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Eastern filbert blight (EFB), caused by the pyrenomycete Anisogramma anomala (Peck) E. Müller, is a devastating disease of European hazelnut (Corylus avellana L.) in the Pacific Northwest. Host genetic resistance from ‘Gasaway’ has been used extensively for breeding hazelnuts at Oregon State University. Concern over the durability of this single-gene resistance prompted a search for new sources of resistance. In this study, 86 accessions from 11 countries were evaluated for their response to greenhouse inoculation with the pathogen. Nine accessions showed complete resistance, including one from Chile (‘Amarillo Tardio’), two from Serbia (‘Crvenje’ and ‘Uebov’), one from southern Russia (OSU 495.072) and five from Moscow, Russia. These new sources of EFB resistance have geographically diverse origins and will broaden the genetic base of EFB-resistant hazelnut germplasm. The previously reported resistance of ‘Grand Traverse’ from Michigan and the susceptibility of ‘Closca Molla’ from Spain were confirmed.

Eastern filbert blight (EFB) of European hazelnut (Corylus avellana L.), caused by the pyrenomycete Anisogramma anomala (Peck) E. Müller, is a major disease problem and production constraint in Oregon’s Willamette Valley. Host genetic resistance is viewed as the most economical means of controlling this disease. Marker-assisted selection has been extensively used for ‘Gasaway’ resistance in the hazelnut breeding program at Oregon State University (OSU). Concern over potential breakdown of this single resistance gene prompted a search for new sources of resistance. Selection OSU 408.040 showed no signs or symptoms of the fungus after a series of disease inoculations, and resistance was transmitted to half of its offspring, indicating control by a dominant allele at a single locus. In this study, we identified six random amplified polymorphic DNA (RAPD) and 11 simple sequence repeat (SSR) markers linked to EFB resistance from OSU 408.040. The new markers supplement the previously identified amplified fragment length polymorphism (AFLP) markers. A linkage map constructed in the progeny OSU 245.098 × OSU 408.040 spanned a distance of 19.5 cM with the resistance locus cosegregating with AFLP marker A8-150 and located between SSR markers LG675 and LG682. Using SSR markers as anchor loci, OSU 408.040 resistance was assigned to linkage group 6 (LG6). Comparison with the previously mapped ‘Gasaway’ resistance locus showed that resistance from OSU 408.040 maps to the same location.

The hundred-year history of the european hazelnut (Corylus avellana L.) industry in the Pacific northwestern United States is threatened by eastern filbert blight (EFB) caused by the fungus Anisogramma anomala (Peck) E. Müller. Marker-assisted selection has been extensively used for ‘Gasaway’ resistance in the hazelnut breeding program at Oregon State University. Concern over possible breakdown of this single resistance gene provides an incentive to look for new sources of resistance. OSU 759.010, a selection from the Republic of Georgia, has remained free of EFB after inoculations over several years. Random amplified polymorphic DNA (RAPD) markers linked to resistance were identified by screening primers against three resistant seedlings, three susceptible seedlings, and the parents of a segregating seedling population. For the progeny OSU 759.010 × OSU 653.068, 13 linked markers were identified. The markers most closely linked to resistance were 695-1800 on the proximal side and H12-640, 373-700, 349-450, and F08-700 on the distal side. Four of the five markers also segregated in the progeny OSU 759.010 × OSU 665.076, whereas H12-640 was monomorphic. Segregation for disease response in the first population showed a surplus of resistant seedlings, approaching a 3:1 ratio, with closely linked RAPD markers showing similar ratios. In the second population, the observed segregation for disease response and associated markers did not deviate from the expected 1:1 ratio. Based on cosegregation with simple sequence repeat (SSR) markers, resistance from OSU 759.010 was assigned to linkage group 2. Resistance to EFB from ‘Gasaway’ and ‘Ratoli’ was previously mapped to linkage groups 6 and 7, respectively. Therefore, OSU 759.010 provides a novel source of EFB resistance and markers 695-1800, 373-700, 349-450, and F08-700 have potential for use in marker-assisted selection to pyramid EFB resistance alleles.

Pollen–stigma incompatibility in european hazelnut (Corylus avellana L.) is of the sporophytic type and under the control of a single locus with multiple alleles (haplotypes). The S-locus was previously assigned to linkage group 5 (LG5) and linked DNA markers were identified. The loci that control leaf color and style color are linked to the S-locus. We investigated segregation for leaf and style color and S-alleles in two progenies, mapped the loci, and compared the two new maps with the LG5 reference map using simple sequence repeat (SSR) markers. Segregation for color, S-alleles and SSR markers fit expectations. The color loci and the S-locus mapped to LG5 between SSR markers B028 and B774. The three maps aligned and the SSR markers were collinear. The SSR markers closest to the S-locus are KG819, KG847, and BR259. In progeny 05050, which segregated for style and leaf color, no recombination was observed between the two traits. Recombination between the S-locus and the style color locus was 5.4 cM in progeny 05050 and 10.1 cM in progeny 00064. The style color locus was placed very close to SSR marker B028 in both progenies. On the reference map, random amplified polymorphic DNA (RAPD) markers 564-500M, 345-1050dF, and 204-950dF and intersequence simple sequence repeat (ISSR) marker 815-540dF are very close to the S-locus. The identification of closely linked markers will facilitate the map-based cloning of the S-locus and color loci in hazelnut.

European hazelnut (Corylus avellana L.) is a significant crop in Oregon, where 99% of United States hazelnuts are produced. Eastern filbert blight (EFB) caused by Anisogramma anomala (Peck) E. Müller is an important disease that infects the trees, reduces yield, and causes premature death. Managing the disease through cultural methods and fungicide applications is laborious and expensive, and genetic host resistance is considered the most viable option for control. Genetic resistance from ‘Gasaway’ has been used to develop resistant cultivars including Yamhill and Jefferson, but concern about the durability of this single resistance gene stimulated a search for additional sources of resistance. This study used three recently identified sources of EFB resistance: ‘Culplà’ from Spain, ‘Crvenje’ from Serbia, and OSU 495.072 from southern Russia. RAPD markers linked to resistance from ‘Gasaway’ were absent in all three accessions. Disease response was noted in segregating progenies following greenhouse or structure inoculation, and the resistance loci were mapped using microsatellite markers. In only four of the nine progenies did segregation for disease response fit the ratio of 1 resistant:1 susceptible expected for a single locus, a heterozygous resistant parent, and a dominant allele for resistance. Three progenies showed an excess of resistant seedlings while two showed a deficiency of resistant seedlings. The reciprocal translocations reported in several leading hazelnut cultivars may be present in the parents of the studied progenies, and affecting the segregation ratios. Microsatellite marker A614, previously mapped to linkage group (LG) 6, was closely linked to resistance from all three sources. Maps were constructed for LG6 for each resistant parent using microsatellite markers. The three resistance loci mapped to the same region on LG6 where resistance from ‘Gasaway’ and OSU 408.040 are located. The resistance alleles in all five accessions may be the same, or more likely are a cluster of different resistance genes in the same region. Markers LG628, LG610, and LG696 will be useful to breed new hazelnut cultivars with resistance from Culplà, Crvenje, and OSU 495.072.