Development of cisgenic lines of apple to enhance resistance to fire blight
Giovanni Broggini: Molecular Plant Breeding, Institute of Agricultural Sciences, ETHZ
<div><span lang="EN-US"><span face="Calibri" style="font-family:Calibri;" size="3">Almost all commercially successful apple cultivars are susceptible to fire blight, a devastating disease caused by the bacterium </span><i><span face="Calibri" style="font-family:Calibri;" size="3">Erwinia amylovora</span></i><span face="Calibri" style="font-family:Calibri;" size="3">. To control the disease in apple orchards, several approaches were attempted, including large-scale eradication programs and application of antibiotics or biocontrol agents. In addition, apple genotypes showing natural resistance to the disease were identified and allowed the study of the genetic architecture underlying the resistance mechanism. Breeding for fire blight resistant cultivars of commercial value was initiated, but this process is hampered by the long juvenility and the allogamy of apple. With each cross the traits of a successful parent cultivar are recombined. The breeder must identify a superior combination of favorable traits, leading to a new cultivar, amidst a large number of seedlings. The investigation of the </span><i><span face="Calibri" style="font-family:Calibri;" size="3">Malus</span></i><span face="Calibri" style="font-family:Calibri;" size="3"> x </span><i><span face="Calibri" style="font-family:Calibri;" size="3">robusta</span></i><span face="Calibri" style="font-family:Calibri;" size="3"> 5 resistance led to the cloning of the fire blight resistance gene</span><b><i><span><span face="Calibri" style="font-family:Calibri;" size="3"> </span></span></i></b><i><span face="Calibri" style="font-family:Calibri;" size="3">FB_MR5</span></i><span face="Calibri" style="font-family:Calibri;" size="3">, encoding for an NBS-LRR protein. </span><i><span face="Calibri" style="font-family:Calibri;" size="3">FB_</span><span><span face="Calibri" style="font-family:Calibri;" size="3">MR5</span></span></i><span face="Calibri" style="font-family:Calibri;" size="3"> was used to generate C44.4.146, a fire blight resistant cisgenic line of the cultivar ‘Gala Galaxy’. The cisgenic approach, i.e. the genetic modification resulting in a genotype carrying exclusively genes from a sexually compatible donor, should retain the original cultivar characteristics adding the desired resistance. For three years,</span><span><span face="Calibri" style="font-family:Calibri;" size="3"> </span></span><span face="Calibri" style="font-family:Calibri;" size="3">the phenotype of C44.4.146 has been investigated in a field trial at the “Protected Site”. This is a three hectares plot dedicated to field experiments with genetically modified plants located in Zurich, Switzerland. First results of the phenotypic and the molecular characterization of the fire blight resistant cisgenic line C44.4.146 will be</span><span><span face="Calibri" style="font-family:Calibri;" size="3"> </span></span><span face="Calibri" style="font-family:Calibri;" size="3">presented.</span></span></div>
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