The use of compost made from the leaves of Juglans regia has long been controversial because of its inhibitory effect due to the presence of juglone. Therefore, the aim of our study was to replicate ...the typical habits of farmers and gardeners, where the dried leaves are collected at the end of the season and placed in a composter. Then, the effects of the different treatments on the yield of the plant (lettuce), secondary metabolism, and possible toxicity of the compost of the grown plant were evaluated. The lowest yield of lettuce was obtained in soil with composted walnut and hazelnut leaves, while the highest yield was recorded in in soil with compost control, soil with composted walnut leaves and grass with the addition of composting agent and soil with composted walnut leaves with addition of composting agent. Some allelochemicals were still present in the compost but at such low levels that they did not affect yield. We suggest that dry walnut leaves and cut grass can be used for composting, while dry hazelnut leaves still contain some allelochemicals after two years that significantly inhibit plant growth and thus yield, so we would not recommend their use for composting.
Phenolic acids (chlorogenic, caffeic, p-coumaric, ferulic, sinapic, ellagic, and syringic acid) as well as syringaldehyde and juglone were identified in ripe fruits of 10 walnut cultivars: Adams, ...Cisco, Chandler, Franquette, Lara, Fernor, Fernette, Alsoszentivani 117 (A-117), Rasna, and Elit. Analyses were done using a high-performance liquid chromatograph equipped with a diode array detector. Significant differences in the contents of identified phenolics were observed among cultivars. Phenolics were determined separately in the kernel and in the thin skin of the walnut, termed the pellicle. Not only in the kernel but also in the pellicle did syringic acid, juglone, and ellagic acid predominate (average values of 33.83, 11.75, and 5.90 mg/100 g of kernel; and 1003.24, 317.90, and 128.98 mg/100 g of pellicle, respectively), and the contents of ferulic and sinapic acid (average values of 0.06 and 0.05 mg/100 g of kernel and 2.93 and 2.17 mg/100 g of pellicle, respectively) were the lowest in all cultivars. The highest differences in the sum of all identified phenolics were observed between Rasna and Fernette fruits; in Rasna there were >2-fold higher contents of identified phenolics in both kernel and pellicle. It was found that the walnut pellicle is the most important source of walnut phenolics. The ratio between the contents in pellicle and kernel varied by at least 14.8-fold for caffeic acid (cv. Adams) and by up to 752.0-fold for p-coumaric acid (cv. Elit). Keywords: Juglans regia L.; walnuts; kernel; pellicle; phenolic compounds
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•WHF-infested kernels turn from bright colour to brown, dark brown and even black.•Infested kernels are less aromatic, crispy and oily, but more bitter than healthy ones.•Phenolic ...contents of the kernels decrease due to WHF infestation.•Hydrolysable tannins and TPC closely correlate with kernels' sensory properties.•The response to the infestation is cultivar and infestation-time related.
Walnut husk fly (WHF) is the main pest of common walnut. Its negative impact on external fruits’ properties is frequently reported, while inner kernel quality loss remains unknown. Brown (Bw), dark brown (Db) and black (Bl) kernels, infested by WHF were compared with non-infested bright kernels (B) in ten walnut cultivars in order to see how much sensory attributes of the kernels and their phenolic contents are affected due to WHF infestation. The changes of phenolic content and intensity ratings of sensory traits significantly depended on the WHF-infestation time and the cultivar. Infested kernels were less aromatic, crispy and oily, having a 1.2-fold (Db) to 5.5-fold (Bl) lower total phenolic content (TPC) than bright kernels. Besides TPC, ten compounds belonging to phenolic acids (PA), flavanols (FL) and hydrolysable tannins (HT) as the predominant group were quantified in the kernels of all colour classes. HT and TPC showed the strongest impact on the kernels’ sensory properties. Correlation between sensory attributes and phenolics increased with kernels’ darkening. In Db kernels, TPC defined bitterness, HT were a key source of aroma, oily taste and overall walnut flavour, whilst PA and FL closely correlated with the perception of crispness. An effictive protection, particularly against early-season WHF infestation, which resulted in dark brown and black kernels, is essential in order to avoid the loss of inner quality of walnut kernels.
In rejuvenated annual shoots of the walnut cultivars Elit, Franquette, Hartley and Sampion the content of eight phenolic compounds was investigated during the growing season by the high-performance ...liquid chromatography (HPLC) with the photodiode array (PDA) detector. Seasonal alterations in phenolic composition as well as linkage between the phenolic content and resistance of the shoots to walnut bacterial blight (
Xanthomonas campestris pv.
juglandis) was determined. The phenols concentration was significantly influenced by the cultivar, sampling date, and the cultivar
×
sampling date interaction. Each phenolic group had its own curve of seasonal fluctuations of concentrations depending on ontogenetic stage of the shoots. Catechin and myricetin that belong to the group of flavonoids increased from the spring growth cycle in May to the summer flush of growth in August. Phenolic acids (vanillic, syringic, ellagic and chlorogenic) had an opposite seasonal curve compared to flavonoids. Their content was the highest in spring and the lowest at the end of summer. In juglone and 1,4-naphthoquinone from the group of quinones the lowest content was measured at the end of May. It was followed by increase during the resting-time between the spring and summer growth. In juglone negative correlation to the shoot growth intensity was clearly expressed. Seasonal alterations in phenolic compounds have a stronger effect on susceptibility of the shoots to bacterial blight compared to the phenolics concentrations. Based on the seasonal decrease of 1,4-naphthoquinone determined in the very susceptible cultivar Sampion we conclude that 1,4-naphthoquinone could be involved in the defence mechanism of the shoots against bacterial blight. Since the initial concentrations of ellagic acid that were measured in the less susceptible cultivars Franquette and Elit were higher than in Sampion, ellagic acid also seems to affect the sensitivity of the shoots. None of the two researched flavonoids seemed to have influence on the bacterial infection of the shoots.
Hazelnut (
Corylus avellana
L.) is one of the most important tree nut crops in Europe. Germplasm accessions are conserved in ex situ repositories, located in countries where hazelnut production ...occurs. In this work, we used ten simple sequence repeat (SSR) markers as the basis to establish a core collection representative of the hazelnut genetic diversity conserved in different European collections. A total of 480 accessions were used: 430 from ex situ collections and 50 landraces maintained
on-farm
. SSR analysis identified 181 genotypes, that represented our whole hazelnut germplasm collection (WHGC). Four approaches (utilizing MSTRAT, Power Core, and Core Hunter’s single- and multi-strategy) based on the maximization (M) strategy were used to determine the best sampling method. Core Hunter’s multi-strategy, optimizing both allele coverage (Cv) and Cavalli-Sforza and Edwards (Dce) distance with equal weight, outperformed the others and was selected as the best approach. The final core collection (Cv-Dce30) comprised 30 entries (16.6% of genotypes). It recovered all SSR alleles and preserved parameter variations when compared to WHGC. Entries represented all six gene pools obtained from the population structure analysis of WHGC, further confirming the representativeness of Cv-Dce30. Our findings contribute towards improving the conservation and management of European hazelnut genetic resources and could be used to optimize future research by identifying a minimum number of accessions on which to focus.
European hazelnut (
Corylus avellana
L.), cultivated in several areas of the world including Europe, Anatolia, and the USA, is an economically important nut crop due to its high mineral, oleic acid, ...amino acid, and phenolic compound content and pleasant flavor. This study examined molecular genetic diversity and population structure of 54 wild accessions and 48 cultivars from the Slovenian national hazelnut collection using amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers. Eleven AFLP primer combinations and 49 SSR markers yielded 532 and 504 polymorphic fragments, respectively. As expected for a wind-pollinated, self-incompatible species, levels of genetic diversity were high with cultivars and wild accessions having mean dissimilarity values of 0.50 and 0.60, respectively. In general, cultivars and wild accessions clustered separately in dendrogram, principal coordinate, and population structure analyses with regional clustering of the wild material. The accessions were also characterized for ten nut and seven kernel traits and some wild accessions were shown to have breeding potential. Morphological principal component analysis showed distinct clustering of cultivars and wild accessions. An association mapping panel composed of 64 hazelnut cultivars and wild accessions had considerable variation for the nut and kernel quality traits. Morphological and molecular data were associated to identify markers controlling the traits. In all, 49 SSR markers were significantly associated with nut and kernel traits
P
< 0.0001 and LD value (
r
2
) = 0.15–0.50. This work is the first use of association mapping in hazelnut and has identified molecular markers associated with important quality parameters in this important nut crop.
The paper reports the phenolic content of kernels, bagasse pellets (residue of oil pressing) and oils from five different cultivars and a mix of cultivars. Phenolic compounds were identified by ...high-performance liquid chromatography coupled with mass spectrometry. Two compounds, glansreginin A and glansreginin B, were detected for the first time in hazelnuts. The main polyphenolic subclass comprised of mono- and oligomeric flavan 3-ols, which accounted between 34.2 and 58.3% in hazelnut kernels and between 36.7 and 48.6% in pellets of the total phenolics detected. In hazelnut oils four compounds have been detected, their content levels ranged from 0.97 to 0.01 mu g g super(- 1). Total phenolic content ranged from 491.2 to 1700.4 mg GAE kg super(- 1) in kernels, from 848.4 to 1148.5 mg GAE kg super(- 1) in pellets and only from 0.14 to 0.25 mg GAE g super(- 1) in oils. The percentage of radical scavenging activity ranged from 60.0 to 96.4% for kernels, 63.0 to 73.2% for pellets and from 17.7 to 29.9% for oil. The study provides clear evidence on high phenolic contents and similarly high antioxidant potential of hazelnut kernels and bagasse pellets. The latter could be used as ingredients in cooking and baking or even for production of plant-based pharmaceuticals.
Sensory characteristics of walnut fruits were tested by students and employees at the Biotechnical faculty, separately, to determine the differences among cultivars ‘Chandler’, ‘Adams’, ‘Cisco’, ...‘Fernette’, ‘Fernor’, ‘Franquette’, ‘Rasna’, ‘Alsószentiváni 117’ (‘A-117’) and ‘Elit’. First of all, visual properties of inshell walnuts (shell smoothness, shell colour and seam closeness) and appearance of kernel (pellicle colour, internal colour of a kernel, and kernel brightness) were evaluated, then the kernel was tasted to assess its flavour, bitterness, astringency, texture, crispness and oiliness. Visual appearance of inshell walnuts was evaluated similarly by both groups of assessors. ‘Rasna’ and ‘Fernor’ walnuts had the roughest shell. ‘Rasna’ also had the least brightness of the kernel, the darkest pellicle and it was one from among the least crispy cultivars. Shell colour of ‘Fernette’, as well as pellicle and internal colour of ‘Fernor’ were the lightest. However, each group of assessors had quite different perceptions for tasting internal traits of the kernels. In the present study useful data of sensory characteristics of walnut fruits were obtained. Some of 12 descriptors, which were evaluated in the research, could be used as a custom method for testing and introducing of new walnut varieties in Slovenia.
Relationship of bud production (axillary and terminally) of annual shoot (1Y) and/or the content of bud-derived indol-3-acetic acid (IAA) to branching of the 1Y was studied in common walnut (Juglans ...regia L.), cvs. Franquette and Lara. Cultivar-related branch architecture was determined. Lara tended to branch more densely than Franquette (53 vs. 42%). Significantly more fruiting off-spring shoots (FO) than vegetative ones (VO) grew-out per 1Y in both cultivars, whereas the ratio FO/VO of Lara exceeded that of Franquette by four times. An acrotonic branching pattern was more strongly expressed in Lara compared to Franquette. Bud-derived IAA was influenced by the cultivar (Franquette had 3.6 times more cumulative IAA along the 1Y than Lara), and by the relative position (terminal, subterminal, medial and basal) of the buds along 1Y. An opposite relationship between branching density and cumulative IAA content was established in both cultivars. At the 1Y relative position level, the opposite ratio between branching density and IAA content was clearly shown only on the basal position of the bud along 1Y in the Lara cultivar. Such an inconsistent linkage between bud production and the IAA spatial distribution along the 1Y illustrated that hormonal factors probably weakly affect the branching of Franquette and Lara. The length of the parent 1Y, the position of the buds along the 1Y-length, and the fate of the buds seemed to have a stronger influence on the bud out-growth and further development of the off-springs. In further analyses, seasonal fluctuations of the IAA, and the following activity of the buds should be investigated in order to improve the understanding of a complex branching phenomenon in walnut.
Three cultivars and three selections from Oregon State University's (OSU) hazelnut ( Corylus avellana ) breeding program were investigated in a yield trial during the period 1997 to 2007 in ...northeastern Slovenia with the Italian ‘Tonda Gentile delle Langhe’ as the standard. All OSU genotypes had higher cumulative yield and yield efficiency than the standard, all exceeded the kernel percentage of 45%, and all had at least 76% good kernels. OSU 228.084 is promising due to good vegetative growth and the highest yields and yield efficiency. It set many catkins and had the highest percentage of marketable kernels. Its disadvantage could be early flowering and large yield reduction due to low temperatures in early spring. Cultivars/selections that were late flowering (‘Lewis’ and OSU 244.001) had longer durations of pistillate flower receptivity (‘Willamette’ and OSU 238.125) and had lower sensitivity to unfavorable weather conditions in early spring (‘Clark’) expressed the best climatic adaptation. Unmarketable nuts were mainly blanks and poorly filled nuts. ‘Clark’ is precocious early maturing, and well-suited to the kernel market. Due to its upright growth habit, ‘Clark’ could be planted more densely than others. ‘Lewis’ yielded well and had medium yield efficiency, and is suitable for in-shell and kernel markets. Excellent pellicle removal was observed in OSU 244.001 and OSU 238.125. All OSU cultivars and selections showed relatively low susceptibility to hazelnut weevil ( Balaninus nucum ).
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