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  • Author or Editor: Shawn A. Mehlenbacher x
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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.

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‘Jerseydawn’ is an early-ripening, yellow-fleshed, semi-freestone peach [Prunus persica (L.) Batsch] for the fresh market. The fruit ripens 10-14 days before ‘Redhaven’ and was introduced to meet the need for a quality peach in this season. The tree is of medium vigor and is productive. The leaves and fruit are resistant to bacterial spot [Xanthomonas campestris pv. pruni (Smith) Young et al.]. Flower bud hardiness appears to be slightly less than that of ‘Redhaven’. Split pit has not been a problem. ‘Jerseydawn’ is performing well in trials at Geneva, N.Y.; East Lansing, Mich.; and throughout New Jersey.

Open Access

The Oregon State Univ. breeding program is developing improved hazelnut cultivars for the kernel market. Most traits of interest are quantitative, yet there is little information available on their heritability. In this study, the heritability of 10 morphological and 4 phenological traits was estimated by regression of offspring means on midparent values. Seedlings from 35 crosses among 41 parents made in 1988 and 1989 were used. The parents represented the wide genetic diversity used in the breeding program. Estimates were all high, ranging from 0.56 for amount of kernel fiber and 0.58 for time of catkin elongation to 0.87 for percent kernel and 0.89 for nut depth.

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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.

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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.

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