Chestnut Orchards Research Articles

Growth analysis of sweet chestnut burr in two seasons with differing weather conditions

In Italy, most of the traditional sweet chestnut (Castanea sativa Mill.) orchards are still non-irrigated since they are located in mountain-hill areas with climate conditions that used to be optimal to sustain the vegetative and reproductive growth of this nut tree species. Nowadays, the increase of summer temperatures and the decrease of rainfall (due to climate change) are affecting negatively chestnut physiological performances. The aim of this experiment was to study sweet chestnut burr growth in two seasons, one warm/dry and one mild/rainy (2017 and 2018, respectively). The study was carried out in a traditional rainfed chestnut orchard. The seasonal burr growth was measured weekly from 30 days after full bloom (DAFB) to the beginning of burr valves opening. Air temperature and daily precipitation were measured at a nearby weather station. The results of this study highlighted that chestnut burr growth seems to be affected by seasonal weather conditions. Indeed, in 2017, the high summer temperatures and the moderate rainfall in summer (227 mm) and winter-spring (385 mm) appeared to affect negatively burr absolute growth rate (AGR; 0.31 mm day-1 ) and consequently final burr size (46.2 mm). The mild and rainy weather conditions that occurred in 2018 (663 and 340 mm of winter-spring and summer precipitation, respectively) positively influenced burr AGR (0.54 mm day-1 ) and therefore its final size (60.8 mm). These preliminary results suggest that the introduction of irrigation as a common management practice for chestnut orchards may promote their resilience to climate change with a positive effect on their productivity and fruit quality.

An Automatic UAV Based Segmentation Approach for Pruning Biomass Estimation in Irregularly Spaced Chestnut Orchards

The agricultural and forestry sector is constantly evolving, also through the increased use of precision technologies including Remote Sensing (RS). Remotely biomass estimation (WaSfM) in wood production forests is already debated in the literature, but there is a lack of knowledge in quantifying pruning residues from canopy management. The aim of the present study was to verify the reliability of RS techniques for the estimation of pruning biomass through differences in the volume of canopy trees and to evaluate the performance of an unsupervised segmentation methodology as a feasible tool for the analysis of large areas. Remote sensed data were acquired on four uneven-aged and irregularly spaced chestnut orchards in Central Italy by an Unmanned Aerial Vehicle (UAV) equipped with a multispectral camera. Chestnut geometric features were extracted using both supervised and unsupervised crown segmentation and then applying a double filtering process based on Canopy Height Model (CHM) and vegetation index threshold. The results show that UAV monitoring provides good performance in detecting biomass reduction after pruning, despite some differences between the trees’ geometric features. The proposed unsupervised methodology for tree detection and vegetation cover evaluation purposes showed good performance, with a low undetected tree percentage value (1.7%). Comparing crown projected volume reduction extracted by means of supervised and unsupervised approach, R2 ranged from 0.76 to 0.95 among all the sites. Finally, the validation step was assessed by evaluating correlations between measured and estimated pruning wood biomass (Wpw) for single and grouped sites (0.53 < R2 < 0.83). The method described in this work could provide effective strategic support for chestnut orchard management in line with a precision agriculture approach. In the context of the Circular Economy, a fast and cost-effective tool able to estimate the amounts of wastes available as by-products such as chestnut pruning residues can be included in an alternative and virtuous supply chain.

Ectomycorrhizae determine chestnut seedling growth and drought response

Although agriculture focuses on row crops in the Midwestern US, chestnut (Castanea) would be a possible multipurpose agroforestry crop in erodible locations within this region. As ectomycorrhizal (ECM) colonization is often crucial for tree establishment and production, we addressed the importance of ECM colonization on chestnut performance by assessing: (1) natural ECM colonization in an established chestnut orchard, and (2) the effect of ECM inoculation on seedling establishment and drought response in a greenhouse. We selected 50 Chinese American hybrid chestnuts trees in a commercial orchard and assessed their level of mycorrhizal colonization in relation to distance from an adjacent forest, the source of inoculum. In the green house, we grew 80 seedlings from this orchard with and without mycorrhizal inoculation. Half were harvested to assess inoculation success and biomass; the remainder were subjected to experimental water stress which was evaluated with chlorophyll fluorescence using Fv/Fm values. In the orchard planted with uninoculated plants, ECM colonization decreased with distance from adjacent oak forest (P = 0.015), the putative ECM source, with an average of 29% root tips colonized. ECM inoculation increased seedling aboveground biomass by 16.4% in the greenhouse and generated 1.14 times more, but smaller stomata on leaves. Water stress in ECM inoculated seedlings also recovered faster from an experimental drought having significantly higher Fv/Fm value (P = 0.004) than uninoculated seedlings. Our study clearly indicates that ectomycorrhizal colonization can help chestnut trees in their early growth and stress tolerance and should be included into field plantings to minimize dependence on agricultural amendments.

Large Chestnut Trees (Castanea sativa) Respond Poorly to Liming and Fertilizer Application

Establishing a fertilization plan for large trees is particularly difficult due to the high soil volume that the roots exploit and the buffer effect of the perennial woody structure on the concentration of nutrients in the leaves. This work evaluates the response of chestnut, a very large tree, to different fertilizer solutions. The study was conducted in two chestnut orchards planted in acid soils that were subjected to the application of lime plus phosphorus (Lime+P), lime plus a compound NPK fertilizer (Lime+NPK), and an unfertilized control (Control). The effects of the treatments on soil properties, nutritional status and photosynthetic performance of the trees, and nut production, were assessed from field and laboratory analyses. Liming significantly increased soil pH and exchangeable calcium (Ca). Treatments did not significantly influence leaf P and K levels, although leaf N concentrations were significantly higher in the Lime+NPK treatment on two of the three sampling dates. In one of the trials, the average accumulated nut yield was higher in the Lime+NPK (71.7 kg tree−1) treatment compared with the control (59.6 kg tree−1) and the Lime+P (51.7 kg tree−1) treatments, although without significant differences at P < 0.05. Overall, the results show the chestnut tree to be a species tolerant of soil acidity. The results also show that the buffer capacity of the plant in regulating the nutrient concentration in the leaves seems to be higher for P than for N, and therefore, concentrations of N in the leaves require the regular application of the nutrient as a fertilizer.

Public Preferences for Farmed Landscapes: the Case of Traditional Chestnut Orchards in South Tyrol

Abstract Sweet chestnuts are, from a farming point of view, a marginal crop in South Tyrol, though historically rooted. Chestnut orchards represent a cultural heritage, as well as an important aesthetic element of the cultural landscape, besides assuming a high ecological value for many animal and plant species. Public awareness towards this ecosystem is generally higher in autumn, when fruit consumption sees its peak and events take place. Using a Choice Experiment, we assessed whether seasonality interferes in people’s willingness-to-pay for a traditional chestnut orchard and its ecosystem services. We also investigated the importance of respondent origin (residents vs tourists) and, finally, a Latent Class analysis allowed us to depict segments of society in relation to their preferences. Our results show that tourists are ready to pay more than locals for chestnut orchards and for fruits, whereas seasonality has generally a low impact.

Combined Addition of Bovine Bone and Cow Manure: Rapid Composting of Chestnut Burrs and Production of a High-quality Chestnut Seedling Substrate

In China, chestnut burrs (CB) are produced at a rate of a million tons per year as the major byproduct of chestnut orchards. It is necessary to utilize the chestnut forest green waste and convert it into a valuable seedling media for the sustainable cultivation of chestnut seedlings. In this study, we composted CB with two waste products of cattle farming, namely cow manure (CM) and bovine bone (BM). We also evaluated the potential of CB compost application in chestnut forest sustainability. Results indicated that the best combination was the addition of 15% BM and 55% CM. This combination significantly improved the composting environment by increasing pH, enhancing phosphorus concentration and mineral elements such as Ca, Na, Mg and Zn, and shortened the composting period to 38 days. This combination also resulted in the highest content of citric acid-P (109.20 times than the control treatment) and the lowest content of NH4+–N (0.28 times than control treatment) indicating a better N and P structure of the final compost product. This combination achieved a greater degradation rate of CB cellulose (61.45%), hemicellulose (37.87%), and a more significant degradation of outer epidermis structure. When CB compost was used as a growing media, a significant decrease in photosynthesis stress of chestnut seedlings was observed, which was mainly manifested as a decrease in photochemical quenching (qP) and an increase of the maximum efficiency of PSII photochemistry under dark-adaption (Fv/Fm). Addition of 10% CB compost (in volume basis) is suggested, which resulted in the tallest chestnut seedlings (59.83 cm) with a stem diameter of 0.91 cm after six months of growth. In summary, this research provides an environmentally friendly strategy for chestnut orchard sustainability: rapid composting of CB, then immediate application as a high-quality substrate for chestnut seedlings.

Modeling light below tree canopies overestimates net photosynthesis and radiation use efficiency in understory crops by averaging light in space and time

By averaging in time and/or space, models predict less variable light patterns under tree canopies than in reality. We measured light every minute in 24 positions in a grid under different chestnut orchards, for several clear and overcast days. We also modelled this light with a purposely created 3D, spatially explicit, ray-tracing light interception model, where canopy porosity was calibrated to match measured daily light. Finally, we used both the measured and modeled light patterns transmitted under the tree canopies to estimate the daily net photosynthesis (An) and radiation use efficiency (RUE) of an understory wheat leaf. As expected, modeled light was more uniform than measured light, even at equal daily light. This resulted in large overestimation of daily An and RUE of the understory leaf. Averaging light in time increased the overestimations even further. A sensitivity analysis showed that this overestimation remained substantial over the range of realistic values for leaf photosynthetic parameters (i.e. Vc,max, Jmax, Rd) of the understory crop.

MECHANIZED MANAGEMENT OF PRUNING RESIDUES IN SWEET CHESTNUT ORCHARDS

In Italy, Dryocosmus kuriphilus is a major insect pest of chestnut orchards causinggall formation and significant yield losses. The use of the parasitoid wasp Torymussinensis is an effective biological control method that requires the appropriatemanagement of the pruning residues, to preserve the woody galls in which T.sinensis adults overwinter. An innovative tractor-pulled combined mechanicalshredder was tested for treating the residues, once the pruning operations arecompleted. The machine processes the residues in a single-step, picking-up theprunings from the orchard floor, shredding them to appropriate size, and collectingthem into a rear container. The shredded residues may then be concentrated into afew piles for the long-term field storage, until next spring. The aim of the studywas to evaluate the machinery’s operative performance, the quality of the shreddedbiomass and the impact on gall integrity. In the field trials, the machineryeffectively shredded the residues achieving an average operative capacity of 1.19ha∙h-1 and a work capacity of 1.79 t∙h-1. Moisture content, apparent bulk density,and particle size distribution of the shredded biomass were determined. Over 95%of wood chips were included in the 3.15-45 mm size range, making them suitablefor use in residential biomass furnaces. The calorific power of the chestnut residueswas similar to that reported for other hardwood species (18-20 MJ∙kg-1). Also, themechanical action of the shredder preserved at least two thirds of the winter galls,safeguarding the parasitoid’s life cycle.

Bird response to woody pastoral management of ancient chestnut orchards: A case study from the southern Alps

Wood-pasture abandonment is an important cause of structural homogenisation in traditionally managed forest landscapes across the Alps. In the present study, bird response to the restoration of ancient abandoned chestnut orchards was investigated by a pairwise-comparison of species richness and community composition in 94 managed and unmanaged chestnut orchards on the southern slope of the Swiss Alps.Sixty-one bird species were tracked during four breeding seasons. Although managed orchards were more environmentally heterogeneous, the average number of bird species was only slightly higher in managed than unmanaged orchards, and no differences were found in species abundance and composition. We found, instead, five times as many bird species associated with managed chestnut orchards (i.e., five indicator species and 10 species exclusively observed in managed orchards) as compared to unmanaged orchards that only had one indicator and two exclusive species. We also found 11 species to be significantly associated with managed orchards that have higher bird species richness and are mainly characterized by low tree coverage (<62.5%).We hypothesise that these results are mainly due to: (i) the high mobility of birds and the small patch size of managed orchards which may have mitigated the stronger effects expected on bird communities, and (ii) the naturally small populations of those bird species favoured by restoration which were masked by the most frequent and dominant species. Moreover, the resilience of bird communities to restoration could also be due to the long history of forest management and wildfires south of the Alps. When planning chestnut orchard restoration and management, we recommend considering a tree cover threshold of below 62.5% as a measure that promotes high bird species richness.

Effect of different feeding sources on lifespan and fecundity in the biocontrol agent Torymus sinensis

Torymus sinensis Kamijo (Hymenoptera, Torymidae) is a biocontrol agent released to control outbreaks of the Asian chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu (Hymenoptera, Cynipidae). This wasp is mass reared in controlled conditions in order to be released on a large scale in chestnut orchards and coppices, thus factors such as food quality may deeply influence the effectiveness of parasitoids. To identify different diets that could be used to increase mass rearing, performance, longevity and fecundity of T. sinensis were assessed using honey (diet 1), honey plus pollen (diet 2), pollen (diet 3), and water (diet 4), compared to unfed wasps (control) in laboratory experiments.In the present study diet quality greatly influenced survival and reproductive output in T. sinensis. Adults using honey plus pollen as food had the longest life span, and significantly increased fecundity compared to pollen alone, water, and unfed wasps. Median lifespan (day at which 50% of the initial number of wasps are still alive) was 31, 31, 2.5, 4, 1.5 days, in the honey, honey plus pollen, pollen, water, control, respectively.The egg production in wasps fed with honey and honey plus pollen observed over lifetime showed that the newly emerged specimens had an average of 2.40 ± 0.21 and 0.14 ± 0.12, respectively at day 0. The number of mature eggs increased rapidly reaching in diet 1 the highest average number, 26.60 ± 2.48, at day 6, and 30.2 ± 1.59 at day 7 in diet 2. No significant difference in the mean number of mature eggs between diets 1 and 2 was observed during all 13 weeks except for week 11. The mean number of reabsorbed eggs was 0 both in diet 1 and 2 at day 0. The mean number increased till 2.80 ± 0.66 at day 10 and 1.40 ± 0.24 at day 14 in diet 1 and 2, respectively.The cumulative lifetime mean egg load was 1012.67 and 1095.82 for honey and honey plus pollen, respectively, which was significantly higher than 32.40 for pollen, 58.40 for water and 43.57 for control.Based on our studies, feeding the female wasps with honey and pollen increased lifespan by 33-fold, and fecundity by 2.3-fold at day 4 over unfed wasps.This work contributes to a better understanding of the influence of different diets on lifespan and fecundity in the parasitoid wasp T. sinensis, to the refinement of mass rearing in controlled conditions, and to the optimization of classical biocontrol programs. Prior to the field release, it seems advisable to supply insects with sugar-rich diets to improve their performance in fields and to enhance parasitoid egg expenditure.

Variance in leaf spot susceptibility in chestnut trees of different species and hybrids

Prior to the first occurrence of chestnut blight in 1976, leaf spot caused by Cylindrosporium castaneae was one of the most important diseases of European chestnut trees in Slovakia. In 2011, extensive damage of leaves by leaf spot was recorded in young chestnut trees in an experimental chestnut orchard in Pribelce, Slovakia, where seedlings and grafts of different species and hybrids (Castanea sativa, Castanea crenata, and C. sativa × C. crenata) exhibited visible differences in the extent of leaf spot. Morphological observations of the fungal species causing leaf spot were conducted, and the disease symptoms were described. Digital images of particular leaves were evaluated using Quick Micro Photo software, and the ratio of infected leaf area was calculated. Trees species showed a significant effect on the proportion of leaf spot area, indicating that the response to fungal attacks has a strong genetic determinism, with resistance being clearly influenced by species. The lowest leaf spot infection was recorded in C. crenata seedlings.

Estimation of effective pollen dispersal distance for cross-pollination in chestnut orchards by microsatellite-based paternity analyses

Chestnut (Castanea spp.) is mainly self-sterile, so interplanting of different cultivars in orchards is recommended. However, effective pollen dispersal distances for cross-pollination in chestnut orchards have not been determined. We examined pollen dispersal in three chestnut fields by tracking the movement of cultivar-specific pollen through paternity analysis based on simple sequence repeat (SSR) markers. We genotyped 48 major cultivars with 20 SSRs and constructed a reference database, from which we inferred the pollen parent of each seed. In Field A, which consisted of a single row of pollinizer ‘Riheiguri’ and four rows of ‘Porotan’ at distances of 4, 8, 12, and 16 m from the pollinizer row, the percentage of seeds sired by the pollinizer pollen was higher at 4 and 8 m from the pollinizer trees (65.3% and 61.1%, respectively) than at 12 and 16 m (37.5% and 43.1%, respectively). The percentages of bur set and yield per tree decreased as the distance from the pollinizer row increased (66.2%, 42.4%, 33.7%, and 24.8%; 7.0, 2.5, 1.6, and 1.1 kg: 4, 8, 12, and 16 m, respectively). In analyses of two other fields, which contained interplanted rows of different cultivars, the percentages of seeds sired by pollen from cultivars planted in adjacent rows were much higher than from cultivars planted in more distant rows. These results suggest that it is important to plant different cultivars in adjacent rows.

Seasonal fluctuations of goat moth (Cossus cossus L.) in chestnut orchards in İzmir and Manisa, Turkey

Seasonal fluctuations of goat moth (<i>Cossus cossus</i> L.) in chestnut orchards in <b>İ</b>zmir and Manisa, Turkey

Testing chestnut hybrids for resistance to Cryphonectria parasitica

Asiatic pathogen Cryphonectria parasitica produced dramatic diebacks of American chestnut (Castanea dentata) and European or sweet chestnut (Castanea sativa) throughout their natural or artificial range, both in forests and orchards. Fungus chemical treatment is a useless (curative) to a less important (preventive) tool. Biological control of Cryphonectria parasitica has various levels of efficiency (from very good to very low), according to compatibility of local strain and fungus mycoviruses. In Romania all the sweet chestnut orchards have been largely destroyed. Till now, searching for natural resistance of European and American chestnut has largely failed. Therefore, chestnut breeding in order to improve resistance to pathogen is imperative both for horticulture and silviculture. In this paper, we tested transferring resistance to C. parasitica from Japanese (Castanea crenata) to European chestnut (C. sativa) in the Carpathian basin, Romania. Open pollinated interspecific hybrids (C. crenata × C. sativa and C. sativa × C. crenata) have been used as tested variants. Sweet chestnuts seedlings of local origin were used as a first control; the second control was a sweet chestnut forest situated at 50 km from the breeding trial. All chestnut material has been under pressure of Cryphonectria parasitica natural infection. We used several characteristics to evaluate the chestnut resistance: presence of fungus (fruitbody, mycelium, and infections), cankers, shoot/branch/stem infections, water sprouts, secondary woody fungus. Complementary, we tested the biological control of C. parasitica. Hybrids' resistance to Cryphonectria parasitica looked very promising, with just a small number of hybrids developing fruit bodies or cankers. On the contrary, first control sweet chestnut collections were severely damaged by the Asian pathogen. Biological control was very efficient both in European chestnut and interspecific hybrids. The untreated forest (second control) was dramatically affected by the fungus. At present, the health status of the chestnut hybrids is very good, showing a very good acclimatization in Carpathian continental climate.

The effect of irrigation on chestnut physiology and production (Castanea sativa)

This study aims to evaluate the influence of irrigation on the chestnutRSQUOs physiology, nut calibre and yield. The study was carried out during 2015 and 2016, in a chestnut orchard of the 'Judia' cultivar, located in Braganca in the northeast of Portugal. Two irrigation systems were installed in 10 trees each: drip (TI) and micro-sprinkler (SI). Irrigation was triggered when stem water potential fell below -1.2 MPa. Ten other sample trees were kept in rainfed conditions (NI). From June to October the stem water potential, chlorophyll fluorescence, photosynthetic and transpiration rates were monitored and production per tree was weighted. The total mean amount of water furnished was of 470 and 925 m3 ha-1 in 2015 and 2016, respectively. On both years the photosynthetic and transpiration rates were higher for irrigated trees (8.6 µmol CO2 m-2 s-1 and 1.9 mmol H2O m-2 s-1) than for non-irrigated ones (7.6 µmol CO2 m-2 s-1 and 1.8 mmol H2O m-2 s-1). Chestnut production was 26% higher for irrigated trees with 48.2 kg tree-1 and nut size was smaller in non-irrigated trees (93 nuts kg-1) than for the irrigated ones (75 nuts kg-1). Despite of these differences the climatic conditions, particularly the hotter temperatures in 2016, affected production and nut size. From 2015 to 2016 production decreased 16, 27 and 33% for SI, TI and NI, respectively. Nut size also decreased 90, 45 and 24% for NI, TI and SI, respectively, when the temperature sum (May-October) varied from 2348 to 2504°D. The introduction of irrigation in the chestnut orchard is beneficial but temperature plays an important role in the tree physiology and production.

Short communication: Farmers’ opinions on chestnut (Castanea sativa Mill.) supply chain development strategies: A case study in Central Italy

Aim of the study: To identify the priority strategy for the strengthening of the chestnut supply chain through a participatory approach.Area of study: Mugello-Val di Sieve inTuscany region (Italy).Material and methods: The data were collected by administering a questionnaire to a sample of 126 chestnut growers (83 chestnut growers enrolled and 43 not enrolled in the Consortium of “Marronedel Mugello Protected Geographical Indication”) to identify the priority objectives and activities to develop the chestnut supply chain.Main results: It is necessary to develop a diversified strategy to stimulate the chestnut production and simultaneously enhance the marketing of the product in order to revive the chestnut cultivation inTuscany region. The main activities to be pursued are the implementation of silvicultural treatments of chestnut orchards and the integrated fight against chestnut gall wasp to increase the productivity and strengthen the “Marronedel Mugello Protected Geographical Indication” brand.Research highlights: Participatory approach is a fundamental instrument to define a common strategy to strengthen chestnut supply chain at local level.

First Report of Shoot Canker on Chestnut Caused by Diaporthe nobilis in Shandong Province of China.

Chinese chestnut (Castanea mollissima) is an economic tree widely cultivated for nut production. In May 2015, for the first time, canker and severe twig dieback were observed in the chestnut orchards in Yantai, Shandong Province, China. The cankers appeared on shoots, twigs, and branches with sunken reddish-brown/tan symptoms. The shoots died above the infected area when girdled. However, fruit rot was not observed. In later summer, numerous small black pycnidia were formed along the lenticels on the surface of diseased bark with curly slim and pale-yellow spore-tendrils being released from the pycnidia after rainfall. To identify the causal agents, tissue fragments (5 mm²) were excised from the canker lesions, and 10 isolates were obtained on potato dextrose agar (PDA) (Bai et al. 2015). These isolates formed creamy white mycelia with concentric rings on PDA. Black pycnidia developed in culture and produced two types of conidia: hyaline, fusiform-elliptic to oblong-elliptic alpha conidia and hyaline, filiform, slightly curved or hooked beta conidia. The size of alpha conidia varied from 7.5 to 12.5 × 2.1 to 2.8 μm, and that of beta conidia ranged from 26.8 to 30.2 × 1.2 to 1.7 μm. Based on morphological characteristics, these 10 isolates were close to Diaporthe nobilis CBS 587.79 (Gomes et al. 2013). To confirm the identification, DNA was extracted from the mycelium of three monoconidial isolates (CHNut1, CHNut2, and CHNut3). The internal transcribed spacer region (ITS), a partial sequence of calmodulin (CAL), histone H3 gene (HIS), translation elongation factor 1-α gene (TEF1), and β-tubulin gene (TUB) were amplified and sequenced using primers ITS1/ITS4, Bt2a/Bt2b, H3-1a/H3-1b (Glass and Donaldson 1995), EF1-728F/EF1-986R, and CAL-228F/CAL-737R (Carbone and Kohn 1999), respectively. The consensus sequences (GenBank accession nos. MG920017 for ITS, MG926648 for CAL, MG926649 for TEF1, MG926650 for TUB, and MG926651 for HIS) were aligned using BLASTn in GenBank showing high homology (99, 100, 99, 100, and 100%) with the sequences of ITS (KC343153), CAL (KC343395), TEF1 (KC343879), TUB (KC344121), and HIS (KC343637) from D. nobilis complex (Gomes et al. 2013). The ITS sequence obtained in this study showed 99% similarity with that of the strain Ch1 (JF812647), which caused stem canker on cherry in China (Wang et al. 2011). Pathogenicity of the three isolates was performed in the field and under laboratory conditions. Briefly, 30 stems from 5-year-old chestnut trees were wounded with a scalpel on the phloem tissues and inoculated with an inoculum suspension (10⁶ alpha conidia/ml), which were then wrapped with moist cheesecloth and sealed with Parafilm. The wounded phloem tissues of 10 stems were inoculated with sterile distilled water as noninoculated controls. After 2 weeks, necrotic lesions (32 to 55 mm in diameter) developed on inoculated shoots, which resembled the symptoms on infected chestnut shoots in the field. In contrast, control plant tissues did not show any disease symptoms. The pathogen was reisolated from symptomatic shoots and was confirmed as D. nobilis based on morphological and molecular analysis. The experiment was conducted three times. To our knowledge, this is the first report of D. nobilis causing shoot canker and dieback on chestnut in China, and even worldwide. This study provides important information for necessitating new disease-management practices.

Irrigation positively affects the chestnut’s quality: The chemical composition, fruit size and sensory attributes

Abstract In the northeast of Portugal there is a tendency to introduce irrigation system on the chestnut orchards but the effect of irrigation on the chestnut’s quality has not been studied yet. This study aims to evaluate the effect of irrigation on the ‘Judia’ cultivar chestnuts quality concerning its chemical composition, fruit size and tastiness. Three treatments were applied during 2015 and 2016: the drip system, the micro-sprinkler system and a non-irrigated treatment. In both years the bigger chestnuts and production were always present in irrigated treatments. Significant differences among treatments were found in ashes, starch, soluble sugars, and crude protein contents in 2015, but in 2016 no significant differences were found. Moreover, the non-irrigated chestnuts were the sweetest but with smaller calibre. The chestnuts from micro-sprinkler were the firmest and they were as sweet as the drip's chestnuts. Results suggest that irrigation, namely with sprinkler system, valorise the chestnuts by increasing its size and keeping its nutritional value and its sensory quality.

Relating plant and soil water content to encourage smart watering in chestnut trees

Chestnut orchards are facing new limitations due to scarce of soil water during summer times, mainly attributed to the low precipitation amount typically occurred on such period. The present study aims to define a methodology to improve in a smart way the utilization of water on chestnut irrigation. Based on leaf gas exchanges parameters, there is done a transposition for the soil water content and matric potential, to allow an optimization of the irrigation scheduling in chestnut trees. Trial was installed in a loamy soil at the northeast of Portugal between 2013 and 2016 with micro-sprinkler and drip irrigation system. Stem water potential, photosynthetic rate, soil water content and soil water potential were monitored during the vegetative cycle (June–October). The stem water potential was dependent on air’s temperature and soil moisture. The higher photosynthetic rate (9–11 μmolCO2·m−2 s−1) was reached when midday stem water potential ranged between −1.2 to −0.5 MPa and the regression between stem water potential and soil water content on the top 10–40 cm of soil was of r2 = 0.38. According to these, it was admissible to trigger irrigation when the probe registers 16% and watering must keep soil’s moisture near 23%. The regression between stem and soil water potential was of r2 = 0.43 and irrigation scheduling may be triggered when ‘Watermark’ sensor at 30–60 cm soil depth is above −100 cbar to promote good tree water status although this last is air temperature dependent.

Sclerotinia pseudotuberosa as the cause of black rot of chestnuts in Greece

In November 2014 a disease was observed on nuts collected from chestnut orchards in Northern Greece (Kozani) causing significant yield losses (ca. 50%). Diseased fruits of European chestnut (Castanea sativa) were black and rotted, although appearing healthy and without external symptoms.