scholarly journals Asymptomatic spread of huanglongbing and implications for disease control

2015 ◽  
Vol 112 (24) ◽  
pp. 7605-7610 ◽  
Author(s):  
Jo Ann Lee ◽  
Susan E. Halbert ◽  
William O. Dawson ◽  
Cecile J. Robertson ◽  
James E. Keesling ◽  
...  
Keyword(s):  
Disease Spread ◽  
Initial Infection ◽  
Young Leaves ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus ◽  
Asymptomatic Phase ◽  
And Control ◽  
Unknown Length ◽  
Asymptomatic Disease ◽  
Citrus Trees

Huanglongbing (HLB) is a bacterial infection of citrus trees transmitted by the Asian citrus psyllid Diaphorina citri. Mitigation of HLB has focused on spraying of insecticides to reduce the psyllid population and removal of trees when they first show symptoms of the disease. These interventions have been only marginally effective, because symptoms of HLB do not appear on leaves for months to years after initial infection. Limited knowledge about disease spread during the asymptomatic phase is exemplified by the heretofore unknown length of time from initial infection of newly developing cluster of young leaves, called flush, by adult psyllids until the flush become infectious. We present experimental evidence showing that young flush become infectious within 15 d after receiving an inoculum of Candidatus Liberibacter asiaticus (bacteria). Using this critical fact, we specify a microsimulation model of asymptomatic disease spread and intensity in a grove of citrus trees. We apply a range of psyllid introduction scenarios to show that entire groves can become infected with up to 12,000 psyllids per tree in less than 1 y, before most of the trees show any symptoms. We also show that intervention strategies that reduce the psyllid population by 75% during the flushing periods can delay infection of a full grove, and thereby reduce the amount of insecticide used throughout a year. This result implies that psyllid surveillance and control, using a variety of recently available technologies, should be used from the initial detection of invasion and throughout the asymptomatic period.

scholarly journals Metabolome and Microbiome Signatures in the Roots of Citrus Affected by Huanglongbing

2019 ◽  
Vol 109 (12) ◽  
pp. 2022-2032 ◽  
Author(s):  
Emily M. T. Padhi ◽  
Nilesh Maharaj ◽  
Shin-Yi Lin ◽  
Darya O. Mishchuk ◽  
Elizabeth Chin ◽  
...  
Keyword(s):  
High Throughput Sequencing ◽  
Water Soluble ◽  
Resonance Spectroscopy ◽  
Its Gene ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus ◽  
Citrus Leaves ◽  
Citrus Varieties ◽  
And Control ◽  
The Impact

Huanglongbing (HLB) is a severe, incurable citrus disease caused by the bacterium ‘Candidatus Liberibacter asiaticus’ (CLas). Although citrus leaves serve as the site of initial infection, CLas is known to migrate to and colonize the root system; however, little is known about the impact of CLas infection on root metabolism and resident microbial communities. Scions of ‘Lisbon’ lemon and ‘Washington Navel’ orange grafted onto ‘Carrizo’ rootstock were grafted with either CLas-infected citrus budwood or uninfected budwood. Roots were obtained from trees 46 weeks after grafting and analyzed via 1H nuclear magnetic resonance spectroscopy to identify water-soluble root metabolites and high-throughput sequencing of 16S rRNA and ITS gene amplicons to determine the relative abundance of bacterial and fungal taxa in the root rhizosphere and endosphere. In both citrus varieties, 27 metabolites were identified, of which several were significantly different between CLas(+) and control plants. CLas infection also appeared to alter the microbial community structure near and inside the roots of citrus plants. Nonmetric multidimensional scaling (NMDS) and a principal coordinate analysis (PCoA) revealed distinct metabolite and microbial profiles, demonstrating that CLas impacts the root metabolome and microbiome in a manner that is variety-specific.

Spatiotemporal dynamics of Candidatus Liberibacter asiaticus colonization inside citrus plant and Huanglongbing disease development

2020 ◽  
Author(s):  
Sheo Shankar Pandey ◽  
Fernanda N.C. Vasconcelos ◽  
Nian Wang
Keyword(s):  
Passive Movement ◽  
Infection Process ◽  
Active Movement ◽  
Candidatus Liberibacter Asiaticus ◽  
In Planta ◽  
Mature Leaves ◽  
Young Leaves ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus ◽  
Different Tissues

Candidatus Liberibacter asiaticus (CLas), the causal agent of citrus huanglongbing, colonizes inside the phloem and is naturally transmitted by the Asian citrus psyllid (ACP). Here, we investigated the spatiotemporal CLas colonization in different tissues post ACP transmission. At 75 day-post-ACP-removal (DPR), CLas was detected in roots of all trees, but in the mature leaf of only one tree, of the nine plants that were successfully infected via ACP transmission, consistent with the model that CLas moves passively from the source to sink. CLas was detected in 11.1%, and 43.1% mature leaves, which were unfed by ACPs during transmission, at 75, and 365 DPR, respectively, unveiling active movement to the source tissue. The difference in colonization timing of sink and source tissues indicates CLas is capable of both passive and active movement with passive movement being dominant. At 225 DPR, leaves fed by ACPs during the young stage showed the highest ratio of HLB symptomatic leaves and highest CLas titer, followed by that of leaves emerged post ACP removal, and mature leaves not fed by ACPs. Importantly, our data showed that ACPs were unable to transmit CLas via feeding on mature leaves. It is estimated that it takes at most three years for CLas to infect the whole tree. Overall, the spatiotemporal detection of CLas in different tissues after ACP transmission helps visualize the infection process of CLas in planta and subsequent HLB symptom development, and provides the knowledge supporting that young leaves should be the focus of HLB management.

scholarly journals Temporal Progression of ‘Candidatus Liberibacter asiaticus’ Infection in Citrus and Acquisition Efficiency by Diaphorina citri

2014 ◽  
Vol 104 (4) ◽  
pp. 416-421 ◽  
Author(s):  
Helvecio D. Coletta-Filho ◽  
Matthew P. Daugherty ◽  
Cléderson Ferreira ◽  
João R. S. Lopes
Keyword(s):  
Transmission Efficiency ◽  
Management Tool ◽  
Diaphorina Citri ◽  
Candidatus Liberibacter Asiaticus ◽  
Infection Level ◽  
Plant Infection ◽  
Citrus Production ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus ◽  
Asymptomatic Phase

Over the last decade, the plant disease huanglongbing (HLB) has emerged as a primary threat to citrus production worldwide. HLB is associated with infection by phloem-limited bacteria (‘Candidatus Liberibacter’ spp.) that are transmitted by the Asian citrus psyllid, Diaphorina citri. Transmission efficiency varies with vector-related aspects (e.g., developmental stage and feeding periods) but there is no information on the effects of host–pathogen interactions. Here, acquisition efficiency of ‘Candidatus Liberibacter asiaticus’ by D. citri was evaluated in relation to temporal progression of infection and pathogen titer in citrus. We graft inoculated sweet orange trees with ‘Ca. L. asiaticus’; then, at different times after inoculation, we inspected plants for HLB symptoms, measured bacterial infection levels (i.e., titer or concentration) in plants, and measured acquisition by psyllid adults that were confined on the trees. Plant infection levels increased rapidly over time, saturating at uniformly high levels (≈108 copy number of 16S ribosomal DNA/g of plant tissue) near 200 days after inoculation—the same time at which all infected trees first showed disease symptoms. Pathogen acquisition by vectors was positively associated with plant infection level and time since inoculation, with acquisition occurring as early as the first measurement, at 60 days after inoculation. These results suggest that there is ample potential for psyllids to acquire the pathogen from trees during the asymptomatic phase of infection. If so, this could limit the effectiveness of tree rouging as a disease management tool and would likely explain the rapid spread observed for this disease in the field.

scholarly journals An Improved Method to Track Changes of Candidatus Liberibacter asiaticus Titer in HLB-affected Citrus Trees

HortScience ◽  
2019 ◽  
Vol 54 (8) ◽  
pp. 1357-1360 ◽  
Author(s):  
Ed Etxeberria ◽  
Pedro Gonzalez ◽  
Ariel Singerman ◽  
Timothy Ebert
Keyword(s):  
Sampling Method ◽  
Sampling Period ◽  
Tree Canopy ◽  
Candidatus Liberibacter Asiaticus ◽  
Improved Method ◽  
Destructive Sampling ◽  
Candidatus Liberibacter ◽  
Random Variability ◽  
Liberibacter Asiaticus ◽  
Citrus Trees

Monitoring the health of Huanglongbing-affected citrus trees by following changes in leaf Candidatus Liberibacter asiaticus (CLas) titer has an inherent element of imprecision because CLas titer varies considerably within the tree canopy and with calendar seasons. In addition, the destructive sampling method used to determine CLas titer entails a different set of leaves per sampling period adding to the inconsistency and inexactitude of the results. To overcome these ambiguities and to reduce the numerical variability between samples, we developed an experimental method that analyzes portions of the same treated leaves for up to four sampling periods. By assaying subsamples of adjacent locations of the same leaf, random variability was significantly reduced, and comparative analysis can be carried out with greater precision.

scholarly journals Volatile compounds of Persian and Mexican lime associated with HLB (Huanglongbing) symptoms

2018 ◽  
Vol 44 (1) ◽  
pp. 19 ◽  
Author(s):  
Estrella Mendoza-Peña ◽  
Juan Cibrián-Tovar ◽  
Julio Velázquez-González ◽  
Felipe Tafoya-Rangel ◽  
Ausencio Azuara-Domínguez
Keyword(s):  
Early Detection ◽  
Volatile Compounds ◽  
Solid Phase ◽  
Diagnostic Strategy ◽  
Candidatus Liberibacter Asiaticus ◽  
Mass Selective Detector ◽  
Selective Detector ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus ◽  
And Control

The bacterium Candidatus Liberibacter asiaticus is the pathogen that causes the disease known as Huanglongbing (HLB) in citrus. During the course of the disease, the bacterium affects citrus plant phloem tissues, but their leaves remain asymptomatic for HLB for months to years after initial infection. This limits the early detection and control of the bacterium in infected trees. Therefore, in order to design a diagnostic strategy for HLB, the aim of this study was to quantify the abundance and concentration of the volatile compounds released from young shoots of the Persian lemon (Citrus latifolia Tanaka) and the Mexican lemon [Citrus aurantifolia (Christm.) Swingle] with and without HLB symptoms. The volatiles emitted by young shoots were captured by Solid Phase Microextraction (SPME) and analyzed in a gas chromatograph coupled to a mass selective detector (CG / MS). The results clearly indicate that young shoots with and without HLB symptoms released different abundances and concentrations of volatile compounds. The compounds: D-limonene, β-ocimene, and caryophyllene were collected at higher concentrations in the young shoots of both lemon species with HLB symptoms. This result shows the feasibility of designing a strategy for early detection of the disease in different species of lemon through recognition of patterns and concentrations of volatile compounds released from infected trees.

scholarly journals Genome Sequence Resource of ‘Candidatus Liberibacter asiaticus’ strain 9PA From Brazil

Plant Disease ◽  
2021 ◽  
Vol 105 (1) ◽  
pp. 199-201
Author(s):  
P. A. Silva ◽  
J. Huang ◽  
N. A. Wulff ◽  
Z. Zheng ◽  
R. Krugner ◽  
...  
Keyword(s):  
Genome Sequence ◽  
Sweet Orange ◽  
Whole Genome Sequence ◽  
Whole Genome ◽  
Candidatus Liberibacter Asiaticus ◽  
Citrus Production ◽  
Candidatus Liberibacter ◽  
Citrus Huanglongbing ◽  
Liberibacter Asiaticus ◽  
And Control

‘Candidatus Liberibacter asiaticus’, an unculturable α-proteobacterium, is associated with citrus huanglongbing (HLB), a devastating disease threatening citrus production in Brazil and worldwide. In this study, a draft whole-genome sequence of ‘Ca. L. asiaticus’ strain 9PA from a sweet orange (cultivar Pera) tree collected in São Paulo State, Brazil, is reported. The 9PA genome is 1,231,881 bp, including two prophages, with G+C content of 36.7%. This is the first report of a whole-genome sequence of ‘Ca. L. asiaticus’ from Brazil or South America. The 9PA genome sequence will enrich ‘Ca. L. asiaticus’ genome resources and facilitate HLB research and control in Brazil and the world.

scholarly journals ‘Candidatus Liberibacter asiaticus’ Titers in Citrus and Acquisition Rates by Diaphorina citri Are Decreased by Higher Temperature

Plant Disease ◽  
2013 ◽  
Vol 97 (12) ◽  
pp. 1563-1570 ◽  
Author(s):  
S. A. Lopes ◽  
F. Q. B. F. Luiz ◽  
E. C. Martins ◽  
C. G. Fassini ◽  
M. C. Sousa ◽  
...  
Keyword(s):  
Quantitative Polymerase Chain Reaction ◽  
Disease Spread ◽  
Diaphorina Citri ◽  
Candidatus Liberibacter Asiaticus ◽  
Ambient Temperatures ◽  
Air Temperatures ◽  
Temperature Regimes ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus ◽  
Higher Temperature

‘Candidatus Liberibacter asiaticus’ is the most prevalent Liberibacter sp. associated with huanglongbing (HLB) in Brazil. Within São Paulo state (SP), HLB has spread more rapidly to and reached higher incidence in regions with relatively mild (cooler) summer temperatures. This suggests that climate can influence disease spread and severity. ‘Ca. L. asiaticus’ titers on soft, immature leaves from infected ‘Valencia’ sweet orange plants exposed to different temperature regimes and adult Diaphorina citri fed for 48 h on these plants for ‘Ca. L. asiaticus’ acquisition were determined by quantitative polymerase chain reaction in two experiments. The first experiment included plants with three levels of infection, three incubation periods (IPs), and air temperatures favorable (14.6 to 28°C) and unfavorable (24 to 38°C) to ‘Ca. L. asiaticus’. The second included plants with severe late-stage infections, 10 IPs (based on 3-day intervals over 27 days), and three air temperature regimes (12 to 24, 18 to 30, and 24 to 38°C). Overall, ‘Ca. L. asiaticus’ titers and the percentages of ‘Ca. L. asiaticus’-positive psyllids were lower in plants maintained at the warmer temperature regime (24 to 38°C) than in plants maintained in the cooler regimes. The results suggest that the lower incidence and slower spread of ‘Ca. L. asiaticus’ to warmer regions of SP are related to the influence of ambient temperatures on titers of ‘Ca. L. asiaticus’ in leaves.

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