Evaluation of Mobile Heat Treatment System for Treating In-Field HLB-Affected Trees by Analyzing Survival Rate of Surrogate Bacteria

Ghatrehsamani, Shirin; Czarnecka, Eva; Verner, F. Lance; Gurley, William B.; Ehsani, Reza; Ampatzidis, Yiannis

doi:10.3390/agronomy9090540

Cited by 8 publications

(3 citation statements)

References 21 publications

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“…Such qPCR negative results are typical for hot summer months, as the bacteria clears in the shoots due to high temperatures, which were in the range of 100-120 °F during May-August. Although well-documented, this problem substantially complicates qPCR-based diagnostics of HLB [31][32][33][34] . The Raman readings, however, reported stable signal intensity of 1610 cm −1 band above 1.925 ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Raman Spectroscopy vs Quantitative Polymerase Chain Reaction In Early Stage Huanglongbing Diagnostics

Sanchez

Pant

Mandadi

et al. 2020

Sci Rep

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Raman spectroscopy (RS) is an emerging analytical technique that can be used to develop and deploy precision agriculture. RS allows for confirmatory diagnostic of biotic and abiotic stresses on plants. Specifically, RS can be used for Huanglongbing (HLB) diagnostics on both orange and grapefruit trees, as well as detection and identification of various fungal and viral diseases. The questions that remain to be answered is how early can RS detect and identify the disease and whether RS is more sensitive than qPCR, the "golden standard" in pathogen diagnostics? Using RS and HLB as case study, we monitored healthy (qPCR-negative) in-field grown citrus trees and compared their spectra to the spectra collected from healthy orange and grapefruit trees grown in a greenhouse with restricted insect access and confirmed as HLB free by qPCR. Our result indicated that RS was capable of early prediction of HLB and that nearly all in-field qPCR-negative plants were infected by the disease. Using advanced multivariate statistical analysis, we also showed that qPCR-negative plants exhibited HLB-specific spectral characteristics that can be distinguished from unrelated nutrition deficit characteristics. These results demonstrate that RS is capable of much more sensitive diagnostics of HLB compared to qPCR. Plant diseases can be caused by a variety of different pathogens, such as viruses, fungi and bacteria. Huanglongbing (HLB), or citrus greening, is a devastating disease that plagues citrus trees in Asia, Africa, and more recently the Americas 1. In the United States, HLB is associated with Candidatus Liberibacter asiaticus (CLas), a gram-negative bacterium that inhabits the plant phloem in uneven and variable titers 2,3. Limited knowledge is available on CLas bacterium due to our inability to culture it in the laboratory. The bacterium is transmitted by the highly mobile Asian citrus psyllid (Diaphorina citri) enabling proliferation of HLB on large agricultural areas. The disease is also able to spread by grafting. In late stages, HLB-infected plants have asymmetric mottling on the leaves and lopsided and green fruits. HLB causes fruit drop and poor fruit quality, e.g. smaller size, less juice yield, higher acidity and lower sugar content. Early stages of the disease, however, have minimal to no symptoms and the bacteria can remain undetectable even by quantitative polymerase chain reaction (qPCR) in the trees for several years after initial infection 4. This, wherein, lies a significant challenge in regard to HLB management. Farmers are reluctant to remove trees that have normal, healthy appearances and keep producing fruits. However, if such trees have CLas bacteria, they allow for psyllids to quickly spread this devastating disease over large distances. Therefore, it becomes critical to detect HLB at the early (pre-symptomatic) stage and develop appropriate intervention strategies for HLB containment. In disease diagnostics, the most predominant methods used to confirm a pathogen are PCR and/or enzyme-linked immunosorbent as...

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Section: Resultsmentioning

confidence: 99%

Raman Spectroscopy vs Quantitative Polymerase Chain Reaction In Early Stage Huanglongbing Diagnostics

Sanchez

Pant

Mandadi

et al. 2020

Sci Rep

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“…MHTS was also evaluated in the field by using a bio-based sensor (a surrogate bacterium, Klebsiella oxytoca). It was reported that the system showed good killing efficiency (3.35 log reductions in colony-forming units to the complete elimination of the bacteria) at a raised maximum temperature of 54 °C for 250 s [ 264 ]. Therefore, thermotherapy treatment could be one of the effective control strategies in an integrated management of HLB.…”

Section: Triangular Management Strategiesmentioning

confidence: 99%

Huanglongbing Pandemic: Current Challenges and Emerging Management Strategies

Ghosh

Kokane

Savita

et al. 2022

Plants

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Huanglongbing (HLB, aka citrus greening), one of the most devastating diseases of citrus, has wreaked havoc on the global citrus industry in recent decades. The culprit behind such a gloomy scenario is the phloem-limited bacteria “Candidatus Liberibacter asiaticus” (CLas), which are transmitted via psyllid. To date, there are no effective long-termcommercialized control measures for HLB, making it increasingly difficult to prevent the disease spread. To combat HLB effectively, introduction of multipronged management strategies towards controlling CLas population within the phloem system is deemed necessary. This article presents a comprehensive review of up-to-date scientific information about HLB, including currently available management practices and unprecedented challenges associated with the disease control. Additionally, a triangular disease management approach has been introduced targeting pathogen, host, and vector. Pathogen-targeting approaches include (i) inhibition of important proteins of CLas, (ii) use of the most efficient antimicrobial or immunity-inducing compounds to suppress the growth of CLas, and (iii) use of tools to suppress or kill the CLas. Approaches for targeting the host include (i) improvement of the host immune system, (ii) effective use of transgenic variety to build the host’s resistance against CLas, and (iii) induction of systemic acquired resistance. Strategies for targeting the vector include (i) chemical and biological control and (ii) eradication of HLB-affected trees. Finally, a hypothetical model for integrated disease management has been discussed to mitigate the HLB pandemic.

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“…Currently, many strategies have been developed for HLB mitigation, including application of antimicrobials ( Zhang et al, 2011a , 2012 , 2014 , 2021 ; Hu and Wang, 2016 ; Hu et al, 2018 ; Yang et al, 2018 ), thermotherapy ( Hoffman et al, 2013 ; Fan et al, 2016 ; Yang et al, 2016b ; Doud et al, 2017 ; Ghatrehsamani et al, 2019 ; Vincent et al, 2019 ), macro-and micronutrients ( Spann and Schumann, 2009 ; Gottwald et al, 2012 ; Rouse et al, 2017 ; Mattos-Jr et al, 2020 ; Dong et al, 2021 ; Zhou et al, 2021 ), plant defense inducers ( Canales et al, 2016 ; Li et al, 2016 , 2019 , 2021a ; Hu et al, 2018 ; Wang, 2021 ), control of the insect vector ( Grafton-Cardwell et al, 2013 ; Boina and Bloomquist, 2015 ; Cocuzza et al, 2017 ; Pierre et al, 2021 ), biocontrol ( Trivedi et al, 2011 ; Hopkins and Wall, 2021 ; Nan et al, 2021 ; Poveda et al, 2021 ), and eradication of HLB symptomatic citrus trees ( Bassanezi et al, 2013 ; Yuan et al, 2020 ). However, these strategies have shown limited success in field applications and effective HLB management remains a challenge.…”

Section: Introductionmentioning

confidence: 99%

An Overview of the Mechanisms Against “Candidatus Liberibacter asiaticus”: Virulence Targets, Citrus Defenses, and Microbiome

Yang

Ancona

2022

Front. Microbiol.

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Citrus Huanglongbing (HLB) or citrus greening, is the most destructive disease for citrus worldwide. It is caused by the psyllid-transmitted, phloem-limited bacteria “Candidatus Liberibacter asiaticus” (CLas). To date, there are still no effective practical strategies for curing citrus HLB. Understanding the mechanisms against CLas can contribute to the development of effective approaches for combatting HLB. However, the unculturable nature of CLas has hindered elucidating mechanisms against CLas. In this review, we summarize the main aspects that contribute to the understanding about the mechanisms against CLas, including (1) CLas virulence targets, focusing on inhibition of virulence genes; (2) activation of citrus host defense genes and metabolites of HLB-tolerant citrus triggered by CLas, and by agents; and (3) we also review the role of citrus microbiome in combatting CLas. Finally, we discuss novel strategies to continue studying mechanisms against CLas and the relationship of above aspects.

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Evaluation of Mobile Heat Treatment System for Treating In-Field HLB-Affected Trees by Analyzing Survival Rate of Surrogate Bacteria

Cited by 8 publications

References 21 publications

Raman Spectroscopy vs Quantitative Polymerase Chain Reaction In Early Stage Huanglongbing Diagnostics

Raman Spectroscopy vs Quantitative Polymerase Chain Reaction In Early Stage Huanglongbing Diagnostics

Huanglongbing Pandemic: Current Challenges and Emerging Management Strategies

An Overview of the Mechanisms Against “Candidatus Liberibacter asiaticus”: Virulence Targets, Citrus Defenses, and Microbiome

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