Institut für Züchtungsforschung an Obst
The most environmentally friendly and sustainable strategy to control the risk of fire blight in pome fruit orchards is to breed resistant varieties using resistance genes. This is especially true since most commercial varieties are highly susceptible to the causative bacterium - Erwinia amylovora - and the use of antibiotics for control is prohibited in Germany. Accession MAL0045 of the wild apple species Malus fusca is resistant to fire blight. On linkage group 10 of MAL0045, a BAC clone (46H22) containing Mfu10 containing a candidate gene was identified after fine mapping of locus FB_Mfu10 on 1888 individuals. Inoculations of the original F1 population with differentially aggressive E. amylovora isolates led to the suggestion that MAL0045 has additional resistance factors/loci that could not be mapped. In DFG project AOBJ: 661177 (EM295/3-1), the candidate gene was transformed into a susceptible cultivar to test its function, and QTL mapping in F2 populations led to the identification of two previously undetected significant QTLs on linkage groups 4 and 15. In addition, Nanopore minion resequencing of the BAC sequence of 46H22 assembled a single contig that allowed identification of two additional candidate genes, both serine/threonine kinase genes. Transformation experiments to overexpress the first candidate gene have led to the establishment of 10 transgenic lines, although these remain to be functionally characterized. In this project, work will continue to transform and functionally characterize the two additional candidate genes into a susceptible background. The genome from the donor M. fusca will be sequenced and assembled to gain information about the QTL regions on linkage groups 4 and 15.
German Research Foundation
