2018 ASHS Annual Conference

Eastern filbert blight (EFB) caused by Anisogramma anomala was first discovered in Oregon's Willamette Valley in 1986 and remains a costly concern of the US hazelnut industry. Host resistance is the most effective method of disease control. A very high level of EFB resistance, discovered in ‘Gasaway’, is controlled by a dominant allele at a single locus. This resistance may not be durable, as new races of the fungus able to overcome this R-gene could be introduced or arise from mutation or recombination. The pyramiding of multiple resistance genes in a single genotype is a promising approach for more durable resistance. Segregation for EFB response was studied in seedlings from a controlled cross of resistant ‘Estrella #1’ and susceptible selection OSU 1174.033. Estrella #1 was released by private breeder Cecil Farris and is a hybrid of C. heterophylla sutchuensis x C. avellana. The seedlings were exposed to EFB spores under a structure topped with diseased branches as well as field exposure. Disease severity was rated 18–20 months after exposure on a scale of 0 (absence of disease) to 5 (severe disease symptoms). DNA of the seedlings was extracted and amplified with several microsatellite primer pairs, and correlation coefficients calculated between disease response and marker allele scores. ‘Estrella #1’ resistance was assigned to linkage group 6 (LG6) based on high correlation of disease response with marker scores at mapped LG6 microsatellite markers. A total of 14 markers on LG6 showed correlation coefficients >0.7, and these map to the same region as ‘Gasaway’ resistance. A linkage map was constructed for the 'Estrella #1' resistance region and aligned with the 'Gasaway' resistance region. ‘Estrella #1’ provides a novel source of EFB resistance, for which linked markers will be useful for marker-assisted selection and the pyramiding of EFB resistance alleles from different sources.