Internal Browning Research Articles

New insights into early biochemical prediction of internal browning disorder in 'Conference' pears

This study aimed to identify markers in pear capable of predicting the development of internal browning disorder (IBD) at harvest or during early storage. ´Conference´ pears were harvested from different orchards at commercial maturity and stored under high CO2 atmosphere conditions to induce disorders. The predictive markers studied were associated with 1-aminocyclopropane-1-carboxylic acid (ACC) metabolism, antioxidants and the tricarboxylic acid cycle (TCA cycle). The partial least square (PLS) model built for prediction at harvest identified ACC, malonyl ACC (MACC), and dehydroascorbic acid (DHA): the oxidized form of ascorbate, as the best markers for defining initial fruit sensitivity to IBD. A clear relationship was also found between increases in succinate levels during the first two weeks of storage and the incidence and severity of IBD after storage. Collectively, the results presented in this work reinforce the idea that IBD is determined by initial fruit maturity. They also question the current dogma concerning ascorbate, suggesting that rather than ascorbate, the most reliable marker for sensibility at harvest is DHA. Our results also highlighted that increased succinate levels should be considered one of the earliest responses to damaging storage conditions and offer an interesting short-term marker for IBD. The paper discusses how succinate is regulated during storage in relation to IBD development and an explanatory model is presented.

AcbHLH144 transcription factor negatively regulates phenolic biosynthesis to modulate pineapple internal browning.

Internal browning (IB), a major physiological disorder of pineapples, usually happens in postharvest processes, but the underlying mechanism remains elusive. The bHLH transcription factors are involved in regulating various biological processes, but whether they could regulate tissue browning in fruit during storage remains unknown. Here we showed that the phenolic biosynthesis pathway was activated in pineapples showing IB following 9days of storage. AcbHLH144 expression was the highest of the 180 transcription factors identified, downregulated in pineapple with IB, and negatively correlated with the major phenolic biosynthetic genes. AcbHLH144 was shown to be localized in the nucleus and its transient overexpression in pineapples and overexpression in Arabidopsis decreased phenolic biosynthesis. The yeast one-hybrid assay and electrophoretic mobility shift assay showed that AcbHLH144 directly bound to the Ac4CL5 promoter and the dual-luciferase reporter assay showed that it inactivated Ac4CL5 transcription. These results strongly suggest AcbHLH144 as a repressor for phenolic biosynthesis. Abscisic acid (ABA) alleviated IB, reduced phenolic accumulation, and downregulated phenolic biosynthetic genes, including Ac4CL5. Transcriptomic analysis showed that AcbHLH144 was the most upregulated of all 39 bHLHs in response to ABA. ABA enhanced AcbHLH144 expression, reduced phenolic contents, and downregulated phenolic biosynthetic genes in pineapples transiently overexpressing AcbHLH144. Moreover, ABA enhanced enzyme activity of GUS driven by the AcbHLH144 promoter. These results showed that AcbHLH144 as a repressor for phenolic biosynthesis could be activated by ABA. Collectively, the work demonstrated that AcbHLH144 negatively regulated phenolic biosynthesis via inactivating Ac4CL5 transcription to modulate pineapple IB. The findings provide novel insight into the role of AcbHLH144 in modulating pineapple IB during postharvest processes.

Discrimination of internal browning in pineapple during storage based on changes in volatile compounds

Internal browning (IB) is a physiological disorder without external symptoms of postharvest pineapples, but whether and how IB influences pineapple volatiles remain unknown. We examined eigenvalues of volatiles in ‘Comte de Paris’ pineapples with or without IB using electronic nose (E-nose) and gas chromatography-mass spectrometry (GC–MS). Correlation coefficients between the responses of E-nose sensors S7 and S9 and IB were 0.836 and 0.804, respectively. The multilayer perceptron neural network and radial basis function neural network models classified IB degree with accuracy of 94.77% and 91.67%. GC–MS analysis revealed 30 volatile substances upregulated in pineapple with IB compared to those without, of which 15 were esters. IB regulated volatile compound synthesis through the lipoxygenase pathway which involved lipoxygenase, pyruvate decarboxylase 1, alcohol dehydrogenases, acyl-CoA oxidase 1, and alcohol acyltransferase genes and their related enzymes. These results suggested that volatiles regulated by IB could be used to discriminate IB severity in pineapples.

Effect of storage temperature transfer on the internal browning and other fruit qualities of GP3 and MD2 pineapple clones after postharvest applications of ABA, chitosan and decrowning

Changes in pineapple storage temperature accelerate the increase in internal browning (IB) incidence. This study aims for postharvest applications with changes in storage temperature affecting IB incidence and severity. This research was conducted on ‘GP3’ and ‘MD2’ pineapple clones when they were ripe for export. The experimental were a completely randomized design of storage temperatures (T1: at 7°C for 30 days and T2: at 7°C for 28 days followed by 16°C for 2 days), clones (‘GP3’ and ‘MD2’), decrownings (crown and crownless), and coatings [chitosan 1%, ABA 50mg/L, ABA+chitosan mixture, and control (H2O)]. The results showed that T2 had a significant effect on the increase IB incidence in ‘MD2’ and IB severity in ‘GP3’ compared to T1. Ascorbate acid decreased in ‘MD2’ stored at T2, but had no effect on ‘GP3’. Soluble solid content (SSC) of ‘MD2’ was higher than ‘GP3’. Titratable acidity (TA), SSC/TA ratio, and mold severity were not significantly affected by treatments. The T2 had a significant effect on fruit temperature (FT), with an increase of 2.77-2.88ºC. An increase in FT was positively correlated with maturity, fruit weight loss, and skin dehydration. During the 28 to 30 days of storage, the T2 treatment increased in ripeness by 81.25%.

Detection of Internal Browning Disorder in ‘Greensis’ Pears Using a Portable Non-Destructive Instrument

Internal browning caused by prolonged cold storage poses a significant challenge to the visual appearance and flavor of Asian pears, which are economically valuable and a primary fruit exported from Korea. To address this issue, we established a cost-effective portable non-destructive piece of testing instrument using visible and near-infrared spectroscopy, focusing on the detection and discrimination of internal browning in ‘Greensis’ pears. Our investigation underscores the challenge of visually confirming browning, necessitating alternative methods for accurate assessment. Through comprehensive analysis involving three to four segments of 32 ‘Greensis’ pears, a robust calibration equation was derived. By employing partial least square regression on the absorption spectra within a 650–950 nm range, we developed a predictive model for detecting and quantifying browning. Through principal component analysis, normal pears were distinctly segregated from those exhibiting browning symptoms (discrimination accuracy of 95%). Furthermore, we established that pears with a browning index of 25 ± 2.0 are highly susceptible to browning following extended cold storage. Consequently, our proposed portable non-destructive instrument serves as a pivotal tool for farmers and fruit distributors, enabling efficient and precise selection of high-quality pears in an instance. Overall, our study introduces a practical solution to a pressing issue in the Asian pear industry.

Identification and stability evaluation of polyphenol oxidase substrates of pineapple fruit

Pineapple as an important tropical fruit in the world is prone to internal browning (IB) caused by the oxidation of phenolic substances. To address the occurrence of IB, endogenous polyphenol oxidase (PPO) substrates were extracted, separated, and purified from pineapple fruit, and then four compounds were obtained and identified as catechin, epicatechin, chlorogenic acid and pyrocatechol. The contents of these substrates increased, reached the maximum value in the middle storage period, decreased gradually, and then maintained a relatively stable level by the end of storage. Meanwhile, pineapple PPO substrates were unstable in structure and susceptible to be degraded under the condition of light, high temperature (>40 °C), alkalinity (pH > 9) or metal ion (Ca2+, Cu2+, Fe2+, Pb2+ and Zn2+). Additionally, the presences of O2 and H2O2 increased the enzymatic oxidation of the pineapple PPO substrates, whereas CO2, N2, Vc (Vitamin C), l-cysteine, Na2SO3 and Na2S2O5 inhibited this oxidation.

Chilling-related browning of ‘Wonhwang’ pear cortex is associated with the alteration of minerals and metabolism

‘Wonhwang’ pear (Pyrus pyrifolia Nakai) is affected by a wide range of physiological disorders, especially internal browning (cortex browning) during long-term cold storage and subsequent shelf life. Postharvest fruit quality and metabolic changes of many Asian pears (P. pyrifolia) are well characterized, but little is known about the minerals and metabolites associated with internal browning induction and development in ‘Wonhwang’ pear during cold storage. The present study compares minerals and metabolites in cortex tissue of healthy fruit as well as symptomatic (browned) and sound tissues from fruit with internal browning that developed during long-term cold storage. P, K, Ca, sorbitol, shikimic acid, palmitic acid (C16:0), linoleic acid (C18:2), α-linolenic acid (C18:3), methionine, 1-hexenol, and (Z)-3-hexenal were lower in browned tissue than in healthy and sound tissues. In contrast, levels of glucose, fructose, fumaric acid, valine, leucine, isoleucine, lysine, phenolic compounds, lignoceric acid (C24:0), ethyl esters, and some volatile aldehydes were highest in browned tissue, compared with the other tissues. Many ethyl esters, aromatic amino acids, branched-chain amino acids, phenolic compounds, soluble solids content, fructose, and glucose were associated with internal browning. Furthermore, “tryptophan metabolism”, “arginine biosynthesis”, “alanine, aspartate, and glutamate metabolism”, “α-linolenic acid metabolism”, and “glycine, serine, and threonine metabolism” were the processes most impacted by internal browning. Overall, the largest metabolic differences appeared between damaged and asymptomatic cortex as several metabolic processes were influenced by internal browning.

Cinnamon essential oil vapor alleviates the reduction of aroma-related volatiles in cold-stored "Feicheng" peach using HS-GC-IMS.

"Feicheng" peach is popular for its unique aroma, but its defect of being highly sensitive to chilling injury (CI) often leads to aroma loss and internal browning. Essential oils (EOs) are often used to enhance the antioxidant capacity of plants and fruits, as well as to trigger their defense against biotic/abiotic stresses. This study aimed to examine the effect of cinnamon essential oil (CEO) vapor treatment on the aroma quality of peach fruit during cold storage using HS-GC-IMS. The results showed that 50 μL/L CEO vapor reduced the severity of internal browning (IB) in peaches at the stage of 7 ~ 21 d during refrigeration (Significantly, the L* value was higher and the IB index was lower than that of control, p < 0.05). Meanwhile, the evident reduction or loss of aroma content caused by CI was restored to a higher level than the control (p < 0.05). Furthermore, CEO treatment promoted the release of aroma-related volatiles as evidenced by more propyl acetate, and the dimer of amyl acetate, isoamyl acetate, butyl acetate detected than that on harvest day and no-treated group after 21 d of cold storage plus 2 d of shelf life. Genes of PpLOX1, PpLOX2, PpHPL1 and PpADH1 associated with aroma-related volatile biosynthesis revealed higher transcript abundance in peach fruits treated with CEO than the control (p < 0.05). Overall, our study demonstrated that CEO in vapor phase may be beneficial to alleviate the quality deterioration in aroma and flesh color of "Feicheng" peaches caused by CI, which lays a theoretical reference for maintaining postharvest quality of peach fruits.

Chitosan-based fruit coating as postharvest treatments on two pineapples (Ananas comosus L. Merr) clones

Production of fresh pineapple fruit is dominated by the MD2 clone, while the GP3 clone is used as canned fruit. To be promoted as fresh fruit, the GP3 has some defects, namely a less sweet taste and sensitivity to internal browning (IB) disorders. The clones need fruit coatings, and the two might get responded differently. This study aimed to study the effects of chitosan-based fruit coating mixed with palm stearin and Aloe vera gel on the fruit qualities of the two clones, as well as to seek the potential of the GP3 clone as a fresh fruit. The study used 2 x 4 factorials. The first factor was two clones (GP3 and MD2). The second factor was fruit coatings (control, chitosan, palm stearin + chitosan, and Aloe vera gel + chitosan). The fruits were stored at 7 °C. The results showed that the GP3 started to show the incidence of IB disorders on the 21st day, 2 weeks earlier than the MD2. The MD2 showed a °Brix of 16.82% and vitamin C of 391.45 mg/L, which were significantly higher than the GP3. Meanwhile, the GP3 showed 0.60% acidity, which was significantly higher than the MD2. These indicated that the GP3 should not be used for fresh fruit consumption, mainly because of its sensitivity to IB and lower sweetness compared to the MD2 clone. The chitosan treatment, which was added with Aloe vera or palm stearin, showed a higher vitamin C value than the other treatments.

Tissue structural analysis for internal browning sweet potatoes using magnetic resonance imaging and bio-electrochemical impedance spectroscopy

Occurrence of internal browning in sweet potato tuber has recently been confirmed, and its chemical and bacterial characteristics have been reported. However, the structural characteristics of such tissues are unknown. We investigated the tissue structural characteristics inside a browning sweet potato through magnetic resonance imaging (MRI) and bio-electrochemical impedance spectroscopy (BIS) and the relationship was discussed. The high-resolution proton density-weighted (PDW) and proton spin–spin relaxation time (T2)-weighted (T2W) images of cutting out samples obtained from micro-imaging revealed changes in the physical structure surrounding the browning tissues. The T2 distribution maps of the same browning samples assumed the changes in the water distribution and water mobility, which generally changes under the influence of solutes, such as metabolites, starch, protein, and metal ions. BIS further confirmed the variation in the distribution of electrolytes in the tissues. MRI may provide a non-destructive assessment of the internal browning of whole sweet potatoes.

EjCML19 and EjWRKY7 synergistically function in calcium chloride-alleviated chilling injury of loquat fruit

The regulatory function of calcium chloride (CaCl2) in chilling injury (CI) has been proven in loquat fruit. Nevertheless, its physiological and molecular mechanisms are relatively still unclear. In this work, the CaCl2 treatment reduced the CI in loquat fruit, with a lower internal browning index, firmness, and higher extractable juice in comparison with the control. Moreover, CaCl2 application impacted the contents of phenolic acids in cold-stored loquat fruit. Transcriptome analysis identified a total of 5416 differently expressed genes (DEGs), and the key DEGs were enriched in many metabolic pathways, including phenylpropanoid biosynthesis, biosynthesis of secondary metabolites, plant hormone signal transduction, phenylalanine metabolism, membrane lipid degradation, starch and sucrose metabolism. The fold change and the expression intensity of EjCML19 and EjWRKY7 in loquat fruit during cold storage were higher, and EjCML19 could interact with EjWRKY7 in yeast cells. The qRT-PCR analysis found that CaCl2 induced the transcription of EjCML19 and EjWRKY7 but down-regulated browning-related genes EjRBOHC and EjPPO in loquat fruit. The genes (EjRBOHC and EjPPO) contain W-box elements in their promoters, implying that they might be target genes of EjWRKY7. Therefore, EjCML19 and EjWRKY7 were selected and cloned from loquat fruit to explore their regulatory role of EjRBOHC and EjPPO. Further investigation revealed that EjWRKY7 negatively modulated the expression of EjRBOHC and EjPPO by binding to their promoters. EjCML19 enhanced EjWRKY7-mediated transcriptional repression of EjPPO in loquat fruit under cold stress. Taken together, EjCML19 and EjWRKY7 synergistically regulated the transcription of browning-related genes, which functioned a positive role in CaCl2-alleviated chilling injury in loquat fruit under refrigeration.

Exogenous inoculation of endophyte Penicillium sp. alleviated pineapple internal browning during storage

Pineapple is ranked sixth in terms of global fruit production and the most traded tropical fruit worldwide. Internal browning (IB), a physiological disorder of pineapple fruit after harvest, limits the export and industry development of pineapple. Evidence confirmed that endophyte played a pivotal role in plant disease. This study investigated the relationship between endophyte fungi community structure, population abundance in healthy and IB pineapple fruit; as well as the effect of endophyte Penicillium sp. inoculation on pineapple IB. Intended to explore a new effective measure for controlling IB and reducing postharvest losses in pineapple by an economical and environmentally friendly approach. We found the abundance of endophyte fungi in healthy pineapple fruit was different from that in IB fruit by high-throughput sequencing. The results emphasized that the endophyte Penicillium sp. inoculation dramatically alleviated pineapple IB intensity and severity, delayed crown withering and fruit yellowing, and maintained the exterior quality traits during the postharvest period at 20 °C. Penicillium sp. retarded H2O2 accumulation and increased the total phenols level in pineapple. Application of Penicillium sp. also maintained the higher antioxidant capacity by increasing antioxidant enzyme activity and ascorbic acids levels, regulated of the homeostasis of endogenous hormones, and increased the abundance of Penicillium sp. in the fruit. In summary, Penicillium sp. retarded the occurrence of IB and enhanced the storability of pineapple at postharvest, and this economical and environmentally friendly technology is convenient to spread in agriculture.

ABA and GA3 differentially regulate pineapple internal browning through modulating spermidine metabolism

Spermidine is one of the secondary metabolites (SM) related to plant tissue browning caused by chilling, but whether it plays a role in pineapple internal browning (IB) occurred at ambient temperature remains unknown. In this study, pineapples affected by severe IB after 9-d storage showed dramatic changes in SMs, with 94.94% of 79 being upregulated. Among the 4 downregulated were spermidine. Exogenous abscisic acid (ABA) suppressed and gibberellin (GA3) aggravated IB and they differentially regulated SMs and spermidine. Compared with the control, ABA downregulated 65 of 70 SMs and upregulated spermidine, while GA3 upregulated 7 of 24 SMs and did not obviously affect spermidine. Exogenous spermidine alleviated IB, confirming the role of spermidine in regulating IB. ABA upregulated spermidine biosynthesis genes AcARG1 and AcSPDS, while GA3 upregulated AcPAO2. ABA downregulated and GA3 upregulated SAM, ACS and ACO. ABA reduced 1-aminocyclopropane 1-Carboxylate (ACC) and GA3 did not. ABA upregulated NCED, ABA2 and AAO3 and increased endogenous ABA, while GA3 showed opposite effects. Collectively, the findings indicate spermidine play an important role in regulating IB of pineapple. Moreover, this work may provide novel insight into the mechanism underlying interactions of spermidine with ABA and GA in regulating quality of harvested fruit.

Impacts of dynamic controlled atmosphere and temperature on physiological disorder incidences, fruit quality and the volatile profile of 'Braeburn' apples

DCA-CD Plus is a novel dynamic storage technology that determines both the optimum oxygen partial pressures (pO2) and room temperatures for the storage of apples, based on monitoring the fruit CO2 production (CD). This study evaluated the effects of DCA-CD Plus on the physiological disorder incidences, fruit quality and the volatile profile of ‘Braeburn’ apples after eight months of storage and seven days shelf life. This was achieved by comparison to storage under regular atmosphere (RA), controlled atmosphere (CA, 1.3 kPa O2) and one-factor dynamic controlled atmosphere (DCA-CD, dynamic oxygen), while incorporating the influence of 1-methylcyclopropene (1-MCP). RA-stored fruit had the highest respiration rate and ethylene production and the lowest flesh firmness, while CA, DCA treatments and 1-MCP application slowed down fruit ripening. 1-MCP application increased browning and cavity symptoms in ‘Braeburn’ apples. Storage under DCA-CD and DCA-CD Plus resulted in lower browning incidences than RA or static CA treatments. Dynamic storage temperatures in DCA-CD Plus did not accelerate fruit ripening but showed no effect on the development of physiological disorders. Most volatile organic compounds showed a negative response to low pO2 and 1-MCP application, as the highest levels of key alcohols and esters were measured in RA. Storage under DCA conditions and RA correlated with increased levels of anaerobic metabolites. No correlation between internal browning symptoms and specific alterations in the volatile profile could be detected.

Influence of different origins, CA storage conditions and storage times on internal browning in apple and pear cultivars

Influence of different origins, CA storage conditions and storage times on internal browning in apple and pear cultivars

Comparative Effect of Melatonin and 1-Methylcyclopropene Postharvest Applications for Extending ‘Hayward’ Kiwifruit Storage Life

Kiwifruit, like many other fruits, is susceptible to dehydration, leading to texture changes and a loss of flavour during storage. Exposing kiwifruit to suboptimal temperatures can control these changes but can cause internal browning. Postharvest treatments with substances such as 1-methylcyclopropene (1-MCP) are some of the most successful commercial technologies in the conservation of fruits and vegetables. In recent years, there has been a growing interest among researchers in alternative technologies based in postharvest treatments with plant growth regulators. In this sense, melatonin (MT) has been shown to improve fruit quality, extending shelf life. The aim of this study was to compare these two different technologies applied at postharvest to evaluate the impact on kiwifruit quality. Optimal 1-MCP fumigations and MT solutions were assayed on ‘Hayward’ kiwifruit under similar conditions. Quality parameters were evaluated at 14-day intervals during 84 days of cold storage plus 5 days at 20 °C. The results showed that both treatments were similarly effective in maintaining quality parameters such as weight loss, respiration, firmness, and acidity. Although 1-MCP treatments delayed the evolution of kiwifruit colour and chlorophyll degradation as compared to MT, MT treatments controlled chilling injury better than 1-MCP. This effect was not related to a greater cell membrane integrity since fruit batches treated with 1-MCP were the ones that showed the lowest electrolyte leakage level. In conclusion, both treatments maintained fruit quality and delayed ripening in a similar way. In this sense, the results suggest that MT immersion treatments could act as efficient delaying senescence as fumigations with 1-MCP maintaining kiwifruit quality during refrigerated storage.

Synthetic data for X-ray CT of healthy and disordered pear fruit using deep learning

Over the last years, deep learning (DL) models have led to an enormous breakthrough in a wide range of computer vision tasks, including the classification and quantification of internal defects in fruit using X-ray CT images. However, developing these models typically requires large annotated datasets. Obtaining such datasets faces multiple challenges as the availability of defect fruit is unpredictable and it is unclear whether the disordered fruit in the dataset are representative of all possible defects. This work proposes a method to circumvent these problems by generating synthetic CT images using a conditional Generative Adversarial Network (cGAN) that learns the underlying distribution of gray values for different classes (“healthy tissue”, “internal browning”, “background, core and cavities”) in manually annotated images of pear fruit. The performance of the predictor was evaluated by quantitative metrics and visual inspection. To generate new synthetic data, operations are suggested and tested on annotated data to create as much variation as possible in the generated pears. The Fréchet Inception Distance (FID) and visual observations showed that the cGAN was effective in image-to-image translation, generating CT images of both healthy and disordered fruit based on their annotations. The best performing model obtained a low FID score of 10.2 and produced detailed visual features in the synthetic CT data, such as vascular bundles. The high potential and broad applicability was further demonstrated on augmented image annotations for generating new healthy and disordered pears with different appearances of defects. The proposed method can be used to produce additional training data when datasets are limited and laborious to manually annotate. Furthermore, the robustness of other DL models might increase by including new synthetic samples with a high variety of disorders during training.

Impact of exogenous pre and postharvest salicylic acid applications on MD2 pineapple quality

Salicylic acid (SA) is a natural plant compound that has been proven to enhance the quality of fruits; therefore, its impact on pineapple should be further studied, especially in the most marketable hybrids. This study aimed to evaluate the effect of SA treatments on MD2 pineapple quality. The experiment consisted of two parts with applications pre and postharvest following the next treatments, control: No use of SA, and 5, 7 and 9 mM of SA. The total soluble solids, total acidity, ascorbic acid content, respiration rate, together with the severity and incidence of internal browning and flesh translucency were determined, after 40 days of cold storage. The treatment using 9 mM of SA in pre and postharvest delivered the best results, having the most elevated ascorbic acid (526.75 mg kg-1) and total acidity (0.8%), the lowest severity and incidence outcomes of internal browning and flesh translucency (0% in both cases), with the most reduced respiration rate values during postharvest. In conclusion, SA treatments with concentrations of 9 mM applied in pre and postharvest on MD2 pineapple can improve its quality after 40 days of cold storage.

Phytophthora pseudocryptogea, P. nicotianae and P. multivora Associated to Cycas revoluta: First Report Worldwide.

A dieback was observed on three-year-old pot-grown plants of Cycas revoluta in Sicily (Italy). Symptoms, including stunting, yellowing and blight of the leaf crown, root rot and internal browning and decay of the basal stem, closely resembled the Phytophthora root and crown rot syndrome, common in other ornamentals. Isolations from rotten stem and roots, using a selective medium, and from rhizosphere soil of symptomatic plants, using leaf baiting, yielded three Phytophthora species, P. multivora, P. nicotianae and P. pseudocryptogea, were obtained. Isolates were identified by both morphological characters and DNA barcoding analysis, using three gene regions: ITS, β-tub and COI. Phytophthora pseudocryptogea was the sole species isolated directly from the stem and roots. The pathogenicity of the isolates of the three Phytophthora species was tested on one-year-old potted plants of C. revoluta, using both stem inoculation by wounding, and root inoculation through infested soil. Phytophthora pseudocryptogea was the most virulent and, like P. nicotianae, reproduced all the symptoms of natural infections, while P. multivora was the least virulent and induced solely very mild symptoms. Phytophthora pseudocryptogea was identified as the causal agent of the decline of C. revoluta, as it was re-isolated from both the roots and stems of artificially infected symptomatic plants, thus fulfilling Koch's postulates.

Pineapple responses to postharvest applications of ABA, chitosan, and decrowning on the severity of internal browning and other fruit qualities

The shelf life of pineapple is significantly influenced by storage temperature and can be prolonged by maintaining an optimal temperature range of 5-12°C. However, there is still the problem of internal browning (IB) in the long-term storing of fresh harvest at cold temperatures. Postharvest application of 380 µM ABA (Abscisic Acid) to the crown, which is a source of ABA endogenous was found to suppress IB, while the concentration of 95 µM was not effective. Therefore, this research aimed to determine the response of GP3 and MD2 clones to postharvest treatment with the application of 50 mg/L ABA, chitosan and decrowning on the IB severity and other fruit qualities. The experimental design used a Completely Randomized Design with 3 factors of clone (GP3 and MD2), decrowning (crown and crownless), and fruit coating [chitosan 1%, ABA 50 mg/L, ABA + chitosan mix, and control (H2O)]. The fruits were kept at 7oC and observed at 0, 3, 6, 9, 16, 23, 30, and 37 days. The results showed that MD2 was significantly lower IB than GP3 and IB severity negatively correlated with ascorbic acid (AsA) content. MD2 had lower fruit weight loss (FWL) and skin dehydration (SD), higher AsA, soluble solid content (SSC), and SSC/titratable acidity (STA) ratios compared to GP3. The crown + ABA treatment decreased the IB severity of GP3, with a level of 0.75% after 37 days which was lower than crown + H2O by 9.17% and crownless + H2O by 8.42%. ABA treatment also showed higher SD and FWL, while AsA, SSC, TA, and STA were not different from the control.