Potato Petiole Research Articles

Primary Non-Inversion Shallow Tillage Versus Moldboard Plowing Prior to Growing Potatoes: Short-Term Impacts on Potato Yield and Soil Properties in Eastern Canada

Potato (Solanum tuberosum L.) production often requires intensive tillage with the moldboard plow (MP), which involves deeper soil tillage and turning of the soil to provide enough loose soil for proper tuberization. Although tillage with the MP allows better potato seedbed preparation and lower weed pressure, it is also associated with increased soil compaction, soil aggregate destruction, and increased soil organic matter (SOM) mineralization. The objective of this four-year (2019–2022) study conducted in 14 commercial fields was to compare the use of MP with primary non-inversion shallow tillage (ST) in terms of their effect on selected soil health indicators, soil moisture, potato petiole nitrate concentration, potato yield, and specific gravity. Commercial fields ranged from 1.5 ha to 19 ha where the main field was split in half, with one side tilled using MP (22.5–30 cm plowing depth) and the other half using ST (15–30 cm plowing depth). Soil and plant tissue samples were taken within four sub-replicates (91 m2) created per each treatment per each site and three to four sites were used as replicates per each year. Compared to MP, ST increased active carbon by an average of 9%, soil respiration by an average of 26%, and aggregate stability by an average of 8%. Biological N availability (BNA) increased by an average of 20% with ST, and the effect was statistically significant in three out of four years. Soil moisture at 20 cm depth tended to be higher with MP than ST in three out of four years. Although not statistically significant, when averaged across four years, potato petiole nitrate concentrations were 5% and 12% higher with ST than MP in samples collected at the flowering and post-potato flowering stages, respectively. Total and marketable potato yields, along with specific gravity, were comparable for the two tillage regimes. Signs of soil improvement were observed at the early stages of ST adoption. Marketable yield was negatively correlated with the soil nitrate levels measured during the growing season but was positively correlated with active carbon, aggregate stability, and soil moisture. Future studies could compare both tillage regimes over multiple growing seasons to assess their impacts over a full cycle of rotation. The novelty of the present study was that it was conducted in real-life conditions across large growers’ fields with different conditions and across four years.

Nitrous oxide emissions and productivity of irrigated potato: Effects of nitrogen fertilization options

AbstractImproved N management is needed in intensive agriculture to mitigate nitrous oxide (N2O) emissions while sustaining high yields. We assessed the effectiveness of polymer‐coated urea (PCU); nitrification inhibitor 2,4‐dimethylpyrazol succinic acid (DMPSA), a biostimulant; and their combinations with granular urea and ammonium sulfate nitrate (ASN) fertilizers to reduce N2O emissions and to improve potato (Solanum tuberosum L.) productivity under irrigation. Sites were located in Lethbridge and Brooks, Alberta, Canada over two growing seasons. Tuber yield, grade, specific gravity, and N uptake were quantified. We used the chamber method to measure N2O fluxes from potato hills and furrows. The N2O emissions from furrow positions were at least two‐fold greater than those from hills at the Lethbridge site. Peak N2O emissions and increased N concentrations in potato petiole and soils occurred shortly after fertilizer applications. The overall average emission factor (EF) of N2O was 0.056% kg N2O–N kg−1 N fertilizer (accounting for emissions from unfertilized controls). Urea alone commonly exhibited the highest N2O fluxes. Admixing DMPSA with either urea or ASN lowered N2O emissions in only certain cases. For instance, in one growing season at the Brooks site, adding DMPSA to urea reduced the N2O emissions by 57%. Likewise, in one of the four site‐years in the study, 36% higher potato marketable yields were obtained when applying either ASN treated with DMPSA or PCU compared with the unfertilized controls (45 vs. 33 Mg ha−1). Results showed that under specific conditions, N application strategies using DMPSA admixed with either urea or ASN can maintain high potato yields while reducing N2O emissions relative to soils receiving these fertilizers without this additive.

New approach to estimate macro and micronutrients in potato plants based on foliar spectral reflectance

Tissue testing used to assess the chemical contents in potato plants is considered laborious, time-consuming, destructive, and expensive. Ground-based sensors have been assessed to provide efficient information on nitrogen using leaf canopy reflectance. In potatoes, however, the main organ required for tissue testing is the petiole to estimate the elements of all nutrients. This research aims to assess whether there is a correlation between the chemical contents of potato petioles and leaf spectrum, and to examine whether the spectrum of dried or fresh leaves have higher correlation values. Petiole chemical contents of all elements were tested as a reference point. Leaves were split equally into dried and fresh groups for spectral analysis (400–2500 nm). Lasso Regression models were built to estimate concentrations in comparison to actual values. The performances of the model were tested using the Ratio of (standard error of) Prediction to (standard) Deviation (RPD). All elements showed reasonable to excellent RPD values except for sodium. All elements showed higher correlation in the dried testing mode except for nitrogen and potassium. The models showed that the most significant wavebands were in the visible and very near infrared range (400–1100 nm) for all macronutrients except magnesium and sulfur, while all micronutrients had the most significant wavebands in full range (400–2500 nm) with a common significant waveband at 1932 nm. The results show high potentials of a new approach to estimate potato plant elements based on foliar spectral reflectance.

Evaluating phosphorus nutritional status of potato by instant testing of petiole phosphate concentration

ABSTRACT The split application of P can increase the yield and P use efficiency of potato，however, there is currently a lack of a reliable method for determining the timing and rates for the split application of P fertilizers to optimize potato production. In this three-year field experiment, we tested the possibility of establishing a potato plant P diagnosis method with a reflectometer RQflex. Potato petiole Pi content was linearly correlated to plant P contents and was significantly sensitive to soil phosphorus supply, suggesting that petiole P content determined by a RQflex meter is a good indicator of potato plant P status. Moreover, the relationship between relative potato yield and petiole Pi content fits a linear platform equation, suggesting that RQflex meter may be useful for rapidly determining the threshold petiole P level. Our results will help in developing a viable method for recommending P-fertilizer application rates during potato growth to optimize potato tuber yields.

Cover crops prove effective at increasing soil nitrogen for organic potato production

Many farms in northeast California are experimenting with organic production to take advantage of price premiums and niche markets. A common challenge in organic farming is finding dependable nitrogen sources to meet the needs of vegetable and grass crops, especially in fields with low soil nitrogen. This study assessed the use of cover crops and organic amendments for increasing soil nitrogen for potato production at the Intermountain Research and Extension Center in Tulelake. Researchers evaluated several cover crop species, three planting dates and multiple cover crop mixes. Amendments included composts, manures, bloodmeal and soymeal. The data collected in the study included total nitrogen from cover crops and amendments, plant-available nitrogen in the soil, potato petiole nitrate and crop yield and quality. Vetches and field peas, managed as green manure, were successful at satisfying potatoes' in-season nitrogen demand. These cover crops, grown alone or in mixes with non-legume species, produced potato crops whose yield and quality were similar to crops grown with conventional fertilizers. The cover crops' influence on potato pest pressure was neutral. Chicken manure was the most cost-effective amendment for satisfying potatoes' in-season nitrogen demand.

THE IMPACT OF TRIFENDER WP ON THE CONTENT OF CHLOROGENIC ACIDS IN POTATO PLANTS INFECTED BY Phytophthora infestans (Mont.) de Bary

Five potato cultivars were grown in a micro-plot field experiment (under conditions of natural infection by pathogens). In experimental treatments, potatoes were treated with Trifender WP, whereas control plants were not treated with growth regulators. A greenhouse experiment, conducted simultaneously, involved three treatments: 1. control (no biostimulant treatment, no inoculation), 2. inoculation (potato plants inoculated with P. infestans), 3. Trifender WP+inoculation (soil and foliar application of Trifender WP followed by inoculation with the pathogen 2 days after the last treatment). The research material was potato petioles, in which changes in the concentration of analyzed chlorogenic acids were determined using the Waters Acquity UPLC technique. In comparison with the control treatment, higher concentrations of the 5-caffeoylquinic acid (5-CQA), 4-caffeoylquinic acid (4-CQA) and 3‑caffeoylquinic acid (3-CQA) were found in potatoes treated with Trifender WP, and in cultivars with blue-purple and red-colored flesh than in those with yellow and cream-colored flesh (field experiment). In the greenhouse experiment, the content of individual chlorogenic acids increased in the petioles of potatoes inoculated with P. infestans and inoculated with the pathogen after the application of Trifender WP, compared with the control treatment

Possibility of Recommending Potassium Application Rates Based on a Rapid Detection of the Potato Petiole K Status with a Portable K ion Meter

Because of the variations in the K amount required to produce 1 t potatoes and the poor relationship between soil potassium content and potato yield, recommended K-fertilizer rates based on soil tests are unreliable for potato production. This research was set to test the possibility of establishing a potato plant K diagnosis method with a portable K ion meter. The results confirmed the luxury absorption of K by potato. Moreover, the potato petiole K content by a portable K ion meter was linearly related to the vine and tuber K contents as well as the plant accumulated K level. Therefore the petiole K concentration is a good indicator of plant K status. Furthermore, the relationship between the relative potato yield and the petiole K content fits a quadratic equation, thus the threshold petiole K content could be calculated based on the minimum petiole K content at the highest relative yield. Debido a las variaciones en la cantidad de K requerida para producir 1 t de papas, y la pobre relacion entre el contenido de potasio en el suelo y el rendimiento de papa, los niveles de fertilizantes de K recomendados con base a las pruebas del suelo, no son confiables para la produccion de papa. Esta investigacion se establecio para probar la posibilidad de establecer un metodo de diagnostico de K en la planta de papa con un ionmetro de K portatil. Los resultados confirmaron la absorcion de lujo de K por la papa. Aun mas, el contenido de K en el peciolo de la papa por el ionmetro de K portatil estuvo relacionado linealmente a los contenidos de K del follaje y del tuberculo, asi como al nivel de K acumulado en la planta. De aqui que la concentracion de K en el peciolo es un buen indicador de la situacion del K en la planta. Mas aun, la relacion entre el rendimiento relativo de la papa y el contenido de K en el peciolo se ajusta a una ecuacion cuadratica, entonces el umbral del contenido de K en el peciolo pudiera calcularse con base en el contenido minimo de K en el peciolo en el rendimiento relativo mas alto.

Efficiency of P Fertigation for Drip-Irrigated Potato Grown on Calcareous Sandy Soils

Most potato growers apply phosphorus (P) before cultivation and there is little information available about P fertigation for drip-irrigated potato. A field experiment was conducted during 2017 and 2018 to study the effect of P fertigation on P uptake and yield of potato (Solanum tuberosum L.) grown on a calcareous sandy soil. Three frequencies of P fertigation (daily, every 2 days and every 3 days) and two forms of P (urea phosphate (UP) and monopotassium phosphate (MPP)) were examined. UP reduced the soil pH by 7.2% and increased the P availability by 24% compared to MPP. Daily P fertigation increased P concentrations in the petioles of potato by 19–47% compared to the application every 3 days. Water and P were used more efficiently under daily P fertigation treatments and the use of acidic fertiliser (UP) was more efficient in this respect. The injection of UP with irrigation water every day caused a 22% increase in the marketable yield of potato compared to the injection of MPP every 3 days. It can be recommended that for potato grown on sandy calcareous soils, UP must be added daily to obtain high economic return and minimise the negative environmental effects of unsustainably high P rates.

NITROGEN DEFICIENCY CALCULATION OF LEAVES USING ARTIFICIAL NEURAL NETWORK

In this proposed work, we are estimating the nitrogen content and calculating the nitrogen deficiency in pomegranate leaves. We collect different Nitrogen deficient leaves. We had measured the chlorophyll content of the collected leaves. We captured the images of collected leaves under the closed environment. These leaves are sent to the chemical analysis for the nitrogen estimation. Extracting the statistical features of images and creating the database. The captured images are compared with database and then find the nitrogen deficiency of leaf. For irrigated crops, plant analysis can be used as an aid in making decisions about nutrient applications such as nitrogen and some micronutrients. One example is petiole testing in irrigated potatoes. Nitrate nitrogen levels in the potato petiole are determined weekly, and the information is used to help make nitrogen fertilization decisions all season long. Plant analysis is also used in fruit and vegetable crops as a guide for nutrient application during the season.

Phosphorus Uptake by Potato from Biochar Amended with Anaerobic Digested Dairy Manure Effluent

Sorption of plant nutrients from dairy storage lagoons by biochar and use as a supplemental fertilizer is a beneficial strategy to reduce nutrient contamination around dairies and supply nutrients to potato (Solanum tuberosum L.) and other crops. This research evaluated potato growth responses and P partitioning from several rates of P applied as either mono‐ammonium phosphate (MAP) or as P recovered from anaerobic digested dairy manure using biochar. Single‐stemmed plants of the potato cultivars Ranger Russet and Umatilla Russet were grown in 7‐L pots containing Quincy sand soil (mixed, mesic Xeric Torripsamment). Biochar amended with dairy effluent applied at 5.7 and 11.4 Mg ha–1 with fertilizer application rates equivalent to 55 and 110 kg P ha–1 maintained adequate P levels in potato petioles of both cultivars through 85 d after planting. Total plant P uptake was greater for treatments receiving MAP. Total potato biomass and tuber yields of Umatilla Russet were 30 and 27% lower when amended with basic or enriched biochar compared to MAP treatments, respectively. Tuber biomass declined 10 and 20% for Ranger Russet and Umatilla Russet for the 11.4 Mg ha–1 amended biochar, respectively compared to MAP fertilized treatments. Similar declines were found for the aboveground biomass and roots. The 5.7 Mg ha–1 of enriched biochar supplied 70 to 80% of the P requirement for potato growth. These findings are an important step in providing evidence of the benefits of using recovered P as a fertilizer supplement to reduce the reliance on rock phosphates.

Protein profiling of the potato petiole under short day and long day photoperiods

In potato (Solanum tuberosum), a signal is delivered from the leaf to underground organs to activate tuber formation. Short-day (SD) conditions induce tuberization and long-day (LD) inhibits the process. Recent studies have implicated a mobile RNA, StBEL5, as a potential signal in this process. The petiole constitutes an important vascular channel for the transport of light-mediated signals originating from the leaf blade and is also the transcriptional source of StBEL5 RNA. Hence, identifying the proteins in the petiole and their differential expression under SD and LD photoperiods will be helpful in further understanding the downstream signaling process. Thus, we have undertaken a proteomic analysis of proteins isolated from potato petioles (PP) grown under LD and SD photoperiod conditions using 2-dimensional gel electrophoresis (2-DE) followed by mass spectrometry based identification of proteins (a total of 125 proteins were identified from 185 spots). Sixty-seven differentially expressed proteins were identified in response to SD or LD photoperiods and an additional 43 putative phosphoproteins were identified through affinity enrichment. Numerous poly(U)-binding proteins which contain RNA recognition motifs have also been isolated and identified. This is the first comprehensive proteomics study that examines and catalogs proteins present in the potato petiole.

Proteomics analysis of the regulatory network involved in long‐distance signaling in potato

In potato (Solanum tuberosum), BEL5 mRNA is a mobile RNA which is involved in the signaling system that activates tuber formation. Short day (SD) induces tuberization and long day (LD) inhibits the process. The mobility of StBEL5 RNA is induced by a SD photoperiod. It is likely that the movement of StBEL5 is facilitated by the formation of a RNA‐protein complex. To verify this proposed mechanism we have undertaken a proteomic analysis. Proteins from potato petioles (as the transcriptional source of StBEL5 RNA is leaf veins and petioles) grown under LD and SD photoperiod conditions were separated by 2‐dimensional gel electrophoresis (2‐DE). Proteins which were differentially expressed in response to changes in photoperiods were analyzed by Progenesis SameSpots software and identified by MALDI MS/MS. Phosphoproteins (phosphorylation of proteins is central to signal transduction) and RNA binding proteins were also enriched from LD and SD potato petioles, separated on 2‐DE and analyzed by MALDI MS/MS. We have identified many proteins that are differentially expressed in response to LD or SD photoperiods. A comprehensive profile of the phosphoproteomes of LD and SD potato petioles has been established. Significantly, the presence of the RNA‐binding protein, elF‐5A, has been detected in multiple phosphorylation states only under LD conditions. Numerous RNA‐binding proteins have also been isolated and identified.

Boron Fertilization and Evaluation of Four Soil Extractants: Russet Burbank Potato

Yield‐response correlations with old and improved soil extraction methods for boron (B) are needed. Russet Burbank potato (Solanum tuberosum L.) was grown with two, four, and six B treatments applied in 2004, 2005, and 2006, respectively. Zero and 1.1, 2.2, or 3.4 kg B ha−1 soil and 0.22 or 0.28 kg B ha−1 foliar treatments were applied. Boron fertilization did not significantly increase tuber yield or quality despite initially low hot‐water‐extractable B (0.34–0.50 mg kg−1), although postseason B for unfertilized treatments increased (0.51–0.57 mg kg−1). Soil‐applied B generally reflected B application relative to the untreated control and the low foliar rates in all three years for the four soil extractions utilized [hot water, pressurized hot water, diethylenetriaminepentaacetic acid (DTPA)–sorbitol, and Mehlich III]. Boron content of potato petiole did reflect application of B in 2 years, but tuber and peel tissues did not consistently reflect application of B.

Leaf nitrogen estimation in potato based on spectral data and on simulated bands of the VENμS satellite

Relationships between leaf spectral reflectance at 400-900 nm and nitrogen levels in potato petioles and leaves were studied. Five nitrogen (N) fertilizer treatments were applied to build up levels of nitrogen variation in potato fields in Israel in spring 2006 and 2007. Reflectance of leaves was measured in the field over a spectral range of 400- 900 nm. The leaves were sampled and analyzed for petiole NO3-N and leaf percentage N (leaf-%N). Prediction models of leaf nitrogen content were developed based on an optical index named transformed chlorophyll absorption reflectance index (TCARI) and on partial least squares regression (PLSR). Prediction models were also developed based on simu- lated bands of the future VENlS satellite (Vegetation and Environment monitoring on a New Micro-Satellite). Leaf spectral reflectance correlated better with leaf-%N than with petiole NO3-N. The TCARI provided strong correlations with leaf-%N, but only at the tuber-bulking stage. The PLSR analysis resulted in a stronger correlation than TCARI with leaf-%N. An R 2 of 0.95 (p \ 0.01) and overall accuracy of 80.5% (Kappa = 74%) were determined for both vegetative and tuber-bulking periods. The simulated VENlS bands

Assessing organic potato cropping systems at the end of the first cycle of four-year rotations using principal component analysis

A single or a few variables may not be sufficient to evaluate management practice effects in a complicated cropping system, so six plant and 13 soil variables were integrated using principal component analysis (PCA) to examine nine 4-yr organic potato rotations. The rotations were combinations of three forage levels (0, 1, and 2 yr of forages) with three soil amendments (monogastric compost, ruminant compost, and alfalfa meal). Quantities of amendments were estimated by soil test recommendations and amendment nutrient availabilities. In the 4th potato year, one half of each original plot was not amended ("the 4th year unamended plots"), while the other half received soil amendments ("4th year amended plots"). The first three principal components explained 67 and 63% of the overall variation for the 4th-yr amended and unamended plots, respectively. PCA ordination plots indicated that, overall, the type of soil amendments had larger effects on soil and plant variables, but forage frequencies were influential for the amendments showing weaker effects. PCA loading plots indicated that plant nutrient uptake and potato total tuber weight would be the best single variables for characterizing the current cropping systems. Plant variables, except for potato petiole nitrate, were closely displayed, but they were not strongly correlated with soil variables, which may reflect the high background fertility of this site. Applications of soil amendments in the 4th yr affected the relationships among variables, most notably the strength of relationships between soil pH and soil N variables. The results suggest that PCA provides an effective way to compare complex cropping systems, especially in situations with high site heterogeneity. Key words: Principal component analysis, soil amendment, livestock system, forage, potato, organic crop rotation

Effect of fish emulsion used as a preplanting soil amendment on verticillium wilt, scab, and tuber yield of potato

Fish emulsion is used mainly as a fertilizer for crop production but, in a previous study, we have demonstrated its efficacy in suppressing damping-off [Rhizoctonia and Pythium spp.] in radish and cucumber in a peat-based substrate or soil. In the present study, fish emulsion was tested as a preplanting soil amendment to control soilborne diseases of eggplant and potato such as verticillium wilt [Verticillium dahliae and Verticillium albo-atrum] and scab [Streptomyces spp.]. Tests were conducted on 11 soils with different characteristics (pH, 5.2–7.2; organic-matter content, 1.0%–3.7%), originating from commercial potato fields in Ontario, New Brunswick, and Prince Edward Island with a history of verticillium wilt and scab. The amendment of soil with fish emulsion at rates of 0.5% and 1% (m/m) protected eggplant from verticillium wilt, and the 1% fish-emulsion treatment increased fresh and dry plant biomasses in the greenhouse. Microplot experiments with potato showed that the 1% fish-emulsion treatment significantly (P < 0.05) reduced scab severity (by 0.6–2.1 units on a scale of 0–6) in seven soils with low to moderate scab-disease pressure and significantly increased total tuber yield (by 41%–170%) in nine soils, compared with the control treatments. Fish emulsion also reduced potato petiole infection by V. dahliae in one soil. In potato field trials at two sites in 2004, treatment with 1% fish emulsion (20 000 L/ha) significantly (P < 0.05) reduced scab severity (by 0.8–1 units) and significantly increased scab-free tubers (by 132%–366%) and marketable-tuber (surface scab < 5%) yield (by two fold), compared with the control treatments. Total tuber yield was reduced at one site and not affected at the other. No effect of fish emulsion on scab and verticillium wilt or tuber yield was observed in a 2005 field trial. The reduction of scab or verticillium wilt by fish emulsion was not soil-specific and varied from year to year. The results indicated that fish emulsion was not effective in soils with high disease pressure.

Efficient Agrobacterium tumefaciens-mediated transformation of sweet potato (Ipomoea batatas (L.) Lam.) from stem explants using a two-step kanamycin-hygromycin selection method

To achieve reliable stable transformation of sweet potato, we first developed efficient shoot regeneration for stem explants, leaf disks, and petioles of sweet potato (Ipomoea batatas (L.) Lam.) cultivar Beniazuma. The shoot regeneration protocol enabled reproducible stable transformation mediated by Agrobacterium tumefaciens strain EHA105. The binary vector pIG121Hm contains the npt II (pnos) gene for kanamycin (Km) resistance, the hpt (p35S) gene for hygromycin (Hyg) resistance, and the gusA (p35S) reporter gene for β-glucuronidase (GUS). After 3 d co-cultivation, selection of calluses from the three explant types began first with culture on 50 mg l−1 of Km for 6 wk and then transfer to 30 mg l−1 of Hyg for 6–16 wk in Linsmaier and Skoog (1965) medium (LS) also containing 6.49 μM 4-fluorophenoxyacetic acid and 250 mgl−1 cefotaxime in the dark. The selected friable calluses regenerated shoots in 4 wk on LS containing 15.13 μM abscisic acid and 2.89 μM gibberellic acid under a 16h photoperiod of 30 μmol m−2s−1. The two-step selection method led to successful recovery of transgenic shoots from stem explants at 30.8%, leaf dises 11.2%, and petioles 10.7% stable transformation efficiencies. PCR analyses of 122 GUS-positive lines revealed the expected fragment for hpt. Southern hybridization of genomic DNA from 18 independent transgenic lines detected the presence of the gusA gene. The number of integrated T-DNA copies varied from one to four.

High-efficiency regnerationin vitro from potato petioles with intact leaflets

The shoot/plantlet regenerationin vitro of seven potato (Solanum tuberosum L.) cultivars from petioles with intact leaflets was assessed using six treatment combinations-a basal medium with or without silver thiosul-phate (STS) or thidiazuron (TDZ) at two concentrations (2 or 0.5 mg/l) of the indoleacetic acid (IAA). The basal medium consisted of Murashige and Skoog (MS) salts and vitamins supplemented with 3 mg/1 6-benzylaminopurine, and 1 mg/1 gibberellic acid, 30 g/l sucrose, and 7.0 g/l PHYTOAGAR. Two full sets repeats and one partial set repeat of independent experiments were conducted and all produced similar results. Silver thiosulphate decreased the regeneration frequency and number of shoots per callus. No significant changes were observed with thidiazuron. Regeneration rates of (100% ) with up to 20 shoots/plantlets per callus were achieved at 2 mg/1 IAA with cultivars Desiree, Kennebec, Niska, and Lenape. These cultivars still showed high regeneration rates (87%–98% ) on media with 0.5 mg/1 IAA, and good regeneration rates were also achieved by the other three cultivars (48%, 94%, and 50% for Chieftain, Russet Burbank, and Shepody, respectively). Even with the single medium protocol (0.5% IAA without thiosulphate or thidiazuron), Desiree, Lenape, and Niska exhibited a regeneration rate of 98%. The use of petiole-with-leaflet explants could be ideal for the regeneration step of potato genetic transformation protocol because of their high regeneration efficiency and their small cut surface area forAgrobacterium elimination after co-incubation.

Nutrient concentrations in potato stem, petiole and leaflet in response to potassium fertilizer

Chemical composition of potato stem, petiole and leaflet were evaluated in response to the application of K fertilizer. Potassium was applied at six different rates (0, 60, 120, 240, 480 and 960 kg ha-1 of K2O), as K2SO4 and was placed in the furrow during planting. Two plants per plot were sampled 48 days after plant emergence to evaluate N, P, K, Ca, Mg, S, Cu, Mn and Zn concentrations in stems, petioles and leaflets of the youngest fully expanded leaf. It is recommended using potato petioles to evaluate the N, P, K, Ca, Mg and Cu status and using potato leaflet to evaluate the S, Mn and Zn status. The stem was not a good indicator of S nutritional status. Petiole N, P and Cu concentrations associated with the maximum tuber yield (30.5 t ha-1, with 353.4 kg ha-1 of K2O) were 25.9 g kg-1, 1.4 g kg-1 and 9.7 mg kg-1, respectively, while, the leaflet S, Mn and Zn concentrations associated with the maximum tuber yield were 4.0 g kg-1, 155.2 mg kg-1 and 59.4 mg kg-1, respectively. This information should be used to build data banks of adequate nutrient concentration at different portions of potato plant and like this, to aid the nutrient diagnosis in potato crops.

Glyphosate application and timing of tillage of red clover affects potato response to N, soil N profile, and root and soil nematodes

The effects of glyphosate application and time of tillage of red clover on soil NO3-N profiles, the response of the subsequent potato crop to varying rates of N fertilizer application, and root and soil nematodes, were evaluated. The study was conducted over three cropping seasons on a Charlottetown fine sandy loam on Prince Edward Island. Red clover was moldboard ploughed in mid-September (early fall), or moldboard or chisel ploughed in mid-October (late fall), or moldboard ploughed in the spring. Glyphosate was applied in early fall and the dead clover was moldboard or chisel ploughed in mid-October or left undisturbed until spring. A barley control, where barley was harvested and straw incorporated with a tandem disc harrow in early September, was included. Potato were planted with 6 rates of N (0 to 250 kg ha–1 in 50-kg increments) band applied at planting. The barley control treatment produced lower potato yield without fertilizer N in all 3 yr of the study compared to red clover treatments, but potato yields were similar at high rates of applied N. Potato tuber yields after spring moldboard ploughing of red clover were higher at low N rates and lower at high N rates than yields after late fall treatment in one year of the study. Concentrations of nitrate-N in the soil in mid-November were highest following the early fall moldboard ploughing and lowest in the undisturbed clover plots. Fall soil nitrate-N levels were intermediate following the glyphosate application and late fall tillages. Early spring soil nitrate-N levels in the surface 30 cm were generally highest with the spring and late fall tillage and lowest with the early fall tillage. Levels of nitrate-N in potato petioles increased with increased rates of N application and generally increased as tillage of the red clover was delayed from early fall to late fall to spring. In general, cultivation and the application of glyphosate did not affect soil and root nematode populations. In two instances, the moldboard plough tillage treatments were associated with higher levels of the clover-cyst nematode, Heterodera trifolii. One of the tillage treatments was combined with glyphosate, but this was the only case where the herbicide had an impact on nematodes. To maximize the benefits to the subsequent potato crop and to minimize leaching of nitrate, incorporation of legume residue should be delayed until the rate of mineralization and nitrification of the legume N is minimized. It is suggested that incorporation of red clover be delayed until after mid-October for clover–potato systems on PEI. Key words: Glyphosate, nematodes, nitrate leaching, petiole nitrate-N, potato, soil nitrate-N, tillage time