scholarly journals Temperature, Leaf Wetness, and Isolate Effects on Infection of Minneola Tangelo Leaves by Alternaria sp.

Plant Disease ◽  
1999 ◽  
Vol 83 (5) ◽  
pp. 429-433 ◽  
Author(s):  
Y. Canihos ◽  
T. L. Peever ◽  
L. W. Timmer
Keyword(s):  
Polynomial Equation ◽  
Brown Spot ◽  
Effect Of Temperature ◽  
Leaf Wetness ◽  
Significant Difference ◽  
Alternaria Brown Spot ◽  
Detached Leaves ◽  
Alternaria Sp ◽  
Response To Temperature

Alternaria brown spot causes necrotic lesions on immature leaves, twigs, and fruit of tangerines and their hybrids, reducing yield and fruit quality. The effect of temperature, leaf wetness, and isolate was evaluated in an in vitro system using immature detached leaves of Minneola tangelo Infection was greatest at 27°C, decreased gradually as the temperature declined to 24, 20, and 17°C, and dropped sharply at 32°C. Levels of infection were low at 4 and 8 h of leaf wetness and continued to increase with longer wetting periods up to 36 h. A polynomial equation was developed that provided a good fit for the data (adjusted R2 = 0.93). Isolates differed in aggressiveness, but there was no significant difference among isolates in their response to temperature and leaf wetness duration.

scholarly journals RESISTANCE TO ALTERNARIA BROWN SPOT OF NEW CITRUS HYBRIDS

2017 ◽  
Vol 39 (5) ◽  
Author(s):  
KELLY APARECIDA FERNANDES DE CAMPOS ◽  
FERNANDO ALVES DE AZEVEDO ◽  
MARINÊS BASTIANEL ◽  
MARIÂNGELA CRISTOFANI-YALY
Keyword(s):  
Sweet Orange ◽  
Fungal Spores ◽  
Brown Spot ◽  
Disease Symptoms ◽  
Alternaria Brown Spot ◽  
Detached Leaves ◽  
In Vitro Inoculation ◽  
High Level ◽  
Citrus Hybrids

ABSTRACT Alternaria brown spot (ABS) disease is caused by the fungus of Alternaria alternata f. sp. citri, which causes injury in leaves, branches and fruits of citrus. The action of the pathogen is directly related to the presence of toxin receptors in susceptible genotypes. The objective of this study was to characterize a population of citrus hybrids obtained from controlled crosses between Pêra de Abril sweet orange and the hybrid of Murcott tangor x Pêra sweet orange (TM x LP 163) for response to ABS through the in vitro inoculation of fungal spores in young detached leaves. The fungus was isolated from the lesions of Murcott tangor fruits that exhibited ABS symptoms. Two hundred thirty-five hybrids were evaluated, and 70 (30%) showed different levels of disease symptoms on detached leaves after 72 hours of inoculation with the fungus, and 165 (70%) were asymptomatic. The frequency of segregation observed (165R:70S) and high level of heritability (h2g = 0.91) suggest that few genes may be involved in controlling the inheritance of ABS resistance in citrus.

scholarly journals The effect of temperature on spontaneous action potential discharge of the isolated sinus venosus from winter and summer plaice (Pleuronectes platessa)

1995 ◽  
Vol 198 (1) ◽  
pp. 137-140 ◽  
Author(s):  
A A Harper ◽  
I P Newton ◽  
P W Watt
Keyword(s):  
Action Potential ◽  
Discharge Rate ◽  
Cardiac Pacemaker ◽  
Intrinsic Rate ◽  
Effect Of Temperature ◽  
Pacemaker Activity ◽  
Duration Of Action ◽  
Diastolic Depolarization ◽  
Significant Difference

The spontaneous cardiac pacemaker activity and conformation were recorded in vitro, using intracellular recording methods, from heart tissue of summer- and winter-caught plaice. The effects of changing temperature on the pacemaker rate, duration of action potential and diastolic depolarization were investigated by altering the temperature of the superfusing medium. The resting intrinsic rate of discharge was significantly greater in pacemaker cells from winter plaice (P=0.05), but there was no significant difference between winter and summer fish in the apparent Arrhenius activation energies for this process. However, there was a significant difference in the estimated intercept, indicating a thermal shift in the processes underlying the spontaneous pacemaker rhythm. There was no significant difference in the diastolic depolarization duration recorded from winter and summer fish over the temperature range 4­22 °C. The major effect of previous environmental temperature was on the duration of the action potential (P<0.02), indicating that the observed changes in pacemaker discharge rate were not influenced by the processes that determine the duration of the pacemaker diastolic depolarisation but were modulated by the channel events that give rise to the action potential.

scholarly journals Evaluation of the Alter-Rater Model for Timing of Fungicide Applications for Control of Alternaria Brown Spot of Citrus

Plant Disease ◽  
2003 ◽  
Vol 87 (9) ◽  
pp. 1089-1093 ◽  
Author(s):  
Alka Bhatia ◽  
P. D. Roberts ◽  
L. W. Timmer
Keyword(s):  
Disease Control ◽  
Fruit Quality ◽  
Alternaria Alternata ◽  
The Other ◽  
Brown Spot ◽  
Leaf Wetness ◽  
Yield Losses ◽  
Copper Fungicides ◽  
Alternaria Brown Spot

Alternaria brown spot, caused by Alternaria alternata, results in serious yield losses of tangerines and their hybrids in Florida. The Alter-Rater model predicts the need for fungicide applications based on daily cumulative points that are assigned on the basis of rainfall, leaf wetness, and temperature. Previously, Alter-Rater threshold or trigger values of 50, 75, 100, and 150 points for application of copper fungicides were suggested for groves with different cultivars and disease histories. In this study, we evaluated thresholds of 50, 100, and 150 points in four Minneola tangelo and Murcott tangor groves in 2000 and 2001. For comparison, copper fungicides were applied according to the DISC Copper Model in 2000 and according to calendar sprays in 2001. Use of the Alter-Rater model resulted in fewer sprays in three of the four groves in 2000 and better fruit quality in the other grove than the Copper Model. Compared to a calendar spray schedule in 2001, use of the Alter-Rater model resulted in fewer sprays in two of the four groves but more sprays in one grove. The results confirmed that the Alter-Rater is a valuable tool for timing fungicide applications and that its use results in better disease control or fewer sprays.

scholarly journals Positive relationship between citrus leaf miner and alternaria brown spot

2015 ◽  
Vol 45 (7) ◽  
pp. 1160-1163 ◽  
Author(s):  
Fernando Alves de Azevedo ◽  
Ivan Bortolato Martelli ◽  
Denis Augusto Polydoro ◽  
Camilla de Andrade Pacheco ◽  
Evandro Henrique Schinor ◽  
...  
Keyword(s):  
Alternaria Alternata ◽  
Brown Spot ◽  
Leaf Miner ◽  
Lesion Area ◽  
Citrus Leaf ◽  
The World ◽  
Alternaria Brown Spot ◽  
Detached Leaves ◽  
The Relationship ◽  
Diagrammatic Scale

Alternaria brown spot, or ABS (Alternaria alternata), is the most prevalent fungal disease of tangerines in the world. Field observations have revealed ABS lesions on leaves wounded by the citrus leaf miner (CLM). Thus, the objective of this study was to assess the relationship between CLM and ABS. Leaves from young Murcott tangor plants and detached leaves from 16 different varieties of tangerines with and without lesions caused by CLM were inoculated with A. alternata. The symptoms of the plants were subsequently quantified by counting the number of lesions, and the lesion area was estimated using a diagrammatic scale. The presence of CLM damage aggravates the severity of Alternaria alternata fungus infections in susceptible tangerine varieties.

scholarly journals Effect of Temperature on Urediniospore Production and Germinability in Puccinia arachidis1

1994 ◽  
Vol 21 (2) ◽  
pp. 79-81
Author(s):  
P. V. Subba Rao ◽  
P. Subrahmanyam ◽  
D. McDonald
Keyword(s):  
Arachis Hypogaea ◽  
Effect Of Temperature ◽  
Optimal Temperature ◽  
Puccinia Arachidis ◽  
Arachis Hypogaea L ◽  
Different Temperatures ◽  
Percent Germination ◽  
Detached Leaves

Abstract Effect of temperature on urediniospore production in Puccinia arachidis was investigated under monocyclic infection using detached leaves of the susceptible peanut (Arachis hypogaea L.) cultivar TMV 2. Urediniospores produced at different temperatures were also examined for their germinability in vitro. The optimal temperature for urediniospore production was at about 20 and 25 C. Temperatures below 20 C or above 30 C were highly detrimental to urediniospore production. There were also marked differences in the percent germination of urediniospores produced at different temperatures. Urediniospores produced at 20 and 25 C showed the highest germination percentages. The interaction of temperature with urediniospore production and germinability is important in understanding the development of peanut rust epidemics.

scholarly journals Effects of Light, Temperature, and Leaf Wetness Duration on Daylily Rust

Plant Disease ◽  
2003 ◽  
Vol 87 (4) ◽  
pp. 442-445 ◽  
Author(s):  
D. S. Mueller ◽  
J. W. Buck
Keyword(s):  
Light Intensity ◽  
Effect Of Temperature ◽  
Leaf Wetness ◽  
Disease Development ◽  
Lesion Development ◽  
Leaf Wetness Duration ◽  
Different Temperatures ◽  
Controlled Environments ◽  
Incubation Temperatures

Experiments in controlled environments were completed to determine the influence of light intensity, temperature, and leaf wetness duration on daylily rust caused by Puccinia hemerocallidis. As light intensity increased, there was a significant decrease in urediniospore germination (R2 = 0.88 and Y = 96 - 0.6x). Urediniospores germinated in vitro between 7 and 34°C with an optimal temperature of 22 to 24°C. To test the effect of temperature on infection efficiency, plants were inoculated with urediniospores, incubated under high relative humidity at 4, 10, 22, 30, or 36°C, and then transferred to a greenhouse at 23°C for 15 days. Plants incubated at 22°C had an average of 13 lesions cm leaf-1. Incubation temperatures of 4, 10, 30, or 36°C resulted in less than 1.5 lesions cm leaf-1. Plants were inoculated, incubated at 22°C for 24 h, and then incubated at different temperatures for 15 days to test the effect of temperature on disease development. There were no significant differences in disease development at 22 and 30°C; however, there were significantly fewer lesions at 10°C and no lesions developed at 36°C within 15 days. Five to six h of leaf wetness were required for lesion development and as the duration of leaf wetness increased, there was a significant increase in the number of lesions that developed. These studies indicate that for disease development of P. hemerocallidis on daylily, temperatures around 22°C and 5 h of leaf wetness are required during infection. However, once a daylily is infected, disease development is not as sensitive to environmental conditions.

scholarly journals Evaluation of Models for Alternaria Brown Spot of Mandarin Under Mediterranean Conditions by Partial Receiver Operating Characteristic Curve Analysis

2017 ◽  
Vol 107 (6) ◽  
pp. 721-731 ◽  
Author(s):  
Daniel D. M. Bassimba ◽  
Jose L. Mira ◽  
Antonio Vicent
Keyword(s):  
Receiver Operating Characteristic Curve ◽  
False Positive ◽  
Operating Characteristic ◽  
Disease Incidence ◽  
Characteristic Curve ◽  
Brown Spot ◽  
Leaf Wetness ◽  
Alternaria Brown Spot ◽  
Positive Rate ◽  
Operating Characteristic Curve

Alternaria brown spot (ABS) is a serious fungal disease of mandarin in the Mediterranean Basin. Due to the rigorous fruit quality standards, models for ABS should avoid false negatives. Experiments were conducted with susceptible ‘Fortune’ and ‘Nova’ inoculated at different temperatures and leaf wetness durations, including interrupted periods. Effects of temperature and time elapsed after inoculation were also studied. Disease incidence data were fitted to generalized additive models and a generic infection model. Exposure of trap plants in affected orchards was used for model evaluation, including the Alter-Rater and a simple rule system (SRS). The predictive ability of the models was analyzed using the partial area under the receiver operating characteristic curve in the high-sensitivity range between 0.9 and 1. Postinoculation temperature had a significant effect on disease incidence, with maximum symptom expression after 30 h on Fortune and 60 h on Nova. ABS incidence did not increase after a leaf wetness interruption of 1 h on Nova and 2 h on Fortune. All the models evaluated had high false-positive rates on Fortune. Only the SRS showed a substantial strength of agreement in Nova, with a true-positive rate of 0.93 and false-positive rate of 0.16.

scholarly journals Comparison of Four Systems to Test the Tolerance of ‘Fortune’ Mandarin Tissue Cultured Plants to Alternaria alternata

Plants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1321
Author(s):  
Margarita Pérez-Jiménez ◽  
Olaya Pérez-Tornero
Keyword(s):  
Culture Filtrate ◽  
Alternaria Alternata ◽  
In Vitro Selection ◽  
Culture Media ◽  
Severe Disease ◽  
Mutation Breeding ◽  
Brown Spot ◽  
Fungus Culture ◽  
Alternaria Brown Spot

Alternaria brown spot is a severe disease that affects leaves and fruits on susceptible mandarin and mandarin-like cultivars, and is produced by Alternaria alternata. Consequently, there is an urge to obtain new cultivars resistant to A. alternata, and mutation breeding together with tissue culture can help shorten the process. However, a protocol for the in vitro selection of resistant citrus genotypes is lacking. In this study, four methods to evaluate the sensitivity to Alternaria of mandarin ‘Fortune’ explants in in vitro culture were tested. The four tested systems consisted of: (1) the addition of the mycotoxin, produced by A. alternata in ‘Fortune’, to the propagation culture media, (2) the addition of the A. alternata culture filtrate to the propagation culture media, (3) the application of the mycotoxin to the intact shoot leaves, and (4) the application of the mycotoxin to the previously excised and wounded leaves. After analyzing the results, only the addition of the A. alternata culture filtrate to the culture media and the application of the mycotoxin to the wounded leaves produced symptoms of infection. However, the addition of the fungus culture filtrate to the culture media produced results, which might indicate that, in addition to the mycotoxin, many other unknown elements that can affect the plant growth and behavior could be found in the fungus culture filtrate. Therefore, the application of the toxin to the excised and wounded leaves seems to be the most reliable method to analyze sensitivity to Alternaria of ‘Fortune’ explants cultured in vitro.

scholarly journals In Vitro Mutagenesis followed by Polymorphism Detection Using Start Codon Targeted Markers to Engineer Brown Spot Resistance in Kalanchoe

2019 ◽  
Vol 144 (3) ◽  
pp. 193-200
Author(s):  
Rui Li ◽  
Lu Fan ◽  
Jingdong Lin ◽  
Mingyang Li ◽  
Daofeng Liu ◽  
...  
Keyword(s):  
Disease Resistance ◽  
Brown Spot ◽  
Start Codon ◽  
Chemical Mutagenesis ◽  
In Vitro Mutagenesis ◽  
Aesthetic Value ◽  
Disease Resistant ◽  
Detached Leaves ◽  
Mutant Lines

Kalanchoe (Kalanchoe blossfeldiana) is a common potted flower that is popular throughout the world. Brown spot (caused by Stemphylium lycopersici) is one of the common foliage diseases in kalanchoe. This disease tends to infect leaves of kalanchoe plants in hot and humid environments, reducing their aesthetic value. The current investigation aimed to generate mutations resistant to brown spot in ‘Mary’ kalanchoe through chemical mutagenesis followed by molecular marker identification. Putative mutants were developed by treating embryogenic calluses with ethyl methanesulfonate (EMS) at median lethal doses (LD50)–either a 0.8% concentration for 2 hours or a 1.0% concentration for 0.5 hours. Brown spot crude toxin solution was used as the selection agent to identify disease-resistant calluses during tissue culture. The optimal crude concentration (60%) was determined by soaking calluses with different concentrations of crude pathogen: 0%, 20%, 40%, 60%, and 80% (v/v). A total of 32 anti-brown spot lines were regenerated and tested for disease resistance with detached leaves. Three regenerated EMS mutant lines showed no obvious brown spot lesions on their leaves after the disease resistance assay and were subjected to polymorphism identification by start codon targeted (SCoT) molecular markers. Three (SCoT40, SCoT71, and SCoT72) of 45 selected primers were chosen to identify the mutants. This work may lay the foundation for further development of new disease-resistant cultivars of kalanchoe.

scholarly journals Environmental Factors Affecting Production, Release, and Field Populations of Conidia of Alternaria alternata, the Cause of Brown Spot of Citrus

1998 ◽  
Vol 88 (11) ◽  
pp. 1218-1223 ◽  
Author(s):  
L. W. Timmer ◽  
Z. Solel ◽  
T. R. Gottwald ◽  
A. M. Ibañez ◽  
S. E. Zitko
Keyword(s):  
Alternaria Alternata ◽  
Field Studies ◽  
Brown Spot ◽  
Leaf Wetness ◽  
Average Wind Speed ◽  
Susceptible Host ◽  
Spore Trap ◽  
Factors Affecting ◽  
Average Wind ◽  
Alternaria Brown Spot

Alternaria brown spot, caused by Alternaria alternata pv. citri, affects many tangerines and their hybrids, causing loss of immature leaves and fruit and reducing the marketability of the remaining fruit. Conidial production of A. alternata was greatest on mature leaves moistened and maintained at near 100% relative humidity (RH) for 24 h, whereas leaves that had been soaked or maintained at moderate RH produced few conidia. Conidial release from filter paper cultures and infected leaves was studied in a computer-controlled environmental chamber. Release of large numbers of conidia was triggered from both substrates by sudden drops in RH or by simulated rainfall events. Vibration induced release of low numbers of conidia, but red/infrared irradiation had no effect. In field studies from 1994 to 1996, air sampling with a 7-day recording volumetric spore trap indicated that conidia were present throughout the year with periodic large peaks. The number of conidia captured was not closely related to rainfall amounts or average wind speed, but was weakly related to the duration of leaf wetness. Likewise, disease severity on trap plants placed in the field weekly during 1995 to 1996 was not closely related to conidial numbers or rainfall amounts, but was weakly related to leaf wetness duration. Sufficient inoculum appears to be available to allow infection to occur throughout the year whenever susceptible host tissue and moisture are available.

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