Cork Spot Research Articles

An innovative fusion feature method of spectrum and visual image for diagnosing ‘Akizuki’ pear cork spot disorder

Cork spot disorder is a common physiological disease that severely affects the quality and yield of the ‘Akizuki’ pear. In this study, we propose a novel method, Near-infrared spectra and Visual images with Neural Architecture Search (NV-NAS), to achieve a highly accurate diagnosis of cork spot disorder. This method automatically generates fusion features by combining near-infrared spectral and visual image features and then searches for the best-performing model structure. The best result was obtained with near-infrared spectral features preprocessed by first derivatives (FD) and the visual image features extracted by DenseNet121 in the NV-NAS method. On the validation set, the accuracy was 95.5%, and on the test set, the accuracy was 88.2%. Compared to the modeling results of a single feature, the accuracy improved by 26.3% over spectra and by 11.2% over images on the test set. Additionally, in experiments with models of different depths, deep image features were more conducive to feature fusion, with accuracy improvements of 21.7% and 30.1% compared to features from the middle or bottom layers, respectively. The results indicate that the model built on the fusion feature shows high generalization performance and holds significant reference value for the more accurate diagnosis of the ‘Akizuki’ pear cork spot disorder.

Use of coal ash- and lignite-enriched compost to improve soil biological properties and reduce pineapple disease in Ultisols of Central Lampung

Ultisols used for pineapple cultivation are classified as suboptimal lands because of their low soil fertility. Application of compost enriched with other soil ameliorants, such as coal ash in the form of fly ash, bottom ash (FABA), and lignite, can be a good alternative to improve soil properties, including increasing the soil microbial and fauna populations, which play an important role in improving soil fertility and reducing the incidence of pineapple disease. The purpose of this study was to investigate the effects of FABA- and lignite-enriched compost on microbial and earthworm populations and the incidence of pineapple disease. FABA- and lignite-enriched compost at a dose of 50 tons/ha was applied using a spread-and-row technique in the pineapple plantation area in Central Lampung. The parameters observed included the microbial population (Pseudomonas, Bacillus, Actinomycetes, Trichoderma), functional microbial populations (nitrogen-fixing bacteria, phosphate-solubilizing microbes, siderophore producers), earthworm population, and incidence of pineapple diseases (marbling, brown spot, cork spot, and pink diseases). Generally, all treatments with FABA- and lignite-enriched compost showed better results than the control for all observed parameters. The treatment of FABA-enriched compost applied with a row technique was the best compared to other treatments because it tended to increase the population of Pseudomonas, Bacillus, Actinomycetes, and nitrogen-fixing bacteria, as well as earthworm abundance and biomass. In addition, in this treatment, there was no incidence of pineapple fruit disease. The abundance of earthworms and soil microbes, especially Pseudomonas was one of the factors which can create a healthier soil ecosystem to suppress the incidence of pineapple diseases.

A novel transfer method with neural network architecture searching to predict asymptomatic of “akizuki” pear cork spot disorder on near-infrared spectroscopy

“Akizuki” pear cork spot disorder is a physiological disease, the ability to effectively diagnose the diseased fruit can directly affect the fruit quality. To improve the diagnostic performance of asymptomatic samples, this paper proposes a novel spectral transfer modelling method based on neural network architecture searching, named TranNAS_NIR. The experiments show that the model by the proposed TranNAS_NIR method is more effective. The accuracy of the target domain test set reaches 82.61%, which is 5.3% better than the model with transfer component analysis (TCA) and 10.5% better than the model constructed only relying on the target domain data and without the transfer learning method. The novel transfer method with neural network architecture search proposed in this paper for the asymptomatic prediction model of “Akizuki” pear cork spot disorder also further provides a theoretical basis for the NIR model improvement of other asymptomatic diseases.

An early asymptomatic diagnosis method for cork spot disorder in 'Akizuki' pear (Pyrus pyrifolia Nakai) using micro near infrared spectroscopy.

The early symptoms of cork spot disorder in 'Akizuki' pear (Pyrus pyrifolia Nakai) are challenging to distinguish from those in healthy fruits, hindering early identification in production. In this study, samples of cork-browned 'Akizuki' pears, asymptomatic fruits and healthy fruits were examined to determine the content of relevant mineral elements. A micro near-infrared spectrometer collected spectral information, and various pretreatment methods were applied to the near-infrared spectral data. Support vector machine (SVM) modelling using the original data achieved the highest overall recognition accuracy of 84.65% and an F1 value of 84.06%. For identifying fruits without cork spot disease, Autokeras modelled data processed with the SG method, achieving the best accuracy of 90%. These findings establish a reliable basis for the early identification and diagnosis of cork spot disorder in 'Akizuki' pear, enhancing pear production management.

Mineral and Metabolome Analyses Provide Insights into the Cork Spot Disorder on ‘Akizuki’ Pear Fruit

Cork spot is a common physiological disorder in pear fruits, which has been found in some pear cultivars. Mineral nutrition imbalance in fruit is regarded as the principal influence factor for disorder incidence, with some ongoing confusion and controversy. In our research, we explored the cork spot characteristics in Japanese pear ‘Akizuki’ (Pyrus pyrifolia Nakai), adopted metabolome and mineral content analysis for healthy and disordered fruits, and made a correlation analysis of mineral and metabolites. Cork spots are mainly distributed on the outer flesh beneath the fruit peel. In cork spotted tissues, superoxide (SOD) and peroxidase (POD) activities, as well as malondialdehyde (MDA) content, increased. A total of 1024 known metabolites were identified from all the samples and more changes in metabolism were detected between normal and cork spotted flesh tissues. Correlation analysis displayed that Ca, especially the Mg/Ca in fruits, could be used to predict whether an orchard will develop cork spot disorder; Mg and B were associated with the appearance of symptoms, and the contents of Zn, Fe, and Mg, as well as Mg/B and Zn/B, might be strongly tied to the formation of cork spots in pears. This research provides insights into the occurrence of pear cork spot disorder and clarifies the role of minerals.

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.

High-Resolution Microstructure Analysis of Cork Spot Disordered Pear Fruit "Akizuki" (Pyrus pyrifolia Nakai) Using X-Ray CT.

Cork spot is one of the most damaging physiological disorders in pear fruit, causing considerable economic loss every year. However, the mechanism of cork spot occurrence requires further examination. In this study, X-ray CT scanning was applied to analyze the microstructure of pear fruit “Akizuki” (Pyrus pyrifolia), a cultivar susceptible to cork spot disorder, to elucidate the fruit texture alteration between healthy and cork spotted fruit. Results showed that cork spotted fruit had much higher porosity (9.37%) than healthy fruit (3.52%). Reconstructed three-dimensional (3D) network skeleton models showed highly branched pore channels in cork spotted fruit and a low degree of pore connectivity in healthy fruit. Even in areas of disordered fruit without cork spot, the pore throat diameter, pore length, and coordinated core number (i.e., 77, 160, and 16, respectively) were much higher than that of healthy fruit. The structure analysis of fruit core showed that core deformation only occurred in cork spotted fruit. A much more highly branched network was observed in cork spotted fruit cores compared with healthy fruit cores. High-resolution observation of flesh tissue directly demonstrated that pore size in cork spotted fruit (87 μm) was four times larger than that of healthy fruit (22 μm). Altered expression of genes related to Ca2+ transport and the uneven distribution of intracellular Ca2+ were also shown to associate with the development of cork spot disorder. Our results suggest that flesh tissue damage likely occurred prior to the initiation of cork spot. The dysfunction of long-distance and transmembrane Ca2+ transport channels could be responsible for the imbalanced distribution of Ca2+ inside the fruit, thus resulting in the development of cork spot.

Nitrendipine-Treatment Increases Cork Spot Disorder Incidence in Pear 'Akituki' (Pyrus pyrifolia Nakai.) by Altering Calcium Distribution Inside the Fruit.

‘Akituki’ (Pyrus pyrifolia Nakai.) is a very popular and profitable pear cultivar in China. However, its high susceptibility to cork spot disorder has limited its expansion of cultivated area. The mechanisms of cork spot disorder have been discussed extensively, focusing on Ca2+ deficiency, yet no consensus has been made. In this study, we applied nitrendipine (NI) as a Ca2+ uptake inhibitor to explore the role of calcium in cork spot disorder occurrence. Results showed that NI treatment on the fruit remarkably increased the incidence of cork spot disorder; alteration of mineral contents happened at the early developmental stage of the fruit, especially on the outer flesh and the peel of the fruit; and this gap was filled gradually along with the expansion of the fruit. Significant differences in the expression levels of Ca2+ transport-related genes were found in the inner flesh, outer flesh and peel during the fruit growth period. The observation of free Ca2+ localization indicated the intracellular imbalance of Ca2+ in the NI-treated fruit. In conclusion, NI treatment reduced the calcium content in the fruit at an early developmental stage, altered the related expression of genes and influenced the cellular Ca2+ balance in the fruit, which prompted the occurrence of cork spot disorder. Measures for the prevention and control of cork spot disorder should be taken at the early stage of the fruit development in the field.

X-ray μCT analysis to characterize cork spot disorder in Chinese pear ‘Chili’ (Pyrus bretschneideri)

Abstract Healthy and disordered fruit of Chinese ‘Chili’ (Pyrus bretschneideri Rehd.), a well-known pear cultivar in China, are used to investigate the cork spot disorder by non-destructive X-ray computed microtomography (μCT) scanning technology, with pixel resolution of 67-70 μm and scanning time of 60 min on intact fruit. The results suggested that X-ray μCT could clearly and accurately distinguish the internal organization, size and location of cork spot in the pear fruit. CT images showed that the spots mostly locate in the pulp tissue between the calyx end and the equator of disordered fruit, and usually within 14 mm below the pericarp. STL format 3D images had great potential to distinguish cork spotted fruit core from healthy one. In addition, total number of pores is strongly decreased while larger pores bigger than 900 μm are considerably increased in disordered fruit as compared to healthy fruit, which indicates that larger pores maybe formed by the extension and interconnection with adjacent pores of some small pores. Further analysis in pore skeleton-network shows that extremely higher porosity and highly branched, more connected and thicker pores are observed in cork spotted fruit than those in healthy fruit. In addition, the average length of the healthy pore throat is 160.08 μm, which is significantly smaller than that of disordered fruit (277.91 μm). Moreover, the coordination number of pores in cork spotted fruit is 2, while it is 0 in healthy fruit. All the above results indicate that X-ray μCT provides a new perspective to the non-destructive visualization, quantification and knowledge of the 3D image structure of pear fruit with cork spot, and it is highly essential for early diagnosis and further study of the pathogenic mechanism of this disorder.

Investigation and analysis of relationship between mineral elements alteration and cork spot physiological disorder of Chinese pear ‘Chili’ (Pyrus bretschneideri Rehd.)

Cork spot is one of the most damaging physiological disorders in pear. However, the mechanism of cork spot is unclear. Ca2+ deficiency is considered as the major agent to cork spot. In this study, we investigated cork spot characteristics in Chinese ‘Chili’ (Pyrus bretschneideri Rehd.) and analyzed the relationship between mineral elements alteration and cork spot occurrence. We found early initiation of cork spot disorder in ‘Chili’ at 80 days after full bloom (DAFB). Cork spot in disordered fruit mostly distributed around the fruit eye with necrotic and brown tissues at the spotted site in flesh. At harvest time, cork spot disordered fruit had a smaller size, higher firmness, lower titratable acidity, higher lignin and cellulose content than healthy fruit, while starch concentration was the same between disordered and healthy fruit. Differences of mineral elements content were also found in both leaves and fruits, and Ca2+ distribution was visualized to be concentrated inside cell wall in disordered fruit cells. Principal components analysis (PCA) of mineral elements data showed that fruit samples could be separated according to their healthy or disordered condition at 80 and 160 DAFB. However, no significant correlation was found between cork spot disorder and mineral elements data. Ca2+ concentration was not suggested as the cork spot biochemical marker in our study. At last, we hypothesized the relationship between cork spot occurrence and Ca2+ distribution in ‘Chili’ and summarized the factors probably contributing to Ca2+ deficiency disorder, which would be useful in designing orchard strategies against cork spot.

Investigation and Prevention of Cork Spot Disorder in ‘Akizuki’ Pear (Pyrus pyrifolia Nakai)

‘Akizuki’ (Pyrus pyrifolia Nakai) is a dominant Asian pear cultivar with gradually increasing cultivation area in Shandong province. However, this cultivar is found susceptible to cork spot disorder in recent years. In this study, we explored the physiological-biochemical mechanism of cork spot disorder in pear fruit, and investigated the effectiveness of spraying calcium (Ca), boron (B) solution or prohexadione calcium (P-Ca) on cork spot incidence. Cork spotted fruit had the characteristics of significantly larger fruit size with shorter fruit pedicels. Compared with normal fruit, cork spotted fruit had lower content of total soluble solids, soluble and reducing sugar, and vitamin C. In addition, cork spotted fruit accumulated much higher levels of N and Mg, and lower levels of K and P. However, Ca deficiency was not observed in cork spotted fruit, on the contrary, we determined high concentrations of Ca and free Ca2+ in disordered fruit. At the same time, the ratios of K/Ca, Mg/Ca, and (K+Mg)/Ca were significantly lower in cork spotted fruit as compared with normal fruit. Among all treatments, spraying with 3500 times dilution of P-Ca at 15-day intervals from 30 to 90 days after full bloom showed promise for reducing cork spot incidence in ‘Akizuki’ pear without affecting fruit quality attributes. This research herein reveals the physiological-biochemical characteristic of cork spot disorder, and implicates P-Ca as a potential tool to reduce cork spot incidence in Asian pear cultivar Akizuki.

ニホンナシ‘あきづき’と‘王秋’に発生するコルク状果肉障害の特徴

ニホンナシ ‘あきづき’ および ‘王秋’ の果実に生じるコルク状果肉障害の発生状況について，果実を5 mm厚に薄くスライスして詳細に調査を行い，成熟期や果実品質との関係を解析するとともに，GA処理の影響について調査した．両品種ともにコルクの発生が認められ，‘あきづき’は成熟の遅い果実に発生が多かった．本試験では，‘王秋’は‘あきづき’ほど成熟時期による違いは明確ではなかった．一方，両品種ともに果実重の大きい果実で発生が多く，特に‘あきづき’では大きい果実ほどコルクの個数が増加し，大きいコルクの発生も多くなった．コルクの発生位置は，果実全体に分布していたが，赤道面よりややこうあ部側に最も多く観察された．GA処理は，両品種ともにコルクの発生個数を有意に増加させ，障害程度を重症化させた．ただし，コルクの発生果率には影響を及ぼさなかった．

Non-destructive Measurement of Calcium and Potassium in Apple and Pear Using Handheld X-ray Fluorescence.

Calcium and potassium are essential for cell signaling, ion homeostasis and cell wall strength in plants. Unlike nutrients such as nitrogen and potassium, calcium is immobile in plants. Localized calcium deficiencies result in agricultural losses; particularly for fleshy horticultural crops in which elemental imbalances in fruit contribute to the development of physiological disorders such as bitter pit in apple and cork spot in pear. Currently, elemental analysis of plant tissue is destructive, time consuming and costly. This is a limitation for nutrition studies related to calcium in plants. Handheld portable x-ray fluorescence (XRF) can be used to non-destructively measure elemental concentrations. The main objective was to test if handheld XRF can be used for semi-quantitative calcium and potassium analysis of in-tact apple and pear. Semi-quantitative measurements for individual fruit were compared to results obtained from traditional lab analysis. Here, we observed significant correlations between handheld XRF measurements of calcium and potassium and concentrations determined using MP-AES lab analysis. Pearson correlation coefficients ranged from 0.73 and 0.97. Furthermore, measuring apple and pear using handheld XRF identified spatial variability in calcium and potassium concentrations on the surface of individual fruit. This variability may contribute to the development of localized nutritional imbalances. This highlights the importance of understanding spatial and temporal variability in elemental concentrations in plant tissue. Handheld XRF is a relatively high-throughput approach for measuring calcium and potassium in plant tissue. It can be used in conjunction with traditional lab analysis to better understand spatial and temporal patterns in calcium and potassium uptake and distribution within an organ, plant or across the landscape.

Foliar Calcium Applications for Controlling Fruit Disorders and Storage Life in Deciduous Fruit Trees

Calcium is involved in several disorders and influences the storage life of different fruit species. Moreover, applying preharvest foliar Ca spray is a standard practice to control fruit Ca concentration in certain deciduous fruit trees. Conversely, the effects of foliar Ca spray on the Ca concentration in fruit and the incidence of disorder are sometimes inconsistent. This article provides an overview of recent works on foliar Ca application and discusses Ca application inconsistencies. Foliar Ca sprays reduced bitter pit, enhanced fruit firmness and storage time, and sometimes reduced the incidence of brown rot during storage in apples; reduced internal browning during storage and the incidence of brown rot in peaches; decreased postharvest decay and cork spot in pears; and increased shelf life in grapes. Experiments using 45 Ca or isolated cuticular revealed the effects of fruit growth stages, atmospheric conditions, and adjuvants on Ca penetration. Finally, three possible reasons for inconsistencies of foliar Ca application are discussed.

Relationships between storage disorders and fruit calcium contents, lipoxygenase activity, and rates of ethylene evolution and respiration in ‘Royal Delicious’ apple (Malus × domestica Borkh.)

SummaryExperiments were conducted to determine the relationships between the occurrence of storage disorders in ‘Royal Delicious’ apple (Malus ×domestica Borkh.) and fruit Ca2+ ion contents, rates of ethylene evolution and respiration, and lipoxygenase (LOX) activity. Apples were stored at 0º ± 1ºC and 90 – 95% relative humidity and sampled each month, up to 6 months, for storage disorders, fruit Ca2+ ion contents, rates of ethylene evolution and respiration, and LOX activity. Storage disorders such as bitter pit, cork spot, and brown core appeared after 3 months and increased in frequency at subsequent samplings. Regardless of the presence or absence of storage disorders, fruit showed a decline in Ca2+ ion concentration during storage. Ca2+ ion concentrations (means of 3, 4, 5, and 6 month samples) were significantly higher in disorder-free fruit [0.419 mg g–1 dry weight (DW)] than in fruit showing bitter pit (0.329 mg g–1 DW) or cork spot (0.340 mg g–1 DW), but were not significantly higher than in fruit with brown core (0.393 mg g–1 DW). Conversely, LOX activity was significantly lower in disorder-free fruit [0.168 µmoles linolenic acid oxidised min–1 g–1 fresh weight (FW)] compared to symptomatic fruit. LOX activity increased with the duration of storage in all fruit samples. The rates of ethylene evolution (58.5 µl C2H4 kg–1 FW fruit h–1) and respiration (16.0 ml CO2 kg–1 FW fruit h–1) were significantly lower in disorder-free fruit than in symptomatic fruit. The rates of ethylene evolution and respiration increased between 3 – 5 months in storage. After 5 months in storage, they remained stable or declined in all fruit. The correlations (R2) between Ca2+ ion content vs. the presence of physiological disorders such as bitter pit (–0.77), cork spot (–0.75), and brown core (–0.64), and between Ca2+ ion contents vs. LOX activity were strongly negative (–0.94). In contrast; the correlation between LOX activity vs. physiological disorders was strongly positive. Our study concluded that an inverse relationship existed between fruit Ca2+ ion content and the occurrence of bitter pit, cork spot, and/or brown core, and between fruit Ca2+ ion content and LOX activity. Moreover, the relationship between LOX activity and the presence of storage disorders was strongly positive.

Calcium Foliar Sprays for Control of Alfalfa Greening, Cork Spot, and Hard End in ‘Anjou’ Pears

ABSTRACT New calcium (Ca) spray materials were made available to test for their possible improvement over the often-used dry form of calcium chloride products. Four orchards of mature ‘Anjou’ pears (Pyrus communis L.) were selected for the experiments. Three Ca materials were used at equal Ca rates, consisting of a dry Ca material derived from calcium chloride (Mora-leaf-Ca) with and without Sylgard; a liquid Ca material derived from CaCl2 (Cal-Plex-12); and a dry Ca material derived from calcium oxide (Mira-Cal) at different concentrations. In one orchard, Mira-Cal Ca at the double rate had the lowest incidence of cork spot and hard end with the highest concentration of cortex Ca and acceptable fruit finish, closely followed by the standard rate of Mora-Leaf-Ca. In a second orchard, Mora-Leaf-Ca plus Sylgard 309 had the lowest incidence of cork spot and alfalfa greening. In the third orchard, Mora-Leaf-Ca had the lowest incidence of cork spot and the highest concentration of fruit Ca in peel and cortex. In the fourth orchard, Cal-Plex-12 Ca produced nearly complete control of cork spot and the highest concentration of fruit Ca in peel and cortex. When comparing commercial spray-machine application of 935 L ha−1, control of cork spot and fruit Ca absorption was improved with six calcium applications versus only two spray applications.

Effects of Rootstock and Training System on Fruit Quality and Peel Nutrient Content in in ‘Bosc’ Pears

In a 3-year trial involving 28 ‘Bosc’ rootstock-training systems combinations, rootstock-training system induced differences were found in only three of the post-storage problem areas (decay, scab, and limb rub) studied for ‘Bosc’ pears. Significant differences occurred among years; however, no one year was considered “good” or “bad” for post-storage problems. Yearly patterns in post-storage problems varied with the problem. The significant differences that occurred between rootstock-training system combinations may have resulted from root-stock or training system combination effects on vigor or modification of the fruit nutrient content which was then related to the post-storage problem area. Significant combination X year interactions occurred for external cork spot and flesh browning. No one rootstock-training system combination had the greatest or least amount of any of the storage problems.

Effects of Rootstock and Training System on Fruit Quality and Peel Nutrient Content in ‘d'Anjou’ Pears

Abstract In a 3-year trial involving 30 ‘d'Anjou’ rootstock-training systems combinations, significant combination induced differences occurred in almost all post-storage problems studied. Variation occurred among years; however, no one year was considered “good” or “bad” for post-storage problems. Yearly patterns in post-storage problems varied with the problem. The significant differences that occurred between rootstock-training system combinations may have resulted from rootstock or training system effects on vigor or modification of the fruit nutrient content which then affected post-storage problems. Combination and year interacted to affect superficial scald and internal cork spot. No one rootstock-training system combination was consistently the “best” or “worst” for all post-storage problems evaluated.

Relationship of fertilizers on soil ph and fruit disorders of apples and pears

In nutrition experiments of fruit‐growing areas of central Washington state, ‘Delicious’ and ‘Golden Delicious’ apple (Malus domestica) orchards and ‘d'Anjou’ pear (Pyrus communis L.) orchards with the lowest soil pH values had a high incidence of fruit disorders and the lowest concentration of leaf calcium (Ca). In contrast, orchards with the highest soil pH values had the highest concentration of soil Ca (meq 100 g‐1) and the lowest incidence offrait disorders (bitter pit for apples and alfalfa greening, black end and cork spot for pears). Apple orchards with the highest soil pH values also had ‘Delicious’ and ‘Golden Delicious’ apples containing the highest concentration of Ca, but Ca concentrations in ‘d'Anjou’ pears were not significantly different among the different soil pH groups.

Effect of calcium sprays, time of harvest, cold storage, and ripeness on fruit quality of ‘anjou’ pears1

Calcium chloride (CaCl2), increased Ca concentrations in fruit cortex and peel of ‘Anjou’ pears (Pyrus communis L.). Calcium sprays reduced the fruit disorders: brown core, cork spot and superficial scald. Fruit size (weight) increased while fruit Ca concentrations decreased with fruit at the later harvest dates. The earliest harvest date was associated with a lower incidence of fruit disorders. Superficial scald increased in fruit held longer in cold storage and in ripened fruit. Shelf‐life and fruit quality of Ca‐sprayed fruit was improved due to higher Ca concentrations in fruit peel and cortex resulting in overall enhancement of fruit appearance, and in improvement in the control of the incidences of cork spot, scald, brown core, and external and internal rots, and in amelioration of fruit juiciness and fruit color.