DEVELOPMENT OF APPLE PRE-BREEDING GENOTYPES HIGHLY RESISTANT TO FIRE BLIGHT BY EARLY FLOWERING
Fire blight, caused by Erwinia amylovora, is a major concern in apple production since no existing control option has been proven to be completely effective and durable. The use of resistant apple cultivars in apple production could and should be an importance piece of an integrated management of the disease. High levels of resistance to Erwinia amylovora have been found in wild or ornamental apples like Evereste. Recent studies showed that this resistance is largely controlled by a single QTL. However, no advanced selections carrying this QTL (Fb_E locus) and displaying satisfactory fruit quality and agronomic performance are yet available. In order to remove all the undesired traits present in a wild apple up to five (pseudo)backcrosses are necessary. Considering that the juvenile phase of apple lasts at least 4-5 years, this can take 20-25 years. Recently, a breeding technology based on the early flowering BpMADS4-transgenic line T1190 was presented. Using this line, the selection of pre-breeding genotypes carrying the Fb_E locus was started in 2009. In each generation foreground selection using molecular markers associated with the locus Fb_E and the transgene BpMADS4 was used to identify the seedlings to consider as parents in the next crosses once these started producing flowers (generally within 2 to 5 months after seed planting). Starting from the BC1 generation, background selection based on SSR markers was also applied on early flowering Fb_E seedlings. The current status of the introduction of the Fb_E locus as well as observations and methods applied to increase the efficiency of the approach will be presented.
Le Roux, P.M., Flachowsky, H., Jänsch, M., Kellerhals, M., Patocchi, A. and Hanke, M.-V. (2014). DEVELOPMENT OF APPLE PRE-BREEDING GENOTYPES HIGHLY RESISTANT TO FIRE BLIGHT BY EARLY FLOWERING. Acta Hortic. 1048, 55-64
Erwinia amylovora, BpMADS4-transgenic, seedling selection, foreground selection, Fb_E locus, Malus × domestica