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Comparison of Methods of Acibenzolar-S-Methyl Application for Post-Infection Fire Blight Suppression in Pear and Apple — Plant Disease

Comparison of Methods of Acibenzolar-S-Methyl Application for Post-Infection Fire Blight Suppression in Pear and Apple — Plant Disease | plant pathology, bacteria and plants | Scoop.it
Greenhouse-grown, 1-year-old potted ‘Bosc’ pear and apple rootstock cultivars ‘M.9’ and ‘M.26’ were inoculated with the fire blight pathogen, Erwinia amylovora, and subjected to trunk paint, root drench, or foliar spray treatments with acibenzolar-S-methyl (ASM, 4 to 30 mg a.i./tree) to induce systemic acquired resistance. Each method of ASM treatment suppressed fire blight canker expansion by 22 to 25%. Furthermore, ASM application method and ASM treatment timing (at or ±3 weeks relative to inoculation) interacted significantly (P ≤ 0.02) in each experiment. A root drench was most effective when applied 3 weeks before inoculation (36% suppression) whereas trunk paints and foliar sprays were more effective at inoculation (43 and 34%, suppression, respectively). Sizes of fire blight cankers in potted apple rootstocks M.9 and M.26 (under scions ‘Gala’ or ‘Cameo’) inoculated directly with the pathogen were reduced by 82 and 87% after two pretreatments of ASM applied as a trunk paint or root drench, respectively. Expression of pathogenesis-related (PR) genes PR-1 and -2 in apple leaves sampled after an ASM trunk paint were elevated significantly (P ≤ 0.05) relative to control trees for at least 9 weeks after treatment. Results of this study are being used to guide field research on postinfection therapy with ASM in 1- to 10-year-old pear and apple trees where fire blight has proven difficult to manage with therapeutic pruning only.

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Fire-blight resistant apples - ETH (2014)

Fire-blight resistant apples - ETH (2014) | plant pathology, bacteria and plants | Scoop.it

Researchers from ETH Zurich and the Julius Kühn Institute in Germany have created the first fire-blight-resistant apple. With the aid of so-called cis-genetic engineering, they transfered a resistance gene from a wild apple into the genome of a Gala apple. Tests in the greenhouse indicate that the gene is effective in protecting the tree against the disease.


Fruit farmers dread fire blight. The infection keeps flaring up again and causes considerable damage to apple plantations. In 2007, when the last major epidemic hit Switzerland, the damage the country suffered cost CHF 50 million and 250,000 trees had to be destroyed. Farmers primarily use sprays containing the antibiotic streptomycin against the pathogen, the bacterium Erwinia amylovora – a controversial method to save fruit trees and harvests. 


A team of researchers headed by ETH-Zurich plant pathologist Cesar Gessler... report a genetically modified apple of the popular Gala variety... that is resistant to fire blight... Gessler and his collaborators were using so-called cis-genetic engineering. Additional genes are incorporated... using the biotechnological methods available. However, these are not foreign to the species, as in the case of so-called transgenic organisms. Instead, the apple only receives genes from another variety of apple... 

 

Although Gessler has now been able to reap the fruits of his years of research and development work, he does not believe that fruit farmers will ever grow these cis-gene apples. On the one hand, there is a still a moratorium on genetic engineering in Switzerland, banning the cultivation of genetically modified organisms (GMO), which also affects cis-gene crops. “Moreover... unlike in the USA, here in this country and the EU we don’t assess individual products for approval, but rather the technology used while growing them. Unless the attitudes and legislation change, the cis-gene Gala apple will never be grown”... 

 

Gessler is not a GMO hardliner looking to push genetically modified crops at all cost. “In the case of crops like the banana, cassava or apples, which can be reproduced via clones, however, the use of genetic engineering makes sense,” he says. Consumers have to realise that an organically grown Gala apple is treated with copper and sulphur at least twenty-five times, which has a serious impact on the soils, air and groundwater. Scab and fire-blight-resistant cis-gene Gala apples do not have to be treated in this way, making them more environmentally friendly than their bio-counterparts.

 

Breeding in the resistance gene via conventional cultivation, however, takes too long, says Gessler. The Gala variety would have to be crossed with a wild apple and the undesired properties of the wild apple bred out again in subsequent generations, which can take many decades and ultimately results in a new variety... 

 

https://www.ethz.ch/en/news-and-events/eth-news/news/2014/03/resistent-gegen-feuerbrand.html


Original article:  http://dx.doi.org/10.1111/pbi.12177

 


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Gene-for-gene tolerance to bacterial wilt in Arabidopsis, in MPMI

Gene-for-gene tolerance to bacterial wilt in Arabidopsis, in MPMI | plant pathology, bacteria and plants | Scoop.it
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Control of fire blight (Erwinia amylovora) on apple trees with trunk-injected plant resistance inducers and antibiotics and assessment of induction of pathogenesis-related protein genes...

Management of fire blight is complicated by limitations on use of antibiotics in agriculture, antibiotic resistance development, and limited efficacy of alternative control agents. Even though successful in control, preventive antibiotic sprays also affect non-target bacteria, aiding the selection for resistance which could ultimately be transferred to the pathogen Erwinia amylovora. Trunk injection is a target-precise pesticide delivery method that utilizes tree xylem to distribute injected compounds. Trunk injection could decrease antibiotic usage in the open environment and increase the effectiveness of compounds in fire blight control. In field experiments, after 1–2 apple tree injections of either streptomycin, potassium phosphites (PH), or acibenzolar-S-methyl (ASM), significant reduction of blossom and shoot blight symptoms was observed compared to water injected control trees. Overall disease suppression with streptomycin was lower than typically observed following spray applications to flowers. Trunk injection of oxytetracycline resulted in excellent control of shoot blight severity, suggesting that injection is a superior delivery method for this antibiotic. Injection of both ASM and PH resulted in the significant induction of PR-1, PR-2, and PR-8 protein genes in apple leaves indicating induction of systemic acquired resistance (SAR) under field conditions. The time separating SAR induction and fire blight symptom suppression indicated that various defensive compounds within the SAR response were synthesized and accumulated in the canopy. ASM and PH suppressed fire blight even after cessation of induced gene expression. With the development of injectable formulations and optimization of doses and injection schedules, the injection of protective compounds could serve as an effective option for fire blight control.
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Engineering fire blight resistance into the apple cultivar ‘Gala’ using the FB_MR5 CC-NBS-LRR resistance gene of Malus × robusta 5 - Broggini - 2014 - Plant Biotechnology Journal - Wiley Online Lib...

Engineering fire blight resistance into the apple cultivar ‘Gala’ using the FB_MR5 CC-NBS-LRR resistance gene of Malus × robusta 5 - Broggini - 2014 - Plant Biotechnology Journal - Wiley Online Lib... | plant pathology, bacteria and plants | Scoop.it

The fire blight susceptible apple cultivar Malus × domestica Borkh. cv. ‘Gala’ was transformed with the candidate fire blight resistance geneFB_MR5 originating from the crab apple accession Malus × robusta 5 (Mr5). A total of five different transgenic lines were obtained. All transgenic lines were shown to be stably transformed and originate from different transgenic events. The transgenic lines express theFB_MR5 either driven by the constitutive CaMV 35S promoter and the ocs terminator or by its native promoter and terminator sequences. Phenotyping experiments were performed with Mr5-virulent and Mr5-avirulent strains of Erwinia amylovora, the causal agent of fire blight. Significantly less disease symptoms were detected on transgenic lines after inoculation with two different Mr5-avirulent E. amylovorastrains, while significantly more shoot necrosis was observed after inoculation with the Mr5-virulent mutant strain ZYRKD3_1. The results of these experiments demonstrated the ability of a single gene isolated from the native gene pool of apple to protect a susceptible cultivar from fire blight. Furthermore, this gene is confirmed to be the resistance determinant of Mr5 as the transformed lines undergo the same gene-for-gene interaction in the host–pathogen relationship Mr5–E. amylovora.

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