First Report of Lasiodiplodia pseudotheobromae causing Postharvest Decay of Strawberries in Florida

Postharvest decay of strawberry (Fragaria × ananassa Duch.) is a major factor causing fruit losses. Strawberries were obtained from various harvests at cooling facilities located in Dover and Plant City, FL during the 2018-19 and 2019-20 seasons. After the fruits were incubated at 22ºC for up to 5 days (d) to promote disease development, Lasiodiplodia decay was observed at up to 3% from some harvests, exhibiting gray mycelia on small lesions that gradually covered the whole fruit. The fungus was isolated onto potato dextrose agar (PDA). Five isolates (SBD18-14, SBD18-277, SBD18-279, SBD19-02 and SBD19-57) were characterized. Fungal mycelia were initially grayish white and then gradually changed to gray to dark gray on PDA at 25oC, and later produced black pigments (Fig. S1). Pycnidia were observed from inoculated strawberries at 14 d. Isolates shared similar conidia morphology: aseptate, hyaline, ellipsoid to ovoid, measuring L × W: 24.0-34.0 (28.3) × 13.0-16.0 (14.3) μm (n =100). Mature conidia were brown, one septate, measuring L × W: 25.0-33.0 (28.8) × 13.0-16.0 (14.5) μm (n =100). The isolates were identified as Lasiodiplodia spp. morphologically (Alves et al. 2008). DNA was extracted from fungal mycelia using an OmniPrep DNA extraction kit, and PCR amplification of ITS and EF1-α genes was performed following the conditions described by White et al. (1990) with some modifications using primers ITS1F-F/ITS4-R (Gardes and Bruns, 1993; White et al., 1990) and EF1-668-F/EF1-1251-R (Alves et al., 2008), respectively. The BLASTn in GenBank showed that the sequences obtained had 99.61 to 100% homology with those of ITS (EF622077) and EF1-α (EF622057) from L. pseudotheobromae CBS116459 (an ex-type strain) (Alves et al., 2008). Sequences of the isolates have been deposited in GenBank with accessions OP326017 to OP326021 for ITS, and OP356202 to OP356206 for EF1-α. Phylogenetic analysis showed that these isolates clustered in the same clade (bootstrap value at 64) with L. pseudotheobromae (Fig. S2). Two fungal inoculum types (mycelia and conidia), two fruit inoculation methods (injury and non-injury) and five fungal isolates were used for pathogenicity tests. Fungal mycelia (2-day-old) on PDA plug (5 mm) or 10 µL of conidial suspension (106 spores/mL) was placed onto each injury (1 x 1 mm in size) or a non-injury area on the surfaces of five strawberry fruits (cv. Florida Brilliance). PDA plug alone or water drops placed on injury or non-injury areas on fruits served as respective controls. Inoculated and control fruits were incubated in a covered plastic container with 100% RH at 22ºC. The experiment was repeated twice. Decay initially appeared as soft and lightly discolored tissue at inoculation areas 2 d post-inoculation (dpi) that extended quickly thereafter. Brown to dark lesions on both injury- and non-injury fruits inoculated with conidia or mycelia were observed at 3 dpi. Decay and gray mycelia gradually developed over the whole fruit at 6 dpi, and pycnidia were observed after 14 dpi (Fig. S1). Disease incidence of 100% was observed on all tests. Control fruits did not develop decay. The results indicate that these isolates are pathogenic to strawberries and infect fruit via both non-injured and injured fruit surfaces. The inoculated fungal isolates were re-isolated, thus, fulfilling Koch's postulates. L. theobromae, Neofusicoccum parvum/N. ribis species complex causing strawberry fruit rot in Florida fields was reported (Oliveira et al., 2019), but not L. pseudotheobromae. To our knowledge, this is the first report of postharvest decay caused by L. pseudotheobromae A.J.L. Phillips, A. Alves & Crous on strawberries in Florida and in the USA, and it should be considered in strawberry disease management.

Effect of green Fe2O3 nanoparticles in controlling Fusarium fruit rot disease of loquat in Pakistan

The subtropical fruit known as the loquat is prized for both its flavour and its health benefits. The perishable nature of loquat makes it vulnerable to several biotic and abiotic stressors. During the previous growing season (March-April 2021), loquat in Islamabad showed signs of fruit rot. Loquat fruits bearing fruit rot symptoms were collected, and the pathogen that was causing the disease isolated and identified using its morphology, microscopic visualisation, and rRNA sequence. The pathogen that was isolated was identified as Fusarium oxysporum. Green synthesized metallic iron oxide nanoparticles (Fe2O3 NPs) were employed to treat fruit rot disease. Iron oxide nanoparticles were synthesized using a leaf extract of the Calotropis procera. Characterization of NPs was performed by different modern techniques. Fourier transform infrared spectroscopy (FTIR) determined the existence of stabilizing and reducing compounds like phenol, carbonyl compounds, and nitro compounds, on the surface of Fe2O3 NPs. X-ray diffraction (XRD) explained the crystalline nature and average size (~49 nm) of Fe2O3 NPs. Energy dispersive X-ray (EDX) exhibited Fe and O peaks, and scanning electron microscopy (SEM) confirmed the smaller size and spherical shape of Fe2O3 NPs. Following both in vitro and in vivo approaches, the antifungal potential of Fe2O3 NPs was determined, at different concentrations. The results of both in vitro and in vivo analyses depicted that the maximum fungal growth inhibition was observed at concentration of 1.0 mg/mL of Fe2O3 NPs. Successful mycelial growth inhibition and significantly reduced disease incidence suggest the future application of Fe2O3 NPs as bio fungicides to control fruit rot disease of loquat.

Fruit rot causing by Athelia rolfsii (Sclerotium rolfsii) on jackfruit (Artocarpus heterophyllus) in China

Artocarpus heterophyllus, known as jackfruit, was a tropical fruit and cultivated extensively as nutritional and medicinal properties in southern China in recent year. During July 2022, fruit rot was observed on the fruits at the bottom of jackfruit trees in an orchard in Zhanjiang, Guangdong (N21°9' 27" E110°17' 54") 3-4 days after typhoon. The incidence rate of fruit was about 0.3%. The initial symptom was white mycelia appearing on the surface of fruits. Mycelia with rhizomorphs spread rapidly over the fruits, formed white, often fan-shaped mats with the rapeseed size sclerotia. The infected fruits were water-soaked, quickly became rotten, and fell off. Sclerotia from disease fruits were incubated on PDA with 50 mg/L ampicillin at 25-28℃ in the dark for 2 days. Hyphae tips were transferred to get the purified isolates. Colonies with a radial growth rate of 23.2 mm/day had abundant aerial mycelia and profuse sclerotia on PDA. Hyphae of the isolates were transparent, branched, with clamp connections at septa, usually 2.9-8.3 µm (Ave. 5.8 µm) (n>30) wide. Aerial mycelia were whitish-cottony, with many narrow rhizomorphs. Spherical sclerotia developed at about 10 days after incubation, and gradually changed from white to tan-to-dark brown, and mature sclerotia were about 1.7 mm in size. The morphological characteristics was similar to those of Sclerotium rolfsii (teleomorph: Athelia rolfsii). To accurately identify the fungus, the internal transcribed spacer gene (ITS) and large subunit rRNA gene (LSU) of isolate CASS-BLM-1 were PCR amplified with primer pairs ITS1/ITS4 (White et al 1990) and V9G/LR5 (Klaubauf et al 2014). The amplicons were sequenced and deposited in GenBank with accession number OP535473 (ITS) and OP535474 (LSU). BLASTn results showed that the nucleotide sequences of ITS and LSU had high identity with corresponding sequences of A. rolfsii isolates CBS 191.62 (ITS: MH858139, 472/474(99.58%); LSU: MH869724, 882/885(99.66%)) (Vu et al 2019). Phylogenetic analysis based on ITS sequence data was obtained according to maximum likelihood method using MEGA analysis software, CASS-BLM1 was grouped in A. rolfsii clade with 100% bootstrap support value. Based on morphology and DNA sequences, the fungus was identified as A. rolfsii (anamorph: S. rolfsii). To fulfil Koch's postulates, healthy fruits on the tree and detached fruits were inoculated with 7-day-old sclerotia of isolate CASS-BLM1. Five unwound sites and five wound sites with a sterile needle were tested on each fruit and a sclerotium was put at each site. Fruits not inoculated with sclerotia were used as control the test was repeated three times. All fruit were enclosed in transparent plastic bags with sterile absorbent cotton moistened with sterile distilled water. The indoor and outdoor temperatures ranged from 25 to 30 ℃. Three days later, white mycelia were observed on all inoculation sites, and 5 days later, the inoculated fruits began to rot, while control fruits remained healthy. The same fungus with identical morphology and DNA sequences was re-isolated from the inoculated sites. Previously, A. rolfsii was reported to cause fruit rot disease on jackfruit in Bangladesh (Elahi et al 2021), this is the first report of A. rolfsii causing fruit rot on jackfruit in China. A. rolfsii is suitable for high temperature and humidity environment (Punja 1985), this report will help farmers to diagnose this disease, especially to strengthen the disease prevention during the typhoon season.

Occurrence of Postharvest Fruit Rot of Mango Caused by Fusarium pernambucanum in China

Mango (Mangifera indica L.) is one of the most important tropical fruits in the world, thanks to its pleasant taste, aroma and high nutritional value (Ibarra et al. 2015). In June 2021, Surveys were conducted in three agricultural markets (113°36'E, 23°11'N) of the Yuancun district in Guangzhou, China. Postharvest fruit rot was observed on mango (about 25% of the fruits showed disease symptoms). Black rot symptomatic lesions were observed on the fruit surface and eventually penetrated the mesocarp of mango fruits. To isolate and identify the pathogen, fruits (n=35) were surface disinfected with 1% NaOCl (1 min), 70% ethanol (30 s) and then washed twice with sterile distilled water. Thirty small pieces (3-5 mm2) were excised from the lesion margins. The excised tissue pieces were cultured on potato dextrose agar (PDA). Pure cultures were obtained by transferring hyphal tips onto fresh PDA. Fungal isolates XTM-5 and XTM-8 were isolated from diseased fruits. All isolates grown on PDA had abundant, fluffy, whitish to yellowish aerial mycelia, and the colony reverse was pale brown. Macroconidia were falcate, slightly curved with 5-7 septa, 29.5-42.2 × 4.3-6.2 μm. Spindle-shaped mesoconidia were abundantly produced, straight to slightly curved with 3-4 septa, 20.3-24.5 × 4.6-4.8 μm. Microconidia were pyriform to obovate with 0-2 septa, 7.3-11.7 × 2.4-3.2 μm. Chlamydospores were globose or irregular, in chains and, hyaline to light brown. Based on the morphological characteristics, the fungus was tentatively identified as Fusarium pernambucanum (Santos et al. 2019). The molecular identity of the isolates was confirmed by sequencing the internal transcribed spacer (ITS), translation elongation factor 1 alpha (TEF1) and RNA polymerase subunit II gene region (RPB2) genes (White et al. 1990; O'Donnell et al. 2022). Sequences of isolate XTM-8 were deposited in GenBank (ITS: ON413679.1, TEF1:ON420221.2, RPB2: ON420222.2). A maximum-likelihood phylogenetic tree based on the concatenated sequences confirmed the isolates as F. pernambucanum (Xia et al. 2019). A pathogenicity test was conducted on mango. Six healthy fruits were inoculated with F. pernambucanum mycelial discs (5 mm in diameter) after being wounded with a needle or unwounded, six control fruits were inoculated with PDA agar. All inoculated fruits were incubated in the dark at 26°C and 95% relative humidity for 7 days post inoculation. Control fruits remained asymptomatic, whereas inoculated fruit developed symptoms on the fruit surface at the point of inoculation. The pathogenicity test was performed three times. The original isolates were confirmed morphologically and molecularly after they were reisolated from the symptomatic fruit, thus confirming Koch's postulates. F. pernambucanum is a widespread pathogen that causes diseases across a wide range of plant hosts in China, such as muskmelon fruit rot (Zhang et al. 2022); mango leaf spots (Guo et al. 2021) and plum leaf blight (Lu et al. 2022). To our knowledge, this is the first report of F. pernambucanum causing fruit rot of mango in China. As mango contamination with Fusarium mycotoxins poses a health risk for consumers, the occurrence of this disease needs to be carefully monitored to ensure effective disease management strategies are implemented in mango production.

Off-target selection of resistance to azoxystrobin in Aspergillus species associated with grape late season rots

Due to recent evidence of Aspergillus uvarum pathogenicity on wine grapes and variable fungicide sensitivity to quinone outside inhibitor (QoI) fungicides, the identity and QoI sensitivity of Aspergillus isolates from the Mid-Atlantic United States was investigated. Phylogenic analysis of 31 isolates revealed 26 as A. uvarum and 5 as A. japonicus, both of which have been previously isolated from grape. The A. uvarum isolates had variable sensitivities to the QoI azoxystrobin, and the genomic region that codes for the target of QoIs, cytochrome b, was sequenced. Translation of the cytochrome b coding sequence revealed that the most resistant isolates (termed cytb3) contained three mutations, S108A, F129L, and A194V, and the moderately sensitive isolates (termed cytb2) contained two mutations S108A and A194V. This is the first report of an amino acid variation in cytochrome b at position 108. Cytb3 isolates were significantly less inhibited than the cytb2 and wild-type isolates (cytbWT) in vitro, and were significantly less inhibited than the cytbWT isolates on detached fruit. Molecular docking analysis revealed similar differences, with azoxystrobin binding most securely in the cytbWT variant of cytochrome b than cytb2 and cytb3. As Aspergillus rot has not been a target disease of fungicide sprays in the U.S., the selection of resistant phenotypes is likely resultant from sprays for other diseases. Resistance is of concern due to the pathogenicity of A. uvarum and A. japonicus on wine grapes, and the ability of these species to be mycotoxigenic or pathogenic for humans.

First Report of Postharvest Fruit Rot on Citrus reticulata Blanco Caused by Fusarium concentricum in China

Nanfeng tangerine (Citrus reticulata Blanco) is highly regarded for its nutritional and economic value. In January 2022, an unknown fruit rot was observed on Nanfeng tangerine fruits harvested from Nanfeng County (27.22 °N, 116.53 °E), Fuzhou City, Jiangxi Province after 70 days in storage (25 °C, 90% relative humidity). The disease mostly started from the pedicel or a wound. Symptoms initiated with dark brown lesions that rapidly expanded between the fruit center and pulp capsule causing total fruit rot. The surface of symptomatic fruit was sterilized with 75% ethanol for 30 s and 2% NaClO for 30 s. Small diseased tissue pieces (2 mm2) between diseased and healthy tissues were placed on potato dextrose agar (PDA) and put in an incubator (25 ± 1 °C) for 3 days. The representative isolate NFMJ-1 was subcultured onto PDA using single-spore purification. Colonies on PDA were light yellow to white, with abundant flocculent aerial hyphae. Microconidia were oval, obovoid to allantoid, 0 septate, occasionally 1 septate, 4.07 to 17.53 × 1.69 to 3.56 μm (average=7.40 μm × 2.55 μm, n=50). Macroconidia were slender, with a beaked apical cell and a foot-shaped basal cell, 3 to 5 septate, 22.99 to 81.12 × 2.34 to 3.81 μm (average=45.04 μm × 3.12 μm, n=50). According to morphological characteristics, the isolate was tentatively identified as Fusarium sp. (Leslie and Summerell 2006). To confirm the identification, the internal transcribed spacer (ITS), translation elongation factor 1-alpha (TEF), RNA polymerase II second largest subunit (RPB2), beta-tubulin gene (TUB2), and calmodulin gene (CaM) sequences were amplified with primers ITS1/ITS4 (Gardes et al. 1993), TEF1/TEF2 (O'Donnell et al. 2010), RPB2-5f2/RPB2-7cr (Liu et al. 1999), Bt2a/Bt2b (Glass and Donaldson 1995), and CL1C/CL2C (Weir et al. 2012), respectively. The obtained sequences (ON184033, ON212051, ON212052, ON212053, ON212054) showed homology with F. concentricum ITS (MW016417.1; 514/514 bp), TEF (MK609902.1; 667/667 bp), RPB2 (LC631461.1; 941/972 bp), TUB2 (MT942588.1; 331/337 bp), and CaM (MK609916.1; 558/597 bp). A phylogenetic analysis of concatenated ITS-RPB2-TEF sequences was performed by MEGA7.0 with the maximum likelihood and Kimura 2-parameter model, revealing that the isolate was placed in the F. concentricum clade. To confirm pathogenicity, 36 healthy tangerine fruits were surface sterilized with 75% alcohol, then 18 disinfected fruits were wounded with sterile needles and 18 remained unwounded. Half of the wounded and un-wounded fruits were inoculated with 10 μL of a conidial suspension (1.0 × 106 conidia/ml) of isolate NFMJ-1 cultured for 7 days on PDA. Half of the wounded and un-wounded fruits were mock-inoculated with sterile water as controls. After incubation in an incubator (25 ± 1°C, 90% relative humidity) for 7 days, the wounded fruits inoculated with F. concentricum showed similar symptoms to the original diseased fruits, while the mock-inoculated fruits were asymptomatic. The pathogenicity test was repeated three times. The pathogen was re-isolated from the wound-inoculated fruits and identified as F. concentricum by morphological and molecular analysis, completing Koch's postulates. F. concentricum has been reported as a pathogen of Podocarpus macrophyllus (Dong et al. 2022), Capsicum annuum (Wang et al. 2013) and Zea mays (Du et al. 2020) in China. This is the first report of fruit rot caused by F. concentricum on Citrus reticulata in China. Appropriate prevention and control measure of the pathogen need to be developed to preserve marketability of this economically important citrus fruit.

First report of Fusarium tricinctum causing fruit rot on navel orange (Citrus sinensis (L.) Osbeck) in China

Citrus sinensis (L.) Osbeck is popular with consumers for its delicious taste. In December 2020, a rot symptom causing about 15% losses of a total of 450 fruits was observed on 'Newhall' navel oranges after 70 d storage (20℃, 85%-90% RH) at Jiangxi Key Laboratory for Postharvest Technology and Nondestructive Testing of Fruits & Vegetables (28.68° N, 115.85° E). The fruits were harvested from an orchard in Ganzhou City, Jiangxi Province, China (25.53° N, 114.79° E). Incipiently, the pedicles of infected fruits were brown, the peels became softened and showed yellowish-brown lesions which, gradually expanded and had white hyphae (Fig. S1A). To isolate the pathogen, the surface of diseased fruits was disinfected with NaClO (2%) for 2 min and ethanol (75%) for 0.5 min, then washed with sterile water three times. Tissues (5 × 5 mm) around the lesion were incubated on potato dextrose agar (PDA) at 28 ± 1℃ (L: D=12: 12) for 5 days. Five cultures with similar morphology were obtained and colonies initially produced white aerial hyphae and became khaki then turned pink on PDA (Fig. S1F, G, H). Abundant microconidia, macroconidia and rare chlamydospores were observed after 10 days on PDA and no glucose PDA media (Zhang et al. 2020). Macroconidia were falciform and curved to lunate, 2-4 septa, 29.38 × 3.75 µm in size (n=50) (Fig. S1K, Fig. S3). Microconidia were oval, napiform or pyriform, 0-1 septa, 12.00 × 3.43 µm in size (n=50) (Fig. S1L1 to L4, Fig. S3). Chlamydospores were found in hyphae, ellipsoidal or orbicular (Fig. S1I-1 to I-2, J-1 to J-2). The morphological features of five isolates were similar to Fusarium (Leslie and Summerell 2006). Genomic DNA of five isolates was extracted with DNA Extraction Kit (Yeasen, Shanghai, China), ITS1/ITS4, EF1Ha/EF2Tb and fRPB2-5F/fRPB2-7cR primers were used to amplify the internal transcribed spacer region (ITS), and the transcriptional elongation factor-1 alpha (TEF-1α), and RNA polymerase II (RPB2) gene sequences (White et al. 1990; Carbone and Kohn 1999; Liu et al. 1999). The ITS, TEF-1α and RPB2 sequences of five isolates were deposited in GenBank and showed 99-100% identity with corresponding sequences from F. tricinctum (Table S1). A phylogenetic tree was constructed with ITS-TEF-1α-RPB2 concatenated sequences in MEGA7.0 (Li et al. 2021) and all five isolates were placed in F. tricinctum clade with 100% bootstrap support (Fig. S2). To confirm pathogenicity, ten healthy C. sinensis fruits were surface-sterilized with 75% ethanol and inoculated with 10 µL spore suspension (1.0 × 106 spore/mL) including five wounded (with sterilized needle) and five unwounded (Fig. S1B to E). Control fruits were inoculated with 10 µL sterile water. All fruits were incubated at 28 ± 1℃, 90% RH for 7 days. The experiment was conducted three times. The lesion diameter of inoculated wounded fruits was 21.01 ± 2.52 mm and showed similar symptoms to original rotten fruits. However, the control and unwounded fruits remained healthy. To fulfill Koch's postulates, F. tricinctum was re-isolated from the inoculated fruits and deposited in Collaborative Innovation Center of Postharvest Key Technology and Quality Safety of Fruits and Vegetables in Jiangxi Province. To our knowledge, F. tricinctum has been reported on apple tree and kiwi plant in China (Zhang et al. 2021; Ma et al. 2022), but this is the first report of F. tricinctum causing fruit rot on navel orange in China. This finding provides important information for preventing postharvest disease of citrus.

Antifungal activity of Zinc nitrate derived nano Zno fungicide synthesized from Trachyspermum ammi to control fruit rot disease of grapefruit

Grapefruit (Citrus paradisi) is a widely grown citrus and its fruit is affected by a variety of biotic and abiotic stress. Keeping in view the hazardous effects of synthetic fungicides, the recent trend is shifting towards safer and eco-friendly control of fruit diseases. The present study was aimed to diagnose the fruit rot disease of grapefruit and its control by using zinc oxide green nanoparticles (ZnO NPs). Fruit rot symptoms were observed in various grapefruit growing sites of Pakistan. Diseased samples were collected, and the disease-causing pathogen was isolated. Following Koch's postulates, the isolated pathogen was identified as Rhizoctonia solani. For eco-friendly control of this disease, ZnO NPs were prepared in the seed extract of Trachyspermum ammi and characterized. Fourier transform infrared spectroscopy (FTIR) of these NPs described the presence of stabilizing and reducing compounds such as phenols, aldehyde and vinyl ether, especially thymol (phenol). X-ray diffraction (XRD) analysis revealed their crystalline nature and size (48.52 nm). Energy dispersive X-ray (EDX) analysis elaborated the presence of major elements in the samples, while scanning electron microscopy (SEM) confirmed the morphology of bio fabricated NPs. ZnO NPs exhibited very good anti-fungal activity and the most significant fungal growth inhibition was observed at 1.0 mg/ml concentration of green NPs, in vitro and in vivo. These findings described that the bioactive constituents of T. ammi seed extract can effectively reduce and stabilize ZnO NPs. It is a cost-effective method to successfully control the fruit rot disease of grapefruit.

First Report of Fusarium equiseti, Causing Fruit Rot Disease of Watermelon in Malaysia

Watermelon (Citrullus lanatus) accounts for almost 13% of all tropical fresh fruit production in Malaysia. They are grown, mostly in Johor, Kedah, Kelantan, Pahang, and Terengganu areas of Malaysia on 10,406 ha and yielding 172,722 Mt. In 2019, a new fruit rot disease was observed in two major production areas in Peninsular Malaysia. Disease symptoms included water-soaked brown lesions on the fruit surface in contact with the soil. The lesions enlarged gradually and ultimately covered the whole fruit with white mycelium leading to internal fruit decay. Disease surveys were conducted in December 2019 and November 2020 in fields at Kuantan, Pahang and Serdang, Selangor. Disease incidence was 10% in 2019 and 15% in 2020. Infected fruits were collected and washed under running tap water to wash off adhering soil and debris. Fruit tissue sections 1 to 2 cm in length were surface sanitized with 0.6% sodium hypochlorite (NaOCl) for 3 min. and washed twice with sterile distilled water. The disinfected air-dried tissues were then transferred onto potato dextrose agar (PDA) media and incubated at 25±2℃ for 3 days. Fungal colonies with whitish mycelium and pink pigment isolated using single spore culture. The pure cultures were placed onto carnation leaf agar (CLA), and the culture plates were incubated at 25±2℃ for 15 days for morphological characterization. On CLA, macroconidia were produced from monophialides on branched conidiophores in orange sporodochia. Macroconindia were thick-walled, strong dorsiventral curvature, 5 to 7 septate with a tapered whip-liked pointed apical cell and characteristic foot-shaped basal cell, 21.9 to 50.98 μm long and 2.3 to 3.60 μm wide. Typical verrucose thick chlamydospores with rough walls were profuse in chains or clumps, sub-globose or ellipsoidal. Based on morphological characteristics they were identified as Fusarium equiseti (Leslie and Summerell 2006). Molecular identification of both U4-1 and N9-1 pure culture isolates were carried out using two primer pair sets; internal transcribed spacer (ITS) ITS-1/ ITS-4 and translation elongation factor 1 alpha (TEF1-α) (EF-1/EF-2). A Blastn analysis of the ITS gene sequence of U4-1(MW362286) and N9-1 (MW362287) showed >99% similarity index to the reference gene sequence of F. equiseti isolate 19MSr-B3-4 (LC514690). The TEF1-α sequences of U4-1 (accession no. MW839563) and N9-1 (accession no. MW839564) showed 100% identity; with an e-value of zero, to the reference gene sequence of F. equiseti isolate URM: 7561 (accession no. LS398490). Each isolate also had a >99% identity with isolate NRRL 34070 (accession no. GQ505642) in Fusarium MLST database that belongs to the F. incarnatum-equiseti species complex (O'Donnell et al. 2015). Based on phylogenetic analysis of the aligned sequences (TEF1-α) by the maximum likelihood method, the U4-1 and N9-1 isolates were confirmed to be F. equiseti as was reported in Georgia, USA (Li and Ji 2015) and in Harbin, Heilongjiang Province, China (Li et al. 2018). Finally, the two pure culture isolates of U4-1 and N9-1 were used to fulfill Koch's postulates. Stab inoculations of five healthy watermelon fruits (cv. 345-F1 hybrid seedless round watermelon) were performed with a microconidial suspension of individual isolates (4x106 spores/mL). Five control fruits were stabbed with double distilled water. The inoculated fruits were incubated under 95% relative humidity at a temperature of 25±2℃ for 48 h followed by additional incubation inside an incubator at 25±2℃ for 8 days. Ten days post-inoculation, the control fruits showed no disease symptoms. However, inoculated fruits exhibited typical symptoms of fruit rot disease like water-soaked brown lesions, white mycelium on the fruit surface and internal fruit decay, which is similar to the farmer's field infected fruits. The suspected pathogen was successfully re-isolated from the symptomatic portion of inoculated fruit and morphologically identified for verification. To our knowledge, this is the first report of F. equiseti causing fruit rot of watermelon in Malaysia. Malaysia exports watermelon year-round to many countries around the world. The outbreak of this new fruit rot disease could potentially pose a concern to watermelon cultivation in Malaysia.

First Report of Colletotrichum karstii Causing Fruit Anthracnose of Carissa grandiflora in Spain

The species Carissa grandiflora A. DC., commonly called Natal plum, is a shrub native to the coastal region of Natal, South Africa. In southern Spain, Natal plum is used as an ornamental plant due to its beautiful flowers and red ripen fruits. In March 2019 and 2020, we surveyed nine public gardens in the cities of Cadiz and Sanlucar de Barrameda (Andalusia, Spain); and Natal plum fruit showing anthracnose symptoms were observed in six (55% prevalence) of them. Affected fruits showed necrotic and circular lesions with acervuli in the center (Fig. 1a) causing the complete mummification of the fruit (Fig. 1b). Affected fruits were collected from four gardens and disinfested according to Moral et al. (2010). Six fungal isolates were recovered from small (3-4 × 1-2 mm) pieces of the affected fruits in Potato Dextrose Agar (PDA), and hyphal tips from them were transferred to fresh PDA to obtain pure cultures. The six isolates were initially identified as Colletotrichum karstii according to their morphology and the sequences of the ITS1-5.8S-ITS2 (ITS) region (Damm et al. 2012). The six Colletotrichum isolates showed similar colony morphology and their ITS sequences were identical. Overall, C. karstii isolates showed cylindrical and straight conidia that were 12.1 to 14.2 μm long and 4.9 to 5.6 μm wide (n = 50). The aerial mycelia of the fungus varied from grayish-white to dark gray. A multilocus approach was conducted for more precise identification of the Colletotrichum species. For that, ITS, beta-tubulin (TUB2), actin (ACT), partial sequences of the chitin synthase 1 (CHS-1), histone 3 (HIS3), and a 200-bp intron fragment of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) of a representative isolate (FITP19001) were amplified and sequenced according to Damm et al. (2012). GenBank Accession Nos. for ITS, TUB2, ACT, CHS-1, HIS3 and GADPH: MT757643, MT759805, MT759806, MT759807, MT759808 and MT759809, respectively. Sequences showed 100% identity with homologous sequences belonging to C. karstii (GenBank taxid:1095194). To test Koch's postulates, 10 unripen and 10 ripen C. grandiflora fruits, harvested from asymptomatic plants, were inoculated. For each group, five fruits were inoculated using a drop of 10 µl of 5 × 104 conidia per ml suspension of C. karstii (FITP19001) and another five fruits were inoculated using a mycelial plug of the same isolate. Inoculated fruits were incubated in a humid chamber at room temperature (19-24ºC) under light for two weeks. Non-inoculated control fruits were treated with sterile water or a PDA plug and incubated under the same conditions. The pathogenicity test was conducted twice. After 10 days, typical anthracnose symptoms developed on both unripen and ripen inoculated fruits, but not on non-inoculated controls. Overall, the severity of anthracnose lesions was higher on ripen fruits than in the unripen fruits. Likewise, the severity of symptoms was higher on the fruits inoculated using a mycelial plug than on those fruits inoculated with a spore suspension. The species C. karstii was reisolated from lesions of all inoculated fruits as described above but not from non-inoculated fruits. The species C. karstii has been described affecting numerous species worldwide (Damm et al., 2012). Previously, C. gloeosporioides was reported causing fruit anthracnose of Natal plum in Florida (Alfieri et al., 1984). To our knowledge, this is the first report of C. karstii causing anthracnose on the fruit of Natal plum in Spain and worldwide.

First Report of Sclerotinia sclerotiorum Causing Strawberry Fruit Rot in Florida

During the 2019-2020 Florida strawberry season (October to April), a strawberry (Fragaria × ananassa) fruit rot was observed in two fields (Plant City and Wimauma, FL) with up to 5% incidence on short-day cultivars SensationTM Florida127, and Florida Brilliance. Symptoms on pink and ripe fruit consisted of softening, discoloration, watery rot with white fuzzy mycelium, and initial sclerotium formation. Diseased tissue was placed on General Isolation (GI) medium (Amiri et al. 2018) and incubated at 25°C under a 12-h photoperiod. A fungus producing spreading cottony white colonies with dark sclerotia near the outer edges of the plates was consistently isolated. One isolate from each cultivar field (20-51 and 20-55) was selected for identification and pathogenicity tests. Apothecial production was induced following the protocol of Li and Rollins (2009), and apothecia (n=30) had an average diameter of 4.5 (3.5 to 7.2) mm. Sclerotia were 3.6 (2.5 to 6.2) mm by 4.5 (3.1 to 5.9) mm (n=30) in size. Dimensions of asci were 130.2 (115.1 to 160.5) μm by 8.5 (6.2 to 13.1) μm (n=30), and those of ascospores were 12.2 (10.8 to 14.6) μm by 6.8 (5.7 to 8.1) μm (n=30). Based on these morphological features, the pathogen was tentatively identified as Sclerotinia sclerotiorum (Lib.) de Bary (Maas 1998). DNA was extracted from the same two isolates using the FastDNA kit (MP Biomedicals, Solon, OH), and the ribosomal internal transcribed spacer (ITS) region was amplified using the primers ITS1 and ITS4 (White et al. 1990). Sequences were deposited in GenBank (accession nos. MT378215 and MT378216). BLASTn searches revealed that isolates 20-51 and 20-55 were 99.62% identical (526 / 528 bp) to S. sclerotiorum CBS 499.50 (MH856725.1). Immature pink fruit of SensationTM 'Florida127' were harvested, surface disinfested in bleach solution (0.08% NaClO) for 90 sec, rinsed twice with deionized water, then placed into styrofoam egg cartons inside clean plastic boxes (30x24x7 cm) containing 150 ml of sterile deionized water to maintain moisture, and kept at 25°C with a 12-h photoperiod. Ascospores and sclerotia were used for inoculation tests with three repetitions in an egg carton containing 12 fruit each per isolate and inoculation method. The experiment was repeated once. Fruit were inoculated by placing 20 μl of a 1 × 106 ascospores/mL suspension or a single sclerotium on the upper half of the fruit. Controls were included, by placing 20 μl of sterile DI water or fruit with no sclerotia. Evaluations were done 6, 10, and 15 days after inoculation (DAI). Control fruit remained healthy, while inoculated fruit developed symptoms of softening and discoloration. For ascospore inoculation, disease incidence was 55 (± 5) and 78% (± 4), for 6 and 15 DAI, respectively, whereas for sclerotia inoculation incidence was 100% 6 DAI. Morphologically identical fungi to the original isolates were re-isolated from the diseased fruit. No other fruit decay fungi were observed. S. sclerotiorum has been previously reported causing strawberry fruit rot in Washington state in the United States, England, Israel, and Scotland (Alcorn 1966; Maas 1998; McLean 1957). It has also been listed in the indices of plant diseases from Florida, North Carolina, and California as causing crown rot (Farr and Rossman 2020). To our knowledge, this is the first report of S. sclerotiorum causing strawberry fruit rot in Florida. The pathogen is an aggressive necrotroph with prolonged survival and affects several vegetable crops grown in Florida (Paret et al. 2018). Because only the strawberry beds are fumigated, sclerotia remaining in the alleys could serve as inoculum sources. Currently, the disease is rare and of minor significance to strawberry production. However, efforts should be implemented to monitor its occurrence and spread.

Occurrence of stem blight and fruit rot caused by Phytophthora capsici on Chinese cucumber (Trichosanthes kirilowii) in China

Chinese cucumber, Trichosanthes kirilowii Maxim, is a perennial liana plant belonging to the Cucurbitaceae family and is an important traditional medicine in Chinese herbalism. The root, fruit and seed possess the medicinal value, and also the seeds are edible (Zhang et al. 2019). With increasing demand, the wild resource was domesticated and has been planted in China. Diseases of T. kirilowii have become more prominent with the expansion of cultivated area and have caused the yield reduction (Zhang et al. 2014). The general disease field has caused a yield reduction of 10% -30%, even up to 80% seriously. Since 2017, fields in Luan city, Anhui province exhibited 10 to 30% of plants with stem blight and fruit rot. The two-week seedlings were infected at the basal part of stem and showed water-soaking, then damping off. In older plants, it is common to see stem blight with brown-to-black lesions, stunted growth, and most diseased plants eventual death. On rot fruit, the symptom of water soaked lesions was firstly observed, and then with white mold, eventual rot. More than 60 samples of symptomatic stems or fruit were collected from Luan and Hefei, Anhui province during April to October 2017. The symptomatic tissues were washed, disinfested with 0.5% sodium hypochlorite for 30 s, rinsed twice in sterile water for 1 min, dried and incubated on V8-juice amended with 50μg ml-1 of ampicillin and rifampicin at 25°C. Based on morphological characteristics, more than 80% of the total 98 isolates generated were similar on the level of morphology, and preliminarily identified as Phytophthora species (Erwin and Ribeiro 1996). Three isolates were selected randomly to further observe and identify up to species level. The isolates produced abundant, aerial, white mycelia on V8 agar plates. Sporangia were produced on sporangiophores in 10% V8 liquid culture medium after 4 days at 25°C, mainly obovoid with one papilla, 38.8 to 50.4 μm× 22.8 to 33.5 μm in size. The single mature sporangium immersed in water quickly released 20 to 40 biflagellate motile zoospores. The isolates were further confirmed by amplification and sequencing of two conserved markers, the internal transcribed spacer (ITS) region and cytochrome c oxidase subunit I (COI) region with primers ITS1/ITS4 (White et al. 1990) and OomCoxILevup/Fm85mod (Robideau et al. 2011), respectively. The GenBank Accession Nos. were MN368092, and MN369544 for ITS and COI, respectively. The BLAST search results showed 100% similarity with ITS sequences (KF700090, KC438376) and COI sequences (MH136864, AY129166) of Phytophthora capsici isolates in Genbank. Koch's postulates were performed by testing the pathogenicity of the sequenced isolate on the Chinese cucumber (cv. 'Wanlou9'). On 1-month-old plants, a flap of bark was cut with a sterile scalpel, and the 2×2 cm plug of 5-day-old mycelium was inserted. The flap was then closed and sealed with Parafilm. The agar plug was treated in the same manner as the inoculated plants as the controls. And also, the intact fruit (one month old) was inoculated with 10 μL of zoospore suspension (2 × 105 zoospore/ml) and kept in growth chamber at 25 °C, with 80% relative humidity, and the control was treated with 10 μL of sterile distilled water. Three days after inoculation, the stems and the fruit inoculated with mycelium and zoospores showed water-soaked lesions. After 10 days, the symptoms on the tissues resembled those observed in the field. No symptoms were detected on the controls. P. capsici was reisolated from the diseased tissues but not from the control. This combination of data confirmed that the pathogen was P. capsici. To our knowledge, this is the first report of P. capsici causing stem blight and fruit rot on Chinese cucumber in China.

Morphological and Molecular Characterization of Pomegranate Fruit Rot Pathogen, Chaetomella raphigera, and its Virulence Factors

A new fungal pathogen was isolated from rotten pomegranates collected from the orchards of different parts of Maharashtra. The pathogen was morphologically identified as Chaetomella raphigera followed by sequencing of ITS and D1/D2 hypervariable region of LSU (28S) of rRNA gene. The pathogen produced pectinase, cellulase, xylanase and protease in liquid medium at a concentration of 71, 13.8, 54.3 and 7 U/ml respectively. Enzyme activity was also determined during pathogenesis in the tissues artificially infected by C. raphigera. Xylanase activity was maximum (25.1 U/g) followed by pectinase (19.2 U/g) and cellulase (1.5 U/g), whereas, protease activity was unnoticed. There was significant correlation (P < 0.05) between disease rating scale and pectinase, xylanase and cellulase activity in infected tissues. This indicates the simultaneous production of hydrolytic enzymes that aids in necrosis of fruit tissues. The elevated levels of these enzymes in infected tissues as compared with control suggest their possible role in pathogenesis. Thus, pectinase, cellulase and xylanase produced by C. raphigera acts as major virulence factors in the development of fruit rot in pomegranates. This is a first report of fungal fruit rot caused by C. raphigera in pomegranate.

Occurrence of Fruit Rot of Melon Caused by Sclerotium rolfsii in Korea

In 2007 to 2008, a fruit rot of Melon (Cucumis melo L.) caused by Sclerotium rolfsii occurred sporadically in a farmer's vinyl house in Jinju City. The symptoms started with watersoaking lesion and progressed into the rotting of the surface of fruit. White mycelial mats appeared on the lesion at the surface of the fruit and a number of sclerotia formed on the fruit near the soil line. The sclerotia were globoid in shape, 1~3 mm in size, and white to brown in color. The hyphal width was measured 3 to 8 µm. The optimum temperature for mycelial growth and sclerotia formation was 30 on PDA. Typical clamp connections were observed in hyphae of grown for 4 days on PDA. On the basis of symptoms, mycological characteristics and pathogenicity to the host plant, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report of the fruit rot of Melon caused by S. rolfsii in Korea.