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Eastern filbert blight (EFB), caused by Anisogramma anomala, is a fungal disease threatening the european hazelnut (Corylus avellana) industry in the Willamette Valley of Oregon. The pathogen is endemic to the eastern United States where it causes little damage to the wild Corylus americana but causes severe cankers on most cultivars of the commercially important european hazelnut. The host genetic resistance in ‘Gasaway’ is conferred by a dominant allele at a single locus on linkage group 6 (LG6), and resistance from several other sources has been mapped to the same region. Some fungal isolates can overcome ‘Gasaway’ resistance, prompting a search for other sources of resistance. Resistance from other sources has been mapped to LG2 and LG7, for which additional simple sequence repeat (SSR) markers would facilitate marker-assisted selection (MAS). In this study, an in silico approach was used to develop new polymorphic SSR markers in the EFB resistance regions on LG2 and LG7. Starting with a search of 17 contigs of the ‘Jefferson’ genome sequence, 45 new polymorphic SSR markers were developed, characterized, and placed on the linkage map. The new SSR markers had an average of 10.18 alleles per locus, and average values for expected heterozygosity, observed heterozygosity, polymorphism information content, and frequency of null alleles of 0.72, 0.65, 0.68, and 0.068, respectively. Of the 42 new polymorphic SSRs segregating in the mapping population, 24 were on LG2, 12 were on LG7, and six were placed on other LGs. The new and previously developed SSR markers were used to study six new sources of EFB resistance, four from Russia and two from Crimea. Six resistant selections were crossed with susceptible selections, resulting in 7 progenies. Phenotyping for disease response revealed that segregation in progenies of the two Moscow selections (#2 and #27), one Russian selection (OSU 1187.101), and one Crimean selection (H3R12P62) fit the 1:1 segregation ratio expected for control of resistance by a dominant allele at a single locus; but in progenies of the other Russian selection (OSU 1166.123) and the other Crimean selection (H3R07P11), there was an excess of resistant seedlings. Correlation of disease scores and alleles at SSR loci indicated that resistance from three Russian selections (Moscow selections #2 and #27 and OSU 1166.123) and the Crimean selection H3R12P62 was on LG7, while resistance from Russian selection OSU 1187.101 was on LG2. Resistance from Crimean selection H3R07P11 was not correlated with markers on LG6, or LG2, or LG7. These sources and new SSR markers will be useful in MAS and the pyramiding of resistance genes in the breeding of new EFB-resistant cultivars.

European hazelnut (Corylus avellana L.) is an economically important edible nut producing species, which ranked sixth in world tree nut production in 2016. European hazelnut production in the United States is primarily limited to the Willamette Valley of Oregon, and currently nonexistent in the eastern United States because of the presence of a devastating endemic disease, eastern filbert blight (EFB) caused by Anisogramma anomala (Peck) E. Muller. The primary commercial means of control of EFB to date is through the development and planting of genetically resistant european hazelnut cultivars, with an R-gene introduced from the obsolete, late-shedding pollinizer ‘Gasaway’. Although the ‘Gasaway’ resistance source provides protection against EFB in the Pacific northwestern United States (PNW), recent reports have shown that it is not effective in parts of the eastern United States. This may be in part because the identification and selection of ‘Gasaway’ and ‘Gasaway’-derived cultivars occurred in an environment (PNW) with limited genetic diversity of A. anomala. The objectives of the current research were to develop a genetic linkage map using double digestion restriction site associated DNA sequencing (ddRADseq) and identify quantitative trait loci (QTL) markers associated with EFB resistance from the resistant selection Rutgers H3R07P25 from southern Russia. A mapping population composed of 119 seedling trees was evaluated in a geographic location (New Jersey) where the EFB fungus is endemic, exhibits high disease pressure, and has a high level of genetic diversity. The completed genetic linkage map included a total of 2217 markers and spanned a total genetic distance of 1383.4 cM, with an average marker spacing of 0.65 cM. A single QTL region associated with EFB resistance from H3R07P25 was located on european hazelnut linkage group (LG) 2 and was responsible for 72.8% of the phenotypic variation observed in the study. Based on its LG placement, origin, and disease response in the field, this resistance source is different from the ‘Gasaway’ source located on LG6. The current results, in combination with results from previous research, indicate that the H3R07P25 source is likely exhibiting resistance to a broader range of naturally occurring A. anomala isolates. As such, H3R07P25 will be important for the development of new european hazelnut germplasm that combines EFB resistance from multiple sources in a gene pyramiding approach. Identification of EFB resistance in high disease pressure environments representing a diversity of A. anomala populations is likely a requirement for identifying plants expressing durable EFB resistance, which is a precursor to the development of a commercially viable european hazelnut industry in the eastern United States.

From the genome sequence of hazelnut (Corylus avellana), 192 new polymorphic simple sequence repeat (SSR) markers were developed, characterized, and used to investigate genetic diversity in 50 accessions. Next-generation sequencing allows inexpensive sequencing of plant genomes and transcriptomes, and efficient development of polymorphic SSR markers, also known as microsatellite markers, at low cost. A search of the genome sequence of ‘Jefferson’ hazelnut identified 9094 fragments with long repeat motifs of 4, 5, or 6 base pairs (bp), from which polymorphic SSR markers were developed. The repeat regions in the ‘Jefferson’ genome were used as references to which genomic sequence reads of seven additional cultivars were aligned in silico. Visual inspection for variation in repeat number among the aligned reads identified 246 as polymorphic, for which primer pairs were designed. Polymerase chain reaction (PCR) amplification followed by agarose gel separation indicated polymorphism at 195 loci, for which fluorescent forward primers were used to amplify the DNA of 50 hazelnut accessions. Amplicons were post-PCR multiplexed for capillary electrophoresis, and allele sizes were determined for 50 accessions. After eliminating three, 192 were confirmed as polymorphic, and 169 showed only one or two alleles in each of the 50 cultivars, as expected in a diploid. At these 169 SSRs, a total of 843 alleles were found, for an average of 4.99 and a range of 2 to 17 alleles per locus. The mean observed heterozygosity, expected heterozygosity, polymorphism information content, and the frequency of null alleles were 0.51, 0.53, 0.47, and 0.03, respectively. An additional 25 primer pairs produced more than two bands in some accessions with an average of 6.8 alleles. The UPGMA dendrogram revealed a wide genetic diversity and clustered the 50 accessions according to their geographic origin. Of the new SSRs, 132 loci were placed on the linkage map. These new markers will be useful for diversity and parentage studies, cultivar fingerprinting, marker-assisted selection, and aligning the linkage map with scaffolds of the genome sequence.

Eastern filbert blight (EFB) is a serious fungal disease of european hazelnut (Corylus avellana) in North America. The causal agent is the pyrenomycete Anisogramma anomala, which is native in the eastern United States where it occasionally produces small cankers on the wild american hazelnut (C. americana). However, most commercial cultivars of european hazelnut are susceptible. Infection leads to perennial cankers, girdling of branches, and premature tree death. Cultural practices including scouting, pruning out infected branches, and fungicide applications are recommended to slow disease spread but are expensive and not completely effective. EFB resistance from ‘Gasaway’ is conferred by a dominant allele at a single locus and has been extensively used in the Oregon State University hazelnut breeding program, but there is concern that this resistance could be overcome by isolates now present in the eastern United States or that a new race of the pathogen could arise in Oregon. Segregation for EFB resistance from ‘Uebov’, a new source from Serbia, was studied in three progenies by a combination of structure exposure and greenhouse inoculation. The frequency of resistant seedlings following structure exposure was about 20% in all three progenies. The ratios failed to fit the expected 1:1 ratio but did fit a ratio of 1 resistant:3 susceptible, which would be expected if resistance were conferred by dominant alleles at two independent loci. Seedlings from a cross of susceptible selection OSU 741.105 and ‘Uebov’ were used to study correlation of disease response and presence of alleles at microsatellite marker loci. Resistance was highly correlated with the presence of alleles at marker loci on linkage group 6 (LG6), and these markers also showed segregation distortion. We conclude that EFB resistance from ‘Uebov’ maps to a single locus on LG6 in the same region as resistance from ‘Gasaway’, although only about 20% of the seedlings are resistant because of segregation distortion. ‘Uebov’ has large, well-filled, round nuts and is suitable as a parent in breeding for the in-shell market, but its low nut yields and a high frequency of shells with split sutures are the drawbacks. Its use would expand options for breeding and ‘Uebov’ resistance could be combined with other resistance alleles with an expectation of more durable EFB resistance. Durable resistance would not only sustain the hazelnut industry in Oregon but would also allow expansion of plantings to new areas.

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.

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.

The european hazelnut (Corylus avellana L.) is native to most of Europe and nearby areas in Asia Minor and the Caucasus Mountains. Cross-pollination is enforced by sporophytic incompatibility under the control of a single locus with multiple alleles (haplotypes). Fluorescence microscopy is routinely used to determine if a pollination is compatible or incompatible, and use of an array of known testers allows identification of the alleles of cultivars and selections. Both alleles are expressed in the stigmas, but often only one is expressed in the pollen because of dominance. Cultivars are highly heterozygous diploids (2n = 2x = 22) and clonally propagated. Most of the world's leading cultivars were selected from local wild populations near where they are now planted on a commercial scale. Genetic improvement efforts are recent and, although tremendous genetic variability is available, such efforts have had little impact outside of Oregon and France. Studies of genetic diversity using simple sequence repeat markers have placed most cultivars in one of the four main groups: Spanish-Italian, Central European, English, or Black Sea. This study presents 17 years of data on incompatibility in hazelnut, including the discovery of six new S-alleles and determination of the dominance relationships among 105 new pairs of alleles. The total number of alleles now stands at 33. The S-alleles of 284 cultivars, 13 interspecific hybrids, and 522 selections of diverse origin are presented. The S-alleles identified in hazelnut cultivars is information that should be useful to breeders in the planning of crosses, to curators of germplasm collections, and to growers and nurseries as they choose cultivars and pollenizers when designing orchards. Differences in S-allele frequency seen in the cultivars and selections are related to geographic origin. The most common alleles of cultivars in the major geographical groups are S2 in the Spanish-Italian group, S5 in the Central European group, S3 in the English group, and S4 in the Black Sea group. Most selections belonged to the Black Sea group, and S4 was by far the most common allele. Differences in allele frequency were also observed among seed lots within a country.

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.

Filbertworm, Cydia latiferreana (Walsingham) (Lepidoptera: Tortricidae), is a key insect pest of hazelnuts in North America. Susceptibility to filbertworm was determined in 25 hazelnut cultivars represented by 44 trees at the USDA National Clonal Germplasm Repository in Corvallis, OR. In addition, shell thickness of 17 of the cultivars was measured at the thinnest and thickest points of the basal scar as well as at the side of the shell wall. Filbertworm infestation, which ranged from 2% to 89% per tree, as well as shell thickness varied significantly among the cultivars. Filbertworm infestation significantly increased with decreasing shell thickness at the basal scar, where filbertworm larvae typically penetrate the nut. The cultivar Siciliana had the overall thickest shells and lowest filbertworm infestation (6% ± 2% average for the cultivar), whereas ‘Frango 2’, ‘Casina’, and ‘Daviana’ had the thinnest shells and 76%, 55%, and 82% infested nuts, respectively. Nut infestation was not correlated with the thickness of the side wall. Our data suggest that a thicker basal scar in hazelnut cultivars contributes to resistance against filbertworm infestation.

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.

‘Tonda Pacifica’ is a new hazelnut (Corylus avellana L.) cultivar for the kernel market. It was released by the Oregon Agricultural Experiment Station in April 2010. Compared with ‘Barcelona’, Oregon’s leading cultivar, ‘Tonda Pacifica’ has smaller trees, higher nut yield efficiency, smaller nuts and kernels, higher kernel percentage, fewer nut and kernel defects, better suitability for the blanched kernel market, and earlier nut maturity. Kernels have a crisp texture, highly rated flavor and nutty aroma. The kernel quality is similar to that of its Italian parent ‘Tonda Gentile delle Langhe’. The small kernel size is well suited to use in chocolate products and baked goods. ‘Tonda Pacifica’ is susceptible to eastern filbert blight caused by Anisogramma anomala (Peck) E. Muller.

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.

Microsatellite-containing sequences for the Betulaceae (Betula, Corylus, and Alnus) were retrieved from GenBank and used to develop twelve new microsatellite marker primer pairs that amplified and were polymorphic in european hazelnut (Corylus avellana). The primer pairs were characterized using 50 european hazelnut accessions. Nine of these microsatellites that segregated in a mapping population were assigned to linkage groups. The 12 new primer pairs will be useful in genetic studies in Corylus and Betula. To investigate transferability of microsatellite primer pairs in the family Betulaceae, we assessed the ability of 129 simple sequence repeat (SSR) primer pairs (75 from Corylus, 52 from Betula, and two from Alnus) to amplify DNA of 69 accessions representing diverse taxa. Microsatellite primer pairs from Betula amplified 92% of Betula, 51% of Alnus, 41% of Corylus, 37% of Carpinus, 35% of Ostryopsis, and 34% of Ostrya accessions. In the 69 accessions, microsatellite primer pairs from Corylus amplified 81% of Corylus, 55% of Carpinus, 53% of Ostrya, 51% of Ostryopsis, 41% of Alnus, and 39% of Betula accessions. An additional 147 SSR primer pairs developed from Corylus, used to amplify a subset of 32 accessions, gave similar values: 92% in Corylus, 33% in Carpinus, 33% in Ostrya, 44% in Ostryopsis, 35% in Alnus, and 54% in Betula. The high transferability (>39%) of microsatellite primer pairs between Betula and Corylus will allow comparative studies of the two genera with the greatest economic importance.

A diverse collection of 58 hazelnut accessions, including Corylus avellana L. and interspecific hybrids, were evaluated for their response to the eastern filbert blight pathogen Anisogramma anomala (Peck) E. Müller after greenhouse inoculation. Evaluations were made using enzyme-linked immunosorbent assay and visual inspection. Forty-five of these became infected, 12 remained free of infection, and one gave inconclusive results. The 12 accessions showing complete resistance were European hazelnuts ‘Culpla’ from Spain and CCOR 187 from Finland; C. americana × C. avellana hybrids ‘G081S’, CCOR 506, and Weschcke selections TP1, TP2 and TP3; C. colurna × C. avellana hybrids Chinese Trazels Gellatly #6 and #11; Turkish Trazel Gellatly #3 and backcross hybrid ‘Lisa’; and C. heterophylla var. sutchuensis × C. avellana hybrid ‘Estrella #1’. In a second test, exposure of potted trees under structures topped with diseased wood confirmed the complete resistance of ‘Santiam’, four pollinizers, and ‘Ratoli’. However, a few small cankers were observed on ‘Closca Molla’ from Spain and OSU 729.012, with resistance from C. californica (A.DC.) Rose, in contrast to the results of earlier greenhouse inoculations.

Six hundred five hazelnut (Corylus avellana L.) seedlings from a diverse germplasm collection made in the Russian Federation and the Crimean peninsula of the Ukraine were inoculated with the eastern filbert blight (EFB) pathogen Anisogramma anomala (Peck) E. Müller and their responses evaluated. Responses were rated on a scale of 0 to 5, in which 0 represents no sign of EFB and 5 represents all branches exhibiting cankers. At final evaluation, eight seedlings showed no signs of the pathogen or symptoms of the disease. Five additional seedlings expressed only very minor signs of the pathogen (rating = 1). The remainder ranged in disease expression from moderately to severely infected to dead with 89.7% (470 of 524) of the surviving seedlings rating 4 or 5. Of the 13 apparently resistant seedlings (rating 0 or 1), seven originated from nuts purchased from roadside vendors near Simferopol, Crimea, Ukraine; five from nuts purchased at an outdoor market near Krasnodar, Russia; and one from nuts obtained from the hazelnut breeding program of the Nikita Botanical Gardens, Yalta, Crimea, Ukraine. Random amplified polymorphic DNA (RAPD) markers generated by the primers UBC 152800 and OP AA12850, which are tightly linked to the single dominant resistance gene ‘Gasaway’, were not present in all 13 resistant seedlings, providing support, along with their geographic origins, that they represent novel sources of genetic resistance to EFB.

Eastern filbert blight (EFB), caused by the fungus Anisogramma anomala (Peck) E. Müller, is an important disease of european hazelnut (Corylus avellana L.) in the Pacific northwestern United States. In 1989, a chance seedling free of EFB was discovered adjacent to a severely diseased orchard near Troutdale, Ore. This selection, subsequently named `Zimmerman', was crossed with three susceptible selections. Based on morphological characters and incompatibility alleles, we speculated that `Zimmerman' (S1 S3) was a hybrid between `Barcelona' (S1 S2) and `Gasaway' (S3 S26). The three seedling populations were inoculated with spores of the pathogen in a greenhouse test and assayed by indirect enzyme-linked immunosorbent assay (ELISA) and by observation of canker incidence. The observed segregation fit a 3 resistant : 1 susceptible ratio in all three progenies, in contrast to the 1 : 1 ratio found when the resistant pollinizer `Gasaway' was crossed to susceptible genotypes. Random amplified polymorphic DNA (RAPD) marker UBC 152800 linked to the resistance gene in `Gasaway' co-segregated with the resistant phenotype in all three populations with 2%, 4%, and 6% recombination, respectively. Seed germination and transplanting records did not provide evidence of selection in favor of resistant seedlings. Pollen germination was 71% in `Gasaway', 29% in `Zimmerman', and 18% in `Barcelona', indicating possible selection at the gametophytic level. Subsequently 16 resistant seedlings of `Zimmerman' were crossed with the highly susceptible selection OSU 313.078. Segregation fit a 3 : 1 ratio in 14 of the 16 progenies, and showed a surplus of resistant seedlings in the other two. None showed a 1 : 1 segregation. Resistance co-segregated with two RAPD markers that flank the `Gasaway' resistance allele. To test allelism of resistance from `Gasaway' and `Zimmerman', VR 6-28 with resistance from `Gasaway' was crossed with `Zimmerman'. Eight resistant selections from this progeny were crossed with OSU 313.078. Five of the eight progenies segregated 3 : 1, two progenies segregated 1 : 1, and OSU 313.078 × OSU 720.056 gave only resistant offspring. The ratios indicate that OSU 720.056 is homozygous resistant and that `Zimmerman' and `Gasaway' share a common resistance allele. Reciprocal translocations have been reported in hazelnut cultivars, including `Barcelona', the leading cultivar in Oregon. `Zimmerman' appears to be a hybrid of `Barcelona' and `Gasaway', but because of cytogenetic abnormalities, `Zimmerman' may have inherited two copies of the chromosome region that contain the resistance locus and flanking RAPD markers. If the region containing the resistance were attached to two independent centromeres, a 3 : 1 segregation ratio for disease response and flanking markers would be expected, and we propose this as the most likely explanation. Resistance from `Gasaway' and `Zimmerman' has been called “immunity” or “complete resistance.” However, we noted a few seedlings with small cankers, nearly all of which lacked sporulating stromata. Flanking RAPD markers indicate that the resistance allele is present in these seedlings. Although not “immune” or “completely resistant,” `Gasaway' and `Zimmerman' transmit a very high level of resistance.

Three microsatellite-enriched libraries of the european hazelnut (Corylus avellana L.) were constructed: library A for CA repeats, library B for GA repeats, and library C for GAA repeats. Twenty-five primer pairs amplified easy-to-score single loci and were used to investigate polymorphism among 20 C. avellana genotypes and to evaluate cross-species amplification in seven Corylus L. species. Microsatellite alleles were estimated by fluorescent capillary electrophoresis fragment sizing. The number of alleles per locus ranged from 2 to 12 (average = 7.16) in C. avellana and from 5 to 22 overall (average = 13.32). With the exception of CAC-B110, di-nucleotide SSRs were characterized by a relatively large number of alleles per locus (≥5), high average observed and expected heterozygosity (Ho and He > 0.6), and a high mean polymorphic information content (PIC ≥ 0.6) in C. avellana. In contrast, tri-nucleotide microsatellites were more homozygous (Ho = 0.4 on average) and less informative than di-nucleotide simple sequence repeats (SSRs) as indicated by a lower mean number of alleles per locus (4.5), He (0.59), and PIC (0.54). Cross-species amplification in Corylus was demonstrated. These microsatellite markers were highly heterozygous and polymorphic and differentiated among genotypes of C. avellana irrespective of geographical origin. They will aid in fingerprinting genotypes of the european hazelnut and other Corylus species, genome mapping, and genetic diversity assessments.

ADDITIONAL INDEX WORDS. Corylus avellana, fi lbert, Anisogramma anomala, marker-assisted selection ABSTRACT. Eastern fi lbert blight (EFB), caused by Anisogramma anomala (Peck) E. Muller, is a devastating disease to european hazelnut (Corylus avellana L.) orchards in the Willamette Valley of Oregon. Selection OSU 408.040 showed no symptoms or signs of the fungus following greenhouse inoculations, and enzyme-linked immunosorbant assays (ELI- SAs) were negative. Segregation ratios in three progenies indicate that a single dominant gene controls the resistance. A total of 64 amplifi ed fragment length polymorphism (AFLP) primer combinations were screened using three resistant and three susceptible individuals as well as the parents of the cross OSU 245.098 × OSU 408.040. Primer combinations that showed no more than one recombinant in these six seedlings were investigated in 30 additional seedlings. Markers that showed

and subtropical fruit and nut species holds 7,685 accessions made up of cultivars, selections, and unique forms (Table 1). The collections include peach and nectarine [Prunus persica (L.) Batsch.], apricot (Prunus armeniaca L.), European plum (Prunus domestica L.), cherry-plum (Prunus cerasifera Ehrh.), sour cherry (Prunus cerasus Ehrh.), apple (Malus xdomestica Borkh.), pear (Pyrus communis L.), quince (Cydonia oblonga Mill.), almond [Prunus dulcis (Mill.) D. A. Webb.], walnut (Juglans regia L.), hazelnut (Corylus avellana L.), pomegranate (Punica granatum L.), fi g (Ficus carica L.), persimmon (Diospyros spp.), Chinese date (Zyzyphus jujuba Mill.), hardy kiwifruit (Actinidia spp.), pawpaw [Asimina triloba (L.) Dunal], lemon [Citrus limon (L.) Burm.], and feijoa or pineapple guava (Feijoa sellowiana Berg.). There are nine departments in the Gardens: fl ora and vegetation, dendrology and fl oriculture, subtropical fruit culture, essential oil-bearing and medicinal plants, agroecology Table 1. Number of accessions of temperate and subtropical fruit and nut species held in collections at the Nikita Botanical Gardens.

A rapid and reliable assay for screening European hazelnut (Corylus avellana L.) genotypes for quantitative resistance to eastern filbert blight [Anisogramma anomala (Peck) E. Müller] was tested by comparing two methods using the same clones. In the first assay, disease spread was followed for five consecutive years (1992-96) in a field plot planted in 1990. Measured responses included disease incidence (the presence or absence of cankers) and total canker length, quantified as the length of perennially expanding cankers. The second assay consisted of annually exposing replicated sets of 2-year-old, potted trees to artificially high doses of pathogen inoculum and measuring incidence and canker lengths at the end of the next growing season. The potted trees were exposed to inoculum in 1990, 1992, 1993, and 1994. Compared to the field plot, disease incidence and total canker length were higher in all the potted-tree experiments. Nonetheless, disease responses of individual clones in the two screening methods were significantly correlated in some contrasts (rs = 0.97 between 1996 field and 1995 potted trees). However, for a few clones (`Camponica', `Tombul Ghiaghli', and `Tonda di Giffoni'), disease developed slowly in the field plot, but disease incidence on these clones averaged > 30% in most of the potted-tree studies. Disease responses also were significantly correlated among some of the potted-tree experiments (rs = 0.72 for the comparison of 1994 to 1995). Highly susceptible and highly resistant hazelnut clones were identified by both methods. However, the field plot method was superior to the potted-tree method for distinguishing among moderately resistant clones. `Bulgaria XI-8', `Gem', `Camponica', `Tombul Ghiaghli', and `Tonda di Giffoni' were identified as promising sources of quantitative resistance to eastern filbert blight.

Eight Corylus L. (hazelnut) species were intercrossed in all possible combinations to reveal genetic relationships. Pollinations were made on either individually bagged branches or trees covered entirely with polyethylene using mixtures of pollen of five genotypes to minimize low cluster set due to single incompatible combinations. Percent cluster set, seed germination, and hybrid seedling survival were determined. Hybridity of seedlings was verified by inspection of morphological traits. Based on percent cluster set, seed germination, and hybrid seedling survival along with observed morphological similarities, Corylus species were placed in three groups: 1) the tree hazels C. colurna L. (turkish tree hazel) and C. chinensis Franchet (chinese tree hazel), 2) the bristle-husked shrub species C. cornuta Marshall (beaked hazel), C. californica (A.DC.) Rose (california hazel), and C. sieboldiana Blume (manchurian hazel), and 3) the leafy-husked shrub species C. avellana L. (european hazel), C. americana Marshall (american hazel), C. heterophylla Fischer (siberian hazel), and C. heterophylla Fischer var. sutchuensis Franchet (sichuan hazel). The two tree hazel species crossed with each other readily, as did the three bristle-husked shrub species. The frequency of blanks was low (C. heterophylla was low. For crosses of species belonging to different groups, set was generally low and the frequency of blanks high. Nevertheless, a few hybrid seedlings were obtained from several combinations. When used as the female parent, C. californica set nuts when crossed with all other species, indicating possible value as a bridge species. Crosses involving C. avellana were more successful when it was the pollen parent. In crosses with C. avellana pollen, cluster set on C. chinensis was better than on C. colurna and the frequency of blanks was much lower, indicating that it might be easier to transfer nonsuckering growth habit from C. chinensis than from C. colurna. Reciprocal differences in the success of crosses was observed. The following crosses were successful C. californica × C. avellana, C. chinensis × C. avellana, C americana × C. heterophylla, C. cornuta × C heterophylla, C. californica × C. colurna, and C. americana × C. sieboldiana, but the reciprocals were not.

Eastern filbert blight is an economically significant disease in European hazelnut (Corylus avellana L.) production in the United States. Since genetic resistance is the only viable disease control strategy to this fungal disease caused by Anisogramma anomala (Peck) E. Müller, greenhouse and field screening of germplasm was undertaken to study the inheritance from known resistant sources and to identify new sources for inclusion in the breeding program. We confirmed that `Gasaway' resistance to this disease is conferred by a single dominant gene. No major gen was identified in the field-resistant cultivar Gem. Representatives of six Corylus species were screened to identify new resistant germplasm. Corylus cornuta Marshall var. cornuta, C. cornuta var. californica (A.DC.) Sharp, C. heterophylla Fischer, and C. sieboldiana Blume were highly resistant, as were most C. americana Marshall genotypes and one C. colurna L. clone tested, but C. jacquenontii Decaisne was highly susceptible. In several cases, hybrids of these species with susceptible C. avellana were also resistant. These new sources of resisstance are being incorporated in the resistance breeding effort.

method should be available. Sometimes, an evaluation method must be developed before breeding for that objective can become routine. The most common approach to breeding these crops is sometimes called “complementary hybridization.” Poehlman (1987) presents a brief outline, and Simmonds (1979) discusses additional information. The parent clones of each cross are chosen such that the weaknesses of one are matched by the strengths of the other, with the hope that a few of their offspring will have the strengths of both parents and none of the weaknesses. Because the parent clones are highly heterozygous, tremendous segregation is apparent in the seedling population. The challenge then is to identify from among the thousands of seedlings the few that have potential as new cultivars. Evaluation typically is stepwise, with the number of selected genotypes decreasing in each step while the number of vegetatively propagated plants of each increases. In the first step, selection is based on the performance of the original seedling plant and is limited to highly heritable traits that can be evaluated quickly and inexpensively. In the second phase of evaluation, a small unreplicated trial is used to study the performance of selections more carefully. Typically, 10 plants of each selection are included. In the third stage of evaluation, advanced selections are grown in a replicated trial and compared to standard cultivars. Often

The effect of parentage, spacing, and sucker removal on precocity of hazelnut (Corylus avellana L.) seed- lings was investigated. Wider spacing (1.2 vs. 0.6 m) within the row doubled the number of nuts per seedling in the 5th year but had no effect on nut count in the 3rd or 4th year, nor did it affect the percentage of seedlings bearing nuts in any of the three years. Differences among the four progenies were highly significant for number of clusters, number of nuts, and percentage of seedlings bearing nuts in all years and for number of years to first fruiting. The progeny 'Barcelona' × OSU 55.097 had the most bearing seedlings in, the 3rd year but was outperformed by 'Casina' × OSU 55.129 in the 4th and 5th years. Number of years to first fruiting varied from 4.3 for 'Casina' × OSU 55.129 to 5.2 for 'Tombul' × 'Tonda di Giffoni'. Sucker removal increased both the percentage of seedlings bearing nuts and the number of nuts per seedlings, but the difference was not significant until the 5th year. Sucker removal reduced the length of the juvenile phase by 3 months. The use of precocious parents was more effective than sucker removal in shortening the juvenile period, while sucker removal and wide spacing within seedling rows increased the number of nuts produced by seedlings in the 5th year. Selection of seedlings for early initiation of bearing will shorten the breeding cycle, and the resulting new cultivars will be precocious when planted in commercial orchards. Juvenility is a major impediment in the genetic improvement of tree fruit and nut species because it increases the length of the breeding cycle. The response to selection per year is lower and the cost per unit of genetic improvement is higher in pro- portion to the length of the juvenile period (Hansche, 1983). Previous research, summarized by Zimmerman (1972), has shown that the length of the juvenile period is influenced by genetic and environmental factors. Genetic differences, expressed as general combining abilities of parent cultivars, have been dem- onstrated in several species (Bell and Zimmerman, 1990; Bla- zek, 1985; Way, 1971), and gene action appears to be primarily additive. In apple (Malus domestics Borkh.) and pear (Pyrus communis L.), the length of the adult vegetative period of grafted trees of the parents is a good measure of their ability to transmit precocity (Visser, 1965), and precocious seedlings, when prop- agated by budding, produce precocious trees (Visser and DeVries, 1970). Several environmental factors affect the length of the juvenile period. In general, seedlings start to flower and bear fruit earlier if grown under conditions that induce rapid growth. By provid- ing ideal conditions in the greenhouse, Aldwinckle (1975) was able to induce flowering in apple seedlings in 16 months rather than the usual 8 years in the orchard. Wide spacing in seedling rows also promotes early fruiting. Way (1971) demonstrated that wide spacing of apple seedlings within the row (0.9 vs. 0.3 m) resulted in a higher fruiting percentage by their 11th year, but questioned whether this was efficient use of land. A similar benefit from wide spacing was demonstrated by Visser (1964). Pruning of roots or shoots prolongs the juvenile phase (Zim- merman, 1972). Hazelnut seedlings bear their first fruit in the 3rd to 6th year, with the 5th year being in the median. The breeding program at Oregon "State Univ. (OSU) currently operates on an 8-year

Ninety hazelnut (Corylus sp.) genotypes were surveyed for response to the eastern filbert blight pathogen (Anisogramma anomala (Peck) E. Muller) following greenhouse inoculation using a combination of enzyme-linked immunosorbent assay (ELISA) and visual inspection for cankers. Most were cultivars of the European hazelnut ( Corylus avellana L.) and a few were interspecific hybrids. Six genotypes did not display signs of the pathogen or symptoms of disease: 'Closca Molla', 'Ratoli', 'Yoder #5', 'Potomac', 'Medium Long' , and 'Grand Traverse'. 'Closca Molla' and 'Ratoli' , both minor Spanish cultivars, are superior in many respects to 'Gasaway', which has been extensively used as a completely resistant parent in breeding. 'Potomac' and 'Yoder #5' have C. americana Marsh. in their pedigrees, 'Grand Traverse' is one-quarter C. colurna, and the origin of 'Medium Long' is uncertain. The random amplified polymorphic DNA (RAPD) marker generated by primer UBC 152, which is linked to the single dominant resistance gene of 'Gasaway', is absent in these six genotypes, and thus they appear to be novel sources of genetic resistance to this devastating disease. Oregon's Willamette Valley is the top pro- ducer of European hazelnuts in the United States, accounting for 99% of the U.S. crop and 3% to 5% of the world crop (Mehlenbacher and Olsen, 1997). Eastern filbert blight (EFB), caused by the pyrenomycete Anisogramma anomala (Peck) E. Muller, is a serious and widespread disease in the Willamette Valley. This disease can destroy the productivity of a moderately susceptible cultivar in 8 to 12 years (Johnson et al., 1996), so its control is an important industry goal. Because of the ex- pense of fungicides and detrimental effects on

The relationship between dormancy of seeds and buds of apple (Malus × domestica Borkh.) might provide breeders with an early opportunity to select for delayed development. Seeds of late-flowering genotypes require much longer exposure to chilling temperatures than those of early flowering" genotypes, and they germinate over a much longer period. In three progenies that exhibit much variation for the two traits, seed germination time was correlated with time of leafing-out of the resulting seedlings, and could be used to select for delayed budbreak. However, selection would be ineffective when little genetic variation for seed germination and budbreak is present. Leafing-out ratings in the nursery in the 2nd year were highly correlated with those in the 3rd year, indicating that selection for late leafing in the nursery during the 2nd year would be more effective than selection based on seed dormancy, especially in progenies exhibiting little genetic variability for this trait. Breeders can effectively use both relationships by first eliminating early germinating seeds and then eliminating early leafing seedlings. Spring frost is a major factor that limits the areas in which temperate zone deciduous tree fruits can be grown and is re- sponsible for much of the year-to-year fluctuations in yield. To minimize frost injury, fruit growers often invest considerable sums of money in wind machines, sprinkler-irrigation, and heat- ers. Trees are most sensitive to frost when in full bloom, and since the probability of frost is largely a function of calendar date, late-flowering selections often avoid injury. In apple, genotypes are known that vary in flowering date by >30 days. The latest blooming genotypes, cider apples from Europe (Mur- awski, 1967; Tydeman, 1958), bloom 3 weeks later than 'De- licious'. These cultivars have higher chilling requirements and higher heat requirements in the post-rest phase (Gianfaga and Mehlenbacher, 1985; Swartz and Powell, 1981). Their use is currently limited because of their unattractive appearance, poor fruit quality, and susceptibility to fire blight (Erwinia amylovora (Burrill) Winslow) (Aldwinkle et al., 1976). However, they represent very valuable germplasm that breeders can use in the development of late-flowerin g selections with improved fruit quality and disease resistance. This has been one of the objec- tives of the apple breeding program at Rutgers Univ. since 1955. As part of this continuing effort, crosses were made in 1984 between late-flowering genotypes and selections resistant to ap- ple scab and fire blight. Date of leafing-out of juvenile seedlings was shown by Tydeman (1964) to be highly correlated with flowering date in the adult trees, and elimination of early leafing seedlings in the nursery during the second season of growth (15 months after seed germination) was very effective in delaying bloom date in the seedling population (Murawski, 1967). A similar strategy has been used at Rutgers. During stratification, it was noted that seeds of the 1984 crosses involving late-bloom- ing parents, compared with crosses between selections flower- ing at the normal time, not only germinated later but they also germinated over a much longer time. Previous studies have

‘Eta’ and ‘Theta’ are two new hazelnut (Corylus avellana L.) pollenizer cultivars. They were released by the Oregon Agricultural Experiment Station in Jan. 2009 as pollenizers for the late-flowering ‘Jefferson’. They have a very high level of resistance to eastern filbert blight caused by Anisogramma anomala (Peck) E. Muller conferred by a dominant allele from ‘Gasaway’. Pollen of ‘Epsilon’ and ‘Zeta’, released in 2002 (Mehlenbacher and Smith, 2004), is shed late but expresses S1 and so is incompatible on females of ‘Jefferson’ (S1 S3). ‘Eta’ and ‘Theta’, which shed pollen very late during the flowering season and are compatible with most cultivars, provide growers with additional pollenizer options.

‘Red Dragon’, tested as OSU 897.078, resulted from a cross of OSU 487.055 · OSU 367.039 (Fig. 1) made in 1997. OSU 487.055 is from a cross of ‘Contorta’ (syn. Corylus avellana var. contorta) · VR 6-28, and OSU 367.039 is a redleaf selection from seeds derived from open pollination of ‘Contorta’. VR 6-28 is from a cross of ‘Riccia di Talanico’ from southern Italy and ‘Gasaway’. We believe that ‘Rode Zeller’ (syn. ‘Rote Zellernuss’) is the donor of the redleaf trait, which is conferred by a dominant allele at the leaf anthocyanin locus. A tree of ‘Rode Zeller’ was near the ‘Contorta’ tree from which open-pollinated nuts were collected. ‘Red Dragon’, OSU 487.055, and VR 6-28 carry in a heterozygous state a dominant allele for complete resistance to EFB in Oregon from ‘Gasaway’ (Mehlenbacher et al., 1991). Contorted growth habit is conferred by a recessive allele from ‘Contorta’ (Smith and Mehlenbacher, 1996). ‘Contorta’ was discovered in a hedgerow in Frocester, U.K., approximately 1863 and has been propagated by graftage or layerage (Wakefield, 1962). The nursery trade often calls it ‘Harry Lauder’s Walking Stick’. Hybrid seeds from the cross OSU 487.055 · OSU 367.039 were harvested in Aug. 1997, stratified, and seedlings with contorted growth habit grown in the greenhouse during the summer of 1998 using standard practices (Thompson et al., 1996). From this cross, 42 seedlings with contorted growth habit were planted in the field in Oct. 1998. The designation OSU 897.078 indicates the row and tree location of the original seedling. Nuts were first observed on the original seedling in 2002. Grafted trees of ‘Contorta’ and 19 contorted selections, three or four trees of each, were planted in a trial in Mar. 2004. The trial was a randomized design in a single row located at the Smith Horticulture Research Farm in Corvallis. Trees in the trial were observed from 2004 to 2008. In 2006 and 2007, 10 nursery growers were invited to take notes on the trees and comment as to which were more desirable. These comments supplemented the notes recorded by the hazelnut breeding program (S.A. Mehlenbacher and D.C. Smith).

A chlorophyll deficiency expressed as yellowing of leaves was observed in hazelnut (Corylus avellana L.) progenies. Segregation ratios approximated 3 green: 1 yellow, indicating control by a single recessive gene designated chlorophyll deficient #1, for which the symbol c, is proposed. `Barcelona', `Butler', `Compton', `Lansing', Willamette', and the ornamental selection `Redleaf #3' are heterozygous. Pedigree analysis strongly suggests that all heteroxygotes inherited the recessive allele from `Barcelona'. A cross of `Barcelona' with the yellow-leafed ornamental Corylus avellana L. var. aurea Kirchn. produced no yellow-leafed seedlings, indicating that the chlorophyll deficiencies from these two sources are controlled by different loci. Progenies segregating simultaneously for this trait and the gene controlling presence of anthocyanin indicated that the two traits are inherited independently. Seedlings deficient in chlorophyll but with anthocyanin were able to survive under field conditions, while leaves of yellow-leafed seedlings lacking anthocyanin became scorched and the trees died.

The cutleaf hazelnut [Corylus avellana L. f. heterophylla (Loud.) Rehder] is an ornamental form with strongly dissected leaf morphology. Its stigmas express incompatibility allele S20 but none of the other 25 S-alleles was detected with fluorescence microscopy. Three seedlings from a cross of the cutleaf hazelnut and VR6-28 lacked S20 and were investigated further. Each expressed an allele from the parent VR6-28 (S2 S26), S26 in OSU 562.031 and OSU 562.048 and S2 in OSU 562.049. S2 and S26 are low in the dominance hierarchy, so we expected the new allele from the cutleaf hazelnut to be expressed in their pollen. Unexpectedly, fluorescence microscopy showed that pollen of all three selections was compatible on their cutleaf parent and on each other, and furthermore, self-pollinations showed the excellent germination and long parallel tubes in the styles that are typical of a compatible pollination. Controlled self- and cross-pollinations in the field verified the self-compatibility of two selections. Cluster set for self-pollinations was very high (75-90%) and within the range observed for compatible cross-pollinations. Furthermore, the frequency of blank nuts was low (28, and its presence in seedlings of `Cutleaf' is indicated by the absence of S20. Controlled pollinations in the field also showed that selection OSU 562.069 (S2 S28) from the cross `Cutleaf' × `Redleaf #3' was self-compatible. Fluorescence microscopy showed that two additional seedlings were self-incompatible [OSU 367.052 (S1 S28) and OSU 367.076 (S6 S28)] while a third [OSU 706.071 (S9 S28)] was self-compatible. Self-compatibility may be limited to genotypes that combine S28 with a second allele that is low in the dominance hierarchy.

‘Gamma’ has incompatibility alleles S 2 and S 10 , but only S 10 is expressed in the pollen because of dominance (Mehlenbacher, 1997a). The trees set many catkins, and pollen is shed in midseason, at about the same time as ‘Daviana’. The pollen-shedding period is short, and thus ‘Gamma’ should not be the sole pollenizer in an orchard. It is a suitable pollenizer for ‘Lewis’ (S 3 S 8 ) and ‘Barcelona’ (S 1 S 2 ), but sheds pollen too early for ‘Clark’ (S 3 S 8 ) and ‘Ennis’ (S 1 S 11 ). It is incompatible on its parent ‘Casina’ (S 10 S 21 ). Nuts and kernels resemble those of ‘Casina’ but are slightly larger (Table 1). Nut maturity is a few days before ‘Barcelona’, and about 80% of the nuts fall free of the husk at maturity. The frequency of moldy kernels is very low. The original seedling tree was vigorous and moderately productive. Bud mite ratings are intermediate. ‘Delta’ has incompatibility alleles S 1 and S 15 ; both are expressed in the pollen. The trees set many catkins, and shed copious amounts of pollen in late midseason with ‘Hall’s Giant’. It is a suitable pollenizer for ‘Lewis’ and for early-emerging females of ‘Clark’, but is incompatible on ‘Barcelona’, ‘Ennis’ (S 1 S 11 ), and ‘Willamette’ (S 1 S 3 ). The nuts are slightly larger than those of ‘Casina’ (Table 1) and mature a few days later than ‘Barcelona’. About 85% of the nuts fall free of the husk at maturity, while a few remain attached to the husk at the edge of the basal scar. The original seedling tree was ‘Gamma’, ‘Delta’, ‘Epsilon’ and ‘Zeta’ are four new hazelnut (Corylus avellana L.) pollenizer cultivars. They were released by the Oregon Agricultural Experiment Station in February 2002. They shed pollen at different times during the fl owering season, spanning the time that female infl orescences of most cultivars are receptive. They have complete resistance to eastern fi lbert blight caused by Anisogramma anomala (Peck) E. Muller. ‘Gamma’ and ‘Delta’ carry resistance from ‘Gasaway’, while ‘Epsilon’ and ‘Zeta’ carry resistance from ‘Zimmerman’. The traditional pollenizers ‘Daviana’ and ‘Butler’, and four selections (VR4-31, VR11-27, VR20-11, and VR23-18) previously released as pollenizers for ‘Barcelona’, express incompatibility allele S 3 in their pollen (Mehlenbacher and Thompson, 1991). Although compatible on ‘Barcelona’ females (S 1 S 2 ), their pollen is incompatible on females of recently released ‘Lewis’ and ‘Clark’ (both S 3 S 8 ) (Mehlenbacher et al., 2000, 2001). ‘Gamma’, ‘Delta’, ‘Epsilon’, and ‘Zeta’ provide growers with additional pollenizer options for recently released and standard cultivars.

The style color of standard hazelnut (Corylus avellana L.) cultivars ranges from pink to dark purple. Styles with an unusual yellow color were first noted in seedlings of the progeny 'Goodpasture' x 'Compton', and the ratio was ≈3 red : 1 yellow. Controlled crosses were made to investigate the genetic control of style color. The same 3:1 ratio was observed in four additional crosses in which both parents had red styles. Two crosses of a red and a yellow parent gave ≈50% yellow styles, while a cross of two selections with yellow styles gave only seedlings with yellow styles. These segregation ratios indicate control by a single locus, with yellow style color recessive to red. Seedlings with yellow styles have green buds and catkins and a more upright growth habit than their siblings with red styles. Inspection of the pedigrees of these progenies shows that 'Daviana', 'Willamette', 'Butler', 'Compton', 'Goodpasture', and 'Lansing #1' are heterozygous. 'Daviana' appears to be the original source of the allele for yellow styles, as it is a known or suspected parent or ancestor of the others. Ratios in a progeny segregating simultaneously for growth habit (normal vs. contorted) and style color indicated independence of the traits. However, in a progeny segregating simultaneously for leaf color (red vs. green) and style color, no redleaf seedlings had yellow styles. The S-alleles of eight genotypes with yellow styles were determined, and indicate a possible linkage between the yellow style locus and the S locus that controls pollen-stigma incompatibility. One expla- nation is that the yellow style trait is conferred by an allele (a ys ) at the anthocyanin (A) locus that controls leaf color. A second explanation is that there is a yellow style locus closely linked to the A locus. The A locus is known to be loosely linked to the S locus. The European hazelnut (Corylus avellana L.) is a monoecious, wind-pollinated shrub that enforces cross-pollination through dichogamy and self-incompatibility. The style color of standard green-leafed hazelnut cultivars ranges from pink to dark purple. Only when branches are bagged to protect female inflorescences from wind-borne pollen do the styles continue to elongate and the color fades from red or pink to light yellow or white. In 1978, in the progeny 'Goodpasture' x 'Compton', styles with an un- usual yellow color (Fig. 1) were noted in ≈25% of the seedlings. The yellow color was present when the styles first emerged and persisted as the flowers aged. We report here the results of an investigation of the genetic control of style color in hazelnut.

The cutleaf hazelnut [Corylus avellana L. f. heterophylla (Loud.) Rehder] is grown as an ornamental for its distinct leaf shape. Its leaves are slightly smaller, more deeply lobed, and more sharply toothed than those of standard hazelnut cultivars. When the cutleaf hazelnut was crossed with cultivars with normal leaves, all seedlings had normal leaves. When seedlings were backcrossed to their cutleaf parent, half of the seedlings expressed the cutleaf trait, and when crossed with each other in pairs, 25% of the seedlings were cutleaf. These segregation ratios indicate that the cutleaf trait is conferred by a single recessive gene for which the symbol cf is proposed. Progenies segregating simultaneously for leaf shape and color indicate that the cutleaf locus is independent of the locus controlling red leaf color and of the locus controlling a chlorophyll deficiency, which appears to be identical to that previously observed in seedlings of `Barcelona'.

442 Eastern filbert blight, caused by the fungus Anisogramma anomala (Peck) E. Muller, is native to the eastern United States where the wild species Corylus americana Marsh. serves as its host. The disease is believed to have been introduced to the Pacific Northwest on nursery stock imported from the East Coast in the early 1960s. The disease is now firmly established in the northern third of the Willamette Valley, the major growing area, and is a serious threat to commercial acreage of the European hazel, Corylus avellana L. The life cycle of the fungus was described by Gottwald and Cameron (1980). Symptoms include perennial cankers that enlarge 30 to 100 cm·year and can exceed 2 m in length, girdling scaffold limbs and the tree trunk. The canopy of older trees of susceptible cultivars is killed in 7 to 10 years. The most common hazelnut orchards in Oregon are planted to ‘Barcelona’, with ‘Daviana’ pollenizers planted every third tree in every third row. ‘Barcelona’ is considered tolerant of the disease, as infected trees remain productive for several years before eventually dying. ‘Daviana’, however, is highly susceptible. As eastern filbert blight spreads from one orchard to another, it is generally found first in the ‘Daviana’ pollenizers. From there, it spreads to the surrounding ‘Barcelona’ trees. ‘Butler’, the second most common pollenizer, is also highly susceptible. ‘Hall’s Giant’ is considered tolerant and is currently recommended as a pollenizer for ‘Barcelona’, although it sheds pollen later than the ideal time. ‘Gasaway’, which is highly resistant to the disease (Mehlenbacher and Thompson, 1991), sheds its pollen very late in the season and, thus, is a poor choice as a pollenizer for ‘Barcelona’. By replacing the highly susceptible pollenizers in a ‘Barcelona’ orchard with resistant genotypes, it should be possible to delay the time of initial infection and to maintain an infected orchard in a productive state for many years. Four resistant pollenizer selections were