Review of fruit cork spot disorder of Asian pear (Pyrus spp.).

Cork spot disorder has affected the fruit of Asian pear since the 1990s and has become serious in recent years with increasingly affected cultivars and areas. The commodity value of affected fruit is greatly decreased, resulting in severe economic losses. Cork spot disorder of pear fruit is a physiological disorder, and the factors responsible are relatively complex. Research on the cause of cork spot disorder is still at an early stage and, thus, further investigations are needed to elucidate the underlying mechanism of the disorder. In this review, current knowledge of the factors associated with the incidence of cork spot disorder in Asian pear fruit is summarized, including fruit growth and development, fruit nutrient status, and environmental factors. Potential preventive measures and priorities for future research are outlined.

Pest categorisation of Xylella taiwanensis.

The EFSA Plant Health Panel performed a pest categorisation of Xylella taiwanensis, a Gram-negative bacterium belonging to the Xanthomonadaceae. The pathogen is a well-defined taxonomic entity, and it is the causal agent of the pear leaf scorch. X. taiwanensis is present in subtropical and temperate areas of the island of Taiwan, where it affects low chilling pear cultivars of the species Pyrus pyrifolia (Asian pear). No other plant species are reported to be affected by the pathogen. The pathogen is not known to be present in the EU territory and it is not included in the Commission Implementing Regulation (EU) 2019/2072. The main pathway for the entry of the pathogen into the EU territory is host plants for planting (except seeds); another possible pathway might be represented by putative insect vectors, though their identity remains unknown. The cultivated area of P. pyrifolia in the EU territory is very limited. Conversely, the genetically related P. communis is widely cultivated in most EU Member States and there is no information so far on the susceptibility of its several cultivars. Should the pest establish in the EU, economic impact is expected, provided that suitable insect vectors are present and P. communis is as susceptible to infection as P. pyrifolia. Phytosanitary measures are available to prevent the introduction and spread of the pathogen into the EU, since plants for planting from Taiwan is a closed pathway; nonetheless, putative vectors, if confirmed and identified, may represent an additional risk of the pathogen's introduction and spread. The lack of knowledge on whether X. taiwanensis can infect P. communis, the identity and presence of suitable vectors in the EU lead to key uncertainties on entry, establishment, spread and impact. X. taiwanensis satisfies the criteria that are within the remit of EFSA to assess for this species to be regarded as a potential Union quarantine pest.

Selective Quantification of Erwinia amylovora Live Cells in Pome Fruit Tree Cankers by Viability Digital PCR.

The accurate assessment of Erwinia amylovora live cell populations in fire blight cankers by classic microbiology methods has major limitations. Some of them are the presence of competitive microbiota in samples that inhibit E. amylovora's growth and the release of toxic compounds by plant material during sample processing, which may hamper the pathogen's ability to form colonies on solid media. Digital PCR (dPCR) combined with the photo-reactive DNA-binding dye propidium monoazide (PMA) allows selective detection and quantification of live E. amylovora cells in woody samples while overcoming the constraints of culture-dependent methods. This work describes a reliable viability dPCR procedure to determine E. amylovora live cell concentrations in fire blight cankers from pome fruit trees. This protocol can be adapted for the analysis of other types of plant material and enables investigation of ecological, epidemiological, and management significance of cankers as a relatively underexplored part of the fire blight disease cycle.

Comparison of freeze-drying and hot air-drying on Asian pear (Pyrus pyrifolia Nakai 'Niitaka') powder: changes in bioaccessibility, antioxidant activity, and bioactive and volatile compounds.

The bioaccessibility, antioxidant activity, and bioactive and volatile compounds of freeze-dried Asian pear powder (FDAPP) and hot air-dried Asian pear powder (HDAPP) were investigated. Compared to FDAPP, HDAPP exhibited significantly (p < 0.05) higher total phenolic, arbutin, and bioaccessible phenolic contents and the ferric reducing ability of plasma for the free phenolic fraction. However, all antioxidant activities for the bound phenolic fraction were lower in HDAPP, which could contribute to the release of bound antioxidant components due to cell rupture in the HDAPP. Based on the volatile profile, hot air drying provided a sweet as well as attractive flavor in the Asian pear powder (APP). Considering economic viability, higher levels of bioactive compounds, and desirable aromatic properties, hot air drying is the better option compared to freeze-drying for APP production, which could be used as a functional ingredient in food products.

Combined Analyses of Chloroplast DNA Haplotypes and Microsatellite Markers Reveal New Insights Into the Origin and Dissemination Route of Cultivated Pears Native to East Asia.

Asian pear plays an important role in the world pear industry, accounting for over 70% of world total production volume. Commercial Asian pear production relies on four major pear cultivar groups, Japanese pear (JP), Chinese white pear (CWP), Chinese sand pear (CSP), and Ussurian pear (UP), but their origins remain controversial. We estimated the genetic diversity levels and structures in a large sample of existing local cultivars to investigate the origins of Asian pears using twenty-five genome-covering nuclear microsatellite (simple sequence repeats, nSSR) markers and two non-coding chloroplast DNA (cpDNA) regions (trnL-trnF and accD-psaI). High levels of genetic diversity were detected for both nSSRs (HE = 0.744) and cpDNAs (Hd = 0.792). The major variation was found within geographic populations of cultivated pear groups, demonstrating a close relationship among cultivar groups. CSPs showed a greater genetic diversity than CWPs and JPs, and lowest levels of genetic differentiation were detected among them. Phylogeographical analyses indicated that the CSP, CWP, and JP were derived from the same progenitor of Pyrus pyrifolia in China. A dissemination route of cultivated P. pyrifolia estimated by approximate Bayesian computation suggested that cultivated P. pyrifolia from the Middle Yangtze River Valley area contributed the major genetic resources to the cultivars, excluding those of southwestern China. Three major genetic groups of cultivated Pyrus pyrifolia were revealed using nSSRs and a Bayesian statistical inference: (a) JPs; (b) cultivars from South-Central China northward to northeastern China, covering the main pear production area in China; (c) cultivars from southwestern China to southeastern China, including Yunnan, Guizhou, Guangdong, Guangxi, and Fujian Provinces. This reflected the synergistic effects of ecogeographical factors and human selection during cultivar spread and improvement. The analyses indicated that UP cultivars might be originated from the interspecific hybridization of wild Pyrus ussuriensis with cultivated Pyrus pyrifolia. The combination of uniparental DNA sequences and nuclear markers give us a better understanding of origins and genetic relationships for Asian pear groups and will be beneficial for the future improvement of Asian pear cultivars.

Chromatographic determination, decline dynamic and risk assessment of sulfoxaflor in Asian pear and oriental melon.

The dissipation pattern of sulfoxaflor in Asian pear cultivated in an open field conditions and in oriental melon grown under plastic house conditions was each studied in two different locations. Residues in field-treated samples were determined using liquid chromatography coupled with an ultraviolet detector and confirmed by liquid chromatography-tandem mass spectrometry. A calibration curve for sulfoxaflor was linear over the concentration range 0.1-5.0 mg/L, with a coefficient of determination of 0.9999. The limits of detection and quantification (LOQ) were 0.007 and 0.02 mg/kg, respectively. Recoveries at three fortification levels (LOQ, 10 × LOQ and maximum residue limit) ranged from 70.5 to 86.2%, with a relative standard deviation ≤5.8%. The dissipation half-lives were 10.8 and 7.9 days in pear and 5.4 and 5.9 days in oriental melon, at sites 1 and 2, respectively. Based on a pre-harvest residue limit curve, it was predicted that, if the residues at 10 days before harvest in Asian pear are <0.54/0.61 mg/kg and those in oriental melon are <1.43/1.26 mg/kg, then the residue level will be below the maximum residue limit at harvest. Risk assessment at zero days showed a percentage acceptable daily intake of 10.80% in Asian pear and 1.77 and 1.55% in oriental melon, for sites 1 and 2, respectively. These values indicate that the fruits are safe for consumption.

The use of the nonlinear models in the growth of pears of 'Shinseiki' cultivar / O uso de modelos não lineares na descrição do crescimento de frutos de pereira cultivar 'Shinseiki'

ABSTRACT: The goal of this study was to elucidate the growth and development of the Asian pear fruit, on the grounds of length, diameter and fresh weight determined over time, using the non-linear Gompertz and Logistic models. The specifications of the models were assessed utilizing the R statistical software, via the least squares method and iterative Gauss-Newton process (DRAPER & SMITH, 2014). The residual standard deviation, adjusted coefficient of determination and the Akaike information criterion were used to compare the models. The residual correlations, observed in the data for length and diameter, were modeled using the second-order regression process to render the residuals independent. The logistic model was highly suitable in demonstrating the data, revealing the Asian pear fruit growth to be sigmoid in shape, showing remarkable development for three variables. It showed an average of up to 125 days for length and diameter and 140 days for fresh fruit weight, with values of 72mm length, 80mm diameter and 224g heavy fat.

RESUMO: Este trabalho teve por objetivo descrever o crescimento e desenvolvimento de frutos de pereira asiática, com base no comprimento, diâmetro e peso fresco obtidos ao longo do tempo, pelos modelos não lineares Gompertz e Logístico. Os parâmetros dos modelos foram estimados utilizando rotinas no software R, pelo método de mínimos quadrados e processo iterativo de Gauss-Newton (DRAPER & SMITH, 2014). Os modelos foram comparados utilizando o desvio padrão residual, coeficiente de determinação ajustado e o critério de informação de Akaike. A correlação residual presente nos dados de comprimento e diâmetro foi modelada por processo auto-regressivo de segunda ordem, tornando os resíduos independentes. O modelo Logístico mostrou-se mais adequado para descrever os dados, comprovando o caráter sigmoidal do crescimento da pera asiática com desenvolvimento acentuado das três variáveis, com até 125 dias para o comprimento e diâmetro e 140 dias para o peso fresco dos frutos, estabilizando-se, em média, com 72mm de comprimento, 80mm de diâmetro e 224g de peso fresco.

Systematics of the east Palaearctic pear psyllids (Hemiptera: Psylloidea) with particular focus on the Japanese and Korean fauna.

The confused taxonomy of the east Palaearctic pear psyllids, serious pests on cultivated pear, is reviewed. Fifty-six nominal species have been reported from Pyrus, 25 of which we consider valid and ten as not being associated with Pyrus. Our taxonomic revision suggests that, in Korea, four Cacopsylla species develop on pear: the univoltine C. burckhardti Luo et al. previously misidentified as C. pyrisuga (Foerster), the polyvoltine, seasonally dimorphic C. jukyungi (Kwon) (winter form 'cinereosignata' Luo et al., summer form 'jukyungi'), commonly found in Korean pear orchards, and C. maculatili Li (winter form 'maculatili', summer form 'qiuzili' Li) previously misidentified as C. pyricola (Foerster) by some authors, as well as the probably polyvoltine but not dimorphic C. sandolbaea (Park & Lee). The former three species (C. burckhardti, C. jukyungi, misidentified as C. chinensis (Yang & Li), and C. maculatili) occur also in Japan. Keys to the adult and fifth instar immatures as well as short biological notes are provided, and C. jukyungi and C. sandolbaea are redescribed. Following nomenclatorial changes are proposed: Cacopsylla betulaefoliae (Yang & Li, 1981) = Psylla heterobetulaefoliae Yang & Li, 1981, syn. nov.; Cacopsylla bidens (Sulc, 1907) = Psylla jiangli Yang & Li, 1981, syn. nov.; Cacopsylla jukyungi (Kwon) = C. cinereosignata Luo et al., syn. nov.; Cacopsylla maculatili Li = C. qiuzili Li, syn. nov.; Cacopsylla nigella (Konovalova), comb. nov. from Psylla. The synonymy of P. obongsana Kwon with C. sandolbaea is confirmed.

Color, bioactive compounds and morphological characteristics of encapsulated Asian pear juice powder during spray drying.

Encapsulated Asian pear juice powder was produced through spray drying using three maltodextrin levels (15, 20, and 25% w/v) and three inlet air temperatures (130, 150, and 170 °C). The impact of maltodextrin concentrations and inlet air temperatures on color, bioactive compounds, and morphological characteristics of encapsulated Asian pear juice powder were investigated. Maltodextrin concentrations and inlet air temperatures significantly influenced L* and b* values of encapsulated Asian pear juice powder. Increasing inlet air temperatures increased total phenolic content, whereas the vitamin C content decreased. Vitamin C content was strongly correlated with particle size, inlet air temperature, and maltodextrin concentration. ABTS+ radical-scavenging activity was highly correlated with total phenol content while DPPH radical-scavenging activity was highly correlated with vitamin C content. Encapsulated powders made with higher inlet air temperature and higher maltodextrin concentration had lowest median particle diameter with a smoother, more regular and rounded outer surface than those of encapsulated powders produced with lower inlet air temperature and lower maltodextrin concentration. Therefore, the results demonstrate that high-quality encapsulated Asian pear juice powder could be manufactured by adding 15% (w/v) maltodextrin and spray-drying at 170 °C.

The disappearance rate and risk assessment of thiacloprid residues in Asian pear using liquid chromatography confirmed with tandem mass spectrometry.

This study was undertaken to quantify the residue levels and propose the dissipation kinetics of thiacloprid formulated as suspension concentrate in field-incurred Asian pears grown under two different open-field conditions. Samples were extracted with 20% distilled water in acetonitrile; partitioned with brine water and dichloromethane; and purified with a Florisil solid phase extraction cartridge. The analyte was identified with an LC ultraviolet detector, and field-incurred samples were confirmed using LC-MS/MS. The calibration curve was linear over the range 0.05-5.0 mg/L with a satisfactory coefficient of determination (R2 = 0.9994). The limits of detection and limits of quantification (LOQ) were 0.003 and 0.01 mg/kg, respectively. The recovery rate fortified to blank samples at LOQ, 10× LOQ, and the maximum residue limit (MRL) were between 73.7 and 86.2% with relative standard deviation ≤9.0%. The residual concentrations at both sites were considerably lower than the MRL (0.7 mg/kg) set by the Korean Ministry of Food Drug Safety, with biological half-lives of 5.0 and 7.4 days, for sites 1 and 2, respectively. From the pre-harvest residue limit curve, it was predicted that if the residues were <1.13 or 1.40 mg/kg 10 days before harvest, the residue level would be lower than the MRL during harvest. Risk assessment on day 0 showed an acceptable daily intake (%) of 13.0% and 11.0% for sites 1 and site 2, respectively, which indicates that the residual amounts are not hazardous to the Korean population.

Pest categorisation of Venturia nashicola.

The Panel on Plant Health performed a pest categorisation of Venturia nashicola, the causal agent of Asian pear scab, for the European Union (EU). The pathogen is a well-defined, distinguishable fungal species affecting Pyrus pyrifolia var. culta, P. ussuriensis and P. bretschneideri in Asian countries. P. communis (European pear) is not a host of V. nashicola, but the host status of other Pyrus species is unclear. V. nashicola is not known to occur in the EU. It is listed in Annex IIAI of Directive 2000/29/EC. The pathogen could potentially enter the EU on host plants for planting and fruit originated in infested countries. There are no climatic factors limiting the potential establishment and spread of the pathogen in the EU, as its epidemiology is similar to those of Venturia inaequalis (apple scab) and Venturia pyrina (European pear scab), which are well-established in the EU. The hosts are present in the EU, but no data were found on their abundance and distribution. In the infested areas, V. nashicola causes premature leaf and fruit drop and fruit distortion resulting in considerable yield/quality losses. The introduction of the pathogen into the EU could cause yield/quality losses and environmental consequences because of the additional fungicide sprays for disease control. Cultural practices and chemical measures applied in the infested areas reduce the inoculum sources but they cannot eliminate the pathogen. Phytosanitary measures are available to mitigate the risk of introduction and spread of the pathogen in the EU. All criteria assessed by EFSA for consideration as a potential Union quarantine pest are met. As V. nashicola is not known to occur in the EU, this criterion assessed by EFSA to consider it as a Union regulated non-quarantine pest is not met.

Decline pattern and risk assessment of cyenopyrafen in different varieties of Asian pear using liquid chromatography and tandem mass spectrometry.

The dissipation pattern of a commercial cyenopyrafen formulation sprayed at the recommended dose on Asian pears (two different species) grown at two different sites was investigated using liquid chromatography-ultraviolet detection. Samples collected randomly over 14 days were extracted using acetone, partitioned using n-hexane/dichloromethane (8/2, v/v), and purified using a Florisil solidphase extraction cartridge. The residues in field-incurred samples were confirmed via liquid chromatography-tandem mass spectrometry. The method was validated in terms of excellent linearity in the solvent (R 2=1); moreover, satisfactory recoveries (89.0-107.3%) were obtained at three fortification levels with a relative standard deviation (RSD)≤5.0% and the limits of detection and quantification of 0.0033 and 0.01 mg/kg, respectively. Although the residual levels at both sites were lower than the maximum residue limit (MRL=1 mg/kg), the dissipation at Site 2 was faster than that at Site 1. Consequently, the half-life (t1/2) in Site 2 (5.2 d) was shorter than that in Site 1 (9.8 d). Risk assessment at zero days showed acceptable daily intakes (%) of 27.25% and 24.52% at Sites 1 and 2, respectively, indicating that these fruit species are safe for consumption.

Characterization of CIPK Family in Asian Pear (Pyrus bretschneideri Rehd) and Co-expression Analysis Related to Salt and Osmotic Stress Responses.

Asian pear (Pyrus bretschneideri) is one of the most important fruit crops in the world, and its growth and productivity are frequently affected by abiotic stresses. Calcineurin B-like interacting protein kinases (CIPKs) as caladium-sensor protein kinases interact with Ca(2+)-binding CBLs to extensively mediate abiotic stress responses in plants. Although the pear genome sequence has been released, little information is available about the CIPK genes in pear, especially in response to salt and osmotic stresses. In this study, we systematically identified 28 CIPK family members from the sequenced pear genome and analyzed their organization, phylogeny, gene structure, protein motif, and synteny duplication divergences. Most duplicated PbCIPKs underwent purifying selection, and their evolutionary divergences accompanied with the pear whole genome duplication. We also investigated stress -responsive expression patterns and co-expression networks of CIPK family under salt and osmotic stresses, and the distribution of stress-related cis-regulatory elements in promoter regions. Our results suggest that most PbCIPKs could play important roles in the abiotic stress responses. Some PbCIPKs, such as PbCIPK22, -19, -18, -15, -8, and -6 can serve as core regulators in response to salt and osmotic stresses based on co-expression networks of PbCIPKs. Some sets of genes that were involved in response to salt did not overlap with those in response to osmotic responses, suggesting the sub-functionalization of CIPK genes in stress responses. This study revealed some candidate genes that play roles in early responses to salt and osmotic stress for further characterization of abiotic stress responses medicated by CIPKs in pear.

Specific and Sensitive Detection of Venturia nashicola, the Scab Fungus of Asian Pears, by Nested PCR.

The fungus Venturia nashicola is the causal agent of scab on Asian pears. For the rapid and reliable identification as well as sensitive detection of V. nashicola, a PCR-based technique was developed. DNA fingerprints of three closely related species, V. nashicola, V. pirina, and V. inaequalis, were obtained by random amplified polymorphic DNA (RAPD) analysis. Two RAPD markers specific to V. nashicola were identified by PCR, after which two pairs of sequence characterized amplified region (SCAR) primers were designed from the nucleotide sequences of the markers. The SCAR primer pairs, designated as D12F/D12R and E11F/E11R, amplified 535-bp and 525-bp DNA fragments, respectively, only from genomic DNA of V. nashicola. The specificity of the primer sets was tested on strains representing three species of Venturia and 20 fungal plant pathogens. The nested PCR primer pair specific to V. nashicola was developed based on the sequence of the species-specific 525-bp DNA fragment amplified by primer set E11F/E11R. The internal primer pair Na11F/Na11R amplified a 235-bp fragment from V. nashicola, but not from any other fungal species tested. The nested PCR assay was sensitive enough to detect the specific fragment in 50 fg of V. nashicola DNA.

Occurrence of Anthracnose on Fruits of Asian Pear Tree Caused by Colletotrichum acutatum.

Anthracnose symptoms often occurred on fruits of Asian pear trees grown in Anseong, Naju, Seonghwan and Pyeongtaek in Korea during the harvesting period from 2000 to 2005. A total of 28 isolates of Colletotrichum sp. were obtained from the anthracnose symptoms. All the isolates were identified as Colletotrichum acutatum based on their morphological and cultural characteristics. Four isolates of the fungus were tested for pathogenicity to fruits of Asian pear tree by artificial inoculation. All the isolates induced anthracnose symptoms on the fruits by wound inoculation but not by unwound inoculation. The anthracnose symptoms induced by artificial inoculation were similar to those observed in the orchard. This is the first report of anthracnose of Asian pear tree caused by Colletotrichum acutatum.

Occurrence of Anthracnose on Fruits of Asian Pear Tree Caused by Colletotrichum acutatum

Anthracnose symptoms often occurred on fruits of Asian pear trees grown in Anseong, Naju, Seonghwan and Pyeongtaek in Korea during the harvesting period from 2000 to 2005. A total of 28 isolates of Colletotrichum sp. were obtained from the anthracnose symptoms. All the isolates were identified as Colletotrichum acutatum based on their morphological and cultural characteristics. Four isolates of the fungus were tested for pathogenicity to fruits of Asian pear tree by artificial inoculation. All the isolates induced anthracnose symptoms on the fruits by wound inoculation but not by unwound inoculation. The anthracnose symptoms induced by artificial inoculation were similar to those observed in the orchard. This is the first report of anthracnose of Asian pear tree caused by Colletotrichum acutatum.

Molecular Detection and Differentiation of Erwinia pyrifoliae and Host Range Analysis of the Asian Pear Pathogen.

The recently described pathogen Erwinia pyrifoliae, isolated from Nashi pear fruit trees in Korea, resembles the fire blight pathogen Erwinia amylovora in some of its properties. The two pathogens were classified into different species by DNA hybridization kinetics and microbiological criteria. From the nucleotide sequences of the 16S rRNA and the internal transcribed spacer (ITS) region as well as extracellular polysaccharide (EPS)-encoding genes, polymerase chain reaction (PCR) primers were designed that specifically detect E. pyrifoliae but not the fire blight pathogen Erwinia amylovora, and these primers were also applied to identify E. pyrifoliae in necrotic plant material. The genomes of several strains were digested with the restriction enzyme SpeI, and the DNA fragments were analyzed by pulsed-field gel electrophoresis (PFGE). Three groups of patterns could be distinguished for the isolated E. pyrifoliae strains, all different from various E. amylovora strains, which produce a relatively homogeneous PFGE pattern after SpeI digests. Typical fire blight host plants were assayed in a growth chamber or an experimental field for their susceptibility to E. pyrifoliae. A strong preference was found for pear varieties, whereas apple, cotoneaster, hawthorn, or raspberry rarely produced necrotic symptoms. E. pyrifoliae was readily detected in samples from pear orchards in South Korea during 1995 to 1998; however, the Asian pear pathogen was not recovered in necrotic plant tissue from 1999 and 2000.