroll virus (PLRV)-induces changes in volatiles emitted by potato plants (Solanum tuberosum L.) that influence settling behavior by Myzus persicae, a principal vector of the virus. Prior work in this pathosystem has utilized a single potato variety, Russet Burbank, but as is true for other plant responses to biotic stresses, responses may differ among plant genotypes. To examine this, PLRV-induced changes in headspace volatile organic compounds (VOCs) and associated aphid responses to these VOCs were compared among four potato varieties (Chipeta, Desiree, IdaRose, and Russet Burbank). Total headspace VOCs differed among the varieties and were differentially induced by PLRV infection such that the effect of variety, infection, and their interaction was significant; two of the varieties had increased concentrations of headspace VOCs, and two did not. MANOVA for the effect of infection and variety on total VOCs and major VOC classes also was significant. A principal component analysis (PCA) partially separated the VOC profiles from the four varieties. Aphid arrestment differed in response to the VOCs of the four varieties, and was greater on those that were more readily infected by PLRV (Desiree and Russet Burbank) as compared with those that were less readily infected (Chipeta and IdaRose). Aphid responses were not clearly related to specific characteristics of blends, such that total VOCs and composition appear to contribute. The four varieties used in this study have distinct pedigrees representative of different cultivated forms of S. tuberosum. Although cultivated potato varieties have been subjected to genetic manipulation by humans, the differences in PLRV induced changes in VOCs nonetheless indicate the potential for complex effects of PLRV infection on host plant VOC emissions, and vector responses in managed, and natural systems.

Multiple Copies of Genes Encoding XEGIPs are Harbored in an 85-kB Region of the Potato Genome

Proteinaceous inhibitors of plant cell wall degrading enzymes can provide a first level of defense from invasive phytopathogens. One recently discovered inhibitor is the xyloglucans-specific endoglucanase inhibitor protein (XEGIP) originally found in tomato. This inhibitor protein has since been found in many solanaceous plants as well as other dicots. As xyloglucans play a major role in maintaining cell wall structure in dicots, protection of xyloglucan is critical. Thus far, only a single potato XEGIP had been identified (AY321357), even though a major pathogen of potato, Phytophthora infestans, has multiple copies of xyloglucan-specific endoglucanase. We now report that potato has nine additional copies of XEGIP, clustered together on a small region of chromosome one. They are located adjacent to the previously described potato XEGIP and represent one of the highest degrees of gene duplication relative to any other potato inhibitor. Synteny with tomato indicates this duplication may have occurred before speciation of Solanum.

Visual inspection of potato seedlings in routine virus diagnosis: validation of a rating method

Visual inspection of seed potato plants is a routine method in virus diagnosis prior to enzyme‐linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) procedures. In this study, the visual rating of potato plants for virus symptoms, together with both these laboratory procedures, was subject to an accreditation by International Standard ISO/IEC 17025 in the plant protection office of Lower Saxony, Germany. The validation of the rating was applied to two samples with 100 single potato plants in each. Each sample was investigated using four ratings, each carried out by three inspectors, consecutively. Standardization was established using inspection under available daylight to assess the degree of virus symptoms. An inspection procedure is suggested which (i) takes into account the light conditions during the inspection and (ii) uses a calibration of the ratings given by the three inspectors obtained from prior inspection jointly of another sample. For each rating the number of plants showing virus symptoms was recorded and ratings were compared using standard statistical methods (mean value, standard deviation and coefficient of variation).

Invasion of Phytophthora infestans at the Landscape Level: How Do Spatial Scale and Weather Modulate the Consequences of Spatial Heterogeneity in Host Resistance?

Strategic spatial patterning of crop species and cultivars could make agricultural landscapes less vulnerable to plant disease epidemics, but experimentation to explore effective disease-suppressive landscape designs is problematic. Here, we present a realistic, multiscale, spatiotemporal, integrodifference equation model of potato late blight epidemics to determine the relationship between spatial heterogeneity and disease spread, and determine the effectiveness of mixing resistant and susceptible cultivars at different spatial scales under the influence of weather. The model framework comprised a landscape generator, a potato late blight model that includes host and pathogen life cycles and fungicide management at the field scale, and an atmospheric dispersion model that calculates spore dispersal at the landscape scale. Landscapes consisted of one or two distinct potato-growing regions (6.4-by-6.4-km) embedded within a nonhost matrix. The characteristics of fields and growing regions and the separation distance between two growing regions were investigated for their effects on disease incidence, measured as the proportion of fields with ≥1% severity, after inoculation of a single potato grid cell with a low initial level of disease. The most effective spatial strategies for suppressing disease spread in a region were those that reduced the acreage of potato or increased the proportion of a resistant potato cultivar. Clustering potato cultivation in some parts of a region, either by planting in large fields or clustering small fields, enhanced the spread within such a cluster while it delayed spread from one cluster to another; however, the net effect of clustering was an increase in disease at the landscape scale. The planting of mixtures of a resistant and susceptible cultivar was a consistently effective option for creating potato-growing regions that suppressed disease spread. It was more effective to mix susceptible and resistant cultivars within fields than plant some fields entirely with a susceptible cultivar and other fields with a resistant cultivar, at the same ratio of susceptible to resistant potato plants at the landscape level. Separation distances of at least 16 km were needed to completely prevent epidemic spread from one potato-growing region to another. Effects of spatial placement of resistant and susceptible potato cultivars depended strongly on meteorological conditions, indicating that landscape connectivity for the spread of plant disease depends on the particular coincidence between direction of spread, location of fields, distance between the fields, and survival of the spores depending on the weather. Therefore, in the simulation of (airborne) pathogen invasions, it is important to consider the large variability of atmospheric dispersion conditions.

METHODS TO ROUTINELY PREDICT THE TEXTURE QUALITY OF POTATOES BY TUBER SPECIFIC GRAVITY

ABSTRACT Information on texture of steam‐cooked potato is of increased importance for consumers of fresh potatoes. As potato texture not only depends on genetic disposition but also on growth conditions, simple and reliable methods are needed to improve characterization of single potato lots. In the present study 65 potato lots were fractionized to 192 tuber samples according to their specific gravity and used for sensory evaluations. The aim was: (1) to further clarify the role of tuber specific gravity, variety and growth condition for texture attributes; and (2) to develop statistical models to predict potato texture objectively and reliably. Texture attributes varied considerably within varieties. The attributes mealiness, dryness, graininess were closely interrelated. Within the varieties, the three attributes as well as sloughing correlated with specific gravity (r = 0.78–0.96). Thus, they were predicted by specific gravity using variety‐dependent models. Alternatively, using variety‐independent models mealiness was predicted by the two parameters specific gravity and sloughing. Softness was related to the variety, but not to specific gravity. The statistical models may be helpful in optimizing the allocation of individual potato lots to specific cooking types for the retail market and for processing.PRACTICAL APPLICATIONSInformation on texture of steam‐cooked potato is of increased importance for consumers of fresh potatoes. We were approached by the potato industry to develop simple and reliable methods for characterization of single potato lots in trade. The objective measurement of texture by instrumental methods is rarely performed for routine testing, probably because of the laborious procedures. The measurement of tuber specific gravity is very simple. However, the relationship between specific gravity and various texture attributes is still not clear. We elaborate the relationship in an extensive evaluation using a broad range of potato lots. The models presented here may be applied directly for routine testing. We also suggest adaptations for routine calibration of new varieties and for routine testing of single lots. Further, the study encourages the scale‐up of technologies which allow the grading of potatoes according to their specific gravity and thereby increase significantly texture homogeneity.

Teaching Aerobic Cell Respiration Using the 5 Es

Ask any group of high school biology teachers what topics their students find most difficult to comprehend and chances are that cell respiration will be among those mentioned. Such a situation presents quite a challenge to biology teachers since national science standards consistently cite information involving cell respiration among the key topics to be covered in high school biology courses. Knowledge of cell structure and the chemical reactions within the cell that provide a flow of energy are listed in Content Standard C of the National Science Education Standards (1996). There are many reasons why students find cell respiration difficult to understand. The abstract nature of the processes, the multitude of details, and a new technical vocabulary make the topic challenging to even the most diligent students. Over the years, I have tried many different approaches to teaching cell respiration, with varying degrees of success. Generally, these approaches involved some combination of lecture, demonstration, and laboratory activity; however the end results were always the same--mediocre test scores and a lack of enthusiasm among the students. Most recently, however, have adopted the 5E model of instruction and I have found it to be quite effective. Figure 1. Overview of the 5 Es. Engage--presents the topic in a way so as to excite the students. Explore--offers opportunities for the students to examine the topic. Explanation--provides students with further description of the topic. Elaborate--encourages the students to further investigate the topic. Evaluate--provides for a means to assess student learning. Unlike the traditional methods such as lecture, the 5E approach provides students with an opportunity to take more active role in their learning (Figure 1). Active-learning strategies like those used in the 5E method involve students in the types of inquiry-based learning called for by Content Standard A of the National Science Education Standards (1996). Since using the 5E method to teach cell respiration my students are more actively engaged in class and their test scores have improved. These findings are consistent with those reported by researchers who found that the use of the 5E method of instruction by biology teachers produced significantly higher grades than did the use of more traditional teaching methods. Furthermore, the researchers found that the students had a more positive attitude toward the study of biology (Lord, 1997; Allard & Barman, 1994). The 5E model is based on a constructivist view of education and consists of five phases: engagement, exploration, explanation, elaboration, and evaluation (Trowbridge, Bybee & Carlson Powell, 2004). The following describes the five components of the method. Taken together, they are designed to appeal to a number of different learning styles (Figure 1). Day 1: Engagement The purpose of the engagement phase of the 5E learning cycle is threefold: to introduce the lesson, to elicit interest and curiosity among the students, and to determine what they might already know about the phenomenon. When teaching cell respiration I try to engage the students by giving a demonstration in which I burn a large potato chip and use the energy released to raise the temperature of a small amount of water in a test tube. The setup for the demonstration involves the use of a ring stand, a clamp, and a test tube. A reconfigured paper clip is used to hold the potato chip and to anchor it to a cork base. Other food sources, such as an almond or a peanut, can also be used. I start the demonstration by asking the students how much energy there is in a single potato chip. After listening to their responses, I tell them that we are going to attempt to find the answer by burning a chip and measuring how much heat energy it releases. First, I give a student a thermometer and have that student measure the initial temperature of 20 ml of water that has been poured into a 25 x 200 mm test tube. …

Cooking kinetics of potato tubers determined by vibration techniques

A laser Doppler vibrometer (LDV) was used for remote sensing of potato cooking behavior. Non-destructive determinations of characteristic tuber resonant frequencies (modes M 1 and M 2 ) displayed in the amplitude–frequency plots (AFP) prior, during, and after steam cooking of the whole tubers were used to establish cooking kinetic coefficients for four different potato varieties. All measurements for a single potato were taken along the extended portion of the tuber at the same location. We found that potato softening during cooking is consistent with the kinetic equation of the first order and that the “two point” test, based on the determination of the AFP prior to and after cooking for 25 (or 15 in one case) min, yields a good estimation of the kinetic coefficient. The results suggest that the application of this method is limited to smaller tubers; the sloughing and cracking of larger tubers induced by longer cooking times confound the measurements.

Ambient air concentrations of pesticides used in potato cultivation in Prince Edward Island, Canada

Ambient air concentrations of nine selected pesticides used in potato cultivation were investigated on Prince Edward Island by collecting samples during the summer of 1998 at three potato farm sites and one non-agricultural site. In 1999, air samples were collected at a single potato farm site during local application of pesticides. The fungicide chlorothalonil was the only pesticide detected in every sample in both years, even in samples with a duration as little as 5 h. In 1998, maximum (45-458 ng m(-3)) and mean (22-193 ng m(-3)) concentrations of chlorothalonil from composite 42 h samples were one to two orders of magnitude greater at agricultural sites than at the non-agricultural site (3.9 and 2.5 ng m(-3), respectively). Maximum and mean concentrations of chlorothalonil from combined 24 h samples at the farm site in 1999 were higher than those measured in 1998 (636 and 284 ng m(-3), respectively). The ubiquitous presence in air of relatively high concentrations of chlorothalonil in agricultural areas on Prince Edward Island is likely related to its repeated use on potato farms where fungicides account for 80-90% of pesticides applied. Eight of nine pesticides were detected at farm sites in 1998 and they are ranked by mean concentration from highest to lowest as follows: chlorothalonil, methamidophos, azinphos-methyl, alpha-endosulfan, beta-endosulfan, pirimicarb, metobromuron, metribuzin, metalaxyl and fluazifop-P-butyl. Concentrations of metalaxyl, pirimicarb, metobromuron and fluazifop-P-butyl in air are among the first reported values for these pesticides. Five pesticides were detected at the Summerside farm in 1999, but only two fungicides (chlorothalonil and metalaxyl) were used locally, while the presence of metribuzin, alpha-endosulfan and methamidophos in air was not associated with local application. Evidence of pesticide drift was observed for chlorothalonil, alpha-endosulfan and methamidophos, and these pesticides were identified as being of high concern in terms of potential wildlife exposure on the Island.