title: Development of the First Cisgenic Apple with Increased Resistance to Fire Blight.
abstract: The generation and selection of novel fire blight resistant apple genotypes would greatly improve the management of this devastating disease, caused by Erwinia amylovora. Such resistant genotypes are currently developed by conventional breeding, but novel breeding technologies including cisgenesis could be an alternative approach. A cisgenic apple line C44.4.146 was regenerated using the cisgene FB_MR5 from wild apple Malus ×robusta 5 (Mr5), and the previously established method involving A. tumefaciens-mediated transformation of the fire blight susceptible cultivar 'Gala Galaxy' using the binary vector p9-Dao-FLPi. The line C44.4.146 was shown to carry only the cisgene FB_MR5, controlled by its native regulatory sequences and no transgenes were detected by PCR or Southern blot following heat induced recombinase-mediated elimination of the selectable markers. Although this line contains up to 452 bp of vector sequences, it still matches the original definition of cisgenesis. A single insertion of T-DNA into the genome of 'Gala Galaxy' in chromosome 16 was identified. Transcription of FB_MR5 in line C44.4.146 was similar to the transcription in classically bred descendants of Mr5. Three independent shoot inoculation experiments with a Mr5 avirulent strain of Erwinia amylovora were performed using scissors or syringe. Significantly lower disease symptoms were detected on shoots of the cisgenic line compared to those of untransformed 'Gala Galaxy'. Despite the fact that the pathogen can overcome this resistance by a single nucleotide mutation, this is, to our knowledge, the first prototype of a cisgenic apple with increased resistance to fire blight.
authors.affiliation: Plant Pathology, Institute of Integrative Biology (IBZ), ETH Zurich, Zurich, Switzerland.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Kost
authors.affiliation: Plant Pathology, Institute of Integrative Biology (IBZ), ETH Zurich, Zurich, Switzerland.
authors.forename: Cesare
authors.initials: C
authors.lastname: Gessler
authors.affiliation: Agroscope, Institute for Plant Production Sciences, Wädenswil, Switzerland.
authors.forename: Melanie
authors.initials: M
authors.lastname: Jänsch
authors.affiliation: Julius Kühn-Institut (JKI), Federal Research Centre for Cultivated Plants, Institute for Breeding Research on Fruit Crops, Dresden, Germany.
authors.forename: Henryk
authors.initials: H
authors.lastname: Flachowsky
authors.affiliation: Agroscope, Institute for Plant Production Sciences, Wädenswil, Switzerland.
authors.forename: Andrea
authors.initials: A
authors.lastname: Patocchi
authors.affiliation: Plant Pathology, Institute of Integrative Biology (IBZ), ETH Zurich, Zurich, Switzerland.|Agroscope, Institute for Plant Production Sciences, Wädenswil, Switzerland.
authors.forename: Giovanni A L
authors.initials: GA
authors.lastname: Broggini
mesh_terms: D004269:DNA, Bacterial / Q000235:genetics; D060467:Disease Resistance / Q000235:genetics*; D044084:Erwinia amylovora / Q000472:pathogenicity; D005838:Genotype; D027845:Malus / Q000235:genetics* / Q000382:microbiology; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D030821:Plants, Genetically Modified / Q000235:genetics / Q000382:microbiology
chemical_list: D004269:DNA, Bacterial; C036483:T-DNA