Fire Blight Research Papers - Academia.edu (original) (raw)

- by Muhammad A Khan
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- Genetics, Molecular Markers, Agricultural Biotechnology, Disease resistance

Trunk injection is a novel delivery method for plant protective compounds in agriculture, which could increase the sustainability of fruit production through target-precise disease control and thus minimal exposure of the environment to the compounds. We evaluated whether trunk-injected antibiotics, copper and structural plant resistance activator prohexadione-calcium (PC) can significantly reduce fire blight on apples due to translocation of these compounds into the canopy. After 1-2 spring injections of oxytetracycline (OX), kasugamycin (KS) and copper chelate (CC), using four replicates per treatment, we evaluated inoculated apple trees for blossom and shoot blight incidence. In a separate study, after one spray or one injection of PC, we evaluated randomly selected and inoculated apple shoots for shoot blight severity. At high disease pressure, OX, KS and CC significantly reduced blossom blight providing control of 60.6, 31.7 and 15.5-17.8%, respectively. Fire blight has spread ...

Fire blight, caused by the necrogenic Gram-negative bacterium Erwinia amylovora, is one of the most destructive bacterial diseases of apple (Malus × domestica) and pear (Pyrus communis), among other members of the Rosaceae family. This disease poses a major economic threat to pome production as there are no available effective control measures. Genetic enhancement of fire blight resistance in apples is the best alternative for averting disease damage, loss of crop, and loss of whole trees. In this review, current knowledge of the molecular mechanisms of E. amylovora pathogenesis will be presented, especially those of effector proteins during bacterial–host interactions, as well as assessment of current understanding of the molecular controls of plant host resistance. Recent studies are elucidating how type III effectors modulate plant susceptibility and promote growth and dissemination of the pathogen. The large multidomain protein DspE is essential for E. amylovora pathogenesis and plays an additional role(s) in inhibiting salicylic acid-mediated innate immunity. On the other hand, the apple host defends itself against E. amylovora invasion by relying on quantitative resistance genes that likely respond to and/or complex with E. amylovora effectors. Thus far, a total of 27 quantitative trait loci (QTL) linked to fire blight resistance have been identified in different apple genetic backgrounds and in response to different E. amylovora strains. In addition to quantitative genetic approaches, microarray analysis of E. amylovora-challenged apple genotypes identified differential transcriptional expression in susceptible and resistant apples. Mechanisms of bacterial pathogenicity and plant host resistance offer intriguing scenarios as to how effector proteins in E. amylovora interact with groups of genes for resistance in the apple host, particularly when considering that these quantitative genes have small effects in plant defense against the invading bacterial pathogen. This collective knowledge will provide insights into bacterial pathogenesis and plant host resistance, as well as highlight implications and opportunities for developing fire blight-resistant apple cultivars.

- by awais khan
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- Genetics, Pathogenesis, Plant Biology, Quantitative Genetics

Trunk injection is a novel delivery method for plant protective compounds in agriculture. It could increase sustainability of fruit production through target-precise disease control. We evaluated trunk-injected antibiotics, copper chelate (CC), and prohexadione-calcium (PC) in control of fire blight on apples. After 1-2 spring injections of oxytetracycline (OX), kasugamycin (KS) and CC, we evaluated inoculated apple trees for blossom and shoot blight incidence. In a separate study, after spraying or injection of PC, we evaluated shoot blight severity after inoculation. At a high disease pressure, OX, KS and CC provided blossom blight control of 60.6, 31.7 and 15.5-17.8%, respectively. The same compounds provided control of shoot blight incidence of 60.7, 42 and 24.5-33.9%, respectively. The results indicate that shoots initially accumulate more of the injected compound than flowers, due to their higher transpiration driven by larger green tissue area. Sprayed PC reduced shoot blight severity for 25.6% and caused expected reduction of shoot length, while trunk-injected PC failed to cause any of these effects. This indicates that PC did not translocate into the canopy due to its strong binding in the xylem. With the development and use of injectable formulations, proper dosing, and optimal injection timing, delivered compounds could have more time for accumulation in the canopy and thus provide better fire blight control. Hence, trunk injection could become an effective option for fire blight control on apple trees.

- by awais khan
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- Genetics, Breeding, Agricultural Biotechnology, Innate immunity
- by Arantza Rico
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- DNA fingerprinting, Fire Blight
- by Stefano Piazza
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- Technology, Biology, Plant biotechnology, Medicine

- by Awais Khan
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- Genetics, Pathogenesis, Plant Biology, Quantitative Genetics

Objective Plant diseases can be a limiting factor in planting in an area. One of the new methods of producing disease resistant plants is the use of molecular markers. Molecular markers are able to detect and analyze important genes of resistance. Therefore, due to the severity of fire blight, the apple tree germplasm evaluation is necessary, so this research was carried out with the aim of determining resistance genes in some apple genotypes in Isfahan province using SCAR and SSR markers. Materials and methods Fresh and young leaves of 70 samples of apple trees in Isfahan were collected in early April and DNA was extracted by CTAB method. Then polymerase chain reaction was performed and DNA fragment was detected and DNAs lengths were measured. Results Results indicated that in all populations, none of the primers have a rare band or a typical band replication in 25 or less than 25% population, and 50 or less than 50% population. Semirom-Hana population had the greatest genetic diversity (Nei diversity index, Shannon, effective and different number of alleles) which shows greater genetic diversity

- by Agricultural Biotechnology Journal
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- DNA Extraction, Fire Blight, MOLECULER MARKERS

Fire blight is a devastating disease of apple and pear caused by the bacterium Erwinia amylovora. One of its main symptoms is canker formation on perennial tissues which may lead to the death of limbs and/or the entire tree. E. amylovora overwinters in cankers which play an important role in initiating fire blight epidemics. However, knowledge of pathogen biology in cankers is scarce, in part due to limitations of classical microbiology methods and the inability of most molecular techniques to distinguish live from dead cells. In this work, a viability digital PCR (v-dPCR) protocol using propidium monoazide (PMA) was developed, allowing for the first time the selective detection and absolute quantification of E. amylovora live cells in apple and pear cankers collected in two time periods. Some key factors affecting the v-dPCR performance were the maceration buffer composition, the target DNA amplicon length, the thermal cycle number and the use of sodium dodecyl sulfate or PMA enhancer for Gram-negative bacteria to improve the effect of PMA. In the future, this methodology could shed light on E. amylovora population dynamics in cankers and provide clues on the effect of management practices, host cultivar, host water/nutritional status, etc., on bacterial survival.

- by Ricardo Delgado Santander and +1
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- Microbiology, Biology, DNA (Forensic Science), Digital PCR
- by Muhammad A Khan
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- Plant Biology, Molecular Markers, Molecular Breeding, QTL mapping

Fire blight is a major pome fruit trees disease that is caused by the quarantine phytopathogenic Erwinia amylovora, leading to major losses, namely, in pear and apple productions. Nevertheless, no effective sustainable control treatments and measures have yet been disclosed. In that regard, antimicrobial peptides (AMPs) have been proposed as an alternative biomolecule against pathogens but some of those AMPs have yet to be tested against E. amylovora. In this study, the potential of five AMPs (RW-BP100, CA-M, 3.1, D4E1, and Dhvar-5) together with BP100, were assessed to control E. amylovora. Antibiograms, minimal inhibitory, and bactericidal concentrations (minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC), growth and IC50 were determined and membrane permeabilization capacity was evaluated by flow cytometry analysis and colony-forming units (CFUs) plate counting. For the tested AMPs, the higher inhibitory and bactericidal capacity was observed for ...

- by Conceição Santos
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- Microbiology, Biology, Fire Blight, Biomolecules

ABSTRACT This research was conducted to evaluate and compare responses to Erwinia amylovora infection by two host species, apple (Malus  domestica Borkh.) and pear (Pyrus communis L.), activated by salicylic acid (SA). Apple rootstocks, ‘MM-111’ (tolerant) and ‘MM-106’ (susceptible), and pear cultivars, ‘Harrow Sweet’ (tolerant) and ‘Spadona’ (susceptible) were inoculated under in vitro conditions from basal parts with E. amylovora Ea273. The pathogen activity was traced by adding bromocresol green, and evaluating the pH variation in the media; measuring necrosis progression rate and counting the number of necrosed internodes in a 240 h period. SA treatments on the in vitro shootlets were categorized by concentration (0.05, 0.1, 0.5, 1, 2, 5, 10 and 0 mg/L as control) and days of shootlets exposure to SA before infection (1, 3, 5, 7 days and 0, as control). SA did not cause similar effects on disease progress in the two tested species. SA failed to reduce symptom progression in apple rootstocks and increased pathogenicity of bacteria. In pear, SA presence in all treatments successfully decreased symptom progression rate in both cultivars. Longer exposure of pear shoots to SA resulted in more effective disease control. In both species, symptoms progression rates significantly corresponded to the pattern and severity of H2O2 generation in host tissues. It appears that apple and pear respond differently to the SAR activation by SA. These dissimilar responses of hosts could be derived from contrasting behavior of reactive oxygen radical scavenging enzymes in the two species.

- by Hamid Abdollahi
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- Horticulture, Biology, Fire Blight, Blight

Fifty-one strains of Erwinia amylovora isolated from nine host plants in Bulgaria were characterized phenotypically and identified by the API 20E and BIOLOG system. The identification was confirmed by PCR amplification of a specific region of the plasmid pEA29 and the genome ams region. The phenotypic diversity of the strains was studied on the basis of their API 20E and BIOLOG metabolic profiles, as well as of their SDS-PAGE protein profile. Metabolic diversity among the strains was established, but no connection with the origin of the strains was revealed. The Bulgarian strains showed API 20E metabolic profiles not found in previous studies of E. amylovora. The strains formed a homogenous group on the basis of their protein profiles. All the strains were sensitive to the antibiotics streptomycin, tetracycline and oxytetracycline. This study was an initial step towards an investigation of the diversity and evolution in the Bulgarian population of E. amylovora, and it was the first ...

- by Katerina Stefanova
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- Biology, Bulgaria, Medicine, Phylogeny
- by George Sundin
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- Biology, Tobacco, Medicine, Biological Sciences
- by Hamid Abdollahi
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- Horticulture, Biology, Fire Blight, Erwinia

Abstract: Fire blight, a devastating disease of apple, pear, and many Rosaceae species worldwide is caused by enterobacterium Erwinia amylovora. At present, disease control mainly relies on antibiotics, prevention, and eradication-based strategies. Prevention and eradication is expensive, while resistance development for antibiotics can reduce their efficacy over time. Apple varieties do, however, exhibit a wide range of relative tolerance to fire blight. As part of our long-term strategy to design sustainable fire blight controls, we ...

- by Awais Khan
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- Biology, Disease resistance, Marker assisted selection, Fire Blight

A fire blight resistance QTL explaining 34.3%–46.6% of the phenotypic variation was recently identified on linkage group 7 of apple cultivar ‘Fiesta’ (F7). However, markers flanking this QTL were AFLP and RAPD markers unsuitable for marker-assisted selection (MAS). Two RAPD markers bracketing the QTL have been transformed into SCAR (sequence-characterized amplified region) markers, and an SSR marker specific for the region was developed. Pedigree analysis of ‘Fiesta’ with these markers enabled tracking of the F7 QTL allele back to ‘Cox’s Orange Pippin’. Stability of the effect of this QTL allele in different backgrounds was analyzed by inoculating progeny plants of a cross between ‘Milwa’, a susceptible cultivar, and ‘1217’, a moderately resistant cultivar, and a set of cultivars that carry or lack the allele conferring increased fire blight resistance. Progenies and cultivars that carried both markers were significantly more resistant than those that did not carry both markers, ind...

- by Charles-eric Durel
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- Genetics, Molecular Markers, Agricultural Biotechnology, Disease resistance

Fire blight caused by the bacterium Erwinia amylovora is a severe threat to apple and pear orchards worldwide. Apple varieties exhibit a wide range of relative susceptibility/tolerance to fire blight. Although, no monogenic resistance against fire blight has been identified yet, recent evidence indicates the existence of quantitative resistance. Potential sources of fire blight resistance include several wild Malus species and some apple cultivars. F1 progenies of ‘Fiesta’×‘Discovery’ were inoculated with the Swiss strain Ea 610 and studied under controlled conditions to identify quantitative trait loci (QTLs) for fire blight resistance. Disease was evaluated at four time points after inoculation. Shoot lesion length and the area under disease progress curve (AUDPC) values were used for QTL analysis. One significant (LOD score of 7.5–8.1, p<0.001) QTL was identified on the linkage group 7 of ‘Fiesta’ (F7). The F7 QTL explained about 37.5–38.6% of the phenotypic variation.

- by Muhammad Khan
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- Plant Biology, Molecular Markers, Molecular Breeding, QTL mapping

- by muhammad Asghar Khan
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- Genetics, Molecular Markers, Agricultural Biotechnology, Disease resistance
- by Brion Duffy
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- Genetics, Molecular Markers, Agricultural Biotechnology, Disease resistance
- by Brion Duffy
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- Plant Biology, Molecular Markers, Molecular Breeding, QTL mapping