Pear Orchards Research Articles

A whole ecosystem approach to pear psyllid (Cacopsylla pyri) management in a changing climate

AbstractWhole ecosystem-based approaches are becoming increasingly common in pest management within agricultural systems. These strategies consider all trophic levels and abiotic processes within an ecosystem, including interactions between different factors. This review outlines a whole ecosystem approach to the integrated pest management of pear psyllid (Cacopsylla pyri Linnaeus) within pear (Pyrus communis L.) orchards, focusing on potential disruptions as a result of climate change. Pear psyllid is estimated to cost the UK pear industry £5 million per annum and has a significant economic impact on pear production globally. Pesticide resistance is well documented in psyllids, leading to many growers to rely on biological control using natural enemies during the summer months. In addition, multiple insecticides commonly used in pear psyllid control have been withdrawn from the UK and Europe, emphasising the need for alternative control methods. There is growing concern that climate change could alter trophic interactions and phenological events within agroecosystems. For example, warmer temperatures could lead to earlier pear flowering and pest emergence, as well as faster insect development rates and altered activity levels. If climate change impacts pear psyllid differently to natural enemies, then trophic mismatches could occur, impacting pest populations. This review aims to evaluate current strategies used in C. pyri management, discuss trophic interactions within this agroecosystem and highlight potential changes in the top-down and bottom-up control of C. pyri as a result of climate change. This review provides a recommended approach to pear psyllid management, identifies evidence gaps and outlines areas of future research.

Multi-Agent Target Allocation and Safe Trajectory Planning for Artificial Pollination Tasks

This paper presents an autonomous multi-agent drone system utilized for an artificial pollination task to address the declining bee population and its impact on natural pollination. The main goal is to visit all the targets (flowers) by drones. The system receives the position of the targets located on a vertical fruiting wall from a single sensor mounted on an unmanned ground vehicle (UGV). Then, it determines the sequence of allocation to minimize the task time and minimize the accumulated distance each drone travels. The limited payload capacity of each drone and the need to refill stock carried by the UGV are also considered. After allocating the targets, a safe trajectory is generated for each drone to avoid collision with other drones, considering uncertainty in the drones’ positions. When a drone reaches a target, the system allocates a new target, and the cycle repeats until the task is completed. The system is reactive to the evolution of the task and adjusts accordingly. An additional tested factor is the impact of the positioning error on the task time. The system was evaluated through dynamic simulations using real datasets of peach and pear orchards and finally in a laboratory proof-of-concept experiment using a micro-drone system.

WOFOST-N: An improved WOFOST model with nitrogen module for simulation of Korla Fragrant pear tree growth and nitrogen dynamics

Few studies have focused on simulating fruit tree growth under fertilization constraints and evaluating nitrogen utilization efficiency. This study aimed to improve the WOFOST (World Food Studies) model by embedding the nitrogen dynamics module into the original WOFOST model (WOFOST-N) to simulate the Korla Fragrant pear tree growth, nitrogen transport, nitrogen use efficiency and nitrogen stress. In addition, we used the BBCH scale to provide a more detailed description of the phenological development process of pear trees to improve phenology simulation performance. Field trials were conducted in 2021 and 2022 in two pear orchards in the Alar region of China. The results showed that the simulated total dry weight (leaves and fruits, TAGPl,f) and leaf area index (LAI) growth dynamics agreed well with the measured values in each treatment in 2021 and 2022. The R2 values of the simulated TAGPl,f was between 0.87 and 0.97, and the R2 values of the simulated LAI were between 0.80 and 0.95. The improved model also showed relatively high simulation accuracy (8.2 % ≤ NRMSE ≤ 20.5 % for TAGPl,f, 7.1 % ≤ NRMSE ≤ 20.1 % for LAI). The improved model had good global simulation performance for soil nitrogen content in six treatments with a good consistency (R2 = 0.87 in 2021 and 0.89 in 2022) and low error (NRMSE = 12.4 % in 2021 and 11.8 in 2022). The simulated yields and nitrogen use efficiencies (NUE) in the two orchards also showed good performance, with R2 = 0.94 and 0.93, NRMSE = 5.2 % and 7.5 % for yields, R2 = 0.93 and 0.96, NRMSE = 10.7 % and 9.6 % for NUE, respectively. The proposed method provides a promising method to simulate fruit trees' growth and nitrogen dynamic effects.

Natural Enemies of the Pear Psylla, Cacopsylla pyri (Hemiptera: Psyllidae), and the Possibilities for Its Biological Control: A Case Study Review in the Western Balkan Countries

The accessible literature covered in this paper commonly highlights psyllids as a significant group of insects affecting pear trees, posing a continual challenge for commercial orchards. With the development of modern pear cultivation systems, Cacopsylla pyri Linnaeus 1758 (Hemiptera: Psyllidae) has emerged as a major pest in pear orchards across many European countries, including those in the Western Balkans. For years, the agricultural sector has primarily relied on chemical insecticides to control pear psyllas, but these methods often fail to produce satisfactory results. This is largely due to C. pyri’s rapid development of resistance to chemical treatments. Consequently, modern agriculture is increasingly shifting towards biological methods to manage C. pyri, involving the identification and conservation of its natural enemies. Although there is an abundance of research on the natural predators of C. pyri and their biocontrol applications across the globe, the Western Balkan region has conducted relatively few studies on the subject. Globally, various parasitoids, predators, and entomopathogenic fungi are often cited as effective against C. pyri. Specific species registered in the agroecological conditions of the Western Balkans include parasitic wasps such as Trechnites insidiosus Crawford, 1910 (Hymenoptera: Encyrtidae) and Prionomitus mitratus Dalman, 1820 (Hymenoptera: Encyrtidae), as well as the predatory bug Anthocoris nemoralis Fabricius, 1794 (Hemiptera: Anthocoridae). However, most Balkan countries have yet to fully utilise the potential of beneficial entomofauna or develop strategies for their commercial application at a national level. Considering that C. pyri is a major pest in pear cultivation and its natural enemies have not been thoroughly explored in most of the Western Balkans, this paper aims to review the literature data on available natural enemies of pear psyllas and to highlight and promote their undeniable potential in biological control.

Bumblebee Foraging Dynamics and Pollination Outcomes for Cherry Tomato and Pear Varieties in Northern China.

Bumblebees (Bombus terrestris) have strong environmental adaptability and high pollen transfer efficiency, making them well-suited pollinators of economic crops. However, bumblebee pollination is still not widely applied in northern China due to the lack of data on foraging behavior and pollination effects. We conducted a three-year experiment involving cherry tomatoes (Solanum lycopersicum L.) and pears (Pyrus spp.) treated with bumblebee pollination to evaluate the foraging behavior and pollination effects on these two crops. Results showed that B. terrestris had enhanced foraging activities as daytime temperatures rose from 18 °C to 26 °C, as indicated by the increased number of bees leaving the hive and returning bees carrying pollen in greenhouses in winter. There were two peaks in the foraging activity of bumblebees in pear orchards in early spring, which was closely related to the temperature change in the daytime. Undoubtedly, cherry tomatoes treated with B. terrestris had higher fruit setting rate, weight, seed number, and fruit yields compared to those with hormone 2,4-dichlorophenoxyacetic acid treatments, as well as a lower rate of deformed fruits. B. terrestris pollination can significantly increase the fruit setting rate and fruit yield of pears, compared with open pollination, and can fully achieve the effect of hand pollination. B. terrestris pollination can improve cultivation efficiency, increase yield, and produce more economic benefits. Moreover, it can also contribute to reducing hormone residues and ensure the safety of agricultural products. We recommend its application to cherry tomatoes in greenhouses in winter and potential application to pears in orchards in early spring in northern China. However, the risk to local bumblebee species of introducing commercially available bumblebees into orchards should be considered and evaluated in future research. This study provides both empirical support and a theoretical basis for the selection of bumblebees as pollinators in the production of economically important crops and the improvement of crop cultivation management in northern China.

Evaluating the use of unmanned aerial vehicles for spray applications in mountain Nanguo pear orchards.

Nanguo pear is a distinctive pear variety in northeast China, grown mainly in mountainous areas. Due to terrain limitations, ground-based pesticide application equipment is difficult to use. This limitation could be overcome by using unmanned aerial vehicles (UAVs) for pesticide application in Nanguo pear orchards. This study evaluated the spraying performance of two UAVs in the Nanguo pear orchards and compared them with a manually used backpack electric sprayer (BES). The study also analyzed the effect of canopy size on droplet deposition and ground loss, and evaluated two sampling methods, leaf sampling and telescopic rod sampling. Compared to BESs, droplet deposition is lower for UAVs, but the actual pesticide active ingredient deposition is not necessarily lower given the solution concentration. The droplet deposition varies among different UAVs due to structural differences. Under the same UAV operating parameters, droplet deposition on trees with smaller canopy sizes is typically greater than that on trees with larger canopy sizes, and the ground loss was also more severe. Although telescopic rod sampling is a quick and convenient method, it can only reflect the trend of droplet deposition, and the data error is greater compared with leaf sampling. UAVs can achieve better droplet deposition in mountainous Nanguo pear orchards and does almost no harm to the operators compared with the BES. However, canopy size needs to be considered to adjust the application volume rate. Telescopic rods can be used for qualitative analyses, but are not recommended for quantitative analyses. © 2024 Society of Chemical Industry.

Transcriptome and metabolome profiling reveal the effects of hormones on current-year shoot growth in Chinese ‘Cuiguan’ pear grafted onto vigorous rootstock ‘Duli’ and dwarf rootstock ‘Quince A’

BackgroundDwarf rootstocks have important practical significance for high-density planting in pear orchards. The shoots of ‘Cuiguan’ grafted onto the dwarf rootstock were shorter than those grafted onto the vigorous rootstock. However, the mechanism of shorter shoot formation is not clear.ResultsIn this study, the current-year shoot transcriptomes and phytohormone contents of ‘CG‒QA’ (‘Cuiguan’ was grafted onto ‘Quince A’, and ‘Hardy’ was used as interstock) and ‘CG‒DL’ (‘Cuiguan’ was grafted onto ‘Duli’, and ‘Hardy’ was used as interstock) were compared. The transcriptome results showed that a total of 452 differentially expressed genes (DEGs) were identified, including 248 downregulated genes and 204 upregulated genes; the plant hormone signal transduction and zeatin biosynthesis pathways were significantly enriched in the top 20 KEGG enrichment terms. Abscisic acid (ABA) was the most abundant hormone in ‘CG‒QA’ and ‘CG‒DL’; auxin and cytokinin (CTK) were the most diverse hormones; additionally, the contents of ABA, auxin, and CTK in ‘CG‒DL’ were higher than those in ‘CG‒QA’, while the fresh shoot of ‘CG‒QA’ accumulated more gibberellin (GA) and salicylic acid (SA). Metabolome and transcriptome co-analysis identified three key hormone-related DEGs, of which two (Aldehyde dehydrogenase gene ALDH3F1 and YUCCA2) were upregulated and one (Cytokinin oxidase/dehydrogenase gene CKX3) was downregulated.ConclusionsBased on the results of transcriptomic and metabolomic analysis, we found that auxin and CTK mainly regulated the shoot differences of ‘CG–QA’ and ‘CG–DL’, and other hormones such as ABA, GA, and SA synergistically regulated this process. Three hormone-related genes ALDH3F1, YUCCA2, and CKX3 were the key genes contributing to the difference in shoot growth between ‘CG–QA’ and ‘CG–DL’ pear. This research provides new insight into the molecular mechanism underlying shoot shortening after grafted onto dwarf rootstocks.

Lower soil nitrogen-oxide emissions associated with enhanced denitrification under replacing mineral fertilizer with manure in orchard soils

Emerging evidence suggests that replacing mineral fertilizers with organic livestock manure can effectively suppress reactive gaseous nitrogen (N) emissions from soils. However, the extent of this mitigation potential and the underlying microbial mechanisms in orchards remain unclear. To address this knowledge gap, we measured nitrous and nitric oxide (N2O and NO) emissions, microbial N cycling gene abundance, and N2O isotopomer ratios in pear and citrus orchards under three different fertilization regimes: no fertilization, mineral fertilizer, and manure plus mineral fertilizer. The results showed that although manure application caused large transient peaks of N2O, it reduced cumulative emissions of N2O and NO by an average of 20 % and 17 %, respectively, compared to the mineral fertilizer treatment. Partial replacement of mineral fertilizers with manure enhanced the contribution of AOA to nitrification and reduced the contribution of AOB, thus reducing N2O emissions from nitrification. Isotope analysis suggested that the pathway for N2O production in the soils of both orchards was dominated by bacterial denitrification and nitrifier denitrification. The manure treatment reduced the ratio of denitrification products. Additionally, the dual isotope mixing model results indicated that partially replacing mineral fertilizers with manure could promote soil denitrification, resulting in more N2O being reduced. N-oxide emissions were on average 67 % higher in the pear orchard than in the citrus orchard, probably due to the differences in soil physicochemical properties and growth habits between the two orchards. These findings underscore the potential of partially replacing mineral fertilizers with organic manure in orchards to reduce gaseous N emissions, contributing to the transition towards environmentally sustainable and climate-smart agricultural practices.

Methods for the Determination of Fire Blight on Pome Fruit Crop Plants in the Western Part of Azerbaijan

Fire blight caused by Erwinia amylovora (Burrill, 1882) Winslow et al., 1920 causes significant production losses in the world’s leading pome fruit crop producing countries. The main route of infection of many fruit crops, including apple and pear trees, is through newly blooming flowers. The bacterium overwinters in the bark tissue along the edges of cankers formed on branches and stems as a result of infection in the previous year and becomes a source of infection in the next year. Determining the prevalence of the disease in areas with a large number of orchards is important from the point of view of disease control. Therefore, the purpose of the work is to study the prevalence of the disease in the Ganja-Dashkesan and Gazakh-Tovuz Economic Regions, as well as the accurate diagnosis of the obtained E. amylovora isolates using classical and molecular methods. For this purpose, trees in the studied apple and pear orchards were examined for the disease, the pathogen was isolated from infected plants, and morphological, biochemical, physiological and molecular analyzes were carried out. Among 36 bacterial isolates obtained from 27 samples of infected plants, Erwinia amylovora was identified in 11 as a result of morphological, biochemical, physiological and molecular tests.

Intrarow Uncut Weed Detection Using You-Only-Look-Once Instance Segmentation for Orchard Plantations.

Mechanical weed management is a drudging task that requires manpower and has risks when conducted within rows of orchards. However, intrarow weeding must still be conducted by manual labor due to the restricted movements of riding mowers within the rows of orchards due to their confined structures with nets and poles. However, autonomous robotic weeders still face challenges identifying uncut weeds due to the obstruction of Global Navigation Satellite System (GNSS) signals caused by poles and tree canopies. A properly designed intelligent vision system would have the potential to achieve the desired outcome by utilizing an autonomous weeder to perform operations in uncut sections. Therefore, the objective of this study is to develop a vision module using a custom-trained dataset on YOLO instance segmentation algorithms to support autonomous robotic weeders in recognizing uncut weeds and obstacles (i.e., fruit tree trunks, fixed poles) within rows. The training dataset was acquired from a pear orchard located at the Tsukuba Plant Innovation Research Center (T-PIRC) at the University of Tsukuba, Japan. In total, 5000 images were preprocessed and labeled for training and testing using YOLO models. Four versions of edge-device-dedicated YOLO instance segmentation were utilized in this research-YOLOv5n-seg, YOLOv5s-seg, YOLOv8n-seg, and YOLOv8s-seg-for real-time application with an autonomous weeder. A comparison study was conducted to evaluate all YOLO models in terms of detection accuracy, model complexity, and inference speed. The smaller YOLOv5-based and YOLOv8-based models were found to be more efficient than the larger models, and YOLOv8n-seg was selected as the vision module for the autonomous weeder. In the evaluation process, YOLOv8n-seg had better segmentation accuracy than YOLOv5n-seg, while the latter had the fastest inference time. The performance of YOLOv8n-seg was also acceptable when it was deployed on a resource-constrained device that is appropriate for robotic weeders. The results indicated that the proposed deep learning-based detection accuracy and inference speed can be used for object recognition via edge devices for robotic operation during intrarow weeding operations in orchards.

Effect of long-term in-row branch covering on soil microorganisms in pear orchards.

Branches covering (BC) is a way to reuse the pruned branches and save the cost of ground cloth. This study investigated the effects of BC and ground-cloth covering on the soil microcosm environment by measuring the chemical properties and microbial communities at different soil depths for 6 years. The results revealed that BC significantly improved soil chemical properties, increased the abundance of bacterial microbial communities and the diversity and homogeneity of bacteria and fungi, while decreased the abundance of fungal microbial communities. There was a threshold value for the regulation of microbial communities by BC, which decreased the high-abundance communities (Proteobacteria, Ascomycota, etc.) and increased the low-abundance communities (Acidobacteriota, Basidiomycota, etc.). Fungi were more sensitive to BC than bacteria. The stability and homogeneity of microorganisms were stronger in the 15-25 cm soil layer. The bacterial phyla were dominated by Proteobacteria, with the top 10 phyla accounting for more than 80% of the relative abundance; the genera were dominated by MND1, with the top 10 genera accounting for about 10%. The fungal phyla were dominated by Ascomycota, with the top 10 phyla accounting for 50-90%; the genera were dominated by unidentified Pyronemataceae sp., with the top 10 genera accounting for 30-60%. The phyla that differed significantly between treatments were mainly Proteobacteria, Ascomycota, Acidobacteriota, and Basidiomycota. In addition, metabolism was the predominant function in bacteria, while Saprotroph was the predominant function in fungi. Bacteroidota correlated strongly with soil chemical properties and bacterial functions, while Chytridiomycota correlated strongly with soil chemical properties and Pathogen-Saprotroph-Symbiotroph. In conclusion, BC can improve soil nutrient content and optimize microbial community structure and function. Through initially assessing the effects of BC on soil nutrients and microorganisms in pear orchard rows, this study provides a reference for excavating key microorganisms and updating the soil row management model.

A crop for a forest: Opuntia ficus-indica as a tool for the restoration of Mediterranean forests in areas at desertification risk

IntroductionThe Mediterranean is the European region with the lowest woody cover and the highest level of habitat degradation, being highly susceptible to climate change effects and desertification risk. In such worrying conditions, increasing woody cover and restoring forests is a major goal established in several international commitments. However, recruitment limitation of woody species is rather frequent both within natural regeneration processes and active restoration programs, particularly due to drought, overgrazing, and a lack of post-planting tending operations. Therefore, finding suitable tools to improve the recruitment success of native woody species is of crucial importance.MethodsWe assessed woody natural regeneration under abandoned prickly pear orchards, olive trees, and nearby open areas in three sites under high desertification risk in central Sicily (Italy). Then, we tested for differences in density, richness, diversity, height, and basal diameter of the woody recruiting species between these three habitats.Results and discussionNatural regeneration was widespread under prickly pear, with 94.6% of the sampled plots showing at least one recruit, in comparison to 61.6% of plots under olive and 22.3% in open areas. Natural regeneration density under prickly pears (114 ± 99 individuals m−2) was significantly higher (p < 0.001) than under olive trees (60.4 ± 76.4) and open areas (4.6 ± 9.3). Recruits’ diversity, basal diameter, and height were also significantly higher under prickly pear, concentrating 94.4% of the individuals higher than 100 cm and all late successional species. Our results indicate a great potential for prickly pears to accelerate the natural regeneration of Mediterranean woody species in pear instead of pears under desertification. However, a site-specific evaluation must be made taking into account prickly pear’s historical presence, temporary income as a crop, management capacity and, especially, its invasive potential.

Use of immuno-flow cytometry and real-time PCR disclose the epidemiological behaviour of Erwinia amylovora populations during the winter in Portuguese pear orchards

AbstractThe persistence and progression of Erwinia amylovora in naturally infected orchards is still not fully understood and the majority of studies have been carried out under controlled or artificial infections. A major hurdle stems from the inability to characterize the viability of the bacterium in its natural state. Most standard tests, including real-time qPCR, fail to differentiate live from dead cells, while culture dependent methods lack sensitivity. Even in orchards with recurring infections, the detection of E. amylovora is erratic. Immuno-flow cytometry (IFCM) is considered a high throughput tool in clinics and food industry but has been rarely used as diagnostic test for plant pathogens. Two pear orchards with fire blight history, located in the central part of Portugal, were selected for epidemiological monitoring between February and June, from 2019 to 2022. A total of 440 samples were tested using EPPO standard diagnostic protocols. To address the epidemiological behaviour of E. amylovora, we devised an IFCM test using specific monoclonal antibodies and viability dyes, validated in a subset of 149 samples, testing positive in routine diagnostic tests. Our IFCM test was able to differentiate live and dead E. amylovora in naturally infected samples with concentrations as low as 3.54 × 104 cell·mL−1, confirming positive results for 91% these samples, while 19.4% were considered positive by isolation, 38% using conventional PCR and 95% for real-time qPCR. Temporal analysis showed the highest number of positive samples regardless of the method employed in April, May and June, while viability values measured with IFCM were the highest in April, coinciding with the exit of dormancy and early flowering of pear trees. Integrative analysis of E. amylovora viability and population dynamics over the growing season allowed identification of distinct outbreak risks associated with these Portuguese pear orchards.

Construction and Optimization of a Collaborative Harvesting System for Multiple Robotic Arms and an End-Picker in a Trellised Pear Orchard Environment

In order to meet the needs of intensive mechanized picking in trellised pear orchards, this paper designed a pick-place integrated end-picker based on the analysis of agronomic characteristics of trellised pear gardens and fruit. In order to realize the accurate positioning of pears in picking, based on the kinematic analysis of robot arms and the construction of a private dataset, the YOLOv5s object detection algorithm was used in conjunction with a depth camera to achieve fruit positioning. The hand–eye system calibration was carried out. Aiming at solving the problems of redundancy, inefficiency, and uneven distribution of task volume in the conventional multiple robot arms algorithm, a simulated annealing algorithm was introduced to optimize the picking sequence, and a task allocation method was proposed. On the basis of studying several key parameters affecting the performance of the algorithm, the picking efficiency was greatly optimized. And the effectiveness of the proposed multi-robot collaborative picking method in a trellised pear orchard environment was demonstrated through experiments and simulation verification. The experiments showed that the picking efficiency of the integrated end-picker was increased by about 30%, and the success rate was significantly higher than that of the flexible grippers. The results of this study can be utilized to advance robotic pear-picking research and development.

Novel single nucleotide variations alter pathogenicity in Korean isolates of Erwinia amylovora

Erwinia amylovora, the causal agent of fire blight disease, has become a serious threat to the pome fruit industry in Korea since 2015. In this study, we showed that two new isolates of E. amylovora, Ea17-2187 and Ea19-7, obtained from pear orchards in Anseong, Korea, exhibited unique pathogenicity than other isolates thus far. Both were non-pathogenic to immature apple fruits, but occasionally caused disease on immature pear fruits at varying reduced rates. Bioinformatic analyses revealed that their genomes are highly similar to those of the type strains TS3128 and ATCC49946, but have different mutations in essential virulence regulatory genes. Ea17-2187 has a single nucleotide substitution in rcsC, which encodes the core components of the Rcs system that activates the exopolysaccharide amylovoran production. In contrast, Ea19-7 contains a single nucleotide insertion in hrpL, which encodes a master regulator of the type III secretion system. In both cases, the mutation can cause premature termination and production of truncated gene products, disrupting virulence regulation. Introduction of the non-mutated rcsC and hrpL genes into Ea17-2187 and Ea19-7, respectively, fully recovered pathogenicity, comparable to that of TS3128; hence these mutations were responsible for the altered pathogenicity observed. Interestingly, virulence assays on immature pear fruits showed that the hrpL mutant of Ea19-7 was still pathogenic, although its virulence level was markedly reduced. Taken together, these results suggest that the two new isolates might act as opportunistic pathogens or cheaters, and that some Korean isolates might have evolved to acquire alternative pathways for activating pathogenicity factors.

Sown Covers Enhance the Diversity and Abundance of Ground-Dwelling Predators in Mediterranean Pear Orchards

Intensive agriculture has a strong impact on the structure of arthropod communities in soil. Sown covers can contribute to their conservation, especially for generalist predators such as spiders and predatory beetles. The aim of this research was to assess the effect of cover crop management on the abundance and diversity of ground-dwelling arthropods. For this purpose, a three-year experiment was conducted in a pear orchard that was divided into three blocks with two plots each: one with a sown cover of mixed plants from different families, including Boraginaceae, Asteraceae, Apiaceae, Brassicaceae, and Fabaceae, and the other with no cover, in which any spontaneous plants were periodically removed without using herbicides. The abundance of ground-dwelling arthropods was sampled using pitfall traps. The sown cover increased the overall richness of arthropods. Additionally, spiders from the families Lycosidae and Linyphiidae, as well as beetles from the families Carabidae and Staphylinidae, were more abundant in the sown cover. Conversely, detritivores such as collembolans and beetles from the family Tenebrionidae were less abundant in the cover. The abundance of ants was not affected by the type of cover. The sown cover increased the diversity of arthropods in the crop, as well as the abundance of generalist predators.

Physiological and autophagy evaluation of different pear varieties (Pyrus spp.) in response to Botryosphaeria dothidea infection.

Ring rot disease is one of the most common diseases in pear orchards. To better understand the physiology, biochemistry and autophagic changes of different pear varieties after Botryosphaeria dothidea (B.dothidea) infection, we evaluated eight different pear varieties for B. dothidea resistance. The susceptible varieties had larger spot diameters, lower chlorophyll contents and higher malondialdehyde contents than the resistant varieties. In disease-resistant varieties, reactive oxygen species (ROS) levels were relatively lower, while the ROS metabolism (antioxidant enzyme activities and the ascorbic acid-glutathione cycle) was also maintained at higher levels, and it induced a significant upregulation of related gene expression. In addition, autophagy, as an important evaluation index, was found to have more autophagic activity in disease-resistant varieties than in susceptible varieties, suggesting that pathogen infestation drives plants to increase autophagy to defend against pathogens. In summary, the results of this study reveal that different resistant pear varieties enhance plant resistance to the disease through a series of physio-biochemical changes and autophagic activity after inoculation with B. dothidea. This study provides clear physiological and biochemical traits for pear disease resistance selection, potential genetic resources and material basis for pear disease control and disease resistance, breeding and points out the direction for research on the mechanism of pear resistance to B. dothidea.

Detecting, mapping and digitising canopy geometry, fruit number and peel colour in pear trees with different architecture

Increasing farm labour and input costs and the requirement for more orchard data are leading to rapid advances in technology to improve management systems in fruit production. The study aimed to (i) validate a sensorised platform to estimate fruit number, peel colour and blush coverage in pear orchards with different pear selections and tree architectures, (ii) establish relationships between fruit number, peel colour and canopy geometry features, and (iii) evaluate the platform for mapping and digitising orchard features. The study was carried out over two years in an experimental ‘ANP-0131′ orchard and in one year in two commercial pear orchards (‘ANP-0131′ and ‘PremP009’). Predictions of fruit number and blush coverage were compared in traditional three-dimensional (3D) and modern high-density two-dimensional (2D) training systems. Overall, prediction errors for fruit number were < 6.5 % in all the training systems, but improved performance was achieved in vertical 2D configurations (% standard errors = 2.2 %). Fruit number and blush coverage per unit of leaf area were higher in 2D compared to 3D training systems. Blush coverage predictions in ‘ANP-0131′ were reliable (R2 = 0.67, RMSE = 3.70 %). Accurate predictions of blush coverage classes were achieved by modifying sample variance. Fruit number and blush coverage were negatively affected by increasing canopy size. The platform proved useful for mapping and digitisation. Spatial heatmaps of orchard features provided a valuable visual aid to identify zones for priority interventions for peel colour enhancement.

A Novel IncX Plasmid Mediates High-Level Oxytetracycline and Streptomycin Resistance in Erwinia amylovora from Commercial Pear Orchards in California.

Isolates of the fire blight pathogen Erwinia amylovora with high-level resistance to oxytetracycline (minimal inhibitory concentration [MIC] > 100 μg/ml) and to streptomycin (MIC > 100 μg/ml) were recovered from four commercial pear orchards in California between 2018 and 2020. The two representative oxytetracycline- and streptomycin-resistant (OxyTcR-SmR) strains 32-10 and 33-1 were as virulent as the antibiotic susceptible strain 13-1 in causing blossom blight of pear and were recovered more than 50% of the time 7 days after co-inoculation to pear flowers with strain 13-1. In the field, inoculation of strain 32-10 to pear flowers that were pretreated with oxytetracycline at 200 μg/ml did not reduce disease compared with an untreated control. Four OxyTcR-SmR strains were subjected to draft genome sequencing to identify the genetic determinants of antibiotic resistance and their location. A 43.6-kb IncX plasmid, designated pX11-7, was detected in each of the four strains, and this plasmid encoded the tetracycline-resistance gene tetB and the streptomycin-resistance gene pair strAB within a large putatively mobile genetic element consisting of the transposon Tn10 that had inserted within the streptomycin-resistance transposon Tn6082. We also determined that pX11-7 was conjugative and was transferred at a rate that was 104 to 105 higher into an E. amylovora strain isolated in California compared with an E. amylovora strain that was isolated in Michigan. The occurrence of high levels of resistance to both oxytetracycline and streptomycin in E. amylovora strains from commercial pear orchards in California significantly limits the options for blossom blight management in these locations.

Consumers’ Preferences for Novel and Traditional Pear Cultivars: Evidence from Sensory Evaluation and Willingness-to-pay Elicitation

A significant challenge faced by the US Pacific Northwest pear industry is the limited availability of diverse pear cultivars beyond conventional selections. This scant availability of new pear options that align with consumers’ consistent quality preferences falls short of their expectations and jeopardizes potential demand growth, which poses a threat to the industry’s long-term economic viability. We use a combined approach of sensory evaluation and contingent valuation to uncover preferences and willingness to pay (WTP) for specific pear cultivars, encompassing both novel and traditional types. The outcomes reveal that the key determinants driving WTP are taste and texture attributes. Particularly for early-season pears, a greater liking score for flavor, firmness, and juiciness corresponds to an elevated WTP. For late-season pears, the range of quality attributes expands to encompass overall appearance and sweetness, in addition to the aforementioned factors. Participants who use social media to access information about pears exhibit a heightened WTP. These findings provide valuable insights for the industry to consider revitalizing existing pear orchards through the incorporation of alternatives to conventional pear cultivars.