The combined effects of temperature, leaf wetness, and inoculum concentration on infection of cucumbers with Pseudoperonospora cubensis

1977 ◽  
Vol 55 (11) ◽  
pp. 1478-1487 ◽  
Author(s):  
Yigal Cohen
Keyword(s):  
Sharp Increase ◽  
Factorial Experiment ◽  
The Other ◽  
Leaf Wetness ◽  
Pseudoperonospora Cubensis ◽  
Disease Development ◽  
Combined Effects ◽  
Single Treatment ◽  
Inoculum Concentration ◽  
Effects Of Temperature

The infection of susceptible cucumber leaves by Pseudoperonospora cubensis was investigated under controlled conditions in a 6 × 3 × 4 factorial experiment with 72 combinations of temperature, inoculum concentration, and leaf-wetness duration. The minimum, maximum, and optimum levels of each factor for symptom production were found to depend on one or both of the other factors. The minimal temperature for infection was 20 °C with 2 h of wetness and this decreased to 10–15 and 5–10 °C with 6 and 12 h of wetness, respectively, according to the inoculum load. The maximal temperature for infection was 25 °C, except for a single treatment in which some infection occurred at 28 °C. Optimal temperatures for infection were 20, 15–20, 10–20, and 5–20 °C at dew periods of 2, 6, 12, and 24 h, respectively. The shortest dew period needed to establish infection was 2 h. A sharp increase in infection was associated with extending the dew period to 6h. Further lengthening of the dew period resulted in more infection under unfavorable combinations of temperature and inoculum concentration. An inoculum load of 10 sporangia/cm2 was minimal for infection under favorable combinations of temperature and wetness, and higher loads were needed under unfavorable combinations. The optimal inoculum concentration was 1000 sporangia/cm2 under most inoculation circumstances. The implications of the variable behaviour of the pathogen to disease development in the field are discussed.

scholarly journals The combined effects of temperature and leaf wetness periods on soybean frogeye leaf spot intensity

2016 ◽  
Vol 37 (1) ◽  
pp. 77 ◽  
Author(s):  
Juliane Nicolodi Camera ◽  
Valéria Cecília Ghissi ◽  
Erlei Melo Reis ◽  
Carolina Cardoso Deuner
Keyword(s):  
Experimental Design ◽  
Leaf Spot ◽  
Leaf Wetness ◽  
Disease Development ◽  
Combined Effects ◽  
Spot Intensity ◽  
Cercospora Sojina ◽  
Frogeye Leaf Spot ◽  
Effects Of Temperature ◽  
Soybean Plants

The frogeye leaf spot, a disease caused by the fungus Cercospora sojina, affects soybean crops worldwide with enormous economic impact. In this study, we evaluated the combined effects of temperature and duration of leaf wetness periods on the intensity of frogeye leaf spot in soybean. Experiments were conducted in a growth chamber with cultivar Don Mario 7.0i at temperatures of 15, 20, 25, 30 and 35°C and leaf wetness periods of 12, 24, 36, 48 and 72 hours. The experimental design was completely randomized with five replications. When soybean plants were grown at 15°C, affected leaflet area, number of lesions per leaflet and diameter of lesions could only be measured after 60 hours of leaf wetness. At the temperatures of 20 and 25°C this period was reduced to 24 hours of leaf wetness, at 30oC, we found the need for 36 hours of leaf wetness and at a temperature of 35°C, 48 hours. The optimal temperatures for disease development were 27°C for diameter and affected leaflet area and 28°C for number of lesions per leaflet with 72 hours of leaf wetness.

scholarly journals Interactive Effects of Temperature and Leaf Wetness Duration on Sporangia Germination and Infection of Cucurbit Hosts by Pseudoperonospora cubensis

Plant Disease ◽  
2012 ◽  
Vol 96 (3) ◽  
pp. 345-353 ◽  
Author(s):  
K. N. Neufeld ◽  
P. S. Ojiambo
Keyword(s):  
Leaf Area ◽  
Downy Mildew ◽  
Disease Severity ◽  
Leaf Wetness ◽  
Pseudoperonospora Cubensis ◽  
Weibull Function ◽  
Leaf Wetness Duration ◽  
Cucurbit Downy Mildew ◽  
Host Type ◽  
Effects Of Temperature

Outbreaks of cucurbit downy mildew caused by Pseudoperonospora cubensis are dependent on the weather but effects of temperature and leaf wetness duration on infection have not been studied for different cucurbits. To determine the effects of these two weather variables on sporangia germination and infection of cucurbit host types by P. cubensis, three host types; cucumber (‘Straight 8’), cantaloupe (‘Kermit’), and acorn squash (‘Table Queen’), were inoculated and exposed to leaf wetness durations of 2 to 24 h at six constant temperatures ranging from 5 to 30°C in growth-chamber experiments. Sporangia germination was assessed after each wetness period, and leaf area infected was assessed 5 and 7 days after inoculation. Germination of sporangia was highest on cantaloupe (16.5 to 85.7%) and lowest on squash (10.7 to 68.9%), while disease severity was highest and lowest on cucumber and cantaloupe, respectively. Host type, temperature, wetness duration and their interactions significantly (P < 0.0001) affected germination and disease severity. Germination and disease data for each host type were separately fitted to a modified form of a Weibull function that characterizes a unimodal response and monotonic increase of germination or infection with temperature and wetness duration, respectively. The effect of host type on germination and infection was characterized primarily by differences in the upper limit parameter in response to temperature. Differences among host types based on other parameters were either small or inconsistent. Temperature and wetness duration that supported a given level of germination or infection varied among host types. At 20°C, 15% leaf area infected was expected following 2, 4, and 8 h of wetness for cucumber, squash, and cantaloupe, respectively. When temperature was increased to 25°C, 15% disease severity was expected following 3, 7, and 15 h of wetness for cucumber, squash, and cantaloupe, respectively. Risk charts were constructed to estimate the potential risk of infection of cucurbit host types by P. cubensis based on prevailing or forecasted temperature and leaf wetness duration. These results will improve the timing and application of the initial fungicide spray for the control of cucurbit downy mildew.

The combined effects of temperature and dilution on the activity and feedback inhibition of yeast aspartate transcarbamylase

1969 ◽  
Vol 47 (4) ◽  
pp. 477-479 ◽  
Author(s):  
J. G. Kaplan ◽  
Irmgard Messmer
Keyword(s):  
Low Temperature ◽  
Sharp Increase ◽  
Specific Activity ◽  
Feedback Inhibition ◽  
Combined Effects ◽  
Regulatory Site ◽  
Aspartate Transcarbamylase ◽  
Small Loss ◽  
Progressive Loss ◽  
Effects Of Temperature

Dilution of a partially purified preparation of yeast aspartate transcarbamylase caused only a small loss of feedback inhibition and no change in specific activity when the assay was carried out at low temperature (0–10 °C). As the temperature of assay was increased, there was in the case of the dilute preparation a progressive loss of feedback inhibition coupled with a sharp increase in specific activity, reaching a level 400–500% that of the concentrated preparations. The data suggest that this is due to a dissociation into subunits possessing high aspartate transcarbamylase activity but lacking the regulatory site.

scholarly journals Combined Effects of Temperature and Toxic Algal Abundance on Paralytic Shellfish Toxic Accumulation, Tissue Distribution and Elimination Dynamics in Mussels Mytilus coruscus

Toxins ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 425
Author(s):  
Yunyu Tang ◽  
Haiyan Zhang ◽  
Yu Wang ◽  
Chengqi Fan ◽  
Xiaosheng Shen
Keyword(s):  
Tissue Distribution ◽  
Combined Effects ◽  
Mytilus Coruscus ◽  
Paralytic Shellfish Toxins ◽  
Rapid Elimination ◽  
Simulated Environment ◽  
Paralytic Shellfish ◽  
Algal Abundance ◽  
Effects Of Temperature ◽  
The Impact

This study assessed the impact of increasing seawater surface temperature (SST) and toxic algal abundance (TAA) on the accumulation, tissue distribution and elimination dynamics of paralytic shellfish toxins (PSTs) in mussels. Mytilus coruscus were fed with the PSTs-producing dinoflagellate A. catenella under four simulated environment conditions. The maximum PSTs concentration was determined to be 3548 µg STX eq.kg−1, which was four times higher than the EU regulatory limit. The increasing SST caused a significant decline in PSTs levels in mussels with rapid elimination rates, whereas high TAA increased the PSTs concentration. As a result, the PSTs toxicity levels decreased under the combined condition. Additionally, toxin burdens were assessed within shellfish tissues, with the highest levels quantified in the hepatopancreas. It is noteworthy that the toxin burden shifted towards the mantle from gill, muscle and gonad at the 17th day. Moreover, variability of PSTs was measured, and was associated with changes in each environmental factor. Hence, this study primarily illustrates the combined effects of SST and TAA on PSTs toxicity, showing that increasing environmental temperature is of benefit to lower PSTs toxicity with rapid elimination rates.

Combined effects of temperature and diet on growth and biochemical composition of the Pacific oyster Crassostrea gigas (Thunberg) spat

2004 ◽  
Vol 35 (12) ◽  
pp. 1131-1140 ◽  
Author(s):  
Cecilia Flores-Vergara ◽  
Beatriz Cordero-Esquivel ◽  
Ana Nallely Ceron-Ortiz ◽  
Bertha O Arredondo-Vega
Keyword(s):  
Crassostrea Gigas ◽  
Biochemical Composition ◽  
Pacific Oyster ◽  
Combined Effects ◽  
The Pacific ◽  
Effects Of Temperature

scholarly journals Ethylene and Lipoxygenase In Relation to Afterripening of Dormant NC-13 Peanut Seeds1,2

1985 ◽  
Vol 12 (1) ◽  
pp. 45-49 ◽  
Author(s):  
D. L. Ketring ◽  
H. E. Pattee
Keyword(s):  
Heat Treatment ◽  
Cold Storage ◽  
Ethylene Production ◽  
Sharp Increase ◽  
Gradual Increase ◽  
The Other ◽  
Immature Seeds ◽  
Positive Correlations ◽  
Mature Seeds

Abstract Following harvest, peanuts are usually subjected to a period of storage. During storage biochemical changes are known to occur. The objectives of this study were to determine the changes and relationship in ethylene production, germination, and lipoxygenase (LG) activity during cold storage of dormant NC-13 peanut seeds. Two seed lots (SL) were used: one grown in Oklahoma (SL80) and the other grown in N. Carolina (SL81). SL80 and SL81 were stored at 2 to 5 C for 193 and 242 days, respectively. Samples were taken at about 28-day intervals for determination of germination, ethylene production, and LG activity. Seeds of two and three maturities were tested for SL80 and SL81, respectively. As afterripening of stored seeds proceeded, ethylene production gradually increased, with the maximum at 48 hours of germination. Germination showed a concomitant gradual increase. Lipoxygenase activity of both seedlots was less for mature than for immature seeds and showed a sharp increase during storage at 2 to 5 C, particularly for immature seeds. After heat-treatment to break dormancy of sublots from SL81, there was a progessive increase in ethylene production and germination, but most notably for mature seeds. In contrast to ethylene production and germination, after heat-treatment LG activity declined. Linear correlation coefficient (r) values between ethylene production and germination were highly significant for mature seeds from SL80 at 48 and 72 hours of germination, but only at 72 hours for immature seeds. For SL81 as for SL80, significant positive correlations were found between ethylene production and germination. However, correlations between LG activity and the other variables were not significant except for mature seeds from SL81. Significant positive correlations for both ethylene production and germination with LG activity also existed for these seeds. But after heat-treatment these correlations no longer occurred. The data indicate that the metabolic processes related to ethylene production and germination are occurring simultaneously with those of LG activity. The possibility that metabolites from LG activity serve as substrates for ethylene production can not be precluded.

Combined Effects of Temperature and Velocity Jump on the Heat Transfer, Fluid Flow, and Entropy Generation Over a Single Rotating Disk

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
A. Arikoglu ◽  
G. Komurgoz ◽  
I. Ozkol ◽  
A. Y. Gunes
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Entropy Generation ◽  
Rotating Disk ◽  
Heat Transfer Fluid ◽  
Combined Effects ◽  
Jump Conditions ◽  
Governing Equations ◽  
Velocity Jump ◽  
Effects Of Temperature

The present work examines the effects of temperature and velocity jump conditions on heat transfer, fluid flow, and entropy generation. As the physical model, the axially symmetrical steady flow of a Newtonian ambient fluid over a single rotating disk is chosen. The related nonlinear governing equations for flow and thermal fields are reduced to ordinary differential equations by applying so-called classical approach, which was first introduced by von Karman. Instead of a numerical method, a recently developed popular semi numerical-analytical technique; differential transform method is employed to solve the reduced governing equations under the assumptions of velocity and thermal jump conditions on the disk surface. The combined effects of the velocity slip and temperature jump on the thermal and flow fields are investigated in great detail for different values of the nondimensional field parameters. In order to evaluate the efficiency of such rotating fluidic system, the entropy generation equation is derived and nondimensionalized. Additionally, special attention has been given to entropy generation, its characteristic and dependency on various parameters, i.e., group parameter, Kn and Re numbers, etc. It is observed that thermal and velocity jump strongly reduce the magnitude of entropy generation throughout the flow domain. As a result, the efficiency of the related physical system increases. A noticeable objective of this study is to give an open form solution of nonlinear field equations. The reduced recurative form of the governing equations presented gives the reader an opportunity to see the solution in open series form.

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