Partners and International Organizations
(English)
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AT, BE, BG, CH, CZ, DE, DK, ES, FI, FR, HU, IE, IL, IT, LT, LU, LV, NL, NO, PL, SE, SI, TR, UK
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Abstract
(English)
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Fire blight is the most destructive bacterial disease in apple orchards worldwide. By classical breeding, researchers are currently introgressing fire blight resistance into new cultivars using genomic markers (marker assisted selection). In parallel, through DNA recombinant technology, apple own genes can be introduced in commercial cultivars without altering desired fruit and tree characteristics. In this manner, by cisgenesis or intragenesis, only own apple genes are finally present in apple. Therefore the interest in the identification of resistance gene has reached a great importance for the agricultural environment. A locus inducing strong fire blight resistance has been previously identified on bottom of LG12 of the ornamental cultivar 'Evereste'. Using bulked segregant analysis (BSA) and amplified fragment length polymorphism (AFLP) techniques, the genomic region was saturated with markers. The resistance locus was accurately localised within 4 cM with two flanking markers and one additional marker located very close to the QTL peak. This marker was used to screen a BAC library developed for Evereste; a resistance-phase BAC clone was isolated by chromosome landing and sequenced. New microsatellites markers were developed and applied to the individuals exhibiting a crossing-over between the two flanking markers from a population of 2703 individuals. Finally the genomic region containing the resistance could be limited to 79 kb carrying 23 genes predicted with Softberry software. A cluster of seven genes with homologies to already known resistance genes against bacterial disease was identified and their transcription verified. From this cluster, two genes were in silico identified as the two most probable fire blight resistance genes. Each gene and both together under the control of a 35S promoter where transferred into a Vector and in Agrobacterium. Currently, using Agrobacterium mediated transfer into the fire blight susceptible cultivar gala, we are multiplying transformants.
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