scholarly journals Development of a Nested Quantitative Real-Time PCR for Detecting Phytophthora cinnamomi in Persea americana Rootstocks

Plant Disease ◽  
2013 ◽  
Vol 97 (8) ◽  
pp. 1012-1017 ◽  
Author(s):  
J. Engelbrecht ◽  
T. A. Duong ◽  
N. van den Berg
Keyword(s):  
Real Time ◽  
Phytophthora Cinnamomi ◽  
Low Cost ◽  
Persea Americana ◽  
Economic Losses ◽  
In Planta ◽  
Phytophthora Root Rot ◽  
Disease Tolerance ◽  
Quantitative Manner ◽  
Pathogen Dna

Phytophthora cinnamomi causes Phytophthora root rot (PRR) in avocado (Persea americana), an important disease that causes severe economic losses to the avocado industry globally. To date, no PRR-resistant avocado rootstock variety has been discovered, although certain rootstock varieties have been shown to be more tolerant than others. In this study, we developed an accurate, low cost assay for in planta quantification of P. cinnamomi to evaluate disease tolerance. A nested real-time polymerase chain reaction assay was developed to sensitively detect pathogen DNA in plant tissues. Root samples from a highly tolerant (Dusa) and less tolerant (R0.12) rootstock were collected at 0, 3, 7, 14, and 21 days after inoculation with P. cinnamomi and used for pathogen quantification. Nested primers developed in this study were specific and sensitive and could detect P. cinnamomi in root tissues. The amount of P. cinnamomi quantified in roots was significantly higher in the less-tolerant R0.12 plants when compared with the highly tolerant Dusa plants at all time points. This study has confirmed the known status of disease tolerance of Dusa and R0.12 avocado rootstocks in a quantitative manner and provides a reliable molecular tool to assist with industry breeding programs for the selection of PRR-resistant avocado rootstock varieties.

scholarly journals Pathogenicity and a TaqMan Real-Time PCR for Specific Detection of Pantoea allii, a Bacterial Pathogen of Onions

Plant Disease ◽  
2019 ◽  
Vol 103 (12) ◽  
pp. 3031-3040 ◽  
Author(s):  
Shabnam Rahimi-Khameneh ◽  
Sanni Hsieh ◽  
Renlin Xu ◽  
Tyler J. Avis ◽  
Sean Li ◽  
...  
Keyword(s):  
Real Time ◽  
Real Time Pcr ◽  
Phylogenetic Analyses ◽  
Similarity Index ◽  
Taqman Probe ◽  
Economic Losses ◽  
In Planta ◽  
Pcr Assay ◽  
Blind Test ◽  
Reliable Detection

Bacterial diseases of onion are reported to cause significant economic losses. Pantoea allii Brady, one of the pathogens causing the center rot on onions, has not yet been reported in Canada. We report the pathogenicity of P. allii on commercially available Canadian green onions (scallions). All P. allii-inoculated plants, irrespective of the inoculum concentration, exhibited typical leaf chlorotic discoloration on green onion leaves, which can reduce their marketability. Reisolation of P. allii from infected scallion tissues and reidentification by sequencing and phylogenetic analyses of the leuS gene suggest that the pathogen can survive in infected tissues 21 days after inoculation. This is the first report of P. allii as a potential pathogen of green onions. This study also reports the development and validation of a TaqMan real-time PCR assay targeting the leuS gene for reliable detection of P. allii in pure cultures and in planta. A 642-bp leuS gene fragment was targeted because it showed high nucleotide diversity and positively correlated with genome-based average nucleotide identity with respect to percent similarity index and identity of Pantoea species. The assay specificity was validated using 61 bacterial and fungal strains. Under optimal conditions, the selected primers and FAM-labeled TaqMan probe were specific for the detection of nine reference P. allii strains by real-time PCR. The 52 strains of other Pantoea spp. (n = 25), non-Pantoea spp. (n = 20), and fungi/oomycetes (n = 7) tested negative (no detectable fluorescence). Onion tissues spiked with P. allii, naturally infested onion bulbs, greenhouse infected green onion leaf samples, as well as an interlaboratory blind test were used to validate the assay specificity. The sensitivities of a 1-pg DNA concentration and 30 CFU are comparable to previously reported real-time PCR assays of other bacterial pathogens. The TaqMan real-time PCR assay developed in this study will facilitate reliable detection of P. allii and could be a useful tool for screening onion imports or exports for the presence of this pathogen.

scholarly journals Expression of several Phytophthora cinnamomi putative RxLRs provides evidence for virulence roles in avocado

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0254645
Author(s):  
Melissa Joubert ◽  
Robert Backer ◽  
Juanita Engelbrecht ◽  
Noëlani van den Berg
Keyword(s):  
Phytophthora Cinnamomi ◽  
Expression Profiles ◽  
Functional Characterization ◽  
Effector Proteins ◽  
Virulence Determinants ◽  
In Planta ◽  
Phytophthora Root Rot ◽  
Host Immune Responses ◽  
Rxlr Effectors ◽  
Pathogen Fitness

Phytophthora cinnamomi is a plant pathogenic oomycete that causes Phytophthora root rot of avocado (PRR). Currently, there is a limited understanding of the molecular interactions underlying this disease. Other Phytophthora species employ an arsenal of effector proteins to manipulate host physiology, of which the RxLR effectors contribute to virulence by interfering with host immune responses. The aim of this study was to identify candidate RxLR effectors in P. cinnamomi that play a role in establishing PRR, and to infer possible functions for these effectors. We identified 61 candidate RxLR genes which were expressed during infection of a susceptible avocado rootstock. Several of these genes were present in multiple copies in the P. cinnamomi genome, suggesting that they may contribute to pathogen fitness. Phylogenetic analysis of the manually predicted RxLR protein sequences revealed 12 P. cinnamomi RxLRs that were related to characterised effectors in other Phytophthora spp., providing clues to their functions in planta. Expression profiles of nine more RxLRs point to possible virulence roles in avocado–highlighting a way forward for studies of this interaction. This study represents the first investigation of the expression of P. cinnamomi RxLR genes during the course of avocado infection, and puts forward a pipeline to pinpoint effector genes with potential as virulence determinants, providing a foundation for the future functional characterization of RxLRs that contribute to P. cinnamomi virulence in avocado.

scholarly journals 14C-Photosynthesis Partitioning in Avocado Trees as Influenced by Shoot Development

HortScience ◽  
1993 ◽  
Vol 28 (8) ◽  
pp. 850-852 ◽  
Author(s):  
Anthony W. Whiley ◽  
Bruce Schaffer
Keyword(s):  
Root Rot ◽  
Liquid Scintillation ◽  
Phytophthora Cinnamomi ◽  
Management Strategies ◽  
Persea Americana ◽  
Plant Tissues ◽  
Quiescent State ◽  
Assimilation Rate ◽  
Phytophthora Root Rot ◽  
C Partitioning

The influence of shoot age on 14C partitioning in potted avocado (Persea americana var. americana Mill.) trees was determined. The oldest leaf of actively growing shoots and the youngest leaf of previously matured shoots were exposed to 14CO2 18 and 34 days after budbreak (DABB) of new shoots. At these times, treated leaves had a positive net CO2 assimilation rate and, therefore, were considered to be net C exporters. Sixteen days after 14C exposure, separate plant tissues were harvested, dried, weighed, and oxidized. The percentage of 14C in each tissue was determined by liquid scintillation spectrometry. Photoassimilates were translocated acropetally and basipetally from all treated leaves. However, at 18 DABB, developing leaves of actively growing shoots seemed to be the strongest sink for C assimilated by the oldest leaf of these shoots, whereas the roots were the strongest sink for C assimilated by the youngest leaf of the previously matured shoots. By 34 DABB, roots were the strongest sink for C assimilated by leaves of new and previously matured shoots. These data are useful in developing improved management strategies for controlling phytophthora root rot (incited by Phytophthora cinnamomi Rands) in avocados by systemic phosphonate fungicides translocated in the photoassimilate pathway. Thus, phosphonates should be applied after shoots have matured and most of the canopy is in a quiescent state for maximum translocation to the roots.

scholarly journals Advances in Understanding Defense Mechanisms in Persea americana Against Phytophthora cinnamomi

2021 ◽  
Vol 12 ◽  
Author(s):  
Noëlani van den Berg ◽  
Velushka Swart ◽  
Robert Backer ◽  
Alicia Fick ◽  
Raven Wienk ◽  
...  
Keyword(s):  
Defense Response ◽  
Defense Mechanisms ◽  
Phytophthora Cinnamomi ◽  
Current Knowledge ◽  
Persea Americana ◽  
Cell Wall Modification ◽  
Callose Deposition ◽  
Important Distinction ◽  
Phytophthora Root Rot ◽  
Important Host

Avocado (Persea americana) is an economically important fruit crop world-wide, the production of which is challenged by notable root pathogens such as Phytophthora cinnamomi and Rosellinia necatrix. Arguably the most prevalent, P. cinnamomi, is a hemibiotrophic oomycete which causes Phytophthora root rot, leading to reduced yields and eventual tree death. Despite its’ importance, the development of molecular tools and resources have been historically limited, prohibiting significant progress toward understanding this important host-pathogen interaction. The development of a nested qPCR assay capable of quantifying P. cinnamomi during avocado infection has enabled us to distinguish avocado rootstocks as either resistant or tolerant - an important distinction when unraveling the defense response. This review will provide an overview of our current knowledge on the molecular defense pathways utilized in resistant avocado rootstock against P. cinnamomi. Notably, avocado demonstrates a biphasic phytohormone profile in response to P. cinnamomi infection which allows for the timely expression of pathogenesis-related genes via the NPR1 defense response pathway. Cell wall modification via callose deposition and lignification have also been implicated in the resistant response. Recent advances such as composite plant transformation, single nucleotide polymorphism (SNP) analyses as well as genomics and transcriptomics will complement existing molecular, histological, and biochemical assay studies and further elucidate avocado defense mechanisms.

scholarly journals An UAV scheduling and planning method for post-disaster survey

2014 ◽  
Vol XL-2 ◽  
pp. 169-172 ◽  
Author(s):  
G. Q. Li ◽  
X. G. Zhou ◽  
J. Yin ◽  
Q. Y. Xiao
Keyword(s):  
Real Time ◽  
High Efficiency ◽  
Population Distribution ◽  
Low Cost ◽  
Economic Losses ◽  
The Real ◽  
The Road ◽  
Scheduling Method ◽  
High Flexibility ◽  
Post Disaster

Annually, the extreme climate and special geological environments lead to frequent natural disasters, e.g., earthquakes, floods, etc. The disasters often bring serious casualties and enormous economic losses. Post-disaster surveying is very important for disaster relief and assessment. As the Unmanned Aerial Vehicle (UAV) remote sensing with the advantage of high efficiency, high precision, high flexibility, and low cost, it is widely used in emergency surveying in recent years. As the UAVs used in emergency surveying cannot stop and wait for the happening of the disaster, when the disaster happens the UAVs usually are working at everywhere. In order to improve the emergency surveying efficiency, it is needed to track the UAVs and assign the emergency surveying task for each selected UAV. Therefore, a UAV tracking and scheduling method for post-disaster survey is presented in this paper. In this method, Global Positioning System (GPS), and GSM network are used to track the UAVs; an emergency tracking UAV information database is built in advance by registration, the database at least includes the following information, e.g., the ID of the UAVs, the communication number of the UAVs; when catastrophe happens, the real time location of all UAVs in the database will be gotten using emergency tracking method at first, then the traffic cost time for all UAVs to the disaster region will be calculated based on the UAVs’ the real time location and the road network using the nearest services analysis algorithm; the disaster region is subdivided to several emergency surveying regions based on DEM, area, and the population distribution map; the emergency surveying regions are assigned to the appropriated UAV according to shortest cost time rule. The UAVs tracking and scheduling prototype is implemented using SQLServer2008, ArcEnginge 10.1 SDK, Visual Studio 2010 C#, Android, SMS Modem, and Google Maps API.

scholarly journals Real-Time Driver Alert System Using Raspberry Pi

2019 ◽  
Vol 17 (2) ◽  
pp. 193-203 ◽  
Author(s):  
Jie Yi Wong ◽  
Phooi Yee Lau
Keyword(s):  
Real Time ◽  
Low Cost ◽  
Economic Losses ◽  
Raspberry Pi ◽  
Alert System ◽  
Driving Experience ◽  
The Road ◽  
Car Accidents ◽  
Passenger Safety ◽  
On The Road

Malaysia has been ranked as one of the country in the world with deadliest road. Based on the statistic, there are around 7000 to 8000 people in the country died on the road among the population of 31 million Malaysians every year. In general, Advances Driver Assistance System (ADAS) aims to improve not only the driving experience but also consider the overall passenger safety. In recent years, driver drowsiness has been one of the major causes of road accidents, which can lead to severe physical injuries, deaths and significant economic losses. In this paper, a vison-based real-time driver alert system aimed mainly to monitor the driver’s drowsiness level and distraction level is proposed. This alert system could reduce the fatalities of car accidents by detecting driver’s face, detecting eyes region using facial landmark and calculating the rate of eyes closure in order to monitor the drowsiness level of the driver. Later, the system is embedded into the Raspberry Pi, with a Raspberry Pi camera and a speaker buzzer, and is used to alert the driver in real-time, by providing a beeping sound. Experimental results show that proposed system is practical and low-cost which could (1) embed the drowsiness detection module, and (2) provide alert notification to the driver when the driver is inattentive, using a medium loud beeping sound, in real-time.

A Diagnostic TaqMan Real-Time PCR Assay for in planta Detection and Quantification of Colletotrichum theobromicola, Causal Agent of Boxwood Dieback

Plant Disease ◽  
2021 ◽  
Author(s):  
Harleen Kaur ◽  
Raghuwinder Singh ◽  
Vinson P. Doyle ◽  
Rodrigo Valverde
Keyword(s):  
Real Time ◽  
Real Time Pcr ◽  
Species Complex ◽  
The United States ◽  
Taqman Probe ◽  
In Planta ◽  
Pcr Assay ◽  
Phytophthora Root Rot ◽  
Specificity And Sensitivity ◽  
Detection And Quantification

Boxwood dieback, caused by Colletotrichum theobromicola, is spreading at an alarming rate in the boxwood industry in the United States. Although C. theobromicola has been accepted as a distinct species within the C. gloeosporioides species complex, it is difficult to distinguish it from other closely related species based on morphology. Moreover, molecular identification of C. theobromicola requires amplification and sequencing of multiple loci, which can be expensive and time consuming. Therefore, a diagnostic TaqMan real-time PCR assay was developed for early and accurate detection and quantification of C. theobromicola in boxwood. The study involved the design of species-specific primers and a TaqMan probe to differentiate C. theobromicola from other closely related Colletotrichum species. The primers and probe discriminate between C. theobromicola and other species in the C. gloeosporioides species complex and can detect C. theobromicola at very low concentrations, illustrating the high specificity and sensitivity of the assay. This TaqMan real-time PCR assay accurately and rapidly distinguishes boxwood dieback from other diseases with similar symptomatology including, Macrophoma blight, Phytophthora root rot, and Volutella blight, as well as some disorders produced by abiotic agents.

Influence of Phytophthora root rot on mineral nutrient concentrations in avocado leaves

1987 ◽  
Vol 27 (1) ◽  
pp. 173 ◽  
Author(s):  
AW Whiley ◽  
KG Pegg ◽  
JB Saranah ◽  
PW Langdon
Keyword(s):  
Root Rot ◽  
Potassium Hydroxide ◽  
Phytophthora Cinnamomi ◽  
Chloride Content ◽  
Persea Americana ◽  
Mineral Nutrient ◽  
Nutrient Concentrations ◽  
Phytophthora Root Rot ◽  
Zinc Levels ◽  
Chloride Concentrations

Leaf nutrient concentrations were measured in avocado trees (Persea americana Mill. cv. Fuerte) which were recovering from root rot (Phytophthora cinnamomi Rands) following treatment with fungicides. Trees with visible Phytophthora root rot symptoms had higher leaf chloride concentrations in 4- month-old leaves (0.35%) which increased to 0.5% in 8-month-old leaves, compared with chloride concentrations in leaves from trees that had regained health of 0.13-0.27% and 0.09-0.24% in 4- and 8-month-old leaves respectively. Leaf tip and marginal burn symptoms in untreated control trees were present in leaves with 0.5% chloride content. Trees which were previously infected, but had regained health, had higher leaf concentrations of nitrogen (2.86-3.02%), phosphorus (0.18-0.19%), sulfur (0.24-0.27%), zinc (33.2 mg kg-1) and boron (13.4-17.7 mg kg-1) than leaves on those trees showing severe root rot symptoms (2.59% nitrogen, 0.16% sulfur, 24.4 mg kg-1 zinc, and 8.1 mg kg-1 boron). Fungicidal treatments, which included the injection of phosphite, potassium hydroxide and zinc sulfate into trees, did not contribute significantly to leaf phosphorus, potassium or zinc levels.

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