scholarly journals Inoculum Dynamics and Infection of Citrus Fruit by Phyllosticta citricarpa

2020 ◽  
Vol 110 (10) ◽  
pp. 1680-1692
Author(s):  
Nga T. Tran ◽  
Andrew K. Miles ◽  
Ralf G. Dietzgen ◽  
Timothy A. Shuey ◽  
Stephen R. Mudge ◽  
...  
Keyword(s):  
Leaf Litter ◽  
Disease Incidence ◽  
Citrus Fruit ◽  
Black Spot ◽  
Summer Rainfall ◽  
Tree Canopy ◽  
Economic Losses ◽  
Citrus Black Spot ◽  
Spore Trapping ◽  
Phyllosticta Citricarpa

Citrus black spot, caused by Phyllosticta citricarpa, is characterized by fruit blemishes and premature fruit drop, resulting in significant economic losses in summer rainfall areas. The pathogen forms both conidia and ascospores during its life cycle. However, the occurrence of these spores and their contributions to infection of fruit in field conditions are not well understood. Our research using direct leaf litter monitoring and volumetric spore trapping in Queensland orchards revealed that pseudothecia and ascospores in leaf litter as well as trapped ascospores had low abundance, while pycnidia and conidia were highly abundant. Both P. citricarpa and endophytic Phyllosticta spp. were identified, with P. citricarpa being dominant. In replicated field trials, we determined that infection of Imperial mandarin fruit by P. citricarpa occurred from fruit set until week 20 of fruit development, with the key infection events taking place between weeks 4 and 16 in Queensland subtropical conditions. These results demonstrate that protecting fruit during weeks 4 to 16 significantly reduced P. citricarpa infection. We found no significant correlation between the disease incidence in fruit and P. citricarpa conidial abundance in leaf litter or ascospore abundance measured by volumetric spore trapping. Therefore, it is suggested that inoculum sources in the tree canopy other than those detected by spore trapping and direct leaf litter monitoring may play a major role in the epidemiology of citrus black spot. Improved knowledge regarding epidemiology of P. citricarpa and an understanding of propagules causing infection may aid in development of more effective disease management strategies.

Effectiveness of essential oils for postharvest control of Phyllosticta citricarpa (citrus black spot) on citrus fruit

2016 ◽  
Vol 121 ◽  
pp. 1-8 ◽  
Author(s):  
Pamela Lombardo ◽  
Andrea Guimaraens ◽  
Jorge Franco ◽  
Eduardo Dellacassa ◽  
Elena Pérez Faggiani
Keyword(s):  
Essential Oils ◽  
Citrus Fruit ◽  
Black Spot ◽  
Citrus Black Spot ◽  
Phyllosticta Citricarpa ◽  
Postharvest Control

scholarly journals Sexual Reproduction in the Citrus Black Spot Pathogen, Phyllosticta citricarpa

2017 ◽  
Vol 107 (6) ◽  
pp. 732-739 ◽  
Author(s):  
Nga T. Tran ◽  
Andrew K. Miles ◽  
Ralf G. Dietzgen ◽  
Megan M. Dewdney ◽  
Ke Zhang ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Culture Media ◽  
Black Spot ◽  
Physical Contact ◽  
Sexual Cycle ◽  
Economic Losses ◽  
Type Locus ◽  
Citrus Black Spot ◽  
Phyllosticta Citricarpa ◽  
The Impact

Citrus black spot (Phyllosticta citricarpa) causes fruit blemishes and premature fruit drop, resulting in significant economic losses in citrus growing areas with summer rainfall across the globe. The mating type locus of P. citricarpa has recently been characterized, revealing the heterothallic nature of this pathogen. However, insight into the occurrence of mating and the impact of completing the sexual cycle of P. citricarpa was lacking. To investigate the occurrence and impact of sexual reproduction, we developed a method to reliably, and for the first time, produce ascospores of P. citricarpa on culture media. To demonstrate meiosis during the mating process, we identified recombinant genotypes through multilocus genotyping of single ascospores. Because the process of fertilization was not well understood, we experimentally determined that fertilization of P. citricarpa occurs via spermatization. Our results demonstrate that P. citricarpa is heterothallic and requires isolates of different MAT idiomorphs to be in direct physical contact, or for spermatia to fulfill their role as male elements to fertilize the receptive organs, in order to initiate the mating process. The impact of mating on the epidemiology of citrus black spot in the field is discussed.

scholarly journals The Effects of Nutrition and Environmental Factors on Conidial Germination and Appressorium Formation of Phyllosticta citricarpa, the Causal Agent of Citrus Black Spot

2019 ◽  
Vol 109 (4) ◽  
pp. 650-658 ◽  
Author(s):  
Nan-Yi Wang ◽  
Megan M. Dewdney
Keyword(s):  
Black Spot ◽  
Nitrogen Sources ◽  
Conidial Germination ◽  
Appressorium Formation ◽  
Potato Dextrose Broth ◽  
Citrus Black Spot ◽  
Fungal Biology ◽  
Biological Studies ◽  
Phyllosticta Citricarpa

Citrus black spot, caused by Phyllosticta citricarpa, has been identified in Florida since 2010 and can reduce fruit yield and marketability. The conditions required for conidial germination have been poorly understood for P. citricarpa, limiting further biological studies. In this study, the effects of citrus juices, concentration, pH, various carbon and nitrogen sources, and environmental conditions were evaluated in vitro. All tested juices, especially ‘Valencia’ (>85%, P < 0.05), favored germination and appressorium formation, whereas sterile water rarely stimulated germination (<1%). The ‘Valencia’ juice effect was concentration and pH dependent, and the maximum rate was reached in 1.5% juice with pH of 3.4. Most carbon, nitrogen, or complex sources did not favor germination or appressorium formation, with the exception of potato dextrose broth. An incubation period of 18 to 24 h at 24°C was required for peak germination and appressorium formation. The further analysis of critical juice components using synthetic citrus juice revealed that sugars, salts, citric acid, and thiamine were most important for germination and appressorium formation (>80%, P > 0.05). These results provide a better understanding of fungal biology of P. citricarpa and a robust and convenient system for further applications such as screening for efficacious fungicides.

scholarly journals Pathogenicity of Phyllosticta citricarpa Ascospores on Citrus spp.

Plant Disease ◽  
2018 ◽  
Vol 102 (7) ◽  
pp. 1386-1393 ◽  
Author(s):  
Nga T. Tran ◽  
Andrew K. Miles ◽  
Malcolm W. Smith ◽  
Ralf G. Dietzgen ◽  
André Drenth
Keyword(s):  
Potential Model ◽  
Black Spot ◽  
Future Studies ◽  
Citrus Black Spot ◽  
Phyllosticta Citricarpa ◽  
Sexual State ◽  
Epidemic Development ◽  
The Impact ◽  
Troyer Citrange

Citrus black spot, caused by Phyllosticta citricarpa, is one of the most important fungal diseases in many citrus-growing regions with hot and humid summers. Ascospores and conidia are known to contribute to epidemic development of the disease. However, pathogenicity testing has never been done for pure ascospores produced from fully characterized P. citricarpa isolates, due to the inability to induce the sexual state in vitro. Recently, an in vitro mating technique was developed to readily produce pure P. citricarpa ascospores for use in host inoculation studies. To test the pathogenicity of P. citricarpa ascospores, we inoculated Troyer citrange leaves and Murcott tangor fruit with ascospores produced in vitro from characterized P. citricarpa isolates. Typical symptoms of citrus black spot occurred. Recovery of P. citricarpa isolates from symptomatic lesions and their characterization using genetic markers enabled us to identify recombinant genotypes among the isolates recovered from ascospore inoculations and, as such, fulfill Koch’s postulates for ascospores. We have also identified Troyer citrange seedlings as a potential model system for citrus black spot inoculation studies, because it allows typical symptoms of citrus black spot to be expressed with a much shorter latent period than on fruit. This will facilitate future studies of epidemiological aspects of P. citricarpa ascospores relative to conidia and improve our understanding of the citrus black spot pathosystem. The susceptibility of Troyer citrange seedlings will also facilitate experimenting with disease management methods, aimed at reducing the impact of citrus black spot.

scholarly journals Interference of spray volume, fruit growth and rainfall on spray deposits in citrus black spot control periods

2016 ◽  
Vol 46 (5) ◽  
pp. 825-831 ◽  
Author(s):  
Demétrius de Araújo ◽  
Carlos Gilberto Raetano ◽  
Hamilton Humberto Ramos ◽  
Douglas Sampaio Ribeiro da Rocha ◽  
Evandro Pereira Prado ◽  
...  
Keyword(s):  
Spray Deposition ◽  
Control Period ◽  
Fruit Size ◽  
Citrus Fruit ◽  
Black Spot ◽  
Fruit Growth ◽  
Citrus Black Spot ◽  
Citrus Diseases ◽  
Significant Difference ◽  
Old Trees

ABSTRACT: Citrus black spot (CBS) caused by Guignardia citricarpa is one of the most serious Brazilian citrus diseases. This study aims to assess the interference of three application volumes in spray deposition citrus fruit, as well as fruit growth and rainfall effects on spray deposit reduction during the CBS control period. The experiment was carried out in a commercial citrus orchard, with sixteen-year-old trees of the Valencia variety, in Mogi Guaçu, São Paulo State, Brazil. The spray volumes were: 3.5 (1333L ha-1), 4.5 (1714L ha-1) and 8.5 (3238L ha-1) litres per tree, sprayed by an airblast sprayer using fungicides at recommended periods for disease control. The spray deposition quantification and residue was done by spectrophotometry using a copper oxychloride tracer. Samples were collected in three height zones of the tree (top, middle and bottom) and placed between trees on line plantation. Spray depositions were significantly smaller in the first application as a consequence of reduced fruit size. The spray losses on average for each day of rainfall ranged from 4.0 to 5.7%. There was no significant difference between application volumes regarding spray deposition on citrus fruit,which makes possible the reduction of application volumes, however, it is necessary to improve spraying techniques for the top zone of the citrus tree.

scholarly journals Validation of Quantitative and Digital Polymerase Chain Reaction Assays Targeting the Mating Types of Phyllosticta citricarpa, the Causal Agent of Citrus Black Spot

2021 ◽  
Author(s):  
Hector Urbina ◽  
Taylor Smith ◽  
Callie Jones ◽  
Xiaoan Sun ◽  
John McVay ◽  
...  
Keyword(s):  
Polymerase Chain Reaction ◽  
Mating Type ◽  
Citrus Fruit ◽  
Black Spot ◽  
Dispersal Ability ◽  
Mating Types ◽  
Chain Reaction ◽  
Citrus Black Spot ◽  
Limited Dispersal ◽  
Polymerase Chain

Citrus black spot (CBS) is a disease caused by the ascomycetous fungus Phyllosticta (formerly Guignardia) citricarpa (Botryosphaeriales, Pezizomycotina) currently present in citrus groves in five counties in southwest Florida. Within Florida, P. citricarpa shows limited reproduction via asexual sporulation due to the presence of only one (MAT1-2-1) of the two required mating types for sexual reproduction. Here we present two novel polymerase chain reaction (PCR) assays standardized in quantitative (qPCR) and digital (dPCR) platforms to distinguish both mating types (MAT1-1-1 and MAT1-2-1) of P. citricarpa, to monitor for the potential introduction of the MAT1-1-1 mating type into Florida and a novel protocol for DNA extraction from asymptomatic leaves. During citrus harvesting season 2018−2019, fruit lesions, as well as asymptomatic leaves adjacent to symptomatic fruit and asymptomatic trees in CBS-infected groves were surveyed for P. citricarpa presence and mating types. Results support the presence of only MAT1‑2-1 mating type in Florida, after surveying more than 1,145 citrus fruit lesions. We also confirmed the limited dispersal ability of the asexual state of P. citricarpa in Florida in ten groves using the enhanced capabilities of the dPCR platform in the detection of P. citricarpa directly from asymptomatic leaves with low pathogen inoculum.

scholarly journals COPPER OXYCHLORIDE APPLIED ALONE TO CONTROL CITRUS BLACK SPOT

2019 ◽  
Vol 32 (3) ◽  
pp. 616-624
Author(s):  
ANTONIO EDUARDO FONSECA ◽  
ANTONIO DE GOES ◽  
FERNANDA DIAS PEREIRA
Keyword(s):  
Control Measure ◽  
Block Design ◽  
Black Spot ◽  
Additional Treatment ◽  
Copper Oxychloride ◽  
Concentrated Suspension ◽  
Citrus Black Spot ◽  
Progress Curve ◽  
Randomized Block Design ◽  
Phyllosticta Citricarpa

ABSTRACT Citrus black spot (CBS) is a disease caused by the Phyllosticta citricarpa fungus that causes lesions in fruits and, in more severe stages, fruit drops. The use of systemic fungicides is the main control measure for CBS; however, an alternative control measure is the use of cupric fungicides applied alone with short intervals. Therefore, the objective of the present work was to evaluate the effect of applications of copper oxychloride at different rates on the control of CBS. The experiment was conducted in Bebedouro, SP, Brazil, in the 2014/2015 crop season, in a randomized block design, using a Citrus sinensis variety (Valencia). The treatments consisted of copper rates (zero - control; 31, 24.5, 18.5, 12.2, and 9.1 mg of metal copper per cubic meter of canopy) using copper oxychloride (concentrated suspension - CS; 588 g L-1 of copper oxychloride or 350 g L-1 of metal copper), and an additional treatment with application of a cupric fungicide (cuprous oxide) and a strobilurin fungicide. The applications were carried out with 14-day intervals, starting when 2/3 of the petals of the plant's flowers were fallen, totaling 14 applications. The incidence and severity of CBS were evaluated five times with 30-day intervals up to mid-November, when the fruits were harvested. The data were used to calculate the area under the disease progress curve (AUDPC). Applications of copper oxychloride CS at rates of 31 and 24.5 mg m-3 with 14-day intervals are efficient for the control of CBS, with similar efficiency to the farm standard treatment.

scholarly journals Clove Essential Oil as an Alternative Approach to Control Postharvest Blue Mold Caused by Penicillium italicum in Citrus Fruit

Biomolecules ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 197 ◽  
Author(s):  
Chuying Chen ◽  
Nan Cai ◽  
Jinyin Chen ◽  
Chunpeng Wan
Keyword(s):  
Essential Oil ◽  
Disease Incidence ◽  
Quantitative Polymerase Chain Reaction ◽  
Citrus Fruit ◽  
Defense Responses ◽  
Economic Losses ◽  
Penicillium Italicum ◽  
Blue Mold ◽  
Gene Expressions ◽  
Clove Essential Oil

Penicillium italicum causes blue mold disease and leads to huge economic losses in citrus production. As a natural antifungal agent, clove essential oil (CEO), which is a generally recognized as safe (GRAS) substance, shows strong in vitro activity against fungal pathogens. However, few studies on CEO for controlling postharvest blue mold disease caused by P. italicum in citrus fruit have been reported. Our aims were to investigate the control efficacy and possible mechanisms involved of CEO against P. italicum. In the present study, CEO treatment inhibited the disease development of blue mold when applied at 0.05% to 0.8% (v/v), and with the effective concentration being obtained as 0.4% (v/v). Besides its direct antifungal activity, CEO treatment also spurred a rapid accumulation of H2O2 compared with untreated fruits, which might contribute to enhancing an increase in the activities of defense-related enzymes, such as β-1,3-glucanase (β-Glu), chitinase (CHI), phenylalanine ammonia-lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO), and lipoxygenase (LOX) in citrus fruit. Results of real time-quantitative polymerase chain reaction (RT-qPCR) showed that the gene expressions of β-Glu, CHI, PAL, POD and PPO were up-regulated in CEO-treated fruits. At the same time, CEO treatment led to down-regulated expression of the LOX gene in citrus fruit. Clove essential oil effectively control the disease incidence of blue mold decay in citrus fruit by motivating the host-defense responses, suppressing the malondialdehyde (MDA) accumulation while enhancing the activities and gene expressions of defense-related enzymes. Our study provides an alternative preservative applying CEO to reduce postharvest fungal decay in citrus fruit.

scholarly journals Effects of Shredding or Treating Apple Leaf Litter with Urea on Ascospore Dose of Venturia inaequalis and Disease Buildup

Plant Disease ◽  
2000 ◽  
Vol 84 (12) ◽  
pp. 1319-1326 ◽  
Author(s):  
Donald K. Sutton ◽  
William E. MacHardy ◽  
William G. Lord
Keyword(s):  
United States ◽  
Leaf Litter ◽  
Venturia Inaequalis ◽  
Disease Incidence ◽  
Tree Canopy ◽  
Northeastern United States ◽  
Moderate Amount ◽  
Primary Inoculum ◽  
Action Threshold ◽  
Previous Autumn

Ascospores produced on diseased leaves in the leaf litter constitute the primary inoculum causing scab in commercial apple orchards in the northeastern United States. Two sanitation practices, shredding the leaf litter with a flail mower and urea application, were evaluated for their potential to reduce the risk of primary scab. Three measures of a treatment's potential were made: leaf litter density was evaluated to determine reduction of the source or primary inoculum; trapped ascospores were counted to measure the reduction of primary inoculum; and scab lesions on trees and seedlings were counted to determine reduction in disease incidence and severity on leaves and fruit. The results show that in the northeastern United States, shredding the leaf litter in November or April will reduce the risk of scab by 80 to 90% if all of the leaf litter is shredded. If 10 to 35% of the leaf litter cannot be shredded because of the limited offset of the flail mower and spread of the tree canopy, then the risk of scab is reduced by 50 to 65%. Urea applied to the leaf litter in November (when approximately 95% of the leaves had fallen) reduced the number of ascospores trapped by 50%. Urea applied to the leaf litter in April (before bud break) reduced the number of ascospores trapped by 66%. The reductions are discussed in relation to a sanitation action threshold that links sanitation to a strategy that reduces the fungicide dose to control primary scab in an orchard assessed with a moderate amount of foliar scab the previous autumn.

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