Markers Linked to Three Sources of Aphid Resistance in Black Raspberry

Black raspberry is a minor but lucrative crop with most of the acreage in the U.S. found in Oregon. Rapid decline of plantings results from virus infection vectored by the North American large raspberry aphid and is the most limiting factor for growing black raspberry. Existing cultivars are susceptible to the resulting Black raspberry necrosis virus (BRNV) and other viruses in the Raspberry mosaic virus complex. BRNV spreads rapidly in the field resulting in plantings that decline in as few as two or three growing seasons. Aphid resistance was discovered in three separate wild black raspberry populations collected from Simcoe, Ontario, Canada (ON), Gardiner, Maine, USA (ME), and Bath, Michigan, USA (MI). Three full-sib black raspberry populations, designated ORUS 4305 (ON), ORUS 4304 (ME), and ORUS 4812 (MI), were used to study the inheritance of the aphid resistance from the three sources. Linkage map construction and phenotypic evaluation of resistance response upon greenhouse aphid inoculation suggest that the three resistance loci are separate but linked and map on Rubus Linkage Group (RLG) 6. Association analysis suggests that sequences from black raspberry genome scaffolds 99, 525 and 684 are important for determining aphid resistance in ORUS 4305. Screening SSRs from these scaffolds identified sixteen SSR loci that co-segregated with aphid resistance. When validated in populations with mixed sources of resistance, two SSRs distinguished individuals with the ON and/or the MI sources of resistance from that of the ME source while one SSR identified resistant individuals irrespective of the source.