Beneficial Effects of Castanea sativa Wood Extract on the Human Body and Possible Food and Pharmaceutical Applications

The aim of this review was to investigate the potential use of Castanea sativa wood extract as a food supplement and to evaluate its beneficial properties for human health. The results of the limited amount of studies suggest promising properties, including potential anti-inflammatory effects. The literature indicates that the extract, which is rich in bioactive compounds such as tannins, offers promising therapeutic possibilities for the treatment of conditions associated with chronic inflammation. Consequently, interest in its use in food and pharmaceuticals is growing. Phytochemical studies have reported antioxidant and antimicrobial activities, and anti-inflammatory, anticancer, hypolipidemic, hypoglycemic, and neuroprotective activities. A suitable extraction method and solvent is crucial for the isolation of bioactive compounds, being green extraction technologies outstanding for the industrial recovery of chestnut wood's bioactive compounds. Nevertheless, it is important to emphasize the importance of adhering to regulatory guidelines and obtaining the necessary approvals from regulatory authorities to ensure product safety and compliance. The regulation of herbal medicinal products with proven efficacy and traditional herbal medicinal products is well defined, monitored by authorized bodies, and subject to strict control measures. It is noteworthy that medicinal products are subject to stringent quality testing to ensure safety and efficacy in use, whereas there are no comparable regulatory standards and specific labeling requirements for dietary supplements. When using herbal products, compliance with established standards in health research is essential.

Ethylene Action Inhibition Improves Adventitious Root Induction in Adult Chestnut Tissues

Phase change refers to the process of maturation and transition from the juvenile to the adult stage. In response to this shift, certain species like chestnut lose the ability to form adventitious roots, thereby hindering the successful micropropagation of adult plants. While auxin is the main hormone involved in adventitious root formation, other hormones, such as ethylene, are also thought to play a role in its induction and development. In this study, experiments were carried out to determine the effects of ethylene on the induction and growth of adventitious roots. The analysis was performed in two types of chestnut microshoots derived from the same tree, a juvenile-like line with a high rooting ability derived from basal shoots (P2BS) and a line derived from crown branches (P2CR) with low rooting responses. By means of the application of compounds to modify ethylene content or inhibit its signalling, the potential involvement of this hormone in the induction of adventitious roots was analysed. Our results show that ethylene can modify the rooting competence of mature shoots, while the response in juvenile material was barely affected. To further characterise the molecular reasons underlying this maturation-derived shift in behaviour, specific gene expression analyses were developed. The findings suggest that several mechanisms, including ethylene signalling, auxin transport and epigenetic modifications, relate to the modulation of the rooting ability of mature chestnut microshoots and their recalcitrant behaviour.

Predicting the effects of in-vitro digestion in the bioactivity and bioaccessibility of antioxidant compounds extracted from chestnut shells by supercritical fluid extraction - A metabolomic approach

Chestnut (Castanea sativa) shells (CS) are an undervalued antioxidant-rich by-product. This study explores the impact of in-vitro digestion on the bioaccessibility, bioactivity, and metabolic profile of CS extract prepared by Supercritical Fluid Extraction, aiming its valorization for nutraceutical applications. The results demonstrated significantly (p < 0.05) lower phenolic concentrations retained after digestion (38.57 µg gallic acid equivalents/mg dry weight (DW)), reaching 30% of bioaccessibility. The CS extract showed antioxidant/antiradical, hypoglycemic, and neuroprotective properties after in-vitro digestion, along with upmodulating effects on antioxidant enzymes activities and protection against lipid peroxidation. The metabolic profile screened by LC-ESI-LTQ-Orbitrap-MS proved the biotransformation of complex phenolic acids, flavonoids, and tannins present in the undigested extract (45.78 µg/mg DW of total phenolic concentration) into hydroxybenzoic, phenylpropanoic, and phenylacetic acids upon digestion (35.54 µg/mg DW). These findings sustain the valorization of CS extract as a promising nutraceutical ingredient, delivering polyphenols with proven bioactivity even after in-vitro digestion.

Effectively Suppresses Nut Rot by Gnomoniopsis castaneae in Chestnut (Castanea sativa Mill.)

Gnomoniopsis castaneae is responsible for brown or chalky nut rot in sweet chestnut (Castanea sativa), causing heavy reductions in nut production. Controlling it is challenging, due to its inconspicuous infections, erratic colonization of host tissues and endophytic lifestyle. Fungicides are not applicable because they are prohibited in chestnut forests and strongly discouraged in fruit chestnut groves. Trichoderma species are safe and wide-spectrum biocontrol agents (BCAs), with a variety of beneficial effects in plant protection. This study tested selected strains of T. viride, T. harzianum and T. atroviride for their ability to suppress G. castaneae. Field experiments were conducted in four chestnut groves (two test plots plus two controls) at two sites with a different microclimate. As the size of the trees were a major drawback for uniform and effective treatments, the Trichoderma strains were delivered directly by trunk injection, using the BITE® (Blade for Infusion in TrEes) endotherapic tool. The BCA application, repeated twice in two subsequent years, significantly reduced nut rot incidence, with a more marked, presumably cumulative, effect in the second year. Our data showed the tested Trichoderma strains retain great potential for the biological control of G. castaneae in chestnut groves. The exploitation of Trichoderma spp. as biopesticides is a novelty in the forestry sector and proves the benefits of these microbes in plant disease protection.

Effect of Dietary Supplementation of Chestnut and Quebracho Tannin Supplementation on Neonatal Diarrhoea in Preweaning Calves

Neonatal calf diarrhoea (NCD) poses a significant health challenge in cattle herds, resulting in considerable economic losses and antimicrobial use. In response to the escalating threat of antimicrobial resistance, viable alternatives are imperative, aligning with European policies. This study evaluated the in-milk supplementation of the chestnut and quebracho tannin extract in preweaning calves on performance, diarrhoea occurrence, Cryptosporidium spp. shedding, protein digestibility, and intestinal health. Twenty newborn calves were divided, after colostrum administration, into two experimental groups for 30 days as follows: the control (CTRL) was fed with whole milk and solid feed, and tannins (TAN) were fed whole milk supplemented with 6/g day of tannin extract and solid feed. Faecal samples were collected on days 0, 3, 7, 14, and 30 for the evaluation of Cryptosporidium oocyst shedding and protein digestibility. Faecal consistency was evaluated during the sampling using the faecal score scale (0-3 scale, considering diarrhoea > 1). The results showed a significant reduction in diarrhoea frequency in the TAN compared to the CTRL group (p < 0.05) over 30 days of the trial. The prevalence of Cryptosporidium spp. was generally low (12%), considering all analysed samples. Protein digestibility revealed comparable values for the TAN and CTRL groups, suggesting that tannins did not negatively affect milk protein availability. In conclusion, the in-milk supplementation of 6/g day of the chestnut and quebracho tannin extract could be considered a valuable functional feed additive to decrease NCD occurrence, thus supporting animal health and decreasing antibiotic use in livestock.

Proliferation of Axillary Shoots of Chestnut in Temporary Immersion Systems

Shoots from European chestnut and hybrids of European and Asian chestnuts can be efficiently proliferated in liquid medium by temporary immersion (TIS) using RITA® and Plantform™ bioreactors. The main challenges of applying TIS to these species were the lack of growth and hyperhydricity; problem solutions included the manipulation of the hormone concentration, the explant type, immersion frequency, and a support for maintaining shoots in a vertical position. After protocol optimization, explants cultured by TIS produced more rootable shoots than explants growing in semisolid medium, enabling increased number of rooted and acclimatable shoots. In this chapter, we will describe the protocols for proliferating chestnut by TIS in RITA® and Plantform™ bioreactors, together with tips for avoiding the main pitfalls of the technique. The strategies applied to chestnut can be useful for culturing other woody plants in bioreactors.

Novel insights into enzymes inhibitory responses and metabolomic profile of supercritical fluid extract from chestnut shells upon intestinal permeability

The health benefits of chestnut (Castanea sativa) shells (CSs) have been ascribed to phytochemicals, mainly phenolic compounds. Nevertheless, an exhaustive assessment of their intestinal absorption is vital considering a possible nutraceutical application. This study evaluated the bioactivity of CSs extract prepared by Supercritical Fluid Extraction and untargeted metabolomic profile upon in-vitro intestinal permeation across a Caco-2/HT29-MTX co-culture model. The results demonstrated the neuroprotective, hypoglycemic, and hypolipidemic properties of CSs extract by inhibition of acetylcholinesterase, α-amylase, and lipase activities. The untargeted metabolic profiling by LC-ESI-LTQ-Orbitrap-MS unveiled almost 60 % of lipids and 30 % of phenolic compounds, with 29 metabolic pathways indicated by enrichment analysis. Among phenolics, mostly phenolic acids, flavonoids, and coumarins permeated the intestinal barrier with most metabolites arising from phase I reactions (reduction, hydrolysis, and hydrogenation) and a minor fraction from phase II reactions (methylation). The permeation rates enhanced in the following order: ellagic acid < o-coumaric acid < p-coumaric acid < ferulaldehyde ≤ hydroxyferulic acid ≤ dihydroferulic acid < ferulic acid < trans-caffeic acid < trans-cinnamic acid < dihydrocaffeic acid, with better outcomes for 1000 µg/mL of extract concentration and after 4 h of permeation. Taken together, these findings sustained a considerable in-vitro intestinal absorption of phenolic compounds from CSs extract, enabling them to reach target sites and exert their biological effects.

Botanical Extracts and Compounds of Castanea Plants and Methods of Use: US20190125818A1 - The United States Patent Evaluation

BACKGROUND

Bacterial infections are increasingly difficult to combat, which makes them a threat to public health on a global level. Staphylococcus aureus is considered one of the main causes of infections in hospitals, as it has a variety of virulence factors, as well as is able to produce bacterial biofilms, which, consequently, bring numerous damages to public health as a result of increased resistance to conventional antibiotics and a longer hospital stay. Therefore, the use of compounds extracted from medicinal plants is a potential pharmaceutically acceptable target, as they do not have toxicity and the potential to disrupt biofilms produced by Staphylococcus aureus already evidenced, thus revealing their relevance to our study.

OBJECTIVE

The objective of this work was to perform a critical analysis of a patent with natural extracts against bacterial biofilms found in the United States Patent and Trademark Office (USPTO) database, to map the possible bioactive compounds that may serve as potential future antimicrobial drugs.

METHODS

A technological survey was carried out to verify existing patents using natural extracts with anti-biofilm potential. For this, it was searched with the keywords: Botanical extracts AND biofilms; which were performed in the United States Patent and Trademark Office (USPTO) database. Thus, the selected patent used a non-aqueous extract partitioned and vacuum-contracted, subsequently lyophilized for assays with antimicrobial potential. Because of this, a patent was analyzed regarding its chemistry, and biological activity, followed by a critical analysis of the technology proposed in the invention.

RESULTS

When using the keywords Botanical extracts AND biofilms in the USPTO, it was possible to find twenty-two inventions; however, only four patents in the USPTO were in agreement with the proposal of the natural extract having antimicrobial activity and an anti-biofilm potential, of which two belonged to the same applicant with similar proposals. The key point of this invention was to enable the compounds of the Castanea sativa plant and its methods of obtaining the extract to present a significant antimicrobial action associated or not with antibiotics, promoting the development of new therapies against bacterial infections capable of disrupting biofilms. The invention developed a methodology for extracting Castanea sativa, in which pentacyclic triterpene compounds were found mostly in its leaves. Whereas for the extraction, the crude methanol extracts called extracts 224 from the ground leaves were made by maceration, filtered, combined, concentrated under pressure in rotary evaporators, and lyophilized. After that, they were resuspended in water and partitioned in succession with hexane, ethyl acetate, and butanol. The most active refined partition was the 224C extract with the solvent ethyl acetate, which was subjected to further fractionation using silica column chromatography. Resulting in the most refined extract, which was 224C-F2, capable of acting directly on the quorum sensing of bacteria, mainly Staphylococcus aureus, blocking the translation of RNAIII, including a series of exotoxins. Regarding the antimicrobial capacity against Staphylococcus aureus, it presented Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of 1.56 μg/mL-1 and > 100 μg/mL -1, respectively.

CONCLUSION

Given the analyzed patent, it was possible to verify the importance of alternatives to reduce the impact of bacterial biofilms, which causes damage to industries in general and to health. From this, the invention analyzed has a promising proposal with antimicrobial potential focusing on the great impact of bacterial biofilms. Therefore, natural extracts with antibiofilmic potential can help to minimize the economic losses caused to health due to these multidrug-resistant microorganisms with different virulence mechanisms.

Metabolomic insights into phenolics-rich chestnut shells extract as a nutraceutical ingredient - A comprehensive evaluation of its impacts on oxidative stress biomarkers by an in-vivo study

The present study attempted for the first time to explore the effects of the daily oral intake of a phenolics-rich extract from chestnut shells (CS) on the metabolomic profiling of rat tissues by liquid chromatography coupled to Orbitrap-mass spectrometry (LC-ESI-LTQ-Orbitrap-MS) targeted to polyphenolics and their metabolites and screen potential oxidative stress biomarkers, validating its use as a promising nutraceutical ingredient with outstanding antioxidant properties for the prevention and co-therapy of lifestyle-related diseases triggered by oxidative stress. The results demonstrated new insights into the metabolomic fingerprinting of polyphenols from CS, confirming their absorption and biotransformation by phase I (hydrogenation) and II (glucuronidation, methylation, and sulfation) enzymes. Phenolic acids were the main polyphenolic class, followed by hydrolyzable tannins, flavanols, and lignans. In contrast to the liver, sulfated conjugates were the principal metabolites reaching the kidneys. The multivariate data analysis predicted an exceptional contribution of polyphenols and their microbial and phase II metabolites to the in-vivo antioxidant response of the CS extract in rats, recommending its use as an appealing source of anti-aging molecules for nutraceuticals. This is the first study that explored the relation between metabolomic profiling of rat tissues and in-vivo antioxidant effects after oral treatment with a phenolics-rich CS extract.

Use of iRNA in the post-transcriptional gene silencing of necrosis-inducing Phytophthora protein 1(NPP1) in Phytophthora cinnamomi

BACKGROUND

Phytophthora cinnamomi is an Oomycetes associated with soil, this Oomycete is one of the most destructive species of Phytophthora, being responsible for the decline of more than 5000 ornamental, forest, or fruit plants. It can secrete a class of protein NPP1 (Phytophthora necrosis inducing protein 1), responsible for inducing necrosis in leaves and roots of plants, leading to their death.

OBJECTIVE

This work will report the characterization of the Phytophthora cinnamomi NPP1 gene responsible for the infection of Castanea sativa roots and will characterize the mechanisms of interaction between Phytophthora cinnamomi and Castanea sativa, by gene silencing NPP1 from Phytophthora cinnamomi mediated by RNAi.

METHODS AND RESULTS

For silencing a part of the coding region of the NPP1 gene, was placed in the sense and antisense directions between an intron and ligated to the integrative vector pTH210. Cassette integration was confirmed by PCR and sequencing on the hygromycin-resistant Phytophthora cinnamomi transformants. Transformants obtained with the silenced gene was used to infect Castanea sativa.

CONCLUSIONS

Plants infected with these transformants showed a great reduction in disease symptoms, confirming iRNA as a potential alternative biological tool in the study of molecular factors, and in the control and management of Phytophthora cinnamomi.

Expression of CsSCL1 and Rooting Response in Chestnut Leaves Are Dependent on the Auxin Polar Transport and the Ontogenetic Origin of the Tissues

The mechanisms underlying the de novo regeneration of adventitious roots are still poorly understood, particularly in trees. We developed a system for studying adventitious rooting (AR) at physiological and molecular levels using leaves excised from chestnut microshoots of the same genotype but with two distinct ontogenetic origins that differ in rooting competence. Leaves were treated with auxin and N-1-naphthyl-phthalamic acid (NPA), an inhibitor of auxin polar transport (PAT). The physiological effects were investigated by recording rooting rates and the number and quality of the roots. Molecular responses were examined by localizing and monitoring the changes in the expression of CsSCL1, an auxin-inducible gene in juvenile and mature shoots during AR. The rooting response of leaves was ontogenetic-stage dependent and similar to that of the donor microshoots. Initiation of root primordia and root development were inhibited by application of NPA, although its effect depended on the timing of application. CsSCL1 was upregulated by auxin only in rooting-competent leaves during the novo root organogenesis, and the expression was reduced by NPA. The inhibitory effect on gene expression was detected during the reprograming of rooting competent cells towards root initials in response to auxin, indicating that PAT-mediated upregulation of CsSCL1 is required in the initial steps of AR in chestnut leaves. The localized expression of CsSCL1 in the quiescent center (QC) also suggests a role for this gene in the maintenance of meristematic competence and root radial patterning.

Simulated Gastrointestinal Digestion of Chestnut (Castanea sativa Mill.) Shell Extract Prepared by Subcritical Water Extraction: Bioaccessibility, Bioactivity, and Intestinal Permeability by In Vitro Assays

Chestnut shells (CSs) are an appealing source of bioactive molecules, and constitute a popular research topic. This study explores the effects of in vitro gastrointestinal digestion and intestinal permeability on the bioaccessibility and bioactivity of polyphenols from CS extract prepared by subcritical water extraction (SWE). The results unveiled higher phenolic concentrations retained after gastric and intestinal digestion. The bioaccessibility and antioxidant/antiradical properties were enhanced in the following order: oral < gastric ≤ intestinal digests, attaining 40% of the maximum bioaccessibility. Ellagic acid was the main polyphenol in the digested and undigested extract, while pyrogallol-protocatechuic acid derivative was only quantified in the digests. The CS extract revealed potential mild hypoglycemic (<25%) and neuroprotective (<75%) properties before and after in vitro digestion, along with upmodulating the antioxidant enzymes' activities and downregulating the lipid peroxidation. The intestinal permeation of ellagic acid achieved 22.89% after 240 min. This study highlighted the efficacy of the CS extract on the delivery of polyphenols, sustaining its promising use as nutraceutical ingredient.

First report of Neopestalotiopsis sp. causing trunk disease on European chestnut in Spain

In April 2021, a brownish-brown vascular lesion was observed in the stemwood of a five-year-old chestnut (Castanea sativa Mill.) rootstock when cutting for grafting in Villaviciosa (Asturias, Northern Spain). To identify the causal agent, a cross section of the steam was cut, surface-sterilized with 96% ethanol and dried, plated on potato dextrose agar (PDA) and incubated at 25ºC. Fungal colonies were consistently isolated and after 5 days developed abundant greyish-white mycelium. For molecular identification, the internal transcribed spacer (ITS) gene region of rDNA of the strain LPPAF-975 was amplified with the ITS1/ITS4 primers (White et al. 1990) using the TerraTM PCR Direct Polymerase Mix (Takara Bio Company, CA, USA). This sequence was deposited in GenBank (accession no: OR002144) and showed 99.80% identity over a 507 pb alignment with the Neopestalotiopsis isolate 328-16 (accession no: OK166668) isolated on blueberry in Serbia and Nespestalotiopsis australis strains LNZH0701 and LNZH0752 (accession nos: OM919511-12) both isolated on blueberry in China. To clarify the identification, beta-tubulin (tub2) and translation elongation factor alpha-1 (tef1-a) were amplified (Glass & Donaldson 1995, Walker et al. 2010, respectively). Beta-tubulin sequence (accession no: OR001747) was 99.52% of identity with sequences of several species of Neopestalotiopsis, and elongation factor (accession no: OR001748) was 99.57% identity with sequences previously deposited for N. clavispora (accession nos: OP684010-11, MZ097377-79). The phylogenetic tree was constructed with the three concatenated sequences using the Maximum Likelihood method based on the Tamura-Nei model (Tamura and Nei, 1993), and their topological robustness was evaluated by bootstrap analysis based on 1,000 replicates using Mega 11 (Tamura et al, 2021). However, strain LPPAF-975 clustered with N. javaensis, N. rosae and N. vacciniicola, therefore the species remains unidentified. Pathogenicity tests were carried out on ten five-year-old chestnut plants on which a half 5-mm-diameter PDA plug from the edge of an actively growing colony of the fungus was inoculated by a cut in the bark of one to three branches per plant and then wrapped with Parafilm©. Five plants inoculated as above but without the fungus were used as controls. Plants were cultivated in pots provided with drip irrigation in a tunnel under natural conditions. The assay was conducted twice. External cankers around the inoculated area were observed a month after inoculation, while control plants did not show any lesions. The fungus was re-isolated on all the inoculated plants, but not from controls. As all the re-isolated strains had the same morphology, one of them was randomly selected and identified by sequencing, thus fulfilling Koch's postulates. Cross-sections of plants showed lesions similar to that initially found, with 100% of the plants damaged at the point of inoculation, and 80 and 65% 1 cm above and below, respectively. Pathogen was newly re-isolated and identified from one of these cross-sections. To the best of our knowledge, this is the first report worldwide of Neopestalotiopsis sp. causing disease on Castanea sativa. This pathogen could represent a threat to the maintenance of the biodiversity of traditional chestnut varieties, multiplied by grafting on rootstocks in nurseries, which would incur considerable economic losses.

The potential of SiK® fertilization in the resilience of chestnut plants to drought - a biochemical study

Silicon is an essential mineral nutrient, that plays a crucial role in the metabolic, biochemical, and functional mechanisms of many crops under environmental stress. In the current study, we evaluated the effect of SiK^® fertilization on the biochemical defense response in plants exposed to water stress. Castanea sativa plants were fertilized with different concentrations of potassium silicate (0, 5, 7.5, and 10 mM of SiK^®) and exposed to a non-irrigation phase and an irrigation phase. The results indicate that silicon promoted the synthesis of soluble proteins and decreased the proline content and the oxidative stress (reduced electrolyte leakage, lipid peroxidation, and hydrogen peroxide accumulation) in tissues, due to an increase in ascorbate peroxidase, catalase, and peroxidase activity, which was accompanied by the rise in total phenol compounds and the number of thiols under drought conditions. This study suggests that exogenous Si applications have a protective role in chestnut plants under water deficit by increasing their resilience to this abiotic stress.

Can Beauveria bassiana (Bals.-Criv.) Vuill. Control the Key Fruit Pests of the European Chestnut Tree, under Field Conditions?

The chestnut moth (Cydia splendana Hübner) and the chestnut weevil (Curculio elephas Gyllenhal) cause serious damage to European producers and companies that transform and market the chestnut. The objective of the present work was to evaluate, under field conditions, the possibilities of Beauveria bassiana (Bals.-Criv.) Vuill. to infect and kill the larvae of the two main carpophagous pests of European chestnut, in treatments directed at the soil. For this purpose, the surfaces of vases were sprayed with two concentrations of conidia/mL 5 × 10⁷ (T1) and 1 × 10⁸ (T2). The control (T0) was sprayed with distilled water. Larval mortality and infection were evaluated on five dates (D8 to D220). Confirmation of the fungus present in the larva was performed by molecular analysis. The results obtained are promising for the use of B. bassiana as a biological control agent against these key pests of the chestnut crop. There were no significant differences in mortality between the T1 and T2 modalities, however, they were significantly higher than the control. In the case of total mortality (dead and infected larvae), no significant differences were observed for C. elephas either. In the case of C. splendana, the T2 modality obtained better results in terms of total mortality.

Chestnut Brown Rot and Gnomoniopsis smithogilvyi: Characterization of the Causal Agent in Portugal

Sweet chestnut (Castanea sativa Miller) is a nutritious food with high social and economic impacts in Portugal. The fungus Gnomoniopsis smithogilvyi (syn. Gnomoniopsis castaneae) is the causal agent of chestnut brown rot, and is currently considered one of the major threats to the chestnut production chain worldwide. Considering the lack of knowledge on both the disease and the causal agent in Portugal, studies were conducted in an attempt to develop the necessary control strategies towards the mitigation of the disease in a timely way. Isolates of G. smithogilvyi were selected from three varieties of chestnut from the northeast of Portugal, and were characterized at the morphological, ecophysiological and molecular levels. Tests of pathogenicity and virulence were also developed. Gnomoniopsis smithogilvyi was confirmed as the causal agent of brown rot disease in Portuguese chestnut varieties, which showed high susceptibility. The fungus showed high adaptability to chestnut substrates. The Portuguese isolates of G. smithogilvyi are morphologically and genetically similar to those from other countries, even though some physiological variability was observed among them.

Utilization of Response Surface Methodology in Optimization of Proline Extraction from Castanea sativa Honey

Proline constitutes approximately 85 % of the amino acid composition of honey. Therefore, the quantitative determination of this amino acid in honey samples is used by many national/international authorities to evaluate the quality of honey types. In this study, it was aimed to achieve maximum proline amino acid extraction from honey samples whose botanical origins were confirmed by melissopalynological analysis. For this reason, based on three different spectrophotometric methods used in the literature for proline analysis, proline extraction was optimized with the Response Surface Method (RSM) and Box-Behnken experimental design. Three independent variables were determined as treatment time (2, 6, and 10 min), treatment temperature (22, 46, and 70 °C), and cooling time (5, 25, and 45 min). As a result of the optimization, it was seen that only significantly effective independent variable on the proline content of honey was the processing temperature. The optimum conditions obtained as a result of the RSM were found to be 2 min for the treatment time, 70 °C for the treatment temperature and 45 min for the cooling time. The composite desirability of the optimum conditions (R² ) was found to be 1.00. It was determined that the method proposed by International Honey Commission (IHC) is efficient for proline analysis, but it provides more proline extraction by reducing of time from 10 min to 2 min in hold time in boiling water bath only during the extraction step. As a result, the conditions to be used in order to achieve maximum proline extraction with different spectrophotometric methods were determined and optimum values were determined. In addition, since the botanical origin of honey samples significantly affects the proline content of honey, it can be suggested that this study be optimized for different monofloral honey samples as well.

Development and Characterization of Functional Cookies Enriched with Chestnut Shells Extract as Source of Bioactive Phenolic Compounds

Chestnut (Castanea sativa) shells (CSs), an undervalued agro-industrial biowaste, have arisen as a source of bioactive compounds with promising health-promoting effects. This study attempted, for the first time, to develop a functional food, namely cookies, using a CS extract obtained by an eco-friendly technology (subcritical water extraction). The cookies were characterized regarding their nutritional composition, total phenolic and flavonoid contents (TPC and TFC, respectively), antioxidant/antiradical activities, phenolic profile, and sensory evaluation. The results demonstrated that the CS-extract-enriched cookies were mainly composed of carbohydrates (53.92% on dry weight (dw)), fat (32.62% dw), and fiber (5.15% dw). The phenolic profile outlined by HPLC-PDA revealed the presence of phenolic acids, flavonoids, and hydrolysable tannins, attesting to the high TPC and TFC. The in vitro antioxidant/antiradical effects proved the bioactivity of the functional cookies, while the sensory evaluation unveiled excellent scores on all attributes (≥6.25). The heatmap diagram corroborated strong correlations between the TPC and antioxidant/antiradical properties, predicting that the appreciated sensory attributes were closely correlated with high carbohydrates and phenolic compounds. This study encourages the sustainable recovery of antioxidants from CSs and their further employment as an active nutraceutical ingredient in functional cookies.

Bark-inhabiting fungal communities of European chestnut undergo substantial alteration by canker formation following chestnut blight infection

Background

Chestnut forests are severely threatened by chestnut blight caused by the fungal pathogen Cryphonectria parasitica and the infected trees exhibit bark canker in the later stage of the disease. European chestnut (Castanea sativa) is further infected by Gnomoniopsis smithogilvyi, another canker-causing fungal pathogen. We explored whether and how chestnut blight is reflected in bark-inhabiting fungal communities of European chestnut and also assessed the co-occurrence of C. parasitica and G. smithogilvyi.

Materials and methods

We initially investigated the fungal communities of European chestnut bark tissues and further monitored changes in these fungal communities with regard to disease progression from infection to canker formation by analyzing bark samples from asymptomatic trees, asymptomatic trees with latent C. parasitica infection, and infected trees with canker tissues, using amplicon sequencing of the ITS2 region of rDNA.

Results

The results showed that fungal community composition and diversity differed between the sample types. The fungal community composition was substantially reshaped by canker formation, whereas latent C. parasitica infection and more specifically pre-canker infection period per se had a weak effect. Fungal communities of canker samples was less diverse and more dissimilar to those of other sample types. C. parasitica dominated the mycobiome of canker samples, whereas G. smithogilvyi was found in only 9% of canker samples at very low abundances. However, G. smithogilvyi was a dominant fungus in the bark of healthy plants.

Conclusion

This study highlights that canker formation is the principal driver of decreasing diversity and altered composition of the mycobiome in bark tissues of European chestnut infected by C. parasitica infection. It additionally emphasizes the scarce co-occurrence of C. parasitica and G. smithogilvyi on European chestnut.

Structural and Physicochemical Properties of Starch from Rejected Chestnut: Hydrothermal and High-Pressure Processing Dependence

The quality standards for the export of chestnuts generate large quantities of rejected fruits, which require novel processing technologies for their safe industrial utilization. This study aimed to investigate the impact of high-pressure processing (HPP) and hydrothermal treatments (HT) on the physicochemical properties of rejected chestnut starch. Chestnuts were treated by HPP at 400, 500, and 600 MPa for 5 min and HT at 50 °C for 45 min. In general, all HPP treatments did not induce starch gelatinization, and their granules preserved the integrity and Maltese-cross. Moreover, starch granules' size and resistant starch content increased with the intensity of pressure. Native and HT chestnut starches were the most susceptible to digestion. HPP treatments did not affect the C-type crystalline pattern of native starch, but the crystalline region was gradually modified to become amorphous. HPP-600 MPa treated starch showed modified pasting properties and exhibited the highest values of peak viscosity. This study demonstrates for the first time that after HPP-600 MPa treatment, a novel chestnut starch gel structure is obtained. Moreover, HPP treatments could increase the slow-digesting starch, which benefits the development of healthier products. HPP can be considered an interesting technology to obtain added-value starch from rejected chestnut fruits.

A comparative study of antimicrobial, anti-quorum sensing, anti-biofilm, anti-swarming, and antioxidant activities in flower extracts of pecan (Carya illinoinensis) and chestnut (Castanea sativa)

Antibiotic resistance, which has increased rapidly in recent years because of uncontrolled and unconscious antibiotic consumption, poses a major threat to public health. The inadequacy of existing antibiotics has increased the need for new, effective, and less toxic antibiotic raw materials or antibiotic derivatives. Pecan (Carya illinoinensis) and Chestnut (Castanea sativa) flowers possess abundant pollen contents and exhibit similar morphological features. The purpose of this study was to compare these two flower extracts in terms of their antimicrobial and antioxidant activities. Total phenolic content, total flavonoid contents, and phenolic components were also analyzed in aquatic and ethanolic extracts. Antioxidant activities were measured using ferric reducing/antioxidant capacity (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods. Antimicrobial and antifungal activities were compared by means of agar diffusion tests against bacteria including Staphylococcus aureus, Bacillus cereus, Mycobacterium smegmatis, Acinetobacter haemolyticus, and Chromobacterium violaceum, and the yeasts Candida albicans and Candida parapsilosis. Anti-quorum sensing (anti-QS), anti-biofilm, and anti-swarming (SW) activities were also studied against Chromobacterium violaceum ATCC 31532, Chromobacterium violaceum ATCC 12472, and Pseudomonas aeruginosa PA01, respectively. Both extracts were rich in ellagic acid and gallic acid and exhibited similar antioxidant properties. Both flower extracts exhibited high antimicrobial and antifungal activities as well as anti-biofilm, anti-QS, and anti-SW activities.

Rapid and Accurate Detection of Gnomoniopsis smithogilvyi the Causal Agent of Chestnut Rot, through an Internally Controlled Multiplex PCR Assay

The fungus Gnomoniopsis smithogilvyi is a significant threat to the production of sweet chestnut (Castanea sativa) nuts in Australia and worldwide. The pathogen causes nut rot, which leads to substantial production losses. Early and accurate diagnosis of the disease is essential to delineate and implement control strategies. A specific and sensitive multiplex PCR was developed based on the amplification of three barcode sequences of G. smithogilvyi. The assay reliability was enhanced by including the amplification of a host gene as an internal control. Primers were thoroughly evaluated in silico before assessing them in vitro. Primer annealing temperature and concentration were optimised to enhance the assay sensitivity and specificity. The assay detection limit ranged between 0.1 and 1.0 pg (5 and 50 fg/μL) of genomic DNA per reaction. No cross-reactivity was observed with genomic DNA from closely and distantly related fungal species. We also characterised Australian G. smithogilvyi isolates phenotypically and genotypically and found significant differences in morphologic and virulence traits of the isolates. An understanding of the virulence of G. smithogilvyi and the availability of a reliable and accurate diagnostic technique will enable earlier detection of the pathogen, which will contribute to effective control strategies for the disease.

Impact of 'brown rot' caused by Gnomoniopsis castanea on chestnut fruits during the post-harvest process: critical phases and proposed solutions

BACKGROUND

The brown rot fungus, Gnomoniopsis castanea, is the main organism responsible for the outbreak of chestnut postharvest decay that is threatening the sustainability of the chestnut market in Europe. Currently, no specific strategy is available to mitigate the impact and remediate the high losses of fruits in postharvest storage. In the present study, the different phases of chestnut handling in a standard facility plant were analyzed by evaluating the amount of fruit rot and infection by G. castanea at each phase.

RESULTS

The warm bath (48 °C) was identified as the critical phase, requiring strict parametrization to effectively inactivate G. castanea in fruits. Laboratory tests indicated that maintaining fruits at 50 °C for a maximum of 45 min provided optimal conditions to completely inactivate G. castanea inoculum during postharvest handling. However, the warm bath at 50 °C and over was not effective in inactivating the complex of fungal taxa responsible for contamination and development of molds. Higher temperatures and extended treatment times caused significant losses in fruit quality, as indicated by taste panel evaluation. Upscaling of postharvest facilities is discussed and critically evaluated.

CONCLUSION

The warm bath (50 °C for 45 min) is effective in completely inactivating G. castanea in fruits but did not reduce the impacts of the complex of molds responsible for external contamination and mycotoxin production. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Localized reshaping of the fungal community in response to a forest fungal pathogen reveals resilience of Mediterranean mycobiota

Mediterranean forests are facing the impact of pests such as the soilborne Phytophthora cambivora, the causal agent of Ink disease, and this impact is made more severe by global changes. The status and resilience of the soil microbial ecosystem in areas with such a disturbance are little known; however, the assessment of the microbial community is fundamental to preserve the ecosystem functioning under emerging challenges. We profile soil fungal communities in a chestnut stand affected by ink disease in Italy using metabarcoding, and couple high-throughput sequencing with physico-chemical parameters and dendrometric measurements. Since the site also includes an area where the disease symptoms seem to be suppressed, we performed several analyses to search for determinants that may contribute to such difference. We demonstrate that neither pathogen presence nor trees decline associate with the reduction of the residing community diversity and functions, but rather with microbial network reshaping through substitutions and new interactions, despite a conservation of core taxa. We predict interactions between taxa and parameters such as soil pH and C/N ratio, and suggest that disease incidence may also relate with disappearance of pathogen antagonists, including ericoid- and ectomycorrhizal (ECM) fungi. By combining metabarcoding and field studies, we infer the resilient status of the fungal community towards a biotic stressor, and provide a benchmark for the study of other threatened ecosystems.

In silico characterization of molecular factors involved in metabolism and pathogenicity of Phytophthora cinnamomi

Phytophthora cinnamomi is classified as one of the most devastating plant pathogens in the world. It has a destructive effect on more than 5000 horticultural and forestry species in the world, and especially on Castanea sativa. The genus Phytophthora belongs to the Class Oomycetes, a group of fungus like organisms which provoke plant diseases via motile zoospores. Control of this organism is considered very challenging because of the limited range of effective chemical inhibitors. The development of sustainable control measures for the future management of P. cinnamomi requires in-depth knowledge of the cellular and molecular bases of development and metabolism. The aim of this review was to identify molecular factors associated with the metabolism of P. cinnamomi by studying the genes implicated in fundamental metabolism using tools of bioinformatics. Also, some genes involved in pathogenicity will be cited and characterized, such as genes coding for transglycosylases. Genomic sequences of P. cinnamomi were analyzed using an open reading frame (ORF) finder. The identified ORFs products (proteins) were compared to sequences already described and with known functions present in databases such as NCBI and fungi database. In this way, homologous proteins were found, with the respective specific domains, to proteins involved in the metabolism and pathogenicity of Phytophthora ssp.

A New Double-Stranded RNA Mycovirus in Cryphonectria naterciae Is Able to Cross the Species Barrier and Is Deleterious to a New Host

Cryphonectria is a fungal genus associated with economically significant disease of trees. Herein we characterized a novel double-stranded RNA virus from the fungal species Cryphonectria naterciae, a species unexplored as a virus host. De novo assembly of RNA-seq data and Sanger sequencing of RACE (rapid amplification of cDNA ends) clones gave the complete, non-segmented genome (10,164 bp) of the virus termed Cryphonectria naterciae fusagravirus (CnFGV1) that was phylogenetically placed within the previously proposed viral family Fusagraviridae. Of 31 field-collected strains of C. naterciae, 40% tested CnFGV1-positive. Cocultivation resulted in within-species transmission of CnFGV1 to virus-free strains of C. naterciae. Comparison of the mycelium phenotype and the growth rate of CnFGV1-infected and virus-free isogenic strains revealed frequent sectoring and growth reduction in C. naterciae upon virus infection. Co-culturing also led to cross-species transmission of CnFGV1 to Cryphonectria carpinicola and Cryphonectria radicalis, but not to Cryphonectria parasitica. The virus-infected C. naterciae and the experimentally infected Cryphonectria spp. readily transmitted CnFGV1 through asexual spores to the next generation. CnFGV1 strongly reduced conidiation and in some cases vegetative growth of C. carpinicola, which is involved in the European hornbeam disease. This study is the first report of a fusagravirus in the family Cryphonectriaceae and lays the groundwork for assessing a hypovirulence effect of CnFGV1 against the hornbeam decline in Europe.

The Physiological and Biochemical Responses of European Chestnut (Castanea sativa L.) to Blight Fungus (Cryphonectria parasitica (Murill) Barr)

The most important disease of European chestnut (Castanea sativa Mill.) is chestnut blight caused by the fungus Cryphonectria parasitica (Murrill) Barr which induces yield reduction in Europe and North America. This study aimed to investigate the impacts of C. parasitica infection on the physiological and biochemical characteristics of European chestnut at two different growth stages, 3 and 6 weeks after the infection. The amount of photosynthetic pigments (chlorophyll-a, chlorophyll-b, and carotenoids), the relative chlorophyll content, and the photochemical efficiency of the photosystem II (PSII) were measured in the leaves above and below the virulent and hypovirulent C. parasitica infections. The highest values were measured in the control leaves, the lowest values were in the leaves of the upper part of virulent necrosis. Antioxidant enzyme activities such as ascorbate peroxidase (APX), guaiacol peroxidase (POD), and superoxide dismutase (SOD), proline, and malondialdehyde concentrations were also investigated. In each of these measured values, the lowest level was measured in the control leaves, while the highest was in leaves infected with the virulent fungal strain. By measuring all of these stress indicator parameters the responses of chestnut to C. parasitica infection can be monitored and determined. The results of this study showed that the virulent strain caused more pronounced defense responses of chestnut’s defense system. The measured parameter above the infection was more exposed to the blight fungus disease relative to the leaves below the infection.

Pheromone-Mediated Mating Disruption as Management Option for Cydia spp. in Chestnut Orchard

(1) Background: Pheromone-based devices are successfully used to control insect pests in agriculture. (2) Methods: Investigations were conducted to evaluate the effectiveness of mating disruption (MD) to control the chestnut tortrix moths, Cydia fagiglandana and Cydia splendana. Surveys were performed in northern Italy in 2019-2020. MD was carried out using the pheromone dispenser Ecodian^® CT. The effectiveness of MD was assessed by recording male adult catches in pheromone-baited sticky traps and larvae in chestnut fruits, comparing MD and control plots. (3) Results: The total number of trapped males was significantly lower in MD plots than in control ones, for all sites and years. Trap catch suppression in MD plots averaged 89.5% and 93.8% for C. fagiglandana and 57.4% and 81% for C. splendana in 2019 and 2020, respectively. The larval infestation rate in fruits did not vary between plots except for one site where a reduction of about 71% in the MD plot was recorded in 2019. (4) Conclusions: Low catches in MD plots turned out to be a good measure of the effectiveness of communication disruption, but no satisfactory data have been obtained regarding fruit infestation, highlighting how the reduction of male catches cannot always be considered as a reliable indicator of successful control. Specific investigations about background population density, dispersal and mating/oviposition behavior are thus essential for a viable management strategy.

Population Dynamics and Tree Damage of the Invasive Chestnut Gall Wasp, Dryocosmus kuriphilus, in Its Southernmost European Distributional Range

Simple Summary

Chestnut cultivation makes it possible to invigorate the economy of many rural areas in Europe. The chestnut gall wasp Dryocosmus kuriphilus is a serious invasive pest that causes severe damage to chestnut cultivation worldwide. Its rapid spread across Europe endangers the continuity of the entire chestnut industry. Despite this growing concern, scarce attention has been paid to the status of D. kuriphilus in its southernmost distributional range in continental Europe and limited knowledge on the factors modelling their populations is available. In this study, we assessed spatio-temporal patterns in the population dynamics, phenology and tree damage in southern Spain, and further evaluated the relationship between these variables and thermal trends. Strong variation in the population dynamics and flight phenology was found both among localities and over time, which was influenced by differences in thermal regimes. Similarly, tree damage evolved differently over time in each locality, thus suggesting that local conditions may determine significant differences in damage evolution. Our work contributes to a better understanding of this pest in countries throughout the Mediterranean basin and can be useful for further improvement of control and management strategies.

Abstract

The invasive chestnut gall wasp (CGW), Dryocosmus kuriphilus, the worst pest of chestnut cultivation, has spread worryingly throughout Europe in less than 20 years. Despite the great concern around this pest, little is known about the status in its southernmost distribution in continental Europe. We assessed spatio-temporal patterns in the population dynamics, phenology and tree damage caused by CGW in southern Spain. Likewise, the relationship between these variables and thermal trends was evaluated. We found strong variation in the population dynamics and flight phenology among localities and over time, which were highly influenced by changes in thermal regimes. Specifically, warmer localities and vegetative periods promoted higher population densities, a partial increase in the survival of immature stages, and advanced flight activity. Moreover, tree damage evolved differently over time in each locality, which suggests that local conditions may determine differences in damage evolution. Our findings evidence that great spatio-temporal variability in the CGW populations takes place across invaded areas in its southernmost European distributional range. Although control mechanisms have been introduced, implementation of further control and management measures are critical to cope with this main threat for the chestnut industry and to prevent its spread to nearing chestnut-producing areas.

The Dynamics of Flower Development in Castanea sativa Mill

The sweet chestnut tree (Castanea sativa Mill.) is one of the most significant Mediterranean tree species, being an important natural resource for the wood and fruit industries. It is a monoecious species, presenting unisexual male catkins and bisexual catkins, with the latter having distinct male and female flowers. Despite the importance of the sweet chestnut tree, little is known regarding the molecular mechanisms involved in the determination of sexual organ identity. Thus, the study of how the different flowers of C. sativa develop is fundamental to understand the reproductive success of this species and the impact of flower phenology on its productivity. In this study, a C. sativa de novo transcriptome was assembled and the homologous genes to those of the ABCDE model for floral organ identity were identified. Expression analysis showed that the C. sativa B- and C-class genes are differentially expressed in the male flowers and female flowers. Yeast two-hybrid analysis also suggested that changes in the canonical ABCDE protein-protein interactions may underlie the mechanisms necessary to the development of separate male and female flowers, as reported for the monoecious Fagaceae Quercus suber. The results here depicted constitute a step towards the understanding of the molecular mechanisms involved in unisexual flower development in C. sativa, also suggesting that the ABCDE model for flower organ identity may be molecularly conserved in the predominantly monoecious Fagaceae family.

Influence of Climate Change on Chestnut Trees: A Review

The chestnut tree (Castanea spp.) is an important resource worldwide. It is cultivated due to the high value of its fruits and wood. The evolution between Castanea biodiversity and humans has resulted in the spread of chestnut genetic diversity. In 2019, the chestnut tree area worldwide was approximately 596 × 10³ ha for fruit production (Southern Europe, Southwestern United States of America, and Asia). In Europe 311 × 10³ t were produced. Five genetic poles can be identified: three in Greece, the northwest coast of the Iberian Peninsula, and the rest of the Mediterranean. Over the years, there have been some productivity changes, in part associated with climate change. Climate is considered one of the main drivers of biodiversity and ecosystem change. In the future, new challenges associated with climate change are expected, which could threaten this crop. It is essential to identify the impacts of climate change on chestnut trees, improving the current understanding of climate-tree interconnections. To deal with these projected changes adaptation strategies must be planned. This manuscript demonstrates the impacts of climate change on chestnut cultivation, reviewing the most recent studies on the subject. Furthermore, an analysis of possible adaptation strategies against the potentially negative impacts was studied.

Expression of Castanea crenata Allene Oxide Synthase in Arabidopsis Improves the Defense to Phytophthora cinnamomi

Allene oxide synthase (AOS) is a key enzyme of the jasmonic acid (JA) signaling pathway. The AOS gene was previously found to be upregulated in an Asian chestnut species resistant to infection by the oomycete Phytophthora cinnamomi (Castanea crenata), while lower expression values were detected in the susceptible European chestnut (Castanea sativa). Here, we report a genetic and functional characterization of the C. crenata AOS (CcAOS) upon its heterologous gene expression in a susceptible ecotype of Arabidopsis thaliana, which contains a single AOS gene. It was found that Arabidopsis plants expressing CcAOS delay pathogen progression and exhibit more vigorous growth in its presence. They also show upregulation of jasmonic acid and salicylic acid-related genes. As in its native species, heterologous CcAOS localized to plastids, as revealed by confocal imaging of the CcAOS-eGFP fusion protein in transgenic Arabidopsis roots. This observation was confirmed upon transient expression in Nicotiana benthamiana leaf epidermal cells. To further confirm a specific role of CcAOS in the defense mechanism against the pathogen, we performed crosses between transgenic CcAOS plants and an infertile Arabidopsis AOS knockout mutant line. It was found that plants expressing CcAOS exhibit normal growth, remain infertile but are significantly more tolerant to the pathogen than wild type plants. Together, our results indicate that CcAOS is an important player in plant defense responses against oomycete infection and that its expression in susceptible varieties may be a valuable tool to mitigate biotic stress responses.

Performance of Pheromone-Baited Traps to Monitor the Seasonal Abundance of Tortrix Moths in Chestnut Groves

(1) Background: Pammene fasciana (L.), Cydia fagiglandana (Zeller), and C. splendana (Hübner) (Lepidoptera: Tortricidae) are considered key moth pests of chestnut in Europe. (2) Methods: Investigations were performed in 2018-2019 in northern Italy. Sticky traps and commercially available pheromones were used for monitoring; moreover, two experimental pheromone blends were tested. All specimens were identified according to male genitalia and molecular analyses. Newly formed chestnut husks and fruits were randomly collected to evaluate the presence of larvae and/or feeding damage, by comparing it to trap catches. (3) Results: P. fasciana was present in all the sites, whereas Cydia species were recorded in three sites of six, with differences in abundance related to pheromone blends studied. Several non-target species, such as Oegoconia novimundi (Busck) and Cydia ilipulana (Walsingham), were present. Data about the seasonal flight activity are provided. (4) Conclusions: This research contributes to ascertaining the presence and abundance of tortrix moths in Italian chestnut groves, and the presence of non-target species highlights the risk of overestimating catches. Fruit damage recorded did not always reflect catches made by pheromone traps, suggesting that monitoring may underestimate the real size of moths' populations. All of the data acquired are important for planning specific control measures.

Leaves and Spiny Burs of Castanea Sativa from an Experimental Chestnut Grove: Metabolomic Analysis and Anti-Neuroinflammatory Activity

Castanea sativa cultivation has been present in Mediterranean regions since ancient times. In order to promote a circular economy, it is of great importance to valorize chestnut groves' by-products. In this study, leaves and spiny burs from twenty-four Castanea trees were analyzed by 1H NMR metabolomics to provide an overview of their phytochemical profile. The Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA) performed on these data allowed us to distinguish 'Marrone' from 'Castagna', since the latter were generally more enriched with secondary metabolites, in particular, flavonoids (astragalin, isorhamnetin glucoside, and myricitrin) were dominant. Knowing that microglia are involved in mediating the oxidative and inflammatory response of the central nervous system, the potential anti-inflammatory effects of extracts derived from leaves and spiny burs were evaluated in a neuroinflammatory cell model: BV-2 microglia cells. The tested extracts showed cytoprotective activity (at 0.1 and 0.5 mg/mL) after inflammation induction by 5 µg/mL lipopolysaccharide (LPS). In addition, the transcriptional levels of IL-1β, TNF-α, and NF-kB expression induced by LPS were significantly decreased by cell incubation with spiny burs and leaves extracts. Taken together, the obtained results are promising and represent an important step to encourage recycling and valorization of chestnut byproducts, usually considered "waste".

Single Nucleotide Polymorphisms as Practical Molecular Tools to Support European Chestnut Agrobiodiversity Management

European chestnut orchards are multifunctional agroforestry systems with a key role in environmental management. Their biodiversity is at risk of erosion and farmers do not have enough tools to protect and valorize traditional ecotypes. In particular, cost effective and reliable molecular markers for cultivar identification are lacking. The aim of this research was to develop a new molecular tool for varietal identification in European chestnuts. A set of cultivars was preliminarily characterized to evaluate the range of genetic diversity using random amplified polymorphic DNA (RAPD) markers. The genetic distances indicated a sufficiently wide variability range among tested genotypes and confirmed they were suitable for our goal. A single nucleotide polymorphism (SNP) mining within 64 expressed sequence tags (EST), covering all the linkage groups, was performed by high-resolution melting (HRM) and validated by target resequencing. Fifty-six SNPs were retrieved by monitoring the variability present on the whole set of considered cultivars in loci uniformly distributed on the genome. A subset of 37 SNPs was finally transformed into kompetitive allele-specific PCR (KASP) markers that were successfully evaluated for varietal discrimination. Three assays (C1083, G0115 and A5096) were identified as necessary and sufficient for distinguishing among the tested cultivars. The developed tools can be effectively exploited by stakeholders for improving the management of the European chestnut genetic resources.

Methodology optimization for the analysis of phenolic compounds in chestnut (Castanea sativa Mill.)

Phenols are bioactive substances of great interest because of their involvement in plant physiology, their use in many industrial processes, and their impact on human health. This work aims to summarize the varied approaches to the phenolic analysis of chestnut (bark and wood of trunk and branches, leaves, catkins, burs, and fruit) and to collate the optimal conditions into an easy to follow and execute protocol. Phenolic compounds were extracted by solid-liquid extraction and separated by liquid-liquid extraction. Total phenols content was determined by Folin-Ciocalteu assay, condensed tannins by vanillin assay, and hydrolyzable tannins (gallotannins and ellagitannins) by high-performance liquid chromatography quantification of methyl gallate and ellagic acid following acid methanolysis. The lowest temperature for conservation (-80 ℃), lyophilization, and milling (liquid N₂) were the most effective pretreatments for samples. For quantification of tannins, the use of water clearly reduced the sensitivity of the analysis of condensed tannins, whilst the more efficient degradation capacity of sulfuric acid improved the methanolysis of hydrolyzable tannins. These findings were validated using a range of chestnut tissues, and thus confirm the utility and effectiveness of this easy to implement, cost-effective, and efficient protocol.

Cloning and expression analysis of an endo-1,3-β-D-glucosidase from Phytophthora cinnamomi

Phytophthora is considered one of the most destructive genus for many agricultural plant species worldwide, with a strong environmental and economic impact. Phytophthora cinnamomi is a highly aggressive Phytophthora species associated with the forest decline and responsible for the ink disease in chestnut trees (Castanea sativa Miller), a culture which is extremely important in Europe. This pathogenicity occurs due to the action of several enzymes like the hydrolysis of 1,3-β-glucans at specific sites by the enzyme endo-1,3-β-D-glucosidase. The aim of this work to analyze the heterologous expression in two microorganisms, Escherichia coli and Pichia pastoris, of an endo-1,3-β-D-glucosidase encoded by the gene ENDO1 (AM259651) from P. cinnamomi. Different plasmids were used to clone the gene on each organism and the real-time quantitative polymerase chain reaction was used to determine its level of expression. Homologous expression was also analyzed during growth in different carbon sources (glucose, cellulose, and sawdust) and time-course experiments were used for endo-1,3-β-D-glucosidase production. The highest expression of the endo-1,3-β-D-glucosidase gene occurred in glucose after 8 h of induction. In vivo infection of C. sativa by P. cinnamomi revealed an increase in endo-1,3-β-D-glucosidase expression after 12 h. At 24 h its expression decreased and at 48 h there was again a slight increase in expression, and more experiments in order to further explain this fact are underway.

Ozone gas as a storage treatment to control Gnomoniopsis castanea, preserving chestnut quality

BACKGROUND

Chestnuts are gluten-free, low-fat, cholesterol-free products. Postharvest decay reduces chestnut shelf life and can cause severe economic losses. In this study we investigated the effect of ozone (O₃ ) gaseous treatment on chestnut rot caused by Gnomoniopsis castanea and the quality parameters of chestnuts.

RESULTS

The results showed that ozone treatment (150 ppb during the day, and 300 ppb during the night) reduced the decay of chestnuts and had a fungistatic effect on isolates of G. castanea. The exposure of chestnuts to ozone did not alter weight losses, sugar content and titratable acidity. The concentration of total phenolics decreased during the storage period, both for treated and untreated nuts. However, after 150 days of treatment the polyphenol content of the chestnuts exposed to ozone was significantly higher than in control nuts.

CONCLUSIONS

Our results suggested that ozone is an appropriate and economical tool to maximize the quality of chestnut shelf life, enabling it to be stored for long periods. © 2019 Society of Chemical Industry.

Cloning, characterization, in vitro and in planta expression of a necrosis-inducing Phytophthora protein 1 gene npp1 from Phytophthora cinnamomi

The soil-borne oomycete Phytophthora cinnamomi is a highly destructive Phytophthora species associated with the decline of forest. This pathogen secretes a novel class of necrosis-inducing proteins known as Nep1-like proteins (NLPs). In this work, we report the sequencing and molecular characterization of one of these proteins, more specifically the necrosis-inducing Phytophthora protein 1 (NPP1). The ORF of the npp1 gene (EMBL database AM403130) has 768 bp encoding a putative peptide of 256 amino acids with a molecular weight of approximately 25 kD. In order to understand its function, in vitro gene expression was studied during growth in different carbon sources (glucose, cellulose, and sawdust), and at different times of infection, in vivo by RT-qPCR. The highest expression of the npp1 gene occurred in glucose medium followed by sawdust. In vivo infection of Castanea sativa roots with P. cinnamomi revealed a decrease in npp1 expression from 12 to 24 h; at 36 h its expression increased suggesting the existence of a complex mechanism of defense/attack interaction between the pathogen and the host. Expression of recombinant npp1 gene was achieved in Pichia pastoris and assessed by SDS-PAGE analysis of the protein secreted into the culture supernatant, revealing the presence of the NPP1 protein.

Chestnut Drying Is Critical in Determining Aspergillus flavus Growth and Aflatoxin Contamination

Chestnut drying is used to prevent postharvest losses and microorganism contamination during storage. Several studies reported the contamination by aflatoxins (AFs) produced by Aspergillus spp. in chestnuts. The effect of drying temperatures (from 30 to 50 °C) was evaluated on the growth of A. flavus and the production of aflatoxins in chestnuts. The influence of the treatment on the proximate composition, the total phenol content and antioxidant activity of chestnuts was considered. Fungal colonization was observed on the nuts dried at 30, 35, and 40 °C; the incidence was lower at 40 °C. The highest concentrations of AFB₁ and AFB₂ were produced at 40 °C. No aflatoxins were detected at 45 or 50 °C. At 40 °C A. flavus was under suboptimal conditions for growth (a_w 0.78), but the fungus was able to synthesize aflatoxins. As the temperatures applied increased, the total phenol content increased, while the antioxidant activity decreased. A drying treatment at 45 °C for seven days (a_w 0.64) could be a promising method to effectively control both the growth of aflatoxigenic fungi and the production of aflatoxins. This study provides preliminary data useful to improve the current drying conditions used in chestnut mills, to reduce both fungal growth and aflatoxin production.

Genetic and Phenotypic Characterization of Cryphonectria hypovirus 1 from Eurasian Georgia

Cryphonectria hypovirus 1 (CHV-1) infects the chestnut blight fungus Cryphonectria parasitica and acts as a biological control agent against this harmful tree disease. In this study, we screened the recently characterized C. parasitica population in Eurasian Georgia for the presence of CHV-1. We found 62 CHV-1 infected C. parasitica isolates (9.3%) among a total of 664 isolates sampled in 14 locations across Georgia. The prevalence of CHV-1 at the different locations ranged from 0% in the eastern part of the country to 29% in the western part. Sequencing of two specific regions of the viral genome one each in ORFA and ORFB revealed a unique CHV-1 subtype in Georgia. This subtype has a recombinant pattern combining the ORFA region from the subtype F2 and the ORFB region from subtype D. All 62 viral strains belonged to this Georgian CHV-1 subtype (subtype G). The CHV-1 subtype G strongly reduced the parasitic growth of C. parasitica isolates from Georgia, with a more severe effect on the European genepool compared to the Georgian genepool. The CHV-1 subtype detected in Georgia provides a valuable candidate for biological control applications in the Caucasus region.

Radial Growth and Wood Density Reflect the Impacts and Susceptibility to Defoliation by Gypsy Moth and Climate in Radiata Pine

Drought stress causes a reduction in tree growth and forest productivity, which could be aggravated by climate warming and defoliation due to moth outbreaks. We investigate how European gypsy moth (Lymantria dispar dispar L., Lepidoptera: Erebidae) outbreak and related climate conditions affected growth and wood features in host and non-host tree species in north-western Spain. There, radiata pine (Pinus radiata D. Don) plantations and chestnut (Castanea sativa Mill.) stands were defoliated by the moth larvae, whereas Maritime pine (Pinus pinaster Ait.) was not defoliated. The gypsy moth outbreak peaked in 2012 and 2013, and it was preceded by very warm spring conditions in 2011 and a dry-warm 2011-2012 winter. Using dendrochronology we compared growth responses to climate and defoliation of host species (radiata pine, chestnut) with the non-host species (Maritime pine). We also analyzed wood density derived from X-ray densitometry in defoliated and non-defoliated trees of radiata pine. We aimed to: (i) disentangle the relative effects of defoliation and climate stress on radial growth, and (ii) characterize defoliated trees of radiata pine according to their wood features (ring-width, maximum and minimum density). Radial growth during the outbreak (2012-2013) decreased on average 74% in defoliated (>50% of leaf area removed) trees of radiata pine, 43% in defoliated trees of chestnut, and 4% in non-defoliated trees of Maritime pine. After applying a BACI (Before-After-Control-Impact) type analysis, we concluded that the difference in the pattern of radial growth before and during the defoliation event was more likely due to the differences in climate between these two periods. Radiata pines produced abundant latewood intra-annual density fluctuations in 2006 and 2009 in response to wet summer conditions, suggesting a high climatic responsiveness. Minimum wood density was lower in defoliated than in non-defoliated trees of radiata pine prior to the outbreak, but increased during the outbreak. The pre-outbreak difference in minimum wood density suggests that the trees most affected by the outbreak produced tracheids with wider lumen and were more susceptible to drought stress. Results of this study illustrate (i) that the pattern of radial growth alone may be not a good indicator for reconstructing past defoliation events and (ii) that wood variables are reliable indicators for assessing the susceptibility of radiata pine to defoliation by the gypsy moth.

Several species of Penicillium isolated from chestnut flour processing are pathogenic on fresh chestnuts and produce mycotoxins

A collection of 124 isolates of Penicillium spp. was created by monitoring fresh chestnuts, dried chestnuts, chestnut granulates, chestnut flour and indoor chestnut mills. Sequencing of the ITS region, β-tubulin and calmodulin, macro-morphology and secondary metabolite production made it possible to determine 20 species of Penicillium. P. bialowiezense was dominant in the fresh chestnuts, while P. crustosum was more frequent in the other sources. A pathogenicity test on chestnut showed that around 70% of the isolates were virulent. P. corylophilum and P. yezoense were not pathogenic, while the other 18 species had at least one virulent isolate. P. expansum and P. crustosum were the most virulent. The isolates were characterized to establish their ability to produce 14 toxic metabolites in vivo: 59% were able to produce at least one mycotoxin. P. expansum was able to produce patulin, chaetoglobosin A and roquefortine, while P. bialowiezense produced C. Mycophenolic acid. Cyclopenins and viridicatins were produced by most of the P. crustosum, P. polonicum, P. solitum and P. discolour isolates. Some of the P. crustosum isolates were also able to produce roquefortine C or penitrem A. Information about the occurrence of Penicillium spp. and their mycotoxins will help producers to set up management procedures that can help to control the fungal growth and the mycotoxin production of chestnuts.

A mass spectrometry and 1H NMR study of hypoglycemic and antioxidant principles from a Castanea sativa tannin employed in oenology

The ethanol extract of the commercial tannin Tan'Activ C, (from Castanea sativa wood), employed in oenology, was subjected to chromatography on XAD-16 affording fractions X1-X5, evaluated for total phenols content (GAE), antioxidant activity (DPPH, ORAC), and hypoglycemic activity (α-glucosidase inhibition). Fraction X3 showed GAE, radical scavenging activity, and α-glucosidase inhibition higher than those of the Castanea sativa extract, and was subjected to chromatography on Sephadex LH-20 to obtain fractions S1-S7, analyzed by HPLC/ESI-MS/MS and ¹H NMR to identify the main active constituents. In fractions with higher antioxidant activity, gallic acid (4), grandinin (5), valoneic acid dilactone (9), 1,2,3-tri-O-galloyl-β-glucose (14), 3,4,6-tri-O-galloyl-β-glucose (15) and galloyl derivative of valoneic acid dilactone (21) were identified as the major constituents. The highest hypoglycemic activity was found in fractions S6 and especially S7; the major constituents of these fractions are valoneic acid dilactone (9), three tetragalloyl glucose isomers (16-18) and 1,2,3,4,6-penta-O-galloyl-β-glucose (23), previously reported as α-glucosidase inhibitors.

Impact of the Asian Chestnut Gall Wasp, Dryocosmus kuriphilus (Hymenoptera, Cynipidae), on the Chestnut Component of Honey in the Southern Swiss Alps

The Asian chestnut gall wasp (ACGW; Dryocosmus kuriphilus Yasumatsu, Hymenoptera, Cynipidae) is considered as one of the most dangerous pests of the genus Castanea. In southern Switzerland, repeated heavy ACGW attacks prevented chestnut trees from vegetating normally for years before the arrival and spread of the biological control agent Torymus sinensis (Kamijo, Hymenoptera, Torymidae). This resulted in a greatly reduced green biomass and flower production. In this paper, we analyze the impact of such an ecosystem alteration of the environment on the composition of produced honey. Six beekeepers were chosen from sites with different densities of chestnut trees, each of which providing series of honey samples from 2010 to 2016. We determined the chestnut component in the honeys via a combined chemical and sensory approach, and correlated the obtained results with the degree of yearly ACGW-induced crown damage and weather conditions during the period in question in the surrounding chestnut stands. The chestnut component in the analyzed honey sample series showed a strong correlation with the degree of ACGW-induced crown damage, whereas meteorological conditions of the corresponding year had a very marginal effect. Decreases in the chestnut component of the honey were statistically significant starting from a ACGW infestation level of 30%.

macrosporum

The plantation and management of sweet chestnut (Castanea sativa Mill.) orchards is a common and traditional land use system in many areas of Europe that offers the advantage of simultaneous production of nuts and timber. During the last decades, sweet chestnut has declined dramatically in many regions because of the profound social changes in rural areas coupled with pathogen attacks. Truffles, the hypogeous ascocarps of the ectomycorrhizal genus Tuber, are currently cultivated using host trees inoculated with these fungi for improving production in truffle orchards. The production of good forestry quality chestnut seedlings inoculated with European truffles in nurseries is essential for multi-cropping plantation establishment, but so far, it has not been implemented in agroforestry practices. Moreover, it is necessary to assess the physiological condition of the seedlings due to the high calcium amendment needed for the growth of Tuber spp. mycelium that can become toxic for the host plants. In this study, seedlings of C. sativa were inoculated with Tuber aestivum and its ecotypes T. uncinatum, T. brumale, and T. macrosporum and were grown in a greenhouse using culture conditions favorable for the production of high-quality plants for forestry purposes. At the end of the assay, levels of root colonization and morphological and physiological parameters of the seedlings were measured. The colonization of C. sativa with T. aestivum, its ecotype T. uncinatum, and T. brumale was successful, and the seedlings showed normal growth. Inoculation protocols with T. macrosporum need to be improved. Tuber species formed well-developed ectomycorrhizae on C. sativa in nursery conditions.

Evaluation of the Antioxidant and Antiglycation Effects of Lactarius deterrimus and Castanea sativa Extracts on Hepatorenal Injury in Streptozotocin-Induced Diabetic Rats

The present study aimed to investigate the beneficial effects of the treatment with extracts from the edible mushroom Lactarius deterrimus (Ld) and the chestnut Castanea sativa (Cs), separately and in combination (MIX Ld/Cs), on oxidative stress and advanced glycation end-product (AGE)-mediated hepatorenal injury in a rat model of streptozotocin (STZ)-induced diabetes by examining pathways responsible for maintenance of redox homeostasis. An experimental model of diabetes was induced in rats by the administration of 40 mg/kg STZ intraperitoneally (i.p.) for 5 consecutive days. The examined extracts were applied separately at a dose of 60 mg/kg i.p. and in combination (60 mg/kg each extract; i.p.) for 4 weeks, starting from the last day of STZ administration. The improvement of hepatorenal function in diabetic rats treated with the extracts was associated with an improved glycemic and lipid status and suppression of oxidative stress and thereby oxidative damage of lipids and DNA. Besides the fact that both extracts inhibited protein glycation and AGE formation in vitro, they also reduced non-enzymatic glycosylation in diabetic rats in vivo. The observed antiglycation activity of the examined extracts (separately and in combination) was accompanied with the inhibition of CML-mediated RAGE/NF-κB activation and reduction of enzymatic O-GlcNAcylation in liver and kidney tissues of diabetic rats. Taken together, these results reveal that the administration of chestnut and mushroom extracts, either individually or together, activates a coordinated cytoprotective response against diabetes-induced hepatorenal injury not only through recovery of the antioxidant defense system of the cell, but also through a marked antiglycation activity.

Freeze-drying duration influences the amino acid and rutin content in honeybee-collected chestnut pollen

Honeybee-collected pollen is gaining attention as functional food for human consumption, due to antiproliferative, antiallergic, antibiotic, antidiarrheic and antioxidant activities. Among the different bioactive compounds, flavonoids from bee-collected pollen are currently recognised as powerful antioxidant and antiradical molecules. Traditional conservation methods influence pollen organoleptic properties as well as the contents of nutrients and nutraceutical compounds. Here, freeze-drying (FD) was proposed as a novel conservation method, estimating its adequacy as drying process by the evaluation of changes in free and total amino acids and proline as well as in their ratios. Honeybee-collected chestnut pollen was taken into consideration and the level of rutin, as main flavonoid, was considered as marker compound highlighting the maintenance of pollen nutraceutical properties. Results showed that FD influenced rutin level, depending on the FD duration. However, the free proline to free amino acid ratio was always below 80%, and the free amino acid to total amino acid ratio remained unaltered indicating the adequacy of the FD treatment, which did not affect the nutritional value of chestnut pollen. Overall, this study shed light on the nutraceutical profile of honeybee-collected chestnut pollen, highlighting the promising potential of FD as a novel method to treat pollen for human consumption.

Characterization of Aspergillus section Flavi isolated from fresh chestnuts and along the chestnut flour process

An extensive sampling of Aspergillus section Flavi considered to be the main agent responsible for aflatoxin contamination, was carried out in the field and along the processing phases of chestnut flour production in 2015. Fifty-eight isolates were characterized by means of biological, molecular and chemical assays. The highest incidence of Aspergillus section Flavi was found in the field. The identification of the isolates was based on β-tubulin and calmodulin gene sequences. A. flavus was found to be the dominant species, and this was followed by A. oryzae var effusus, A. tamarii, A. parasiticus and A. toxicarius. Nineteen percent of the strains produced aflatoxins in vitro and forty percent in vivo. The pathogenicity assay on chestnut showed 56 virulent strains out of 58. The molecular, morphological, chemical and biological analyses of A. flavus strains showed an intraspecific variability. These results confirm that a polyphasic approach is necessary to discriminate the species inside the Aspergillus section Flavi. The present research is the first monitoring and characterization of aflatoxigenic fungi from fresh chestnut and the chestnut flour process, and it highlights the risk of a potential contamination along the whole chestnut production chain.

Phylogenetic and phenotypic characterisation of Sirococcus castaneae comb. nov. (synonym Diplodina castaneae), a fungal endophyte of European chestnut

In this paper we resolve the taxonomic status of the fungus Diplodina castaneae (Ascomycetes, Diaporthales, Gnomoniaceae) which occurs on the European chestnut (Castanea sativa) as endophyte and as the causal agent of Javart disease. Specimens from Switzerland, Spain, and Azerbaijan were sequenced at five nuclear loci (β-tubulin, EF-1α, ITS, LSU, and RPB2). Phylogenies were inferred to place D. castaneae in the Gnomoniaceae family. Moreover, growth rates and morphological characteristics on different agar media were assessed and compared to those of Gnomoniopsis castaneae, which can easily be confused with D. castaneae. Based on morphological and phylogenetic characteristics, we propose to reallocate D. castaneae to the genus Sirococcus, as S. castaneae comb. nov.