Pear Rust Research Articles

Development of a Drone-Based Phenotyping System for European Pear Rust (Gymnosporangium sabinae) in Orchards

Computer vision techniques offer promising tools for disease detection in orchards and can enable effective phenotyping for the selection of resistant cultivars in breeding programmes and research. In this study, a digital phenotyping system for disease detection and monitoring was developed using drones, object detection and photogrammetry, focusing on European pear rust (Gymnosporangium sabinae) as a model pathogen. High-resolution RGB images from ten low-altitude drone flights were collected in 2021, 2022 and 2023. A total of 16,251 annotations of leaves with pear rust symptoms were created on 584 images using the Computer Vision Annotation Tool (CVAT). The YOLO algorithm was used for the automatic detection of symptoms. A novel photogrammetric approach using Agisoft’s Metashape Professional software ensured the accurate localisation of symptoms. The geographic information system software QGIS calculated the infestation intensity per tree based on the canopy areas. This drone-based phenotyping system shows promising results and could considerably simplify the tasks involved in fruit breeding research.

Detection of fruit tree diseases in natural environments: A novel approach based on stereo camera and deep learning

The occurrence of diseases in orchards has a significant impact on fruit yield and quality. Inspection devices equipped with cameras can effectively replace manual intervention in the process of orchard management by swiftly detecting diseases. However, the images captured by such devices often exhibit a wide vision field and contain a significant amount of extraneous information. This paper presented a method for detecting diseases in natural environments based on binocular cameras and deep learning techniques applied to fruit tree leaf images with a wide visual field. Firstly, the ZED2i binocular camera was utilized to capture image pairs from a long distance, simulating the visual field of an inspection device. These image pairs were then processed using the Unimatch stereo matching algorithm to obtain a disparity map and calculated the corresponding depth map. The depth information was used to create a mask, eliminating irrelevant background information from the images. Secondly, a lightweight disease detection (LDD) model was proposed based on the advanced YOLOv5 framework for detecting pear rust and plum perforation diseases. The backbone network consisted of shuffle channel block, inverted shuffle channel block, and convolutional block attention module, with only one detection head used in the classifier part. The final experiments evaluated the segmentation, model improvement, and disease spots detection performance. The results showed that the depth map obtained using Unimatch for stereo matching was more accurate than that obtained using the ZED software development kit. In ablation experiments, LDD achieved a mean average precision of 93.0%, with a model size of only 3.9 MB, outperforming the original YOLOv5-s model. Preprocessed images with depth information exhibited improved detection performance, achieved a F1 score of 93.62%, which was a 10.92% improvement over direct detection of the original images. Overall, the presented method successfully addresses the issue of background interference when detecting diseases of fruit tree leaf with a wide visual field, providing a technical basis for automated orchard inspection operations.

Development of a digital monitoring system for pear rust and fire blight in fruit orchards

Development of a digital monitoring system for pear rust and fire blight in fruit orchards

Pear rust in Belarus because of fungus Gymnosporangium sabinae (Dicks.) G. Winter invasion

Pear rust in Belarus was first registered in 2007, and after 12 years the disease acquired the character of epiphytosis. A map of the distribution of pear rust in the republic has been compiled. The symptoms of damage to pear and juniper, spores of the causative agent (fungus Gymnosporangium sabinae (Dicks.) G. Winter) are described and illustrated. It has been shown that aecio- and teliospores overwintered in the shoots do not germinate in the next growing season. The teliospores of the current year on juniper germinate not only with phragmobasidia with basidiospores, but also with mycelium, which probably ensures the re-infection of this host plant. The high infectious potential of both pear (up to 15 mln aeciospores per 1 cm2 ) and juniper (2 mln teliospores per 1 cm2 ) was determined. The death due to rust of annual shoots of pear and individual plants of the Cossack juniper was ascertained. The invasion of G. sabinae on the territory of Belarus coincides with the wide introduction of susceptible species of juniper into landscaping.

RUST (GYMNOSPORANGIUM SABINAE (DICKS.) G. WINTER) RESISTANCE OF PEAR VARIETIES RELEASED IN BELARUS

The article presents preliminary results of an assessment of field resistance to rust (Gymnosporangium sabinae (Dicks.) G. Winter) of 27 pear varieties released in Belarus. The studies were conducted in 2017–2021 at RUE “Institute of Fruit Growing”. Differentiation of pear varieties according to the degree of rust resistance was revealed: highly resistant (Dessert Rossoshanskaya, Pamiati Yakovlev), medium resistant (Bere Loshitskaya, Viliya, etc.), low resistant (Bere Alexander Luka, Velesa, Duchesse summer, Conference, etc.) and very low resistant (Belarusian late).

Gymnosporangium sabinae development cycle—Peculiarities and influencing factors

AbstractGymnosporangium sabinae (Dicks.) G. Winter, the causal agent of European pear rust, is a heteroecious rust fungus with a demicyclic life cycle—it produces teliospores and basidiospores on junipers, spermatia and aeciospores on pears. Environmental factors and agrotechnical methods influence the progress and duration of each stage, which is why the specifics and mechanisms of each stage of development are to be studied to predict the spread of the disease and its potential severity. A wide‐range study of European pear rust in Latvia started in 2008—the impact of agroecological factors on the biology of G. sabinae was studied. It was concluded that pears' infection depends on basidiospores' development and release, which is mainly influenced by favourable meteorological conditions—precipitation of at least 10 mm and an average air temperature not below 10°C. The pathogen develops on shoots in the same way as on leaves. However, the development on shoots is slower overall, and the pathogen cannot overwinter there.

Fruit trees rust: genus Gymnosporangium pathology spread and host plants of the pathogens

Phytopathological examination of orchards of various forms of ownership reveal that every year the rust of pip fruit trees has become widespread and reached its epiphytosis. In 2008, we detected symptoms of rust on pip fruit trees in the form of single yellow spots on pear leaves in orchards of different ages and forms of ownership. The identifcation found that the fungus Gymnosporangium sabinae G. Winter, (1882) (syn. G. fuscum DC. (1805)) was the causative agent of pear rust. The prevalence of pathology was insignifcant within 3–5 %. Every year the percentage of the pathology spread and development had been increasing and in 2021 it amounted to 55-75% and 4-5 points, respectively. Symptoms of the lesion were observed on leaves, young shoots and fruits. Microscopic studies found several species of pathogens of the genus Gymnosporangium, namely G. sabinae G. Winter, G. dobrozrakovae Mitrof., G. confusum Plowr., dominated by G. sabinae G. Winter that in the pathological complex of the affected organs of the pear there are. In 2012, we detected symptoms of rust on apple tree leaves in the form of single yellow spots, with a prevalence of 3 %. The identifcation established that the fungi G. tremelloides Hartig and G. dobrozrakovae Mitrof. were the causative agents of apple leaf rust are with G. tremelloides Hartig having a signifcant dominance. In 2021, the percentage of prevalence and development of this pathology ranged 25–30 % and 2–3 points, respectively. In the collection fund of the Botanical Garden of BNAU the section of Angiosperms is represented by one genus Cydonia Mill and the species C. oblonga Mill. In 2018, we noted a few small spots on the leaves of quince caused by the pathogen G. confusum Plowr. The microscopic analysis of the affected organs of species of the genus Juniperus L. with the signs of rust reveal that the pathological complex involved four pathogens of the genus Gymnosporangium, which are the causative agents of pip fruit trees rust. Seven species of Juniperus L. are ecological niches for rust pathogens of pear, apple and quince, namely Juniperus communis L. – for G. tremelloides Hartig, Juniperus excels – for G. sabinae Wint., G. dobrozrakovae Mitrof., J.foetidissima – G. sabinae Wint. G. dobrozrakovae Mitrof., G. confusum Plowr., J. oxycedrus – for G. sabinae Wint., G. confusum Plowr., J. phoenicea – for G. sabinae Wint., G. confusum Plowr., J. sabina - G. sabinae Wint., J. macropoda – G. confusum Plowr. Кey words: pip fruit trees, rust, agent, Gymnosporangium, Juniperus L.

Diagnosis and recommendations for management of trees and shrubs in green squares in Warsaw based on research on fungal diseases

Key messageComprehensive management of urban greenery is a key approach to control fungal diseases of trees and shrubs to avoid the deterioration in their health status.Preliminary investigations on the health status related to fungal diseases of trees and shrubs growing in four green squares in Warsaw were conducted in 2017–2019. The examined plants were affected by diseases that are commonly identified in urban greenery, e.g., powdery mildew (causal agents: Sawadaea tulasnei, S. bicornis, Podosphaera leucotricha, Podosphaera sp., Erysiphe alphitoides, E. magnifica, E. berberidis, E. flexuosa and E. adunca), rusts (Gymnosporangium sabinae, Melampsora laricis-populina), apple scab (Venturia inaequalis), tar spot of maple (Rhytisma acerinum), and oyster mushroom (Pleurotus ostreatus). The causal agents of the diseases were identified based on their morphological (macro- and microscopic) features. Preventing and managing fungal plant diseases and reduction of their effects are the key tasks in conscious management of urban greenery. To address this issue, the study presents basic guidelines based on the application of various recommended actions and good practices, which constitute a comprehensive and sustainable strategy for integrated protection of trees and shrubs against these diseases. The implementation of the strategy for complex management of urban greenery is a crucial measure aimed at maintenance of a high health status of urban plants.

A Fruit Tree Disease Diagnosis Model Based on Stacking Ensemble Learning

Fruit tree diseases have a great influence on agricultural production. Artificial intelligence technologies have been used to help fruit growers identify fruit tree diseases in a timely and accurate way. In this study, a dataset of 10,000 images of pear black spot, pear rust, apple mosaic, and apple rust was used to develop the diagnosis model. To achieve better performance, we developed three kinds of ensemble learning classifiers and two kinds of deep learning classifiers, validated and tested these five models, and found that the stacking ensemble learning classifier outperformed the other classifiers with the accuracy of 98.05% on the validation dataset and 97.34% on the test dataset, which hinted that, with the small- and middle-sized dataset, stacking ensemble learning classifiers may be used as cost-effective alternatives to deep learning models under performance and cost constraints.

DANGEROUS FUNGAL DISEASE – PEAR MILDEW (GYMNOSPORANGIUM SABINAE (DICKS.) G. WINTER)

The article provides an analysis of the worldwide prevalence of a harmful disease on a pear – mildew, caused by the
 basidiomycete fungus Gymnosporangium sabinae (Dicks.) G. Winter, the taxonomy and biology of the pathogen is given.
 Preliminary data on disease-resistant samples of pears from the collection of RUE “Institute of Fruit-growing” (Belarus)
 are presented: Allegro, Victoria, Maria, Osoblyva, Smerichka, Souvenir, Shchedra, derived from Pyrgus communis L.;
 Augustovskaya rosa, Vernaya, Desertnaya Rossoshanskaya, Krasnobokaya, Podgoryanka, DU 20-3, Chuspan – from Pyrgus
 ussuriensis Maxim.; Chukhuang – from P. ussuriensis × Pyrgus ovoidea; Feeriya species derived from pear-leaved (sandy)
 Pyrgus pyrifolia (Burm.) Nakai.

Erythritol, an Artificial Sweetener, Is Acaricidal Against Pest Mites and Minimally Harmful to a Predatory Mite.

Erythritol, an artificial sweetener, has shown promise as an organic, human-safe insecticide. Recently, erythritol applications were shown to be successful at controlling pear psylla (Cacopsylla pyricola (Förster)) (Hempitera: Psyllidae), the most important pest of pear in the Pacific Northwest, USA. Twospotted spider mite (Tetranychus urticae Koch) (Trombidiformes: Tetranychidae) and pear rust mite (Epitrimerus pyri (Nalepa)) (Trombidiformes: Eriophyidae) can also be highly damaging pear pests. Their common natural enemy, Galendromus occidentalis (Nesbitt) (Mesostigmata: Phytoseiidae), can provide biological control if selective pesticides are used for managing other pests. Through a series of bioassays, we sought to determine whether erythritol could also be used for controlling either species of pest mite. We also examined whether erythritol had acute or sublethal impacts on G. occidentalis, through a variety of exposure methods. Effects examined included mortality, fecundity, prey consumption, and locomotion. We determined that a high concentration of erythritol (30%) had efficacy against both pest mite species and caused arresting behavior in twospotted spider mite. Erythritol caused little acute mortality in G. occidentalis, but did reduce fecundity and prey consumption through some exposure methods. Through motion-capture software, we determined that this is primarily due to reduced movement, likely caused by difficulty walking on residues and excessive grooming behavior. Because the predatory mite non-target effects were less acute than those for the two pest mites, we concluded that erythritol could likely be integrated into pear IPM with little or no disruption of mite biological control.

Differences in Leaf Morphological Parameters of Pear (Pyrus communis L.) Based on Their Susceptibility to European Pear Rust Caused by Gymnosporangium sabinae (Dicks.) Oerst.

European pear rust is an important disease; however, the relationship between its causal pathogen Gymnosporangium sabinae (Dicks.) Oerst. and host Pyrus communis L. is poorly understood. In this study, disease severity was measured, and leaf samples were collected over three years, and their leaf water content; leaf area; leaf mass per area; and epidermis, mesophyll, and vascular tissue width and stomatal density were measured and compared between susceptible and resistant genotypes for each year. Most genotypes either showed consistent disease symptoms or showed no symptoms during the study in terms of their susceptibility. A correlation between disease severity and mesophyll tissue thickness, and stomatal density and differences between several morphological parameters were found depending on the genotype’s susceptibility. The study showed that the following pear morphological traits were stable between the years: water content, leaf mass per area, spongy mesophyll thickness, phloem thickness, and stomatal density. When selecting for breeding, we found that candidates for traits that discern susceptible genotypes from resistant were mesophyll layer width, stomatal density, epidermis width, and xylem tissue width.

Evaluation of Electrolysed Oxidizing Water for European Pear Rust Management on Pear (Pyrus cv. Conference)

Pear rust is a foliar pathogen of ornamental and fruiting pear trees. Unmanaged, yield and aesthetic losses can be severe. Over-reliance on synthetic fungicides means novel means of pathogen management are required. Field trials were conducted using pear (Pyrus cv. Conference) to assess the efficacy of electrolysed oxidizing water (EO water) as a rust protective compound. A synthetic fungicide (boscalid + pyraclostrobin) spray program used for pear rust management was included for comparison. Each treatment was applied 4 times prior to the visible appearance of rust (April through June, i.e., preventatively). Studies were conducted in 2017 and repeated in 2018. Efficacy of EO water as a rust protectant compound was confirmed (increased leaf chlorophyll content, reduced leaf rust incidence and severity). The degree of leaf rust severity protection conferred was not statistically different from a boscalid + pyraclostrobin spray program. Results suggest 4 spray applications of EO water provides a useful addition to existing methods of pear rust management under field conditions that may have applicability against other foliar pathogens.

Genetic diversity of pear cultivars using SSR markers and their reactions to pear rust (Gymnosporangium fuscum)

Commonly grown in different ecological conditions of Turkey and the world, pear (Pyrus communis L.), as a plant species, has a long cultivation history in Turkey. However, its unique genetic resources are in danger of extinction due to changes in the agro-ecosystem and genetic erosion. In addition, pear rust caused by Gymnosporangium fuscum is one of the significant diseases of pear. Severe economic losses have been reported in some pear orchards near the extensive juniper populations. In the present study, the genetic diversity and sensitivity level to pear rust (Gymnosporangium fuscum) of 25 local and commercially important pear varieties grafted on seedling and Quince A (QA) was determined using 13 SSR primers. The selected verities were clustered into two major groups that were closely related. The SSR markers provided reliable genotyping and demonstrated their usefulness for identifying pear genetic diversity. The difference between years and rootstocks according to disease severity rates was found to be statistically significant. Although none of the pear varieties assessed in these experiments were resistant to rust, the disease severity of the pear varieties of QA rootstock was generally higher than that of the seedling varieties.

Development of SSR markers from transcriptome data for the pear rust pathogen Gymnosporangium asiaticum

AbstractThe pear‐cypress rust Gymnosporangium asiaticum is one of the most significant causal agents of pear rust in Asian pear, severely affecting the pear industry. Research on the genetic diversity of this widespread pathogen has been hampered due to the absence of molecular markers. In the current study, we developed 16 novel microsatellite markers for G. asiaticum from transcriptome data by combining next‐generation sequencing and PCR screening. These polymorphic markers were tested on 96 individuals from nine provinces in China. The number of alleles for these markers ranged from two to nine, with an average of five at each locus. The polymorphic information content ranged from 0.0411 to 0.7666, with an average of 0.4417. In addition, the observed (HO) and expected (HE) heterozygosities were 0.0312–0.6941 and 0.0417–0.8000, respectively. We also observed low‐to‐moderate levels of genetic differentiation and extremely significant gene flow between the nine provinces. Of these 16 developed simple sequence repeat loci, 11 were transferable to other Gymnosporangium species. These new microsatellite markers can be used in future large‐scale studies of the genetic structure and diversity of G. asiaticum.

Pear rust: peculiarities of pathogen biology measures for control and profilactic

Pear rust: peculiarities of pathogen biology measures for control and profilactic

Pear rust in the conditions of north-eastern Forest-Steppe of Ukraine

Studies were conducted during 2017‒2019 based on the training laboratory of horticulture and viticulture of the Sumy National Agrarian University in the conditions of the North-Eastern Forest-Steppe of Ukraine. It was found that the pear was massively affected by rust. This is a fungal disease that was rarely found in fruit orchards of the North-Eastern Forest-Steppe of Ukraine.
 Rust infected pear trees very rarely in previous years. Only single spots were found on the leaves of the pear. Since 2015, the development of the disease has noticeably accelerated from year to year. There was a massive rust damage of the pear in the region in 2019. The prevalence of the disease reached 100 % in almost all varieties. Mostly the leaves were affected, not to a large extent the shoots of the pear. On the fruits of the external signs of the disease were not detected.
 During the years of research, weather conditions were optimal for the spread of fungal diseases. Only the aecial stage of the fungus was observed on the pear. The aecial stage of the pathogen is the most harmful. Affected pear leaves fall prematurely. Studies were conducted on pear varieties Lymonka, Petrovska, Medova, Osinnia Yakovlieva, Chyzhovska, Noiabrska, Bere Desiatova, Uliublenytsia Klappa, which showed different degrees of rust damage. The disease manifested itself most significantly (5 points) on the varieties, Uliublenytsia Klappa and Bere Desiatova. Not one of the varieties did not show high resistance to the pathogen. The pear of the Chyzhovska variety was less affected, with a defeat score of 3 (18.8 %) in 2017 and 4 (32.3 % and 44.1 %) in 2018‒2019.
 It is known that the life cycle of the rust pathogen Gymnosporangium sabinae (Dicks.) G. Winter occurs on two plants: pear and juniper. The pathogen from juniper goes on the pear and vice versa. Pear trees do not become infected from each other. On the territory adjacent to the fruit garden of Sumy National Agrarian University, a survey of plantings of different types of juniper was conducted. There were no visible signs of the disease on the juniper. At the same time, pear trees were highly infected with the pathogen. Perhaps the spores of the fungus can spread far through air currents. But at the same time, possible changes in the life cycle of the pathogen in the conditions of this region. Clarification of this circumstance requires deeper further research.

First report on DMI fungicide resistance in Gymnosporangium asiaticum, the causal agent of Japanese pear rust, in Japan

Japanese pear rust, caused by Gymnosporangium asiaticum Miyabe ex Yamada, is one of the most important fungal plant diseases affecting Japanese pear cultivation. Although sterol demethylation inhibitor (DMI) fungicides have controlled this disease effectively, outbreaks have been frequent in some areas of Japan since 2008. We, therefore, evaluated fungal populations from Fukuoka Prefecture for DMI fungicide sensitivity in vivo. Aeciospores on diseased pear leaves were collected in 2013 from four orchards in Fukuoka Prefecture and one control orchard in Ibaraki Prefecture. Juniperus chinensis var. kaizuka Hort. test plants were sprayed with difenoconazole and fenarimol at recommended rates, and the plants were inoculated with aeciospores. Difenoconazole and fenarimol effectively controlled the population of rust fungus from Ibaraki Prefecture. In contrast, fenarimol and difenoconazole were found to be ineffective against fungal populations from Fukuoka Prefecture. Subsequently, telia were collected from diseased juniper twigs in five areas in Fukuoka Prefecture and one control area in Ibaraki Prefecture in 2013 and 2014. Similarly, test plants of Japanese pear ‘Kousui’ were treated with difenoconazole or fenarimol and inoculated with basidiospores taken from those telia. Both difenoconazole and fenarimol were largely ineffective against the populations from Fukuoka Prefecture. In addition, field trials conducted in an experimental orchard in 2014 and 2015 showed that difenoconazole and fenarimol were not effective in controlling this disease. These results indicate the occurrence of Japanese pear rust resistant to DMI fungicides in Fukuoka Prefecture.

Unveiling Gymnosporangium corniforme, G. unicorne, and G. niitakayamense sp. nov. in Taiwan

Three rust fungi from high mountains and pear-producing areas in Taiwan were described using morphological and molecular data based on 34 specimens. Gymnosporangium corniforme was demonstrated to produce spermogonia and aecia on Sorbus randaiensis based on molecular analyses and inoculation experiments. The pear rust pathogen G. unicorne was discovered in Taiwan for the first time. Gymnosporangium niitakayamense sp. nov. was observed on the leaves of Photinia niitakayamensis. It was distinct from other species in peridial cell wall structures, i.e., smooth outer wall, rugose side wall, and coralloid projections on the inner wall, and in having echinulate aeciospores.

The relationship between an increase in Japanese pear rust and decreased efficacy of DMI fungicides: a retrospective cohort study in Yame region, Fukuoka Prefecture, Japan

The relationship between an increase in Japanese pear rust and decreased efficacy of DMI fungicides: a retrospective cohort study in Yame region, Fukuoka Prefecture, Japan