Hybrid Hazelnuts Research Articles

Identification of Compounds That Contribute to Consumer Aroma Liking of Roasted American-European Hybrid Hazelnuts.

New interspecific hybrid hazelnut crosses between American (Corylus americana) and European (Corylus avellana) hazelnuts are being developed to support a commercial industry in the Midwest region of the United States. In this study, volatile compounds that impact consumer aroma liking of roasted hybrid hazelnuts (C. americana × C. avellana) were investigated by targeted and nontargeted GC/MS flavoromics. Chemical profiles from 10 roasted hybrid hazelnut samples were modeled with consumer aroma liking scores by orthogonal partial least-squares with good fit and predictive performance (R2 ≥ 0.92, Q2 ≥ 0.82, RMSECV = 0.2). Top ranked predictors positively correlated with liking included 12 aroma compounds and 4 profiled volatiles for the targeted and nontargeted methods, respectively. Sensory recombination testing of hazelnut samples with addition of the 12 predictive odorants was preferred by consumers (p < 0.001, Δ aroma liking = 2.2 on 9-point scale) and perceived as more roasty, nutty, and sweet compared to the control (p < 0.05). Addition of the 4 predictive volatiles at subthreshold levels also was preferred (p = 0.02) and perceived as less earthy and mushroom like than the control (p < 0.05).

Characterization and Profiling of Key Odorants in Roasted Hybrid American-European Hazelnuts.

American-European hybrid hazelnuts (Corylus americana × Corylus avellana) are an emerging crop in the Upper Midwest of the United States that have been reported to have unique sensory characteristics compared to traditionally grown European hazelnuts. In this study, key odor-active compounds in a roasted hybrid hazelnut variety (C. americana × C. avellana) were identified and profiled across different hybrid hazelnut varietals to understand sensory differences. Gas chromatography/mass spectrometry/olfactometry analysis identified 33 odorants with high flavor dilution factors (FD ≥ 16) in the roasted hybrid hazelnut, including 2-acetylpyrazine and 2-aminoacetophenone as first reported hazelnut odorants. Descriptive sensory analysis profiles of the roasted hazelnut and an aroma recombination model consisting of 27 odorants quantified above their odor detection thresholds were not significantly different for the six evaluated attributes, confirming the aroma contribution of the identified odorants. Variation in all 33 aroma-active compounds across 12 hybrid and two European hazelnut varieties was visualized through principal component analysis and related to aroma profiles previously characterized by consumers.

Consumer acceptance and sensory perception of roasted American-European hybrid hazelnuts.

Interspecific American-European hazelnut (Corylus americana × C. avellana) hybrids are being developed for the Upper Midwest region of the United States, which have potential economic and ecological benefits. Currently, researchers are working on pre-commercialization initiatives to create a local hazelnut industry. However, a lack of knowledge on the sensory characteristics and consumer acceptability of the hybrid hazelnuts have been identified as potential limitations to production. This study investigated consumer responses to hybrid hazelnuts, employing hedonic ratings and check-all-that-apply (CATA) questions. Twelve roasted hazelnut hybrids were subjected to consumer evaluation for liking (aroma, color, flavor, texture, and overall) and aroma and flavor descriptors. Consumers also evaluated two European hazelnut varieties for comparative purposes. Liking scores were significantly different (p<0.05) across different hybrid varieties and when comparing specific hybrids with European varieties. CATA sensory profiles specific to different varieties were also observed and discriminating attributes were identified using multiple-response methodologies. Penalty analysis based on CATA further identified the attributes roasty, hazelnut-like, caramel-like, chocolate-like, sweet, and salty as primary drivers of aroma/flavor liking, while earthy, burnt, and bitter were identified as primary drivers of disliking. Overall, unique flavors that impacted liking were found in hybrid hazelnuts and, when compared with European hazelnuts, provided insights for breeding and post-processing strategies to optimize product quality.

Comprehensive evaluation of the resistance to shoot shriveling before and after sprouting in different varieties of Ping’ou hybrid hazelnut

IntroductionThe hybrid hazelnut is an important fruit tree species known for its high productivity and disease resistance. However, during the growth process of hybrid hazelnuts, issues such as branch withering and bud wrinkling have attracted significant attention. These phenomena severely impact the normal development and yield of the plants. This study aimed to investigate the relationship between the resistance to shoot emergence and physiological changes in six hazel tree varieties by comprehensively analyzing their resistance to shoot emergence.MethodSix widely cultivated hazelnut hybrid varieties were selected for physiological measurements and field surveys using one-year-old branches and buds as test materials. The resistance to shoot emergence of different hazel tree varieties was evaluated through correlation analysis, principal component analysis, and membership function evaluation.ResultsThe results showed that the length and width of hazel buds gradually increased while the thickness first increased and then decreased before and after bud burst. The carbohydrate levels of the ‘Dawei’, ‘Pingou 110’, and ‘84–237’ varieties were significantly higher than those of other varieties. The content of reducing sugars and starch in hazel buds generally increased and then decreased during the bud burst process, while α-amylase activity showed a decreasing trend followed by an increasing trend. The antioxidative enzyme activity of ‘Dawei’ was significantly higher than that of other varieties on different sampling dates. The soluble protein content, POD enzyme activity, and CAT enzyme activity of hazel buds for the six varieties gradually decreased. The moisture content of ‘Pingou 210’ shoots was significantly higher than that of other varieties during the peak emergence period. The correlation analysis results showed that the bud burst rate of hazel trees was positively correlated with the length, width, thickness, reducing sugar content, starch content, POD enzyme activity, CAT enzyme activity, and shoot moisture content, while it was negatively correlated with α-amylase activity and relative conductivity of shoots. Through a comprehensive evaluation using correlation analysis, principal component analysis, and membership function analysis, the resistance to shoot emergence of the six hazel tree varieties was ranked in the following order: ‘Dawei’, ‘Pingou 110’, ‘84–237’, ‘Pingou 210’, ‘Yuzhui’, and ‘Liaozhen 3’.DiscussionThis study fills a research gap regarding the physiological changes of hazelnuts before and after sprouting, and provides theoretical guidance for further research on the anti-withering ability of hazelnut trees.

The Polydrusus weevils (Coleoptera: Curculionidae) of the United States of America and Canada: identification and insights into the ecology of two nonnative species in hazel (Corylus spp.)

Abstract Seven species of Polydrusus Germar weevils (Coleoptera: Curculionidae) occur in the United States of America and Canada, three of which are introduced from Europe, are polyphagous, and may be displacing native weevil fauna in select areas of North America. We review host plant information for these species and provide distributional maps for each. We also present results on the seasonal phenology and sex ratios of two nonnative species, Polydrusus impressifrons (Gyllenhal) and Polydrusus formosus (Mayer), recorded in 2020 and 2021 in two orchards of hybrid hazelnuts (Betulaceae) in Minnesota, United States of America. These two species may present an episodic threat to the burgeoning hybrid hazelnut industry due to their ability to damage buds, foliage, and roots of hardwoods. We found that adults of these two species began emerging in late May of each year and remained present until mid-July. We found higher numbers of P. formosus than of P. impressifrons on hazel plants. Sex ratios of both species were generally between 50–60% male. We supply a compendium of species descriptions that (1) distinguishes between native and nonnative species and (2) identifies the sex of nonnative species. This research contributes to work on the ecology of Polydrusus, conservation of native species, and the management of tree crops.

Characterisation of oil oxidation, fatty acid, carotenoid, squalene and tocopherol components of hazelnut oils obtained from three varieties undergoing oxidation

SummaryHazelnut oils obtained from three varieties of Chinese hybrid hazelnuts (cv. ‘Liaozhen 3 (LZ)’, ‘Pingou 21’ (PG) and ‘Yuzhui’ (YZ)) were used to compare the lipid oxidation characteristics (peroxide value, p‐anisidine value and conjugated diene value), fatty acid profiles and major active components (squalene, carotenoids and tocopherols) under oxidation condition at 60 °C for 40 days, in addition, the molecular structure changes in the three hazelnut oils were monitored by Raman spectroscopy. The lipid oxidation of the three hazelnut oils had similar tendencies, and the oxidation rate was slower in the early stage and faster in the later stage. Polyunsaturated fatty acids (PUFAs) tended to decrease mainly due to the decrease in linoleic acid. LZ had higher contents of tocopherol, carotenoids and PUFAs than the other varieties, while YZ owned the highest content of squalene. Tocopherol and carotenoids of the three hazelnut oils showed easy loss, while squalene was relatively stable. Raman spectroscopy can effectively indicate the degree of oxidation and carotenoid levels of hazelnut oil. This study can provide a scientific basis for variety selection in planting and utilisation of active ingredients for the hazelnut industry.

In vitro rooting of hybrid hazelnuts (Corylus avellana×Corylus americana) in a temporary immersion system

Commercial micropropagation of hybrid hazelnuts (Corylus avellana L. × C. americana Marshall) has been limited, owing to their poor rooting ability in vitro as well as ex vitro, leading to high mortality of plantlets transplanted in the greenhouse. The objective of this study was to develop an efficient and cost-effective protocol for rooting and plantlet acclimation of in vitro grown hazelnut shoots. Efficient in vitro rooting was accomplished in a rocker-based temporary immersion bioreactor system. The use of a temporary immersion system (TIS) in combination with the inert substrate Oasis® In Vitro Express (IVE) significantly improved the in vitro rooting efficiency (100%) compared with semi-solid medium (27%) after four weeks of culture. A higher density (36 explants/vessel) of shoot explants in the TIS was found to support a significantly greater shoot height, chlorophyll content, and longest root length, compared with the lowest density treatment (12 explants/vessel). Efficiency of rooting and the number of roots formed were similar for both the high and low density of explants in the culture vessels, and the resulting plantlets exhibited &gt; 80% survival in the greenhouse. These results demonstrate the usefulness of rocker-based TIS for commercial micropropagation of hazelnuts and, potentially, other tree species.

Eastern Filbert Blight Resistance in American and Interspecific Hybrid Hazelnuts

Eastern filbert blight (EFB), caused by the fungus Anisogramma anomala, is a primary limitation to european hazelnut (Corylus avellana) cultivation in eastern North America. American hazelnut (Corylus americana) is the endemic host of A. anomala and, despite its tiny, thick-shelled nuts, is a potentially valuable source of EFB resistance and climatic adaptation. Interspecific hybrids (Corylus americana × C. avellana) have been explored for nearly a century as a means to combine EFB resistance with wider adaptability and larger nuts. Although significant progress was made in the past, the genetic diversity of the starting material was limited and additional improvements are needed for expansion of hazelnut (Corylus sp.) production outside of Oregon, where 99% of the U.S. crop is currently produced. Our objective was to determine if C. americana can be a donor of EFB resistance. We crossed 29 diverse EFB-resistant C. americana accessions to EFB-susceptible C. avellana selections (31 total progenies) to produce 2031 F1 plants. In addition, new C. americana germplasm was procured from across the native range of the species. The new collection of 1335 plants from 122 seed lots represents 72 counties and 22 states. The interspecific hybrid progenies and a subset of the American collection (616 trees from 62 seed lots) were field planted and evaluated for EFB response following field inoculations and natural disease spread over seven growing seasons. EFB was rated on a scale of 0 (no EFB) to 5 (all stems containing cankers). Results showed that progeny means of the interspecific hybrids ranged from 0.96 to 4.72. Fourteen of the 31 progenies were composed of at least one-third EFB-free or highly tolerant offspring (i.e., ratings 0–2), transmitting a significant level of resistance/tolerance. Several corresponding C. americana accessions that imparted a greater degree of resistance to their hybrid offspring were also identified. In addition, results showed that 587 (95.3%) of the 616 C. americana plants evaluated remained completely free of EFB. These findings confirm reports that the species rarely expresses signs or symptoms of the disease and should be robustly studied and exploited in breeding.

Timing of Collection and Preparation of Hardwood Stem Cuttings for Propagating Hybrid Hazelnuts 1

AbstractIn previous trials we had found that dormant hybrid hazelnuts crown suckers collected in the fall after leaf drop can be successfully rooted if they are chilled at least until January before being placed in low-cost humidity tents in a greenhouse. The first objective of this experiment was to determine if cuttings could be rooted if started earlier, so as to avoid the heat stress found in the greenhouse in late spring and early summer. The second objective was to see if rooting rates could be improved by collecting non-dormant crown suckers in September and October, before leaf drop. We hypothesized that by collecting stems at a time in the fall when woody plants are translocating resources from leaves to their root systems, we could direct those resources towards growth of adventitious roots. This hypothesis proved to be wrong: stems collected in full leaf died, even with measures to avoid moisture loss from leaves. However, we found that stems collected soon after leaf abscission, in early November, could be rooted if placed in the humidity tents in late November, after only three weeks of artificial chilling at 2 C (36 F). That is much less chilling than we previously thought was needed.Index words: propagation, Corylus americana (Walter), Corylus avellana (L.), rooting, chilling requirement.Chemicals used in this study: indole-3-butyric acid (IBA).Species used in this study: hybrid hazelnuts [Corylus americana (Walter) x Corylus avellana (L.)].

Field Pretreatment of Crown Suckers for Propagating Hybrid Hazelnuts

Abstract Hybrid hazelnuts [Corylus americana (Walter) x C. avellana (L.)] are being developed for their ecological and economic value as a new crop for the Upper Midwest, but lack of economically viable propagation methods is a significant bottleneck to their wide scale adoption. Thus far, mound layering has been the primary propagation method, but layering cannot produce the numbers of plants needed for large-scale production. Rooting hardwood stem cuttings is a possible alternative. In a factorial experiment, we evaluated two pretreatments, blanching with sawdust and application of IBA, applied to rapidly growing first year collar suckers in the field five months ahead of collection for rooting. These treatments simulated mound layering, but without girdling. Sawdust by itself significantly increased both quantity and quality of subsequent rooting, but IBA pretreatment in combination with sawdust produced even better results. Stem cuttings were rooted in a growth chamber, set at 22 C (72 F) and 60% relative humidity, with PAR of 320 umol.m−2 s−1 for 16 hours per day. The lack of heat stress in the growth chamber likely also contributed to relatively high rooting relative to the humidity tents used in previous trials. Index words: Propagation, Corylus americana (Walter), Corylus avellana (L.), rooting, etiolation. Chemicals used in this study: indole-3-butyric acid (IBA). Species used in this study: hybrid hazelnuts [Corylus americana (Walter) x Corylus avellana (L.)].

Optimizing Temperature and Humidity for Rooting Hybrid Hazelnuts from Hardwood Stem Cuttings1

Abstract Hybrid hazelnuts are being developed as a new crop for the Upper Midwest for their ecological and economic value, but lack of economically viable propagation methods is a significant bottleneck to their wide scale adoption. In previous trials we found that hardwood stem cuttings could be propagated in low cost humidity tents constructed of molded plastic tubs covered with white 70% shade plastic. When the plastic was sealed tightly at the sides, these tubs maintained relative humidity near saturation, but also tended to overheat. This trial experimented with the use of ordinary household humidifiers as an alternative way of maintaining humidity while avoiding overheating. We found that it is not necessary to maintain RH near 100% as we had been doing when we kept the humidity tents tightly sealed. Stem survival and, as a consequence, rooting were improved in vented tents in which humidity was maintained with humidifiers, though these required much more management than the sealed tents. Index words: Propagation, Corylus americana (Walter), Corylus avellana (L.), rooting, indole-3-butyric acid Chemicals used in this study: indole-3-butyric acid (IBA) Species used in this study: hybrid hazelnuts [Corylus americana (Walter) x Corylus avellana (L.)]

Optimizing IBA Concentration and Stem and Segment Size for Rooting of Hybrid Hazelnuts from Hardwood Stem Cuttings

Abstract Germplasm improvement of woody crops through plant breeding depends on effective methods of vegetative propagation, both for evaluation of candidate germplasm and for dissemination of improved varieties. Hybrid hazelnuts [Corylus americana (Walter) x C. avellana (L.)] are being developed as a new crop for the Upper Midwest for their ecological and economic value, but lack of economically viable propagation methods is a significant bottleneck to their wide scale adoption. This paper describes two trials to optimize propagation from hardwood stem cuttings in low-cost humidity tents, using dormant crown suckers collected in the fall. We found that: 1) 2 g.L−1 (2,000 ppm) indole-3-butyric acid (IBA) in a 50% ethanol solution is the best concentration for rooting cuttings of a range of sizes and 2) rooting declines with increasing basal diameter of stems, but increases with increasing length of stem. The thicker cortex of large diameter stems may present a physical barrier to emergence of adventitious roots. Conversely, longer stems have larger stores of carbohydrates, which are essential both for keeping the stems alive until roots can be developed, and for providing the building blocks for growing those roots. Index words: Propagation, Corylus americana (Walter), Corylus avellana (L.), rooting, indole-3-butyric acid. Chemicals used in this study: indole-3-butyric acid (IBA). Species used in this study: hybrid hazelnuts [Corylus americana (Walter) x Corylus avellana (L.)].

Equilibrium Moisture Content of Hazelnut Husks, Shells, and Kernels

Abstract. Hybrid hazelnuts that are predominately a cross between the American hazelnut () and the European hazelnut () are being grown and evaluated as part of an effort to develop a thriving hazelnut industry for the Upper Midwest of the U.S. Along with this plant development effort, researchers are investigating and assessing various harvesting and processing methods and equipment in an effort to create a robust and food-safe production industry. One harvesting alternative is to pick hazelnut clusters off plants before the nuts fully ripen and fall to the ground, an approach that requires greater attention to drying. Whether entire clusters are dried or the nuts are separated from the husks prior to drying is a decision that will be influenced by the drying requirements and potential uses for these hazelnut fractions. To this end, a study was undertaken to establish desorption isotherms for the husks, shells, and kernels of hybrid hazelnuts grown in the Upper Midwest. Clusters were hand-picked from shrubs in Wisconsin and immediately placed in 18 different controlled environments (six different relative humidity levels at three different temperatures). Actual moisture conditioning took place over saturated salt solutions in specially fabricated biomaterial moisture conditioning units. After a six-week period during which the clusters reached equilibrium with their environment via desorption, they were separated into husk, shell, and kernel fractions and returned to their respective conditioning units. After another six weeks in the conditioning units, the moisture content (MC) of each fraction was determined by oven-drying at 103°C for 48 h. Under equilibrium conditions, the kernel MC was found to be only 37% of that for shells, whereas the equilibrium moisture content (EMC) values for husks were on average 14% greater than those for shells. On a dry basis, the average cluster mass was 32.9% husk, 43.9% shell, and 23.2% kernel. Likewise, on a dry basis, the average whole nut mass was 65.5% shell and 34.5% kernel. The desorption data were fit to the Modified Henderson, Modified Chung-Pfost, Modified Halsey, Modified Oswin, and Modified GAB equations. Overall, the best fit to the experimental data was provided by the Modified Chung-Pfost equation with parameters determined using equilibrium relative humidity (ERH) as the dependent variable in regression analyses. For ERH values above 0.70, the temperature-modified form of the GAB equation is recommended for predicting desorption EMC values for hazelnut fractions. Keywords: Desorption, Equilibrium moisture content, Equilibrium relative humidity, Hazelnuts, Kernels, Nuts, Shells, Water activity.

Physical Properties of Upper Midwest U.S.-Grown Hybrid Hazelnuts

Abstract. Nuts from F1 hybrid hazelnuts grown in Wisconsin were harvested and dried to eight different moisture contents. Nut dimensions and mass were recorded. Nuts were then subjected to uniaxial compression to determine total deformation required for rupture, rupture force, and rupture energy for each of the three major nut axes. Kernel dimensions, shell thickness, shell mass, and kernel mass of each nut were recorded after rupture. Hybrid hazelnuts and kernels were found to be smaller than European varieties. Nut geometry was found to change with nut size. When a nut is loaded, an initial crack forms along a longitudinal line parallel to the direction of applied load and then rapidly propagates until it has extended along two longitudinal lines (both parallel to the applied load), causing the shell to split into two pieces. Under lateral (Y-axis and Z-axis) loadings, the shell is split into nearly identical halves. Loading along the X-axis required the lowest rupture force, rupture energy, and rupture strain of all loading axes. Rupture force, rupture energy, and stiffness were shown to be highly correlated with moisture content. At lower moisture contents, shells fractured into more pieces. Keywords: Hazelnut, Nut cracking, Nut geometry, Nut rupture force, Shelling, Shell thickness.

Yield, quality and genetic diversity of hybrid hazelnut selections in the Upper Midwest of the USA

The majority of hazelnut plantings in the Upper Midwest of the United States are planted with seedlings from crosses between American hazelnuts (Corylus americana) and European hazelnuts (C. avellana) that were initially made in the 1930’s. To evaluate the potential of this material to support a commercial industry, we have populated replicated field trials at five locations with clonal material of high performing accessions selected from these plantings. The hybrid plants in these trials were found to have high levels of genetic diversity when assessed at 10 microsatellite loci. Principal component analysis shows these Midwestern hybrids group genetically with American hazelnuts from the Upper Midwest region, but separately from European hazelnuts and hybrid hazelnuts developed elsewhere. We conclude that this pool of hybrids has sufficient genetic diversity for a breeding program to support a regional hazelnut industry. The average yield of the eight highest yielding of these genotypes, at ages six to 8 years, was 180 g m−2 of canopy area at the most productive site, which in a production system with 50% of the land covered by the crop canopy would translate to 895 kg of kernel ha−1. This compares favorably with expected yields of similarly aged European tree hazelnuts in Oregon. Though smaller than nuts from European cultivars, kernel quality of the top eight selections was deemed to be adequate for the processed nut market.

The Effects of Relative Humidity and Substrate Moisture on Rooting of Hybrid Hazelnuts from Hardwood Stem Cuttings1

Abstract Hybrid hazelnuts (Corylus americana Walter x C. avellana L.) are currently being bred for use as a cold-hardy perennial crop that could produce profits for Midwestern farms while supporting agroecosystem sustainability. However, asexual propagation techniques for producing germplasm for breeding and dissemination purposes have proven difficult. This study was one of a series attempting to develop a protocol for hardwood stem cutting propagation. This study assessed the impact that relative humidity (RH) and substrate moisture has on rooting of hardwood stem cuttings propagated in low-cost humidity tents. Hardwood stem cuttings retrieved from 14 hybrid hazelnut genotypes were planted into enclosed humidity tents, each housing 64 cuttings. Treatments were RH thresholds of 30%, 50%, 70%, and 90%, which were maintained by daily monitoring and watering to saturate the substrate when a tent's RH fell below its specified RH threshold. Cuttings propagated in 50% and 70% RH tents showed the highest rates of rooting at 16% and 12% respectively, whereas only 7% of cuttings rooted at 90% RH and 3% at 30% RH. By showing that intermediate RH levels and watering regimes are optimal for rooting, these results suggest daily monitoring is not necessary for hardwood stem cutting propagation of hybrid hazelnuts. Index words: propagation, relative humidity, substrate moisture, hardwood stem cuttings, hazelnuts, adventitious rooting. Chemicals used in this study: IBA (indole-3-butyric acid). Species used in this study: hybrid hazelnuts (Corylus americana Walter x C. avellana L.).

STUDIES ON POLLEN VIABILITY AND POLLEN-STIGMA COMPATIBILITY OF HYBRID HAZELNUTS

The studies are to select pollinated cultivars of hybrid hazelnut (Corylus heterophylla Fisch. A— C. avellana L.) by testing the pollen viability and pollen-stigma compatibility. The pollen viability of 5 hybrid hazelnuts was tested with the agar culture method. The pollen-stigma compatibility among 10 hybrid hazelnuts was observed by fluorescence microscope. The result showed that the pollen viability sequence from the highest to the lowest was ‘1-21’, ‘82-11’, ‘Liaozhen 3’, ‘Yuzhui’ and ‘Dawei’. The pollen-stigma compatibility testing result was that only ‘1-21’ showed best pollen-stigma compatibility among the 5 tested hybrid hazelnuts. It was demonstrated that 1-21 was the best pollinated cultivar.

Nitrogen fertilization for young established hybrid hazelnuts in the Upper Midwest of the United States of America

Braun, L. C., Gillman, J. H., Hoover, E. E. and Russelle, M. P. 2011. Nitrogen fertilization for young established hybrid hazelnuts in the Upper Midwest of the USA. Can. J. Plant Sci. 91: 907–918. Hybrids of Corylus avellana, C. americana and C. cornuta are proposed as a new crop for the Upper Midwest. Anecdotal information from midwestern growers suggests that these hybrid hazelnuts have high N requirements, but this has not been confirmed in replicated trials. Current nitrogen (N) recommendations for hazelnut production are based on research from the Pacific Northwest and may not be applicable to these hybrids in the Upper Midwest due to differing soils, climate, genetics, and growing systems. Three years of N rate trials on four plantings, that were 3 to 6 yr old at the start, showed that N responses of hybrid hazelnuts fit patterns for other woody crops: no N responses were found on soils with high organic matter, nor on soils with suspected P or K deficiencies. Where N responses were observed, they suggested that the N requirements of hybrid hazelnuts in the Upper Midwest are relatively low compared with those of European hazelnuts in the Pacific Northwest. Leaf N concentrations were within the expected ranges established for European hazelnuts in Oregon, suggesting that Oregon's standards may be applied to hybrid hazelnuts, except that 2.2% leaf N should be considered adequate, rather than a threshold to sufficiency.

Nutritional and anti‐nutritional compositions of defatted Nebraska hybrid hazelnut meal

SummaryDefatted meal of hybrid hazelnuts may have potential food and value‐added industrial applications. The proximate composition, mineral elements, amino acid profile and anti‐nutritional factors (total phenolics, tannins, condensed tannins and phytates) of defatted meals of ten Nebraska hybrid hazelnut genotypes were investigated. Excluding the amino acid profile, the nutritional and anti‐nutritional compositions of the meals differed significantly, with high protein, carbohydrate, neutral and acid detergent fibre concentrations and energy value. Mineral concentrations were higher than those previously reported. K was the most abundant mineral element, followed by P, Ca and Mg. Seven essential amino acids accounted for approximately 27.8% of the total amino acid contents. Tryptophan was not detected. All essential amino acid contents were significantly lower than the reference levels recommended for human and animal consumption. The high levels of anti‐nutritional factors, such as total phenolics, tannins, condensed tannins and phytate in the meals, could reduce protein and mineral bioavailability.

Nitrogen fertilization for new plantings of hybrid hazelnuts in the Upper Midwest of the United States of America

Braun, L. C., Gillman, J. H., Hoover, E. E. and Russelle, M. P. 2011. Nitrogen fertilization for new plantings of hybrid hazelnuts in the Upper Midwest of the United States of America. Can. J. Plant Sci. 91: 773–782. Seed-propagated hybrids of Corylus avellana and C. americana are a potential crop for the Upper Midwest. Current N recommendations for hazelnuts are based on research on clonally propagated C. avellana in Oregon and may not be applicable in the Upper Midwest due to differing soils, climate, and plant genetics. We established three field plots in 2003 to test N fertilization rates on new plantings, with rates up to 33 g N plant−1as ammonium nitrate applied annually in the spring, starting 2 wk after transplanting. We observed a strong negative linear effect of N rate on plant survival. In the second year we added trials on same-aged plants that had not previously been fertilized and found no N effect on survival. We concluded that waiting 1 yr after transplanting before fertilizing increases plant survival, but even then N requirements during establishment years are very low for hybrid hazelnuts. Standard leaf N concentrations for C. avellana in Oregon are roughly applicable to hybrid hazelnuts, except that the threshold between deficiency and sufficiency should be raised slightly to 1.9% N. The current threshold between deficient and sufficient, 2.2%, should be regarded as a target, rather than as a threshold to be exceeded.