Search results (4)


Rapid movement of <i>Candidatus</i> Liberibacter asiaticus on ‘Hamlin’ sweet orange and ‘Swingle’ citrumelo trunks

Citation
Pulici et al. (2022). PhytoFrontiers™
Names
Ca. Liberibacter asiaticus
Subjects
General Medicine
Abstract
Huanglongbing (HLB), caused by phloem-limited Candidatus Liberibacter asiaticus (CLas) is the primary limiting factor of production in most citrus regions of the world. After infection CLas is transported systemically throughout the phloem tissues following the source-sink movement. Split-root rhizoboxes and one-side graft inoculation above the split trunk was used to understand if vertical distance of the inoculum source and different anatomical structures (grafted or seedlings trees) can affect the speed of the CLas movement as well as the effects of the seasonality on these movements. The time for CLas to reach the roots was not affected by either distance of the inoculum source or tree type. The season infection period appears to have an important effect on CLas movement. Trees inoculated in the summer had fast and uniform movement (first detection at 4 weeks after inoculation). Plants inoculated in the winter had a slow and uneven movement (first CLas detection at 14 weeks after inoculation). Our results indicate that summer and spring are the seasons of CLas down and lateral movement but is independent of vertical distance of inoculum source or anatomical structures of the plants. The findings from this study aid in the management of HLB in the field as well as improve the methods for CLas detection.

Physiological and transcriptomic analysis of Candidatus Phytoplasma pruni infection in Prunus persica

Citation
Wright et al. (2022). PhytoFrontiers™
Names
Ca. Phytoplasma pruni
Subjects
General Medicine
Abstract
Candidatus Phytoplasma pruni is the causative agent of X-disease on peach (Prunus persica) trees. Infected trees exhibit premature yellowing, leaf necrosis causing a shot-hole appearance, limb dieback, and eventual death. How pathogen infection leads to these symptoms is unknown. This study undertook a modern characterization of the disease by assessing the physiological and transcriptomic consequences of phytoplasma infection. Phytoplasma titer was high in the symptomatic tissues and undetected or at low titer in asymptomatic tissues. Symptomatic leaves had a significant decrease in chlorophyll a, chlorophyll b, and carotenoids. Transcriptomic analysis showed alterations in genes related to phytohormone synthesis and signaling, circadian rhythms, lignification, and sugar synthesis and transport. Several transcripts that may be related to symptom development were identified. Collectively these data give a much clearer picture of symptom development in Ca. P. pruni infected P. persica and provide several avenues of further research in determining how Ca. P. pruni interacts with its host to elicit the observed symptoms.

Update and validation of the 16S rDNA qPCR assay for the detection of three ‘Candidatus’ Liberibacter species following current MIQE guidelines and workflow

Citation
Osman et al. (2022). PhytoFrontiers™
Names
Ca. Liberibacter asiaticus Liberibacter
Subjects
General Medicine
Abstract
An updated real-time multiplex quantitative polymerase chain reaction (qPCR) assay was designed and validated for the simultaneous detection of three ‘Candidatus Liberibacter species’ (CLsp), Ca. Liberibacter asiaticus (CLas), africanus (CLaf) and americanus (CLam), associated with the Huanglongbing (HLB) disease of citrus. The multiplex assay was designed based on the previously published qPCR assay by Li et al., 2006, taking into consideration all available CLsp 16S rRNA gene sequences in the GenBank and the MIQE guidelines and workflow for qPCR optimization, which became available after 2006. When using the updated multiplex CLsp qPCR assay compared to singleplex qPCR, no significant increase in Cq values was detected. The specificity and sensitivity of the updated qPCR assay was optimal and measuring the intra and inter assay variations confirmed the reproducibility and repeatability of the assay. The assay was also successfully used with a large number of diverse samples, at independent laboratories in four countries, thus demonstrating its transferability, applicability, practicability, and robustness as different qPCR reaction conditions or instruments had a minor effect on Cq values. This updated multiplex CLsp qPCR assay can be used in a variety of citrus surveys, germplasm, or nursery stock programs that require different pathogen detection tools for their successful operation. Keywords: Citrus greening disease, COX internal DNA control; validation; citrus germplasm; budwood; citrus nursery, citrus survey, regulatory diagnostics, Citrus Clonal Protection Program (CCPP), National Clean Plant Network (NCPN)

Multi-omics Comparison Reveals Landscape of Citrus limon and Citrus sinensis Response to ‘Candidatus Liberibacter asiaticus’

Citation
Chin et al. (2021). PhytoFrontiers™ 1 (2)
Names
Ca. Liberibacter asiaticus
Subjects
General Medicine
Abstract
Comparison of the metabolic changes prior to symptom development upon infection with Candidatus Liberibacter asiaticus (CLas), the bacterium associated with citrus greening disease, between citrus hosts with different tolerances is lacking. The objective of this study was to compare the early response of Lisbon lemon (Citrus limon) and Washington navel orange (Citrus sinensis [L.] Osbeck), two citrus species commercially important to California, to CLas through graft inoculation. Here, we compare the transcriptome, proteome, and metabolome response, using RNA sequencing, liquid chromatography tandem mass spectrometry, and 1H nuclear magnetic resonance, respectively, from our two recently published studies examining the response of the lemon and navel oranges separately, and introduce new micronutrient data from inductively coupled plasma mass spectrometry analysis, focusing on lemons at 10 and 14 weeks postgrafting (wpg), and navels at 8 and 18 wpg, prior to symptom development. Several micronutrients accumulated in presymptomatic infected lemons compared with controls, whereas little change was observed in the navels. Photosynthesis proteins were substantially altered by CLas infection in navels, with fewer changes observed in lemons. The metabolome differed between control and infected navels throughout infection, although differences between control and infected lemons were identified only after symptom expression. Taken together, these findings highlight differences in response to CLas between two varieties with differing tolerances. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .