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Veli Erdogan and David C. Smith

`Barcelona' hazelnut (C. avellana L.) shoots were girdled and stool layered in a factorial design with three tissue removal (leaf, bud and meristem removal) and two hormone (with or without 750 ppm IBA) treatments. Percent rooting, rooting grade (0 to 5), shoot length, shoot diameter, and total number of buds were determined. Average percent rooting was >90% for all treatments. Girdling alone gave as high percent rooting as hormone application. The main effect of IBA was on root quality rather than percent rooting. About 75% of the hormone-treated rooted layers could be directly planted (grades 3 to 5), compared to 44% for the control, but shoot length, shoot diameter and total number of buds decreased with IBA application. Bud removal did not affect average percent rooting while meristem removal reduced it slightly. The percentage of layers having grades 3 to 5 was lower for the meristem and bud removal treatments than for leaf removal. Our results support the adoption of stool layerage with girdling and IBA application for the production of strong, well-rooted trees suitable for planting directly in the orchard.

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Shawn A. Mehlenbacher and David C. Smith

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Shawn A. Mehlenbacher and David C. Smith

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Shawn A. Mehlenbacher and David C. Smith

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 (<10%). The second allele in the cutleaf hazelnut is designated S28, 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.

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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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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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David C. Smith and Shawn A. Mehlenbacher

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Shawn A. Mehlenbacher and David C. Smith

The effect of parentage, spacing, and sucker removal on precocity of hazelnut (Corylus avellana L.) seedlings 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.

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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'.