Identification of RAPD markers linked to a Phytophthora fragariae resistance gene (Rpf1) in the cultivated strawberry

Bulked segregant analysis (BSA) was used to identify seven random amplified polymorphic DNA (RAPD) markers linked to the Rpf1 gene. Rpf1 confers resistance to Phytophthora fragariae var. fragariae, the causal agent of red stele root rot in Fragaria spp. The bulked DNAs represented subsets of a F-1 population obtained from the cross Md683 x Senga Sengana which consisted of 60 plants and segregated in a 1:1 ratio for resistance or susceptibility to race 2.3.4 isolate NS2 of P. fragariae. Seven markers were shown to be linked to Rpf1 and were generated from four primers; five of these markers were in coupling phase and two in repulsion phase with respect to the gene. A linkage map of this resistance gene region was generated using JoinMap 2.0(TM). Th, manner in which Rpf1 and the linked markers co-segregated indicated that they are inherited in a disomic fashion. These markers could enable gene pyramiding and marker-assisted selection of resistance genes in strawberry breeding programmes.