Fruit Disease Research Articles

Intracellular and mitochondrial proteomic analysis reveals antifungal mechanisms of borate on mango black spot pathogen Alternaria alternata

AbstractBoron, in the form of potassium tetraborate, has previously been found to be effective at inhibiting mango black spot disease, caused by Alternaria alternata. However, the mechanisms involved in this inhibition are largely unknown. In this study, A. alternata was treated in vitro with potassium tetraborate at a concentration of 5–10 mM for 48 or 72 h. The intracellular and mitochondrial proteins were extracted from mycelium and separated using two‐dimensional electrophoresis (2‐DE). Differentially expressed proteins (DEPs) were identified using bioinformatics tools and differences between protein spots were derived from mass spectrometry (MS). Using matrix‐assisted laser desorption ionization time‐of‐flight tandem mass spectrometry (MALDI‐ToF‐MS/MS), 96 intracellular and 56 mitochondrial DEPs were identified. The intracellular proteins identified were found to be involved in posttranslational modifications, protein turnover and chaperones, while the mitochondrial proteins were involved in electron transport chains. Our results demonstrate that various metabolic pathways are involved in the antifungal activity of boron. The differential expression of 20 genes was also verified at the mRNA level by reverse transcription‐quantitative PCR. Our study suggests that borate could be used as a potential substitute for synthetic fungicides to control this postharvest disease of mango fruits.

Realistic simulation of fruit mildew diseases: Skin discoloration, fungus growth and volume shrinkage

Time-varying effects simulation plays a critical role in computer graphics. Fruit diseases are typical time-varying phenomena. Due to the biological complexity, the existing methods fail to represent the biodiversity and biological law of symptoms. To this end, this paper proposes a biology-aware, physically-based framework that respects biological knowledge for realistic simulation of fruit mildew diseases. The simulated symptoms include skin discoloration, fungus growth, and volume shrinkage. Specifically, we take advantage of both the zero-order kinetic model and reaction–diffusion model to represent the complex fruit skin discoloration related to skin biological characteristics. To reproduce 3D mildew growth, we employ the Poisson-disk sampling technique and propose a template model instancing method. One can flexibly change hyphal template models to characterize the fungal biological diversity. To model the fruit’s biological structure, we fill the fruit mesh interior with particles in a biologically-based arrangement. Based on this structure, we propose a turgor pressure and a Lennard-Jones force-based adaptive mass–spring system to simulate the fruit shrinkage in a biological manner. Experiments verified that the proposed framework can effectively simulate mildew diseases, including gray mold, powdery mildew, and downy mildew. Our results are visually compelling and close to the ground truth. Both quantitative and qualitative experiments validated the proposed method.

An efficient convolutional neural network-based diagnosis system for citrus fruit diseases.

Introduction: Fruit diseases have a serious impact on fruit production, causing a significant drop in economic returns from agricultural products. Due to its excellent performance, deep learning is widely used for disease identification and severity diagnosis of crops. This paper focuses on leveraging the high-latitude feature extraction capability of deep convolutional neural networks to improve classification performance. Methods: The proposed neural network is formed by combining the Inception module with the current state-of-the-art EfficientNetV2 for better multi-scale feature extraction and disease identification of citrus fruits. The VGG is used to replace the U-Net backbone to enhance the segmentation performance of the network. Results: Compared to existing networks, the proposed method achieved recognition accuracy of over 95%. In addition, the accuracies of the segmentation models were compared. VGG-U-Net, a network generated by replacing the backbone of U-Net with VGG, is found to have the best segmentation performance with an accuracy of 87.66%. This method is most suitable for diagnosing the severity level of citrus fruit diseases. In the meantime, transfer learning is applied to improve the training cycle of the network model, both in the detection and severity diagnosis phases of the disease. Discussion: The results of the comparison experiments reveal that the proposed method is effective in identifying and diagnosing the severity of citrus fruit diseases identification.

Uncovering genetic and metabolite markers associated with resistance against anthracnose fruit rot in northern highbush blueberry.

Anthracnose fruit rot (AFR), caused by the fungal pathogen Colletotrichum fioriniae, is among the most destructive and widespread fruit disease of blueberry, impacting both yield and overall fruit quality. Blueberry cultivars have highly variable resistance against AFR. To date, this pathogen is largely controlled by applying various fungicides; thus, a more cost-effective and environmentally conscious solution for AFR is needed. Here we report three quantitative trait loci associated with AFR resistance in northern highbush blueberry (Vaccinium corymbosum). Candidate genes within these genomic regions are associated with the biosynthesis of flavonoids (e.g. anthocyanins) and resistance against pathogens. Furthermore, we examined gene expression changes in fruits following inoculation with Colletotrichum in a resistant cultivar, which revealed an enrichment of significantly differentially expressed genes associated with certain specialized metabolic pathways (e.g. flavonol biosynthesis) and pathogen resistance. Using non-targeted metabolite profiling, we identified a flavonol glycoside with properties consistent with a quercetin rhamnoside as a compound exhibiting significant abundance differences among the most resistant and susceptible individuals from the genetic mapping population. Further analysis revealed that this compound exhibits significant abundance differences among the most resistant and susceptible individuals when analyzed as two groups. However, individuals within each group displayed considerable overlapping variation in this compound, suggesting that its abundance may only be partially associated with resistance against C. fioriniae. These findings should serve as a powerful resource that will enable breeding programs to more easily develop new cultivars with superior resistance to AFR and as the basis of future research studies.

Combined application of oligochitosan and Pichia carrbbica improves the disease resistance of postharvest tomato fruits

Our previous study showed that postharvest treatment of tomato with Pichia caribbica along with oligochitosan (OCH) significantly alleviated postharvest black spot of tomato fruit compared with P. caribbica alone. This study was to explore the effect of combined application of OCH and P. caribbica on disease resistance of tomato fruits through analyzing the activities of disease resistance-related enzymes, as well as transcriptome analysis of the fruit gene expression. Our findings indicated that P. caribbica, together with OCH, improved the activities of key enzymes associated with disease resistance in tomato fruit. Moreover, the combined application further upregulated the expression of genes involved in α-linolenic acid metabolism, the signal transduction pathways such as Ca2+, MAPK and plant hormone signaling pathways, resistant substance synthesis, and ROS metabolism, which improved the fruit disease resistance. Considering the significance of these results, OCH hold great potential for use in microbial biocontrol strategies against postharvest tomato diseases.

Development of a novel 1-octen-3-ol-loaded agar/curdlan hydrogel for inhibiting peach fruit diseases

Our previous study found that 1-octen-3-ol fumigation treatment could effectively induce the resistance of peach fruit diseases. However, 1-octen-3-ol is a liquid fumigant, which is not conducive to storage and application. Herein, the gel of 1 % agar compound with 1 % curdlan was used as a novel material for covering 1-octen-3-ol. The interaction of agar and curdlan was promoted by adding 1-octen-3-ol, leading to a higher thermostability compared to single-component antibacterial gels. Moreover, 1-octen-3-ol resulted in changes in the internal structure and mechanical properties of gel to form a pore-like structure, which is beneficial to the retention and release of 1-octen-3-ol. Additionally, the 2 % agar gel containing 1-octen-3-ol had the best inhibitory effect on the mycelial growth of Monilinia fructicola and Rhizopus stolonifer in vitro, and the compound hydrogel of 1 % agar and 1 % curdlan with 1-octen-3-ol could most effectively inhibit brown rot and soft rot caused by these two pathogens in vivo. Overall, the data indicated that the novel 1-octen-3-ol-loaded agar/curdlan hydrogels could effectively retain and release 1-octen-3-ol, and induce the resistance of peach fruit diseases.

First report of stem-end rot caused by Botryosphaeria fabicerciana on mango fruits in China.

Mango (Mangifera indica L.), belongs to the family Anacardiacea, and is one of the most popular tropical fruits in the world. Stem-end rot is a major postharvest disease of mango fruit, causing severe losses during storage in China (Chen et al., 2015). In July 2021, the mango fruits harvested from Baise Municipal National Agricultural Science and Technology Park (23.683568 N, 106.986325 E) of Guangxi province in China developed stem-end rot during storage. The disease incidence reached ca. 8.3%. The initial symptoms appeared as light brown lesions surrounding the peduncle, which quickly expanded becoming large dark-brown lesions. Small pieces of epidermis (5 mm × 5 mm) from 8 typical diseased friuts were cut from the edges of lesions surface-sterilized with 2% sodium hypochlorite and rinsed with sterile distilled water. The tissue was plated on potato dextrose agar (PDA) and incubated at 28 ℃ in the dark for 3 days. Fifteen, similarcolonies were isolated from the symptomatic tissue. The representative isolates DF-1, DF-2 and DF-3 were selected for morphological characterization, molecular identification, and pathogenicity testing. The colonies were circular with fluffy aerial mycelium, initially white turning to smoke-gray from the center in upper side and greenish black in reverse side, covering the 90 mm diameter Petri dish after 4 days of incubationon PDAat 28 ℃in dark. Pycnidia were produced on the surface of the colony after 30 days. Conidia were fusiform, aseptate, hyaline, thin-walled with granular contents, apex sub-obtuse, base subtruncate to bluntly rounded, 14.0-20.3 (16.8±1.6) μm × 3.1-7.2 (5.1±0.9) μm (n=50). The sexual stage was absent. Based on morphology, isolates were preliminarilyidentified asBotryosphaeriaspeices.To accurately identify the pathogen, genomic DNA was extracted from the mycelium of the three isolates DF-1, DF-2 and DF-3. The internal transcribed spacer of rDNA region (ITS), elongation factor 1-alpha (EF-1α) and beta-tubulin gene (TUB) genes were amplified using primers ITS1/ITS4, EF1-728F/EF1-986R and Bt2a/Bt2b, respectively (Slippers et al., 2004). The nucleotide sequences were all deposited in GenBank (ITS: OP729176-OP729178 EF-1α: OP758194-OP758196 and TUB: OP758197-OP758199). Based on the BLASTn analysis, the ITS, EF1-α and TUB sequences of three isolates were 100%, 99% and 99% similar to the Botryosphaeria fabicerciana MFLUCC 10-0098 sequences (ITS: JX646789, EF-1α: JX646854 and TUB: JX646839). Multi-locus phylogenetic analyses (ITS, EF-1α and TUB) showed that the isolate DF-1, DF-2 and DF-3 were clustered within Botryosphaeria fabicerciana clade based on the maximum likelihood , Bayesian inference, and maximum parsimony methods. The pathogenicity test was performed by placing discs mycelium around the peduncle of mature mango fruits by pin-prick method. Each treatment carried out with 12 fruits. The inoculated fruits were placed in plastic boxes at 28 ℃ with three replicates. Three days after inoculation, typical symptoms of stem-end rot were observed. The control fruits were inoculated with sterile PDA discs, and remained symptomless. The same fungus was re-isolated from the symptomatic tissue to complete Koch's postulate. Botryosphaeria fabicerciana (basionym: Fusicoccum fabicercianum) was first reported as pathogen causing senescent twig of Eucalyptus spp. in China (Chen et al., 2011; Phillips et al., 2013). To our knowledge, this is the first report of Botryosphaeria fabicerciana causing stem-end rot of Mangifera indica in China.

A Review on Bio-Based Control of Post-Harvest Diseases

Bacillus subtilis non-pathogenic beneficial bacteria, promotes plant growth, disease resistance and tolerance to abiotic stresses. It produces bioactive substances with antibiotic properties and induces physiological features in plant metabolism without adverse effects on the environment or human health. Bacillus subtilis has been used to treat various postharvest diseases during handling, transportation and storage of various fresh fruits and vegetables. It is the first microorganism patented as a postharvest bio control agent for Brown rot of stone fruits, improving the post-harvest physiology of various fruit/vegetables. Bacillus strains AG1 and H110 have been shown to be effective against Vine wood fungal pathogens and post-harvest pathogens. They have been shown to reduce symptoms of Anthracnose in fruit caused by fungal pathogens Colletotrichum gloeosporioides and C. acutatum and White rot caused by Botryosphaeria dothidea. Endophytic Bacillus strains have been developed that can colonize plant tissues and live in the same ecological niches as pathogens, thus preventing post-harvest diseases and improving preservation during storage. Bacillus strains induce auxins, cytokinins, gibberellins, ABA, JA and SA in plants, which can stimulate plant growth under stressful conditions. Endophytic bacteria can induce ISR against pathogens and abiotic stressors, extending the shelf life of stored fruits and vegetables. Microbial antagonists can be applied after harvest to control fruit and vegetable diseases, but a single microbial strain cannot prevent all fruits/vegetables from decaying during storage. Combining diverse antagonistic microorganisms with diverse microbial activity and combining various bio-controlling characteristics can prevent post-harvest decay on fruits/vegetables.

Regioselective Claisen-Schmidt Adduct of 2-Undecanone from Houttuynia cordata Thunb as Insecticide/Repellent against Solenopsis invicta and Repositioning Plant Fungicides against Colletotrichum fragariae.

The U.S. Department of Agriculture (USDA) has established research programs to fight the phytopathogen Colletotrichum fragariae and the invasive red imported fire ant, Solenopsis invicta. C. fragariae is known to cause anthracnose disease in fruits and vegetables, while S. invicta is known for its aggressive behavior and painful stings and for being the cause of significant damage to crops, as well as harm to humans and animals. Many plants have been studied for potential activity against C. fragariae and S. invicta. Among the studied plants, Houttuynia cordata Thunb has been shown to contain 2-undecanone, which h is known for its antifungal activity against Colletotrichum gloesporioides. Based on the mean amount of sand removed, 2-undecanone showed significant repellency at 62.5 µg/g, similar to DEET (N,N-diethyl-meta-toluamide), against S. invicta. The 2-Undecanone with an LC50 of 44.59 µg/g showed toxicity against S. invicta workers. However, neither H. cordata extract nor 2-undecanone had shown activity against C. fragariae despite their known activity against C. gloesporioides, which in turn motivates us in repositioning 2-undecanone as a selected candidate for a Claisen-Schmidt condensation that enables access to several analogs (2a-f). Among the prepared analogs, (E)-1-(3-methylbenzo[b]thiophen-2-yl)dodec-1-en-3-one (2b) and (E)-1-(5-bromothiophen-2-yl)dodec-1-en-3-one (2f) showed promising activity against C. fragariae, revealing a distinctive structural activity relationship (SAR). The generated analogs revealed a clear regioselectivity pattern through forming the C=C alkene bond at position C-1. These data open the window for further lead optimization and product development in the context of managing C. fragariae and S. invicta.

Fusarium equiseti as the pathogen causing stem rot disease of red-fleshed dragon fruit (Hylocereus polyrhizus) in India

Dragon fruit (red skin and red fleshed, Hylocereus polyrhizus), newly introduced cactus plant in Mizoram, India, exhibited stem rot (35.38%) disease in established orchards during 2017–2018. Recorded symptoms included small red-brown spots encircled with yellowish halos. The size of the spots gradually enlarged and later the tissues turned completely watery and rotten. Fusarium species were consistently isolated from the stem rot tissues of red-fleshed dragon fruit. The pathogen associated with the stem rot disease was identified as Fusarium equiseti based on the morphological characters (production of abundant macroconidia, single-celled microconidia, and solitary and intercalary chlamydospores) and multigene phylogenetic analysis of internal transcribed spacer of ribosomal DNA (ITS-rDNA), translation elongation factor 1α (TEF-1) and beta-tubulin (TUB2). The phylogenetic trees showed that all isolates belonged to the F. equiseti, a member of Fusarium incarnatum-equiseti species complex (FIESC). Four isolates were tested for pathogenicity that produced the symptoms of stem rots (up to 57.64% severity) at 15 days after inoculation. Koch's postulate was further established by re-isolating the F. equiseti from artificially infected plants. To our best knowledge, this is the first report of F. equiseti as a pathogen causing the stem rot of dragon fruit (red-fleshed) in India.

Respiratory and energy metabolisms participate in the disease occurrence of fresh Chinese olive caused by Pestalotiopsis microspora

Pestalotiopsis microspora (P. microspore) is the primary pathogen causing postharvest rot and spoilage in Chinese olive (Canarium album L.). This study investigated P. microspore-induced disease development in postharvest Chinese olives in relation to respiratory and energy metabolism. Results suggested that P. microspore-inoculated Chinese olives had higher fruit disease index, fruit disease diameter, and fruit respiration rate, but a lower energy charge. Furthermore, P. microspore-inoculated Chinese olives displayed higher respiratory metabolism-related enzymes (RMREs) activities, higher levels of NAD(H), and lower levels of NADP(H). Additionally, P. microspore-inoculated Chinese olives had lower ATPase activities, as well as lower ATP and ADP contents but higher AMP content. These findings suggest that P. microspore infection exacerbates disease development in postharvest Chinese olives by increasing respiration metabolism and causing energy deficiency.

Antifungal Activity of Cell-Free Supernatants from Lactobacillus pentosus 86 against Alternaria gaisen

Alternaria gaisen is one of the main fungi that cause fruit postharvest diseases due to its wide contamination and toxin production. The application of lactic acid bacteria shows great industrial application as a natural food preserver due to the advantages of being safe and non-toxic. In order to obtain a natural preservative against this fungus, this study aimed to evaluate the effectiveness of cell- free supernatants (CFS) produced by Lactobacillus pentosus 86 as antimicrobials in vitro against A. gaisen. Results indicated that CFS displayed excellent thermostability and enzymatic stabilities with an antifungal activity over 85%. Under thermal (40–100 °C) treatments, different protease solution and acidic conditions (pH 2–4), the antifungal activity of CFS maintained up 80%. However, when the pH reached 6, its antifungal ability completely disappeared. CFS inhibited mycelial growth of A. gaisen by destroying the hyphae membrane, leading to the leakage of nucleic acids and proteins, and hyphae collapsed and shriveled. CFS also changed the spore’s morphology, resulting in cell membrane damage, intracellular leakage, and organelles aggregation. The increase of cell membrane permeability of spores caused a 30% mortality rate. Therefore, the CFS of L. pentosus 86 has the potential for controlling fruit diseases caused by A. gaisen.

CsAP2L transcription factor regulates resistance of citrus fruit to Penicillium digitatum through lignin biosynthesis and ROS metabolism pathways

Green mold, caused by Penicillium digitatum (P. digitatum), is a major cause of post-harvest economic losses in citrus fruit. AP2 transcription factors are associated with growth stress in plants, however, their role in non-model crops like citrus fruit has been little studied. Therefore, this study aims to investigate the function of CsAP2L, which has been discovered and found in the nucleus. We find that CsAP2L can enhance resistance to green mold by using Agrobacterium-mediated transient overexpression in citrus fruit. Meanwhile, it is shown by RT-qPCR, electrophoretic mobility shift assay (EMSA), yeast one hybrid (Y1H) and dual luciferase reporter (DLR) experiments show that CsAP2L can activate the expression of disease resistance genes (CsCOMT1L, CsPOD and CsSOD4A) and repress the transcription of Cs4CL9 and CsSOD4AP. Furthermore, CsAP2L not only can promote the accumulation of lignin content but also can keep ROS in balance. In summary, CsAP2L enhances fruit resistance by regulating disease resistance genes in lignin biosynthesis and ROS metabolism pathways. This study provides new insights into the mechanism of fruit disease resistance.

Hydroxypropyl Methylcellulose and Gum Arabic Composite Edible Coatings Amended with Geraniol to Control Postharvest Brown Rot and Maintain Quality of Cold-Stored Plums.

In this study, the effect of hydroxypropyl methylcellulose (HPMC) and gum Arabic (GA) edible coatings amended with 0.2% geraniol (GE) were evaluated for the control of brown rot, caused by Monilinia fructicola, on artificially inoculated plums (Prunus salicina Lindl., cv. Angeleno) stored for 5 weeks at 1 °C. Brown rot is the most important pre- and postharvest fungal disease of stone fruits, causing severe economic losses worldwide. Geraniol is an important constituent of many essential oils that can be obtained as a byproduct from different industrial procedures, such as those of the juice industry. Fruit postharvest quality was also evaluated after 5 and 8 weeks of storage at 1 °C, followed by 3 days at 7 °C plus 5 days at 20 °C, simulating packinghouse, transport, and retail shelf-life conditions, respectively. HPMC coatings containing 0.2% GE reduced the incidence and severity of brown rot by 37.5 and 64.8%, respectively, compared to uncoated fruit after 5 weeks of storage at 1 °C. HPMC-coated plums, with and without GE, showed the highest level of firmness, the lowest change in external peel color parameters (L*, a*, b*, C*, hue), and the lowest flesh bleeding compared to uncoated control and GA-coated samples throughout the entire storage period, which correlated with a higher gas barrier of these coatings without negatively affecting sensory quality. Furthermore, the HPMC-0.2% GE coating provided the highest gloss to coated plums, showing the potential of this coating as a safe and environmentally friendly alternative to conventional fungicides and waxes for brown rot control and quality maintenance of cold-stored plums.

(E)-2-Octenal suppresses the growth of a prochloraz-resistant Penicillium italicum strain and its potential antifungal mechanisms

Blue mold caused by Penicillium italicum is one of the most devastating postharvest diseases in Citrus fruit. This work aims to determine the antifungal potential of (E)-2-octenal, a component of plant essential oil, on the mycelial growth and disease incidence of a prochloraz-resistant strain of P. italicum isolated from an orchard in Luxi, Hunan Province, China. An in vitro assay revealed that the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of (E)-2-octenal were 0.25 and 0.50 mL L−1, respectively. An in vivo assay showed that wax + 4 × MFC (E)-2-octenal treatment could reduce the blue mold incidence in Ponkan fruit inoculated with P. italicum without impairing fruit quality. Scanning electron microscopy analysis illustrated that the mycelia of P. italicum were anomalously twisted and shrunken upon treatment with (E)-2-octenal. The primary antifungal targets were attributed to the cell membrane instead of the cell wall based on propidium iodide and calcofluor white staining results. In addition, (E)-2-octenal induced massive accumulation of reactive oxygen species in hyphae in a dose-dependent manner, leading to oxidative stress and dysfunction of energy and respiration metabolism. At the same time, the activities of phosphofructokinase (PFK) and pyruvate kinase (PK) were decreased in (E)-2-octenal-treated samples. Taken together, our present study suggested that (E)-2-octenal could exert its antifungal activity against P. italicum by damaging the function of mitochondria and may be a potential antifungal substance for an alternative to chemical fungicides.

Bacteriostasis of bacillus sp. 22T against penicillium expansum and comparison between its ability on pear and grape

In the biological lab of Zhejiang University, we justified and tested a type of bacillus to improve the anti-bacteria ability of commonly affecting diseases of fruits, such as pear and grape, which would lead to a large amount of economic loss and unpredictable negative influence if they were rotten before being sold. Using techniques such as gram staining and bacteriostasis test, this paper explores and confirms the results that bacillus sp. 22T has a strong ability to inhibit the growth of penicillium expansum on pear and grape. After 96 hours of exposure to fermentation broth containing bacillus sp. 22T to suppress the growth of penicillium expansum, 33.33 percent of pear and 16.66 percent of grape were not impacted by the bacterium.

Impact of bacterial synthesized nanoparticles on quality attributes and postharvest disease control efficacy of apricot and loquat.

Postharvest fungal attacks on fruits such as apricots and loquats are common. Diseased fruit samples were collected from Murree's local fruit markets. The disease-causing pathogens were identified utilizing molecular, microscopic, and morphological characteristics. Alternaria alternata and Aspergillus niger were identified as the pathogens responsible for brown rot in loquat and black rot in apricot. To combat these fruit diseases, iron oxide (Fe2 O3 ) nanoparticles were synthesized using Bacillus subtilis and were characterized using various techniques. X-ray diffraction examination validated the size of iron oxide nanoparticles. The presence of several capping agents in the synthesized nanoparticles was confirmed by Fourier transform infrared analysis. Scanning electron microscopy revealed the spherical morphology of nanoparticles, whereas energy-dispersive X-ray proved the presence of different elemental compositions. After completing antifungal activities in vitro and in vivo, it was discovered that a nanoparticle concentration of 1.0mg/mL efficiently suppressed the growth of fungal mycelia. Fungi growth was effectively inhibited in fruit samples treated with 1.0mg/mL nanoparticles. The results of successful in vitro and in vivo antifungal activities imply that iron oxide (Fe2 O3 ) nanoparticles play an important role in ensuring fruit quality against pathogenic attacks. Bacterial-mediated iron oxide can be widely used because it is less expensive and less harmful to the environment than chemically manufactured fertilizers.

Spore Dispersal Patterns of Colletotrichum fioriniae in Orchards and the Timing of Apple Bitter Rot Infection Periods.

Bitter rot is a major disease of apple fruit in warm and humid regions. It is caused by various species in the Colletotrichum gloeosporioides and C. acutatum species complexes, of which C. fioriniae of the C. acutatum species complex is most common in the Mid-Atlantic region of the United States. While bitter rot management begins with good cultural practices, fungicides are generally used for consistent control. Fungicides should be applied before or during infection periods, but the timing of infection is unclear due to the hemibiotrophic lifestyle of the causal species. To determine when infection periods occur, we quantified C. fioriniae spore dispersal throughout three growing seasons and compared the temporal susceptibility of apples in two seasons of field trials. Spores were detected in rainwater from bud break to leaf drop, with the highest spore quantities in the summer and early fall correlating with optimal temperatures for C. fioriniae. Late-season-inoculated fruit had more bitter rot than early-season-inoculated fruit, but this was also positively correlated with periods of optimal temperatures and moisture for infection. In the context of previous experiments, these results suggest that infection periods are primarily determined by temperature and moisture rather than apple fruit phenology. Based on the relative numbers of spores and biotrophic and necrotrophic infections, only a tiny proportion of spores establish viable biotrophic infections, but a relatively high proportion of biotrophic infections switch to necrotrophy. We suggest bitter rot management should focus on preventing initial biotrophic infections by protecting apples during weather conditions that favor infection.

First Report of Fruit Rot Caused by Fusarium graminearum on Ponkan (Citrus reticulata Blanco cv. Ponkan) in China.

Ponkan (Citrus reticulata Blanco cv. Ponkan) is a Chinese citrus species with tasty fruit. In November 2021, an unknown postharvest disease of Ponkan fruit caused nearly 15% losses of 2000 fruits in Nanchang, Jiangxi Province (28.68° N, 115.85° E). The initial fruit's surface necrosis was brown (Xu et al. 2022) (Figure 1A). Disease spots spread to the entire fruit, white or grey hyphae appeared, and the fruit rotted. Twenty diseased fruits were surface-disinfested with 2% sodium hypochlorite and 75% ethanol, then rinsed with sterile distilled water to isolate the pathogen. Diseased tissue sections (5 × 3 mm) were incubated on potato dextrose agar (PDA) for 7 days at 25°C. Twelve of 15 monoconidial isolates have similar morphology. On PDA, the isolates produced copious white aerial mycelia. After 5-7 days on straw juice medium, two types of conidia appeared (Rice straw 60 g, Agar 20 g, distilled water 1000 mL) (Figure 1E-I). Macroconidia were abundant, falcate, slender, and slightly curved with 0-8 septa, mostly 4-5 septa (average 41.70 × 3.81 m, n=100) (Figure 1J). Microconidia were globose, oval, or piriform with 0-1 septa, 2.72 to 8.57 × 2.53 to 7.47 m (average 5.49 × 4.52 m, n=50) (Figure 1L), and chlamydospores were not observed. Conidial and colony morphology identified 12 monoconidial isolates as Fusarium graminearum (Fisher et al., 1982; Yulfo-Soto et al., 2021). Genomic DNA was extracted from three isolates using a DNA Extraction Kit (Yeasen, Shanghai, China). The ITS1/4 region combined with partial gene fragments of translation elongation factor-1 alpha (TEF-1α, primer TEF1/2, O'Donnell et al. 1998), RNA polymerase second largest subunit (RPB2, primer fRPB2-5F/7cR, Liu et al. 1999) and β-tubulin (β-tub, primer Bt2a/2b, Li et al. 2013) from the isolates were amplified and sequenced. The three tested isolates showed identical gene sequences. Sequences amplified from one representative isolate (PG16) have been submitted to GenBank. BLAST searches revealed that ITS (OM019317), TEF-1α (OM048103), RPB2 (ON364348), and β-tub (OM048104) had 99 to 100% identity compared with F. graminearum (MH591453.1, KX087136.1, MF662636.1, and MZ078952.1, respectively) in GenBank. The phylogenetic analysis combined ITS - TEF-1α - RPB2 (O'Donnell et al. 2015) concatenated sequences using MEGA7.0 (Mao et al. 2021) showed the isolate was clustered with the F. graminearum clade with 100% bootstrap support (Figure 2). The isolate PG16 was used for pathogenicity tests. Ponkan fruits were surface-disinfested with 75% ethanol and rinsed with sterile distilled water three times. Then, 30 punctured wound fruits (2-mm-diameter, 2-mm-depth) with a sterile needle and 30 unwounded fruits were inoculated with conidial suspension (10 µL, 3.0 × 105 conidia/mL). while the control fruits were inoculated with 10 µL sterile distilled water. All fruits were incubated at 25°C and 90% relative humidity. Two days later, all wounded fruits inoculated with conidial suspension showed disease spots, similar symptoms to the original rotten fruits (Figure 1D). Control and conidial-inoculated unwounded fruits were healthy (Figure 1B-C). The Pathogenicity test was repeated twice, and similar symptoms were observed. Morphologically and molecularly, the re-isolated fungus matched the inoculated isolate. First report of F. graminearum causing Ponkan fruit rot in China. As Ponkan is an important citrus crop with high economic value in China, identification of the causing agent, F. graminearum, for fruit rot allows the development of control measures to manage this disease.

Perkembangan Penyebab Penyakit Busuk Lunak Pada Tanaman Buah Naga Merah (Hylocereus Polyrhizus) di Kabupaten Banyuwangi

Red dragon fruit (Hylocereus polyrhizus) is one of the most important commodities in Indonesia. The dragon fruit production center in Indonesia is located in Banyuwangi Regency with a production of 82,544 per year. Areas in Banyuwangi that produce large quantities of dragon fruit are Bangorejo, Pesanggaran, Silirangung, Purwoharjo, and Tegaldlimo. Dragon fruit is a type of plant that has a strong resistance, but there are many factors that can cause a decrease in production, one of which is OPT. Soft rot disease in dragon fruit is an example of a pest that attacks dragon fruit plants. This disease can cause physical, physiological, and chemical changes in dragon fruit plants that affect production yields. According to several sources of bacteria that cause soft rot disease is Pectobacterium. Pectobacterium will spread quickly if the surrounding conditions are supportive, such as environmental conditions, weather, temperature, and care carried out by farmers.