Fruit Rot Research Articles

Evaluation of mTERF gene expressions in response to Phytophthora capsici infection in pepper (Capsicum annuum L.) cultivars

Despite resistance to abiotic stresses, some plant species may still show low resistance to pathogens. This biotic stress resistance can provide advantage and increase productivity in agricultural systems. However, while there is extensive research on the pathways involved in abiotic stress tolerance, the impact on the molecular mechanisms underlying pathogen resistance remains poorly understood. Among the pathogens, Phytophthora capsici, an oomycete, causes severe damage as plant pathogen, leading to blight and fruit rot in pepper and other commercially valuable crops. This study investigates the effects of Phytophthora capsici infection on highly resistant (CM334) and susceptible (Sera Demre) pepper varieties. We examined biochemical changes and gene expression across different vegetative periods (seedling, flowering, and fruiting stages). Specifically, we analyzed biochemical pathways and the mitochondrial transcription termination factor (mTERF) gene regions associated with pathogenicity. In pepper seedlings infected with P. capsici, peroxide levels increased at all developmental stages compared to control groups. Additionally, we observed a rise in H2O2 content, a molecule involved in signal transduction, likely due to the oxidative stress caused by the pathogen. The expression patterns of mTERF genes varied significantly depending on both pathogen application and the developmental stage of the plants. In the seedling stage, inoculation with P. capcici resulted in decreased expression of TERF2, mTERF6, and mTERF8 genes in leaf parts of both resistant and susceptible varieties. However, mTERF28 expression showed a significant increase. Interestingly, mTERF14 and mTERF27 gene expressions increased in the resistant variety but decreased in the susceptible one. These findings, although not providing a complete picture of host resistance mechanisms, highlight the crucial role of specific plant genes in the defense pathways against Phytophthora capsici. This knowledge can contribute to selecting pepper varieties with sustainable resistance to this devastating pathogen.

Electronic nose for detecting Colletotrichum coccodes causing anthracnose fruit rots in tomatoes

Electronic nose (EN) technology has several applications targeting various study areas, and food spoilage is one of these sections. This study investigated the ability of the EN, with metal-oxide sensors (MOS), to sense the presence of Colletotrichum coccodes, which cause anthracnose fruit rots, on tomato fruit and to distinguish between different stages and doses of infection. C. coccodes were identified by an appropriate polymerase chain reaction (PCR) program and sequencing, using two different primer sets: ITS1F/ITS4 and Cc1F1/Cc2R1. Three intact homogeneous tomato samples were injected with three different concentrations of conidial fungal suspension: 3 × 104, 3 × 105 and 3 × 106 conidia/ml, and three others were kept as negative controls. Principal component analysis (PCA) was used in analyzing the data acquired from the EN sensors. The results of PCA showed that EN was able to detect the presence of C. coccodes pathogen at early stages (two days of infection and before any symptoms appear). Moreover, EN was able to differentiate between different infection stages. In addition, the concentrations of infected samples on the sixth, eighth and tenth days were clearly differentiated. The use of EN is a promising technique for determining quality assurance and control.

First report of Botryosphaeria dothidea causing fruit rot on Chinese olive (Canarium album Raeusch.) in Guangdong province of China.

Chinese olive (Canarium album Raeusch.) is a traditional Chinese medicinal plant, mainly cultivated in Guangdong and Fujian provinces in China (Lai et al. 2022). In October 2023, Chinese olive fruit spots were observed in all the Chinese olive orchards surveyed in Chaozhou city (23.75°N, 116.67°E) of Guangdong, with an incidence up to 15%. Early disease symptoms on fruits appeared as circular or irregular, dark brown to black spots with yellowish lesions, and later the spots slowly coalesced to form large necrotic areas, which seriously affected the fruit marketability. To isolate the causal agent, small pieces (~0.3 mm2) of fruit tissue were excised from the lesion margins, and surface-disinfested with 75% (v/v) ethanol for 1 min, followed by 1% NaClO for 3 min, and rinsed three times with sterile water. The pieces were then placed on potato-dextrose-agar (PDA) and incubated at 27°C. Ultimately, four fungal isolates were obtained with similar morphology phenotypes, colonies initially appeared white with irregular margins and after 4-6 days turned dark gray gradually with dense aerial myceliu. Microscopy revealed conidia were single-celled, hyaline, aseptate, fusiform to subclavate, and measured 18.1-22.5 μm × 6.4-9.3 μm (19.8 × 7.4 m on average, n = 30), which were consistent with those descriptions of Botryosphaeria dothidea (Vasić et al. 2013; Zhang et al. 2023). To further identity the isolates, partial sequences of ribosomal transcribed spacer (ITS), translation elongation factor 1-α (TEF1-α), and β-tubulin (TUB2) genes were amplified using primers ITS1/ITS5, TEF-F/R, TUB2-F/R, respectively (Xu et al., 2023; Hong et al. 2006). The sequences of four isolates were identical, and those of representative strain GDCZ-1 were deposited in GenBank (ITS, OR584295; TEF1-α, OR685157; TUB2, OR685158). Using Neighbor-Joining algorithm, phylogenetic tree based on concatenated sequences of ITS, TEF1-α, and TUB2 showed that GDCZ-1 clustered with B. dothidea. To fulfill Koch's postulates, pathogenicity tests were performed on healthy Chinese olive fruits using the needle-prick inoculation method. The fruits were wounded with a sterile needle at the equatorial area (depth of 3-4 mm), and inoculated with 10 µL of spore suspension (106 /mL). The control fruits were inoculated with sterile water. Inoculated fruits were placed in sterile plastic containers to maintain high relative humidity (almost 100%) and incubated at 27°C. After 4 days, the inoculated fruits showed similar symptoms with those observed in the field infected fruits, while the control remained asymptomatic. Pathogen re-isolated from the inoculated fruits showed identical morphological characteristics to the original isolate GDCZ-1. As far as we know, fruit rot caused by Alternaria alternata has been recently reported on C. album in China (Shao et al. 2024). To our knowledge, this is the first report of B. dothidea causing fruit rot disease on C. album in Guangdong. Our report will provide crucial information for studying the epidemiology and management of this disease.

First Report of Botryosphaeria dothidea Causing Postharvest Fruit Rot of Plum in China.

The Nai plum (Prunus salicina var. cordata cv. Younai) holds significance as an important deciduous fruit crop in China. In July 2023, symptoms of postharvest fruit rot were observed on Nai plum with a 10% disease incidence of harvested fruits in three supermarkets, located in Nanchang City, Jiangxi Province, China. Infected fruits displayed brown, circular lesions, accompanied by a transition in the surrounding peel color from cyan to red. To investigate the causal agent, small sections (3 to 4 mm2) from the periphery of ten infected fruits were subjected to surface sterilization using 75% ethanol for 30 seconds. Following sterilization, the samples were rinsed three times with sterilized distilled water, air-dried, and aseptically placed on potato dextrose agar (PDA) at 25 ℃ for 3 days. Isolated colonies were subcultured by hyphal tiptransfer. Ten of the resulting 12 fungal isolates showed similar morphological characteristics. The colonies exhibited an initial white hue, gradually transitioning to gray, and featured short and thick aerial hyphae with an irregular colony margin. Microscopic examination revealed conidiogenous cells that were hyaline, aseptate, and narrowly fusiform. The conidia were measured 11.0 to 15.6 × 3.2 to 4.9 µm (x̅ = 13.5 ± 1.4 × 4.0 ± 0.4 µm, n = 30), and were hyaline and subcylindrical. The morphological characteristics were in accordance with those of the Botryosphaeria species (Crous et al. 2006). To identify the strain, two representative isolates, JFRL03-1792 and JFRL03-1793, were selected for further characterization. Amplification of nucleotide sequences from three regions (ITS, TEF1-a and TUB2) was conducted using the primer sets ITS5/ITS4, EF1-728F/EF1-986R, and BT2A/BT2B, respectively (Guo et al. 2023). The resulting sequences were deposited in GenBank under the accession numbers: OR418373 and OR418374 for ITS; OR424405 and OR424405 for TEF1-a; OR424411 and OR424412 for TUB2. A BLASTN homology search of the obtained sequences revealed a high similarity of 99%-100% to the ITS (AY236949, 511/513 nucleotides), TEF1-a (AY236898, 282/282 nucleotides), and TUB2 (AY236927, 431/431 nucleotides) sequences of Botryosphaeria dothidea CWM8000 (ex-type). Maximum likelihood analyses were performed for the combined ITS, TEF1-a, and TUB2 dataset using Phylosuite V1.2.2 (Zhang et al. 2020). The resulting phylogenetic tree indicated that the two representative isolates were clustered together with Botryosphaeria dothidea in a clade with 95% bootstrap support. Based on the comprehensive assessment of morphological and molecular data, the two isolates were conclusively identified as B. dothidea. To confirm pathogenicity, six healthy Nai plum fruits were surface sterilized with 75% ethanol and were subsequently wounded with a sterile needle. A 5-mm-diameter mycelial plug of the isolate JFRL03-1792, cultured on PDA at 25 ℃ for three days, was applied to the wound. Another set of six fruits was inoculated with sterile agar plugs as control. Following incubation in a climatic chamber at 25 ℃ and 80% relative humidity, the fruits were examined after 5 days. The experiment was repeated twice. The fruits inoculated with B. dothidea displayed typical rot symptoms, while the control fruits remained asymptomatic. In adherence to Koch's postulates, the fungus was successfully re-isolated from the inoculated fruits and confirmed as B. dothidea through morphological and molecular analysis. B. dothidea has previously been reported causing fruit rot on kiwifruit, winter jujube, and apple (Tang et al. 2012; Zhou et al. 2015; Marsberg et al. 2017; Xu et al. 2023). In addition, B. dothidea also reported causing Botryosphaeria canker disease on plum (Lin et al. 1994). But to our knowledge, this is the first documentation of B. dothidea causing postharvest fruit rot on plum in China. This discovery imparts critical insights into the management of this high-risk disease affecting plum in China.

PH Responsive Properties of Methyl Red/PVA Polymers for Smart Food Packaging Applications

Responsive polymers in particular have gained increasing interest during the last decades due to their unique properties. Their Ability to exhibit sharp and reversible changes in response to environmental pH condition have made them suitable for various applications. The pH responsive polymeric materials are being developed by the researcher in the recent year for the improvement of food safety issue in the packaging materials. In this study organic methyl red (MR) dye is used as a pH indicator induced with polyvinyl alcohol (PVA) films prepared by solution casting method. The prepared samples were characterized for microstructural, morphological, mechanical, water absorption and pH responsive properties using various analytical techniques. The XRD analysis has shown better crystallinity property which is in good agreement with the mechanical strength of the material. The morphological studies have shown homogeneous dispersion of MR on PVA matrix and change in the morphology of the MR/PVA polymer composites after acid treatment. The MR/PVA films were treated with rotten papaya fruit and change occurred in the samples were identified using UV-vis spectrometric analysis. The prepared MR/PVA pH-responsive polymers have shown good pH reactivity in the range of pH 4.5 to 6.5. Overall, the prepared samples have good pH responsive properties with additional qualities like good optical, structural, and mechanical characteristics.

First report of fruit rot of pomegranate caused by Aspergillus aculeatus from Bangladesh

First report of fruit rot of pomegranate caused by <i>Aspergillus aculeatus</i> from Bangladesh

First report of Lasiodiplodia pseudotheobromae causing soft rot of plum in China.

Plum (Prunus salicina) is one of the most important fruit tree species worldwide (Valderrama-Soto et al. 2021). In June 2023, the postharvest soft rot symptoms were observed on plum fruits in several fruit markets of Guiyang city, Guizhou province, China. The disease incidence in these markets ranged from 20 to 25% with 70% disease severity. Plum fruits showed rotting, which was characterized by water soaked fruit tissue, softening and presence of whitish mycelia four days post inoculation. In severe conditions, whole fruits become rotted and were covered with white fungal mycelia. Small sections (5 × 3 mm) from 6 diseased plum fruits were surface sterilized by using 75% ethanol for 30 s followed by 0.1% mercuric chloride solution for 5 min, rinsed three times with ddH2O, and then transferred onto potato dextrose agar (PDA) and incubated at 25 ± 2°C for three days. Three pure cultures (GUCC23-0001 to GUCC23-0003) were obtained by transferring a single hyphal tip to new PDA plates. Colonies of these isolates were grayish-white initially, gradually turning to whitish brown with fluffy aerial mycelia and uneven edges and finally turned to a dark gray colony after five days of inoculation. The pseudoparaphyses were hyaline, cylindrical, aseptate, and rounded at apex. Conidia were ellipsoidal, hyaline, unicellular, and 24.2 to 28.6 × 12.3 to 15.5 µm in size (n = 30) (Fig. S1), which were similar to the morphology of Lasiodiplodia pseudotheobromae (Alves et al. 2008). Furthermore, fungal DNA was extracted from fresh mycelia of PDA after seven days by using fungus genomic DNA extraction kit (Biomiga, USA). Partial DNA sequences from four loci including internal transcribed spacer (ITS), translation elongation factor 1-alpha (tef1), beta-tubulin (tub2), and polymerase II second largest subunit (rpb2) were amplified with ITS1 and ITS4 (White et al. 1990), EF1-688F and EF1-1251R (Alves et al. 2008), Bt2a and Bt2b (Glass and Donaldson 1995), and RPB2-LasF and RPB2-LasR, respectively (Cruywagen et al. 2017). GenBank accession numbers are OR361680, OR361681, OR361682 for ITS, OR423394, OR423395, OR423396 for tef1, OR423397, OR423398, OR423399 for tub2, and OR423391, OR423392, OR423393 for rpb2, and gene sequencing showed 99.6 to 100% identity with ex-type strain of L. pseudotheobromae (CBS 116459). Phylogenetic analysis also placed our isolates in a highly supported clade with the reference isolate of L. pseudotheobromae (Fig. S2). Another experiment was designed to confirm the pathogenicity test for additional confirmation. Five mm mycelial plugs of L. pseudotheobromae from a three day old culture on PDA were placed on five surface-sterilized and non-wounded plum fruits for 12 hours and incubated at 25°C ± 2°C for four days. Sterilized fungus free PDA plugs were used as a negative control. Mycelial plugs were removed after 12 hours following which whole fruits were incubated in plastic boxes at 25°C ± 2°C. The experiment was repeated twice. The pathogenicity was evaluated under control conditions in laboratory (relative humidity, 70 ± 5% and temperature 25 ± 5˚C). Plum fruits showed rotting, which was characterized by water soaked fruit tissue, softening and presence of whitish mycelia four days post inoculation. These symptoms and signs were similar to the initially observed symptoms on plums in the markets. No disease symptoms were observed on the control fruits. The re-isolated fungus obtained from inoculated plum fruits was very similar to those isolated from diseased samples in morphology, fulfilling Koch's postulates. To the best of our knowledge, this is the first report of L. pseudotheobromae causing postharvest fruit rot of plum in China. In 2022, the total planting area of plum was 1946.5 thousand hectares, which produces approximately 6626300 tons of plum (Food and Agriculture Organization of the United Nations, 2022). Based on the disease incidence and severity reported in the current study, soft rot of plum may be responsible for nearly 35% of yield losses under severe. Therefore, our study laid a theoretical foundation for the prevention and control of this post-harvest disease of plum.

Post-Harvest Fruit Rot on Muskmelon (Cucumis Melo) Caused by Acremonium Potronii in Iraq

Muskmelon (Cucumis melo) is a vital fruit vegetable thriving in arid and warm climates. Fruit rot is a prevalent issue affecting muskmelon, occurring frequently in fields before harvest and during post-harvest stages. Several pathogenic fungi have been identified as the primary causal agents of fruit rot. In the present study, muskmelon fruits displaying irregular white regions were collected from the Penjwen district, Kurdistan region of Iraq. The isolated causal agent was identified as Acremonium potronii based on both phenotypic characteristics and molecular analysis (ITS and LSU gene sequences). A pathogenicity test was conducted to fulfill Koch’s postulates. This represents the first documented association of Acremonium potronii with muskmelon fruit rot.

Inhibitory effect and action mechanism of citral against black rot in pitaya fruit

Blackspot, caused by Alternaria alternata, is a significant postharvest disease in pitaya. Currently, there are limited effective fungicides to manage this disease. This study aimed to evaluate the antifungal activity of citral against the blackspot pathogen and to determine the protective effect of citral on pitaya. Our results demonstrated that citral effectively curtailed the mycelial growth and spore germination of Alternaria alternata, with a minimum inhibitory concentration (MIC) of 0.6 μL/mL. Observations under a light microscope revealed that citral-treated hyphae displayed characteristics such as sparseness, roughness, twisting, shriveling, and irregular internode separation, along with prominent vacuolation. Propidium iodide and 2,7-Dichlorodi-hydrofluorescein diacetate staining results revealed that the mycelia from the MIC citral-treated group emitted robust fluorescence, with the average fluorescence intensities being 4.03 and 8.09 times higher than the control group, respectively. Furthermore, citral treatment resulted in a decline in the lipid content and dry weight of the hyphae, increased nucleic acid and protein leakage, enhanced exosporial conductivity, and augmented superoxide dismutase (SOD) and catalase (CAT) enzyme activities. Additionally, it fostered the accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA). Fruit damage inoculation assays indicated that an appropriate concentration of citral (1/2 MIC, MIC) could notably diminish the fruit spot diameter expansion. Thus, citral shows promise as a potential alternative fungicide for managing postharvest black rot in pitaya.

First Report of Leaf Spot of Pineapple (Ananas comosus (L.) Merr Caused by Neoscytalidium dimidiatum in Malaysia.

In June 2017, severe leaf spots symptoms were observed by growers on pineapple leaves of Josapine variety in in Alor Pongsu (5°01'60.00" N, 100°34' 59.99" E), Perak,northwest of Peninsular Malaysia. The early infection stage shows that several brown spots could be observed, which then would merge to form large brown to creamy white lesions that cover all the leaf surface. This infection finally caused the plant to die after a while. Disease observations conducted from 2018 - 2023 showed that 10-15% incidences of the disease were observed in several pineapple farms located in Johor, Kedah, and Sarawak. The aim of this study to confirm the causal pathogen of the disease by performing isolation, pathogenicity testing, and identification of the primary causal pathogen from 20 samples of infected leaves collected from Alor Pongsu. The leaf tissues between infected and healthy were cut into small pieces (0.5 cm 0.5 cm), and surface sterilized with 1% sodium hypochlorite for 30 seconds, followed by 70% ethanol for 30 seconds, and rinsed thrice with sterilized water before placing on Potato Dextrose Agar (PDA). The PDA plates were incubated at room temperature (28 ± 2℃) in natural light. After five days of incubation, the potential causal pathogen was purified using a single conidial isolation technique for morphological and molecular characterizations. All 32 isolates displayed similar phenotypes. Based on morphological observation on PDA, the colonies were initially white of aerial mycelia but gradually darkened as the culture aged. Microscopic features of the 14-day-old fungal culture showed that the mycelia were branched with 0- 1 septa, pigmented, and brown. Arthroconidia were ellipsoid to ovoid or round shaped, hyaline, with rounded apex, truncate base, and occurring singly or in chains averaging 9 ± 3 × 5 ± 2 μm (n = 20). Based on the morphological characteristics, the fungal isolates were tentatively identified as Neoscytalidium species. A representative isolate of Neoscytalidium coded as UiTMPMD2 was further identified through PCR implication of the internal transcribed spacer (ITS) region using ITS1 and ITS4 primers and BLAST homology search as Neoscytalidium dimidiatum (Penz.) Crous & Slippers based on 100% similarity (575 bp out of 575 bp) to a reference sequence (accession no. KU204558.1). The sequence was deposited in Gen Bank (accession no. OR366479) with reference sequence code of INBio:30A. Pathogenicity tests were performed on 10 whole plants of Josapine pineapple (4 months old) using a leaf inoculating method (Wu et al. 2022) in a glasshouse (25-32°C) and repeated twice. Four mature leaves per each plant were wounded at two points and inoculated with mycelium PDA plugs from 7-days-old cultures of N. dimidiatum. Control plants were wounded in the same manner but inoculated with sterilized PDA plugs. Seven days post inoculation, leaf spot symptoms were observed on treated plants with the pathogen, while the control plants remained symptomless. Pathogen was successfully reisolated from brown leaf spot symptoms in which the cultural and morphological characteristics were identical to those of the originals. Neoscytalidium dimidiatum has a wide range of hosts and it has been reported in Malaysia to cause stem canker on pitahaya (Mohd et al. 2003; Khoo et al. 2023 ) and fruit rot of guava (Ismail et al. 2021). To the best of our knowledge this is the first report of N. dimidiatum causing leaf spots on pineapples in Malaysia. This report establishes a foundation for further study ofN. dimidiatum that can effectively address the disease in pineapple.

Improve the Effectiveness of Inhibiting Pathogenic Fungus and Maintaining the Quality of Rambutan (Nephelium lappaceum L.) Post-Harvest by Indigenous Lactic Bacteria

The change in the quality of rambutan (Nephelium lappaceum L.) fruit after harvest is mainly dehydration. Rambutan fruit peel is often dark (brown) and fruit rot due to fungal disease. This study investigated the effects of Lactobacillus bacteria strains [Lactobacillus plantarum CC6 (CC6), Lactobacillus fermentum DC2 (DC2), Lactobacillus fermentum DGMC2 (DGMC2)] with/without supplement combinations [chitosan 0.03% (Chito), alginate 0.03% (SA) and carboxymethyl cellulose 0.5% (CMC)] on the quality of Java rambutan fruit during storage at 13 °C, and included a sample without treatment with bacteria and chemical considered as the control. The results showed that among 16 treatments on rambutan fruits immediately after harvesting, the four treatments that showed the best results were CC6-Chito, DC2-Chito, CC6-CMC and DC2–SA, and DC2-Chito was more effective than the others. However, all four of these treatments supported the preservation of rambutan fruit, reducing both weight loss and browning of the skin and stem, and kept the infection rate at the lowest level. The brightness and peel color values were highest for these treatments.

Biofunctional features of Pickering emulsified film from citrus peel pectin/limonene oil/nanocrystalline cellulose

SummaryThe application of edible films can be an alternative solution for maintaining the quality of post‐harvest horticultural commodities. This study aimed to determine the effect of adding a stabiliser, cellulose nanocrystals (CNCs), on the functional characteristics of citrus peel pectin and limonene essential oil (LEO)‐based coatings. A formulation comprising pectin (0.5%), CNC (0.075%) and LEO (0.5%) was prepared. The CNC morphology (nanometre scale) was nanorods with pointed ends on both sides, revealed with atomic force microscopy. Gas chromatography–mass‐spectrometry verified the main component of LEO, d‐limonene. All prepared film‐forming solution showed good stability with zeta potential values ranging from −76.34 to −35.33 mV. The developed film had a rougher surface due to the presence of oil aggregates and CNC agglomeration during film preparation. The addition of Pickering emulsion showed improvements in terms of mechanical properties (tensile strength 23.61 MPa, and elongation 65.87%), water barrier and the film clarity compared with regular emulsions with synthetic surfactants. It effectively inhibited the growth of harmful microbes that cause the rotting of fresh fruits, i.e., Penicilium digitatum, by 3.87% and 14.83% compared to the conventional emulsion and pectin‐based film, respectively, through the well diffusion test method. Thus, the combination of pectin/CNC/LEO can be used as an alternative active coating for fresh fruit commodities.

In silico analysis to understand genetic variability, phylogenetic and phylogeographic relationships between Phytophthora capsici isolates infecting various crops

Phytophthora capsici is a major oomycete-based pathogen causing enormous damage to the productivity of peppers and other major crops from different families worldwide by causing fruit rot, root rot and foliar blight diseases. This study utilized molecular signatures present within ITS1-5.8S rRNA-ITS2 and Ras-related GTP binding protein (Ypt1) genes to evaluate haplotype variability and phylogenetic relationships among P. capsici isolates with significant epidemiological implications. Twelve different evolutionary lineages specific to particular hosts and/or geographical regions and differed by SNPs, and 30 haplotypes with maximum diversity in India and Pakistan, were identified by sequence analysis of the ITS regions. It includes country-specific lineages Pc-I and Pc-II in India with multiple host ranges; capsicum-specific lineages Pc-IV, Pc-V and Pc-VIII from Pakistan; papaya-specific lineages Pc-VI from China, and watermelon-specific lineages Pc-VII and Pc-XI from USA. Many lineages showed cross-border infections, such as Pc-III and Pc-X in India and Pakistan, Cocoa-specific lineage Pc-IX in Brazil and Cote d’Ivoire, and Capsicum-specific multi-continental lineage Pc-XII. Similarly, 11 different SNP lineages and 32 haplotypes with maximum diversity in China were identified for the Ypt1 gene. These findings would be very useful for epidemiological surveillance of P. capsici strains worldwide, understanding population and evolutionary dynamics, developing lineage- and haplotype-specific diagnostic assays and disease-resistant varieties.

Efficiency of the application of biological systems of the protection of apple trees against powdy dew and scamb in the conditions of the Western Forest-Steppe of Ukraine

Goal. To study the effectiveness of different biological systems of apple tree protection against scab and powdery mildew in the Western Forest-Steppe of Ukraine.&#x0D; Methods. Phytosanitary monitoring was carried out visually and with the help of pheromone traps. Accounting of the spread and development of diseases was carried out according to generally accepted methods in the phases of apple tree development: «bud swelling», «green cone», «bud extension», «bud separation», «pink bud», «flowering», «end of flowering», «fruit formation», «fruit growth» and «fruit ripening». The technical effectiveness of fungicides was determined after 7 days. Statistical processing of the research results was carried out according to generally accepted methods.&#x0D; Results. The results of monitoring the phytosanitary state of apple plantations established that the most common diseases in 2021—2022 in the conditions of the Western Forest Steppe of Ukraine were scab, which affected 15—29% of leaves and 8—13% of apple fruits, powdery mildew, which affected 15—18% of leaves of apple trees, moniliosis, the prevalence of which was 9—13%, and fruit rot, which affected 13—14% of apple fruits. The research results showed that the use of the biological protection system No. 1 (Fluorescin BT, Bactophyt BT, BioHybervit BT, Trihopsin BT, Fluorescin BT) made it possible to reduce the development of powdery mildew by 59.0%, and to reduce the development of scab on leaves and by 59.1%, 62.2% — scab on apple fruits. The use of biological protection system No. 2 (Bactophyt BT + Trihopsin BT, BioHybervit BT, Fluorescin BT, Trihopsin BT, Fluorescin BT) made it possible to reduce the development of powdery mildew by 43.6%, by 47.7% to reduce the development of leaf scab and by 48.6% — scab on apple fruits. The use of biological protection system No. 3 (Ampelomycin BT + Bactophyt BT, Phytosporin + Fluorescin BT, BioGibervit BT, Biospectr BT, Trihopsin BT + Fluorescin BT) made it possible to reduce the development of powdery mildew by 53.8%, and to reduce the development of scab by 68.2% leaves and 67.6% — scab on apple fruits. Using the studied biological systems to protect apple trees from scab and powdery mildew in the conditions of the Western Forest-Steppe of Ukraine yield indicators of 13.2—13.8 t/ha were obtained. The use of the studied biological protection systems made it possible to obtain from 2946 to 8526 UAH/ha of conditional net income and profitability indicators from 72.7 to 229.4%.&#x0D; Conclusions. The results of the research established that all investigated systems of biological protection of apple trees against scab and powdery mildew in the conditions of the Western Forest Steppe of Ukraine made it possible to protect apple plantations at a reliable level and obtain high yields. The technical efficiency of the applied protection systems against powdery mildew was 43.6—59.0%, against scab on apple leaves — 47.7—68.2%, and against scab on apple fruits — 48.6—67.6%. The yield for the application of the investigated biological systems of apple tree protection against scab and powdery mildew was 13.2—13.8 t/ha. Biological protection system No. 1 was the most effective in terms of profitability — 229.4%, and the highest indicator of conditional net income was obtained from the use of biological system No. 3 — UAH 8526/ha.

Prospective microorganisms for the storage of apple fruitsin the conditions of the refrigerator

Goal. To select prom ising microorganisms from the collection of cultures of microorganisms with agronomically valuable properties of ETI «Biotechnica» of NAAS for storage of apple fruits in the refrigerator.&#x0D; Methods. Research was conducted using generally accepted methods and methodical approaches used in microbiology and biotechnology.&#x0D; Results. A set of studies was conducted to isolate harmful objects that affect apple fruits when stored in refrigeration conditions. As a result of research, such pathogenic microorganisms as: Botrytis (gray fruit rot); Rhizopus (gray mold); Aspergillus (black mold); Penicillium (green mold). In laboratory conditions, a study of the antagonistic activity of promising strains of microorganisms from the collection of ETI «Biotechnica» of NAAS against phytopathogens that were isolated from affected fruits was conducted. To perform the work, fungal and bacterial strains of microorganisms with fungicidal properties were selected from the institute’s collection.&#x0D; Conclusions. It was established that the fungi of the genus Trichoderma showed high antagonistic activity against phytopathogens of fungal etiology. The delay in the growth of harmful objects was at the level of 90—100%. Antagonist fungal strains Gliocladium rozeum and Ampelomuces artemisia pcs. A-1, caused growth retardation zones of phytopathogens in the range of 75—80%, and Soniotirium minitans pcs. C-20 showed absolutely no antagonistic activity against phytopathogens affecting apple fruits. Among the bacterial strains, Pseudomonas aureofaciens pcs. 111 and Pseudomonas fluorenscens pcs. AR33, which suppressed the growth of phytopathogens by 85—90% due to high titers of viable cells and active metabolites. Among the bacterial strains, Pseudomonas aureofaciens pcs. 111 and Pseudomonas fluorenscens pcs. AR33, which suppressed the growth of phytopathogens by 85—90% due to high titers of viable cells and active metabolites.

Diversity and Clonality in Populations of Phytophthora citrophthora and P. syringae Causing Brown Rot of Citrus in California.

Phytophthora citrophthora and P. syringae are currently the primary causal organisms of brown rot of citrus fruits in California. To possibly find an explanation for the prevalence of the previously minor species P. syringae, we determined the population structures of both pathogens in California using next-generation sequencing and population genomics analyses. Whole-genome sequencing and aligning with newly assembled reference genomes identified 972,266 variants in 132 isolates of P. citrophthora and 422,208 variants in 154 isolates (including 24 from noncitrus tree crops) of P. syringae originating from three major growing regions. The resulting data sets were visualized using principal component analysis, discriminant analysis of principal components, unweighted pair-group method with arithmetic mean dendrograms, fastStructure, and minimum spanning networks, and we obtained the index of association, diversity summary statistics, and genetic distance statistics values GST, G''ST, and Jost's D. Subpopulations of both species were mostly defined by their geographic origin indicating restricted dispersal of inoculum. Except for five isolates, the population structure of P. citrophthora (that is heterothallic and unlikely to reproduce sexually) was clonal to semi-clonal, with very little genetic diversity within and among subgroups. In contrast, the population structure of P. syringae was also clonal to semi-clonal, but isolates were placed into four main clusters of much higher diversity. Clonality in both species can be explained by a high level of asexual reproduction. The higher diversity in the homothallic P. syringae is likely due to commonly occurring sexual reproduction. One distinct cluster of P. syringae consisted solely of isolates from noncitrus hosts; therefore, the origin of P. syringae in citrus could not be resolved.

Evaluating Pomegranate Cultivars for Resistance to Anthracnose Fruit Rot, a Severe Fungal Disease in Florida and Southeast United States

Pomegranate (Punica granatum L.) has primarily been cultivated at home in Florida and other southeastern states. Over the past 15 years, growers, nurseries, researchers, and Extension agents have explored the potential of pomegranate as an alternative fruit crop. Early field trials revealed that pomegranates are highly susceptible to Colletotrichum gloeosporioides, causing severe anthracnose fruit rot and premature fruit drop. The development and use of disease-resistant cultivars are considered some of the best methods to manage this disease. This publication presents our findings from evaluating 35 pomegranate cultivars under natural disease pressure in central Florida and by artificial inoculation. The susceptibility of such pomegranate cultivars varied widely, with six exhibiting resistance to anthracnose fruit rot. More comprehensive research is warranted to further develop anthracnose-resistant cultivars and to enhance our understanding of disease resistance in this crop.

Volatile organic compounds produced by Metschnikowia pulcherrima yeast T-2 inhibited the growth of Botrytis cinerea in postharvest blueberry fruits

Postharvest rot of blueberry fruits caused by Botrytis cinerea led to huge economic losses in storage and transportation. In this study, Metschnikowia pulcherrima T-2 was isolated from the surface of blueberry fruits and significantly reduced postharvest rot of blueberry fruits. The weight loss rate of T-2 soaked blueberry fruits was decreased; the contents of total soluble solids, titratable acidity and vitamin C of T-2 treated blueberry fruits were increased at a humidity of 85% and 25 °C. T-2 also enhanced the control of gray mold in blueberry fruits, but could not directly inhibit the growth of B. cinerea in vitro. The volatile organic compounds (VOCs) produced by T-2 could inhibit the growth of B. cinerea, and significantly reduced the postharvest rot of blueberry fruits. According to Gas Chromatography-Mass Spectrometry (GC–MS) analysis and antibacterial analysis, the benzyl alcohol, phenylethyl alcohol, benzaldehyde, 2-ethyl-1-hexanol, acetic acid, octanoic acid, 3-hydroxy-2-butanone, 2, 5-dimethyl-pyrazine and isoamyl acetate were selected. The influence of the above 9 volatiles on B. cinerea growth was assessed by treating B. cinerea in vitro with various concentrations of volatile. The lowest effective amounts of 9 volatiles were established to reduce the postharvest rot of blueberry fruits. These results shed light on the roles of T-2 VOCs in the control of postharvest blueberry fruits to B. cinerea, and provided a new method of postharvest storage.

First Report of Alternaria Leaf Spot Caused by Alternaria alternata on Ulmus parvifolia in Jiangsu, China.

Ulmus parvifolia Jacq. is an important tree with ornamental value, which is widely planted in Hebei and southern regions of China. In September 2022, a leaf spot symptom was observed on about approximately 20% U. parvifolia seedlings growing a tree farm (20000 m2) of Jiangsu Academy of Forestry (118°45'57.30″E, 31°51'27. 94″N). Gray to black spots appeared on leaves of seedlings. Five diseased leaves were collected from five different seedlings. The pieces were excised from the margins between healthy and diseased tissues, surface sterilized in 75% ethanol for 30 s and then in 1.5% NaClO for 90 s, rinsed three times in sterilized distilled water, plated on potato dextrose agar (PDA) and incubated at 25℃ in the darkness. Pure cultures were obtained by monosporic isolation. Six isolates with identical morphological features and the internal transcribed spacer (ITS) sequences were obtained (the isolate rate of 67%), and identified as Alternaria sp. A representative isolate, LY-1-1 was used for the further study. The colony of LY-1-1, growing on PDA was cotton-like and brown in color with gray-white aerial hyphae on their surfaces, and its reverse was dark grey. The conidia were ovate to pear-shaped, brown in color, with 1 to 4 transverse septa and 0 to 1 longitudinal septa, parietal cells extending into the beak, and measured 7.1 to 12.5×3.8 to 7.1 µm (n=35). These characteristics were consistent with the description of Alternaria sp. (Simmons 2007). The regions of ITS, large subunit ribosomal RNA (LSU), small subunit ribosomal RNA (SSU), anonymous region OPA10-2 genomic sequence (OPA10-2), Alternaria 1 major allergen (Alta1), glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and translation elongation factor 1-alpha (TEF1) genes (GenBank Accession No. OR047916, OR051904, OR047919, OR061065, OR061063, OR061064, and OR061062, respectively) were amplified (White et al. 1990; Woudenberg et al. 2015) and sequenced. These obtained sequences showed 99.86-100% similarity to the ITS (514/515 bp) of A. alternata isolate SPM-2 (OR378581), LSU (801/801 bp) of isolate B9 (OR366492), SSU (1019/1020 bp) of strain LSU0766 (MT000349), OPA10-2 (632/633 bp) of strain 19-1 (MN185000), Alta1 (470/470 bp) of strain CMML21-73 (OQ831518), GAPDH (177/177 bp) of isolate CS36-3 (KY814638), and TEF1 (240/240 bp) of isolate SY-6 (OP980553). A neighbor-joining phylogenetic tree was generated by combining all sequenced loci in MEGA7. The isolate LY-1-1 clustered in the A. alternata clade with 98% bootstrap support. Three 3-month-old U. parvifolia seedlings were wounded with a sterile needle and inoculated with 20 μL conidia suspension (1×106 spores/mL) on the left sides of leaves. Inoculation on the right side with 20 µL of sterile water was treated as a control. All inoculated plants were incubated in a greenhouse at 25℃, 80% relative humidity, and a 12-h light/dark cycle. The experiment was repeated three times. After 5 days of inoculation, typical gray to black spots were found on the left sides of all inoculated leaves, and the control did not have any leaf spot symptoms. Subsequently, the same fungus was reisolated and identified based on morphological and molecular traits, fulfilling Koch's postulates. The A. alternata has been reported to cause leaf spot on pecan (Wu et al. 2020), fruit spot on olive (Alam et al. 2019) and fruit rot on lychee (Alam et al. 2017). However, there are no other reports of A. alternata on U. parvifolia in the world. Thus, this study provides an important reference for the biology, epidemiology of A. alternata.

First report Calonectria hawksworthii as an aetiological agent of fruit rot of cocoa in Brazil

AbstractCacao (Theobroma cacoa L.) is an important tropical fruit tree used in chocolate production. Among the biotic problems interfering with fruit production, phytopathogenic fungi stand out. During a visit to cocoa production areas in the municipality of Medicilândia, Pará, Brazil (Amazon region), we observed cocoa fruits with dark lesions and greyish‐white cottony mycelia growth. In order to determine the aetiological agent's identity, we extracted DNA and amplified part of the TEF‐1α and RBP2 genes and compared them with sequences in GenBank using the BLASTn tool. Based on molecular results and phylogenetic analysis, the isolates were identified as Calonectria hawksworthii. Inoculations in cacao fruits showed symptoms after 6 days and were similar to those collected in the field, confirming the postulates. This study is the first report of Ca. hawksworthii causing cocoa bean rot worldwide.