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David C Smith and Shawn A. Mehienbacher

Tyvek housewrap (Du Pont, Wilmington, Delaware), an air-infiltration barrier for use in house construction, has been put to a novel use for making pollination bags for breeding hazelnuts (Corylus avellana L.). Bagged flowers are used in making crosses and incompatiblity testing and remain receptive for up to 3 months. Tyvek has outperformed paper and plastic materials we have tried in terms of durability and cost. Tyvek is a spun-bonded, nondirectionally oriented film of highdensity polyethylene fibers that is permeable to water vapor and air, but is water resistant and pollen-proof, and can be made into bags of any size needed.

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Cheryl R. Hampson and Anita N. Azarenko

Self-incompatibility, a genetic mechanism enforcing out crossing, is most commonly controlled by a single, multi-allelic gene, designated the S-gene. Sporophytic self-incompatibility (SSI), a form of incompatibility determined by the parent plant rather than the gametes, is present in the Brassicaceae, Compositae and other families, and also in hazelnut (Corylus avellana L.). Little is known about the molecular basis of SSI in plants other than crucifers. An S-gene cloned from Brassica oleracea (donated by Dr. June Nasrallah, Cornell University) was used to probe genomic DNA obtained from seven hazelnut genotypes. DNA hybridization was observed in cultivars `Hall's Giant' and `Willamette'. Gene similarity was estimated to be 70-80%.

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Cheryl R. Hampson, Anita Nina Azarenko, and Al Soeldner

Scanning electron microscopy was used to describe pollen-stigma interactions during compatible and incompatible pollinations of hazelnut (Corylus avellana L.), a species possessing sporophytic self-incompatibility. The stigmatic surface is of the dry type and was covered with elongated, rounded papillae. Compatible and incompatible pollen hydrated within 2 hours of pollination. Compatible pollen tubes emerged by 4 hours and grew into the style by 12 hours after pollination. Penetration of stigmatic papillae appeared to be intracellular in some cases. In incompatible pollinations, however, pollen tube emergence was delayed until at least 8 hours. The pollen tubes were distorted and did not penetrate the stigma.

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Nahla V. Bassil, William M. Proebsting, Larry W. Moore, and David A. Lightfoot

Hazelnut (Corylus avellana L.) softwood cuttings of the cultivars Ennis and Casina were propagated under mist during June and July 1987 and 1988. Rooting of stem cuttings was stimulated by both Agrobacterium and IBA treatment; however, IBA caused nearly complete bud abscission. Better rooting and bud retention were observed in `Casina' than in `Ennis' in 1988. Bud retention on Agrobacterium -inoculated cuttings improved as the cuttings approached the semi-hardwood stage. Six months after transplanting, Agrobacterium -inoculated hazelnut cuttings had an extensive root system, characteristic of hairy root. Although the mechanism remains unclear, strains of Agrobacterium rhizogenes are effective rooting agents in hazelnut and may cause less bud abscission than IBA. Chemical name used: 1 H -indole-3-butyric acid (IBA).

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Shawn A. Mehlenbacher and David C. Smith

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'.

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Shawn A. Mehlenbacher

Chilling requirements of 44 genotypes of Corylus avellana L. were estimated by cutting shoots in the field at weekly intervals and forcing them in a warm greenhouse for four weeks. The chilling requirements of catkins, female flowers, and leaf buds were assumed to have been met when development occurred on more than half of the respective plant parts. Chilling requirements were lowest for catkins and highest for leaf buds, and ranged from <100 to 860 hours for catkins, 290-1550 hours for female flowers, and 365-1395 hours for leaf buds. The lowest chilling requirements were observed for the leading cultivars of Turkey and southern Italy. The yellow-leafed ornamental C. avellana var. aure a had very high chilling requirements for all plant parts.

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Shawn A. Mehlenbacher and David C Smith

The contorted hazel, Corylus avellana `Contorta', is an ornamental tree prized for its grotesquely twisted trunk and branches. `Contorta' was discovered in a hedgerow in England about 1863 and has been commercially propagated by layerage or graftage because it was thought to not breed true from seed. We investigated the inheritance of contorted growth habit in the course of our work breeding hazelnuts. Crosses between normal growth habit cultivars and `Contorta' produce all normal seedlings. Sib matings of compatible normal seedlings of `Contorta' produce offspring in the proportion of 3 normal: 1 contorted. The backcross of a normal `Contorta' seedling to `Contorta' gives progeny in the ratio of 1 normal: 1 contorted, indicating control of the trait by a single recessive gene.

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J.L. Olsen, S.A. Mehlenbacher, and A.N. Azarenko

Hazelnuts, (Corylus avellana L.), are wind-pollinated, monoecious, mostly dichogamous, and self-incompatible. About 90% of the cultivars studied are protandrous. Anthesis of the pistillate flower is temperature-dependent and occurs December through February, peaking in January. Stigmatic surfaces may remain receptive for up to 3 months. Four to 5 months separate pollination and fertilization of the ovule; the latter usually occurring between mid-May and the end of June in Oregon. A 10% pollinizer density has been the standard, with a recommended distance of 66 ft (20 m) or less between the main cultivar and the nearest pollinizer. Two or three different pollinizer cultivars, with different times of pollen shed, are recommended. The Oregon hazelnut industry is presently combating the fungal disease, eastern filbert blight, caused by Anisogramma anomala (Peck). Current management recommendations suggest reducing risk of infection are to reduce the most susceptible pollinizer cultivars to a density 5%, then gradually replace those left with immune or more resistant genotypes.

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Cheryl R. Hampson, Anita N. Azarenko, Rebecca McCluskey, and Jeffery Olsen

Many deciduous tree fruit species have a light requirement for floral induction. Floral induction of hazelnut has been reported to occur through the end of May into July. At the end of May, less than 5% full sun reaches the base of the canopy in a mature hazelnut orchard. Leaf area density was estimated to be 7.6. Six levels of shade (0, 30, 47, 63, 73, or 92%) were imposed on caged 7-year-old hazelnut trees (Corylus avellana L. cv. Ennis) to determine effects of shade on yield and nut quality. Shading reduced yield of nuts per tree from 3.43 kg in 0% shade to 0.62 kg in 92% shade and yield efficiency from 70.2 g/cm2 in full sun to 18.3 g/cm2 in 92% shade. Yield and yield efficiency decreased substantially in 30% shade. When shade exceeded 47%, nut and kernel size decreased sharply, but % kernel increased slightly. In comparison to trees in full sun, shaded trees had a higher incidence of moldy or shrivelled kernels and a lower incidence of blanks.

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Kirk W. Pomper, Anita N. Azarenko, Joel W. Davis, and Shawn A. Mehlenbacher

Random amplified polymorphic DNA (RAPD) markers were identified for self-incompatibility (SI) alleles that will allow marker-assisted selection of desired S-alleles and assist in cloning the locus responsible for the sporophytic SI displayed in hazelnut (Corylus avellana L.). DNA was extracted from young leaves collected from field-planted parents and 27 progeny of the cross OSU 23.017 (S1 S12) × VR6-28 (S2 S26). Screening of 10-base oligonucleotide RAPD primers was performed using bulked segregant analysis. DNA samples from six trees each were pooled into four “bulks,” one for each of the following: S1 S2, S1 S26, S2 S12, and S12 S26. “Super bulks” of twelve trees each for S1, S2, S12, and S26 then were created for each allele by combining the appropriate bulks. The DNA from these four super bulks and also the parents was used as a template in the PCR assays. Amplification products were electrophoresed on 2% agarose gels and photographed under UV light after ethidium bromide staining. 200 primers were screened and one RAPD marker each was identified for alleles S2 (OPI-07700) and S1 (OPJ-141700).