European hazelnut (Corylus avellana L.) cultivation has grown worldwide in recent years, even though the world’s production is still fulfilled by a few dozen cultivars well adapted to the local environments of their selection. After Turkey, Italy is the second largest producer of hazelnuts, and the province of Viterbo, in central Italy, is recognized as one of the most suitable districts for hazelnut cultivation. The production in this area relies almost entirely on local cultivar ‘Tonda Gentile Romana’, whereas cultivar ‘Nocchione’ is used as the main pollinizer. More recently, cultivar ‘Tonda di Giffoni’ has been introduced in new local plantations. Cultivation of many cultivars in different areas is of fundamental importance to test their adaptability to different environmental conditions, a need currently accentuated by ongoing climate change. With this aim, a European hazelnut collection field was established in 2000 in Caprarola municipality (Viterbo province), where plants of twelve hazelnut cultivars were observed over four growing seasons for their phenological, agronomic and nut traits. The cultivars studied, namely ‘Barcelona’, ‘Camponica’, ‘Ennis’, ‘Merveille de Bollwiller’, ‘Negret’, ‘Nocchione’, ‘Riccia di Talanico’, ‘San Giovanni’, ‘Tombul’, ‘Tonda di Giffoni’, ‘Tonda Gentile’ and ‘Tonda Gentile Romana’, showed a high diversity in their phenological behaviour, yield efficiency and nut and kernel traits. Cultivars ‘Negret’, ‘Tombul’ and ‘Tonda Gentile’, with poor yields over the years of research, do not seem suitable to be cultivated as main cultivars in the studied environment, contrary to ‘Camponica’ and ‘San Giovanni’, which produced abundantly, reaching a total of almost 30 and 25 kg plant^—1 of in–shell hazelnuts, respectively. Cultivars ‘Tonda Gentile Romana’ and ‘Nocchione’ confirmed their yield consistency, whereas ‘Ennis’, ‘Barcelona’ and ‘Tombul’ seem suitable to be introduced as pollinizers thanks to their male blooming overlapping with the female blooming of the main cultivar ‘Tonda Gentile Romana’. Cultivar ‘Tonda di Giffoni’ did not perform well in the studied environment, despite being recognized as one of the highest-yield cultivars.

European hazelnut (Corylus avellana L.) is a shrub native to temperate zones of the northern hemisphere, and it is the most important species among the Corylus genus, mainly due to its high kernel demand from the confectionery industry. Its spontaneous habitus is characterized by a bushy shape, formed by numerous lignified stems generated by seasonal emission of suckers, which develop from adventitious buds inserted in the collar of stems, or more generally from the stump. Despite the agronomic role of suckers, which are often used to replace diseased, old, or poorly oriented branches, they compete with the plant for water and nutrient uptake, negatively influencing its growth and yield. In addition to promoting mechanical applications during the hazelnut orchard management, sucker removal is a required agronomic operation that must be carried out yearly during the growing season, making this practice expensive and time consuming, especially when performed manually. To date, there are several techniques for hazelnut sucker management, and their application depends on several factors, such as the size of the farm, model of cultivation (conventional or organic), soil orography, and plant training system. This review discusses the most widespread methods applied for sucker control, including manual, mechanical, physical, and chemical control (flame and steam), use of non-suckering rootstocks, disbudding, mulching, nitrogen solution applications, and new automatized control techniques recently proposed at the experimental level, analyzing their advantages and disadvantages.

The European hazelnut is a temperate nut crop, often managed as a multi-stemmed shrub due to its natural aptitude to produce several suckers at the base of the stump, depending on variety. Traditional hazelnut-growing regions such as Italy, Turkey, and Spain typically adopt this architecture, while other hazelnut-producing countries such as the USA, France, and Chile increasingly use single-trunk systems to facilitate orchard management. Multi-stemmed plants allow gradual renewal through sucker selection but may lead to excessively dense canopies, reducing the effectiveness of pest and disease control, increasing biennial bearing, and lowering nut yields in vigorous cultivars. In order to drive the ongoing enlargement of hazelnut cultivation, attempts in designing high-density (HD), and more occasionally super-high-density (SHD), hazelnut orchards are on-going, although these are poorly explored in terms of suitable plant training systems, such that, sometimes, multi-stemmed plant shapes are used; otherwise, single-trunk solutions are adopted. In order to explore new hazelnut planting and training solutions focused on sustainable intensification, a trial was established in 2019 in central Italy to evaluate the eligibility of three training systems (treatment A: regular four-stemmed shrub; treatment B: single-trunk sapling; treatment C: traditional multi-stemmed shrub), applied on unpruned three-year-old plants of the hazelnut cultivar Nocchione, planted in the HD approach (740 plant ha⁻¹). Over five growing seasons (2019–2023), measurements included pruned wood removed, yield, vigor, yield efficiency, nut and kernel traits, and incidence of the main commercial defects. In general, treatment A outperformed other plant-shaping systems, maintaining high yield levels particularly in the two last growing seasons, and showing a mean kernel/nut ratio of 37.7 and a low incidence of defects. Treatment B achieved the highest yield efficiency in 2023 but had lower overall yields. Treatment A demonstrated the most balanced performance, combining high nut quality and stable production, making it the most promising plant training system for HD hazelnut orchards with planting densities above 700 plants per hectare. Future research will assess the long-term adaptability of this plant training system under varying environmental and management conditions.

This study provides the first evidence of anthocyanin and secondary metabolite production in the red-leaf hazelnut cultivar Corylus avellana L. cv. Fructo Rubro. Phenols, flavonoids and anthocyanins were analyzed in both field-grown leaves and in vitro callus cultures, assessing the effects of light quality, physical and chemical elicitors. Field-grown Fructo Rubro leaves exhibited higher content of anthocyanins early in the vegetative season, which then decreased as the chlorophyll content increased. In vitro cultures were successfully established from leaf explants, with callus cultures demonstrating significant anthocyanin biosynthesis under controlled conditions. To enhance metabolite production in callus culture, different LED spectra were used for physical elicitation, with NS1 (a spectrum close to natural sunlight) and G2 (rich in red and far-red light) being the most effective in stimulating anthocyanin biosynthesis. Chemical elicitation with jasmonic and abscisic acid, tested in combination with LED treatments, had a limited impact on anthocyanins. The HPLC analysis identified delphinidin 3-O-glucoside, cyanidin 3-O-glucoside, and cyanidin 3-O-rutinoside as the predominant anthocyanins; furthermore, elicitation of callus culture demonstrated that the levels of these anthocyanins are comparable to or even exceeding those found in field-grown leaves. Additionally, polyphenols and flavonoids showed distinct accumulation patterns influenced by both physical and chemical elicitation. Furthermore, the effect of the extracts on the cell viability of human breast cells, both cancerous and non-cancerous, was preliminarily tested using the MTT assay. Extracts from field-grown leaves exhibited very low IC₅₀ values, indicating a strong ability to reduce the viability of cancerous cells. Notably, physical elicitation with LED light allowed in production of callus-derived extracts with comparable or even enhanced effects. Relevant, none of the extracts showed significant toxicity toward non-cancerous cells, highlighting their promising selectivity and potential safety for therapeutic applications. These findings highlight the potential of LED-enhanced in vitro cultures as a scalable and sustainable alternative for anthocyanin production, providing a controlled platform for optimizing bioactive compound synthesis. This research supports the development of biotechnological strategies for producing high-value phytochemicals that could be of interest for applications in health, food, and cosmetics.

European hazelnut is a suckering woody species traditionally cultivated as a multi-stemmed shrub, even though its structure is usually modified to enhance orchard management efficiency. The present review analyzed the main changes in hazelnut cultivation over the last few decades, with a special focus on the transition from a multi-stemmed shrub to single-trunk system, influencing plant light interception, promoting some mechanized operations and more in general the whole orchard management. Pruning practice is an essential agronomic operation, covering a relevant role in ensuring the healthy status of the plant and maintaining satisfactory levels of production. Traditional approaches and the current direction toward a mechanical pruning operation as a cheap alternative were evaluated. Furthermore, recent trends in orchard layout, characterized by the reduction in planting distances to enhance orchard performance, were investigated. Furthermore, emerging approaches for precision agriculture were reported, such as those related to automated plant canopy management. Overall, this review aims to highlight the strengths and limitations of different plant training and shaping adopted for the species, as well as to identify future research directions in the field of hazelnut canopy management aimed at ensuring consistent crop productivity over the years.

Almond cultivation in the Mediterranean basin is driven by Spanish production, which has combined innovation in cultivation techniques with research on varietal improvement, releasing self-compatible and late-flowering varieties that are better suited to areas prone to spring frosts. The growing demand for almonds has also influenced the Italian nut market, pushing growers towards almond cultivation even in areas that historically have no full vocation due to certain climatic constraints, such as cold winters and spring frosts, which are now less severe and less frequent as a result of climate changes, such as along the Latium coastline in Central Italy. In this new regional context, an almond collection orchard was set up in late 2017 in the rural environment of the municipality of Tarquinia (province of Viterbo) to test the local adaptation of commercial almond cultivars. Phenological observations and data acquisition were conducted for three consecutive growing seasons (2022–2024) and referred to eight cultivars introduced in the orchard: namely Genco, Guara, Lauranne Avijour, Penta, Soleta, Supernova, Tuono, and Vialfas. Each accession was monitored for phenological and ecophysiological traits, plant vigor and yield, yield efficiency, and nut and kernel traits. The trial proved that Lauranne, Penta, and Vialfas, due to their late flowering, were able to avoid possible damage from the spring cold recorded in 2023, while Supernova, Penta, and Genco, with an average yield over the three-year period of 2.51 ± 1.53, 2.44 ± 1.07 and 2.69 ± 1.42 kg plant⁻¹, respectively, showed a higher average yield than the other cultivars tested.