Roughened Walls Research Articles

First Report of Wilt Caused by Fusarium nanum (FIESC 25) on Mungbean (Vigna radiata) in Pakistan.

Mungbean, Vigna radia (L.) R. Wilczek, is ranked 2nd next to chickpea (Cicer arietinum) in total cultivation and production in Pakistan. In August of 2022 and 2023, mungbean plants (cv. PRI Mung-2018) were found wilting in a field at the Ayub Agricultural Research Institute, Faisalabad, Pakistan. Wilted leaves turned yellow, died, but remained attached to the stem. Vascular tissue at the base of the stem showed light to dark brown discoloration. Roots were stunted with purplish brown to black discoloration. Symptomatic mungbean plants were collected from fields at five different locations (20 samples/location). Disease incidence was similar among the five fields, ranging from 5 to 10% at each location depending upon type of germplasm and date of sowing. For fungal isolation and morphological identification, symptomatic stem and root tissues were cut into ~5 mm2 pieces with a sterilized blade. Tissues were surface-sterilized for one min in a 0.5% sodium hypochlorite solution, rinsed twice in sterilized water, air dried on sterilized filter paper, and aseptically placed on potato dextrose agar (PDA) containing 0.5 g/L-1 streptomycin sulphate. Plates were incubated for 3-4 days at 25 ± 2°C with a 12-h photoperiod. Single-spore cultures were used for morphological and molecular analyses. Isolates on PDA grew rapidly and produced abundant white aerial mycelium that turned off-white to beige with age. Macroconidia were hyaline, falcate, typically 3-to-6 septate with a pointed apical cell and a foot-shaped basal cell, measuring 24.5-49.5 x 2.7-4.7 μm (n = 40). Globose to obovate chlamydospores measuring 5.8 ± 0.5 μm (n = 40) were produced singly or in chains and were intercalary or terminal and possessed roughened walls. The morphological data indicated the isolates were members of the genus Fusarium (Leslie and Summerell 2006). To obtain a species-level identification, a portion of translation elongation factor 1-α (TEF1), the largest subunit of RNA polymerase (RPB1), and the second largest subunit of RNA polymerase (RPB2) region were PCR amplified and sequenced using EF1/EF2 (O'Donnell et al. 1998), Fa/G2R (Hofstetter et al. 2007), and 5f2/7cr (Liu et al. 1999) primers, respectively. DNA sequences of these genes were deposited in GenBank under accession numbers MW059021, MW059017 and MW059019, respectively. The partial TEF1, RPB1 and RPB2 sequences were queried against the Fusarium MLST database (https://fusarium.mycobank.org/page/Fusarium_identification), using the polyphasic identification tool. The BLASTn search revealed 99.9% identity of the isolate to F. nanum (Xia et al. 2019), formerly FIESC 25 of the F. incarnatum-equiseti species complex (MRC 2610, NRRL 54143; O'Donnell et al. 2018). To confirm pathogenicity, roots of 3-5 leaf stage mungbean seedlings were soaked in a 106 spores ml-1 conidial suspension of the fungus for 15 min and then planted in 10 cm pots containing sterilized soil. Mock-inoculated plants with sterile water served as a negative control. Twenty pots that were used for each inoculated and control treatment were maintained at 25 ± 2°C, 14:8 h photoperiod, and 80% relative humidity in a growth chamber. After 15 days, leaf yellowing, internal browning from the base of stems and root discoloration was observed in all the inoculated plants. The uninoculated negative control plants remained asymptomatic. Fusarium nanum was re-isolated from artificially inoculated plants and identified by colony growth, conidial characteristics on PDA and molecular analyses (TEF1). To our knowledge, this is the first report of wilt caused by F.nanum on mungbean in Pakistan. In Pakistan, mungbean cultivation in irrigated areas has increased in recent years. It has been introduced frequently in citrus orchards, crop rotation of maize and sesame, intercropping with sugarcane and as green manure. However, citrus, maize, sesame and sugarcane are also hosts of Fusarium spp. Therefore, this information warrants sustainable crop protection and may have an impact on further interaction of F. nanum with other wilt pathogens.

First report of Fusarium equiseti causing leaf spots of Bitter gourd (Momordica charantia) in Pakistan.

Bitter gourd (Momordica charantia L.) is an important vegetable crop of the Cucurbitaceae family widely cultivated in Pakistan and around the world. In October 2020, a nutrition management trial of Bitter gourd cv. Seminis-200) was conducted on an area of 10,860 sq. ft. (99×110 feet) at the Agricultural Research farm of Bahauddin Zakariya University, Multan (30.2601° N, 71.5158° E), Pakistan. Symptoms of large, brown necrotic leaf spots were observed on the leaves of bitter gourd vines. The disease started from the yellowing of leaves within the reticulate venation and turned brown. Irregular brown leaf spots coalesced to form large necrotic areas followed by foliar chlorosis then wilting that occurred very late. There were no crown rot symptoms although there was slight discoloration of roots and when cut longitudinally, browning of tissues was observed. The disease was assessed visually with 37% incidence which resulted in poor quality and yield in terms of reduced size and yellowing of fruit. Infected vines along with the roots were collected for the isolation of pathogen. A total of 34 leaves and 22 root samples were collected from the field for isolation. The leaf, collar and root portions were cut into 0.5 to 1 cm in length and surface disinfected with 1% sodium hypochlorite (NaOCl) for 2-3 minutes followed by washing twice with autoclaved distilled water and after drying, placed on potato dextrose agar (PDA) medium, and incubated at 25±2 °C for one week. The fungal colonies of fluffy white growth with light orange pigment were isolated. For morphological characterization, a total of 4 pure cultures were isolated from leaves, collar region and root by single spore technique on carnation leaf agar (CLA) medium after 15 days of incubation at 25±2℃. Curved and thick-walled macroconidia with elongated or pointed apical characteristic foot-shaped basal cells were produced in sporodochia. Macroconidia with 5-7 septa measured 22.50-41.80 μm × 2.90-4.20 μm (n = 60). Thick, brown with roughened walls and subglobose ellipsoidal chlamydospores were observed in clumps or chains with the dimension of 5.8 to 10.8 μm (n = 20). On morphological characteristics, the fungus was identified as Fusarium equiseti (Corda) Sacc. according to Leslie and Summerell (2006). Two single spore isolates were used for molecular identification by amplifying ribosomal DNA of the internal transcribed spacer (ITS) region with ITS1/ITS4 primers (White et al. 1990) and for β-tubulin gene region, primers T1/Bt-2b (O'Donnell and Cigelnik, 1997) were used. The obtained sequences were deposited in GenBank with accession numbers MW880179 and MW880198 from the ITS region and BLAST search in GenBank showed 100 and 98.11% alignment with previously published sequences of F. equiseti with accessions OM992323.1and MT558569.1 respectively. Accession number OM867571from the β-tubulin region showed 100% sequence similarity with F. equiseti with accession MN653163.1. For pathogenicity, macroconidia from 2-week-old cultures on CLA medium were harvested to prepare spore suspension (1 × 106 conidia/ml). Koch's postulates were confirmed on nine bitter gourd plants (cv. Seminis-200) by applying spore suspension of fungal inoculum at 3-4 leaf stage separately on leaves by automizer, on collar region after making incision spore suspension was applied and in the root zone, 20ml spore suspension was added whereas distilled water was used as a control with three replications. Plants were kept under controlled conditions in the greenhouse with 65% to 75% humidity and the temperature was maintained at 32±2 °C for one week. After 7-8 days, inoculated plants began to exhibit symptoms of brown, necrotic leaf spots on the leaves of bitter gourd vines followed by yellowing of leaves that eventually turned brown. Roots showed slight discoloration and browning of vascular bundles and finally, the plants wilted after four weeks. while control plants remained symptomless. The symptoms resembled those noticed in the field. The fungus was re-isolated from leaves, collar region and roots, followed by morphological identification, and finally confirmed as F. equiseti. To the best of our knowledge, this is the first report of a leaf spot caused by F. equiseti in a bitter gourd from Pakistan. If the disease is not managed properly, it may cause a drastic effect on yield under favorable environmental conditions. The pathogen may also damage other cucurbitaceous crops cultivated in the area.

CFD analysis of Fe transfer on roughened wall caused by turbulent lead-bismuth eutectic flow

Structural material compatibility with lead bismuth eutectic is one of the main challenges for design and operation of the LBE-cooled nuclear systems. To better understand the mechanisms of stainless steel corrosion behavior in LBE flow, the iron mass transfer phenomenon on roughened walls under various LBE pipe flow conditions are numerically investigated in this study. CFD simulations are performed, by applying a low Reynolds number k-ε model, in a range of Reynolds number from 5 × 103 to 105. Meanwhile, various pipe wall roughness conditions are considered, which are simulated by crests with different depths and periodic lengths. Effects of roughness dimensions and Reynolds numbers on the near-wall mass transfer rate are investigated. Results showed that higher flow velocities and shorter crest length led to higher mass transfer coefficient. On the basis of the results, the mass transfer coefficients are proposed both for smooth wall and roughened walls. The mass transfer enhanced by wall roughness is characterized by the ratio of rough-to-smooth mass transfer coefficient, and this ratio is demonstrated by a regression equation, in which dimensionless roughness number, Reynolds number and geometrical ratio of the roughness are included. Moreover, it is found that the ratio of rough-to-smooth mass transfer coefficient is relatively more dependent on Reynolds number.

Impact of non-uniform surface roughness on the erosion rate and performance of a cyclone separator

The present study investigates the influence of non-uniform surface roughness on the performance and erosion rate of a Staimand cyclone separator. Non–uniform roughness is considered for the cylindrical part, cone, and vortex finder of the cyclone. Three-dimensional simulations are performed using the Reynolds stress turbulence model (RSM). The Eulerian-Lagrangian approach is used for tracking solid particles. The results reveal that non-uniform surface roughness affects the flow pattern, collection efficiency, erosion rate, and pressure drop significantly. The maximum tangential velocity in the cyclones with the roughened surfaces is 1.3 times the inlet velocity. The maximum tangential velocity is reduced when the range of roughness height decreases. As the range of roughness height is enhanced, the axial velocity increases considerably. For instance, at the axial position of y = 0.75D, the value of axial velocity is about 0.34 and 0.08 times the inlet velocity for states 1 and 6 of the descending non-uniform roughness (DNUR) case, respectively. It is observed that the pressure drop in the cyclones with non-uniformly roughened surfaces is less than that in the cyclone with smooth walls. For the cut-off size diameter d100, four states of the ascending non-uniform roughness (ANUR) cyclone can completely collect the particles with diameters of 4.8, 4.9, 5, and 6 µm, while the smooth-walled cyclone can collect 7-µm particles with the collection efficiency of 100%. Besides, it is demonstrated that the erosion rate of cyclones with non-uniformly roughened walls is less than that of smooth-walled one for all mass loads.

First report of Fusarium incarnatum causing spikelet rot on rice in China.

Rice (Oryza sativa L.) is the most important and widely grown crop, covering about 29.9 million ha of total cultivation area in China. In the last decade, spikelet rot disease on rice became much more frequent in the middle and lower reaches of the Yangtze River, China. Fusarium proliferatum (Matsush.) Nirenberg ex Gerlach & Nirenberg was reported to be a causal agent of spikelet rot on rice in Hangzhou, Zhejiang province (Huang et al. 2012). In September 2019, a survey was conducted to understand the etiology of the disease in the main rice growing regions of Jinshan District of Shanghai. Symptomatic panicles exhibiting reddish or brown discoloration on the glumes were collected from different rice fields, where disease incidence was estimated to be between 20 to 80%. Diseased glumes were cut into small sections (5 × 5 mm) from the boundary of necrotic and healthy tissues, surface-sterilized with 75% ethanol for 30 s and 3% sodium hypochlorite for 90 s, rinsed twice with sterile distilled water, then placed onto 1/5 strength potato dextrose agar (PDA). After 3 to 5 days of incubation at 28°C in the dark, fungal growth with Fusarium-like colonies were transferred to PDA and purified by the single-spore isolation method. A total of 12 isolates were obtained and colonies showed loosely floccose, white mycelium and pale-yellow pigmentation on PDA. Microconidia were ovoid mostly with 0 to 1 septum, and measured 4.2 to 16.6 × 2.5 to 4.1 μm (n = 50). After 5-7 days of inoculation on carnation leaf agar (CLA), macroconidia produced usually had 3 to 5 septa, slightly curved at the apex, ranging from 15.7 to 39.1 × 3.3 to 5.0 μm (n = 50). Chlamydospores were produced in hyphae, most often solitary in short chains or in clumps, ellipsoidal or subglobose with thick and roughened walls. Molecular identification was performed on the representative isolates (JS3, JS9, and JS21). The rDNA internal transcribed spacer (ITS), translation elongation factor (TEF-1α) and β-tubulin (β-TUB) genes were amplified and sequenced using the paired primers ITS1/ITS4 (White et al. 1990), EF1/EF2 (O'Donnell et al. 1998) and T1/T22 (O'Donnell and Cigelnik 1997), respectively. The obtained sequences were deposited in GenBank under accession numbers MT889972 to MT889974 (ITS), MT895844 to MT895846 (TEF-1α), and MT895841 to MT895843 (β-TUB), respectively. BLASTn search of the sequences revealed 99 to 100% identity with ITS (MF356578), TEF-1α (HM770725) and β-TUB (GQ915444) of Fusarium incarnatum isolates. FUSARIUM-ID (Geiser et al. 2004) analysis showed 99 to 100% similarity with sequences of the F. incarnatum-equiseti species complex (FIESC) (FD_01651 and FD_01628). In addition, a phylogenetic analysis based on the concatenated nucleotide sequences placed the isolates in the F. incarnatum clade at 100% bootstrap support. Thus, both morphological observations and molecular criteria supported identification of the isolates as F. incarnatum (Desm.) Sacc (synonym: Fusarium semitectum) (Leslie and Summerell 2006, Nirenberg 1990). Pathogenicity tests were performed on susceptible rice cultivar 'Xiushui134'. At pollen cell maturity stage, a 2-ml conidial suspension (5 × 105 macroconidia/ml) of each isolate was injected into 10 rice panicles. Control plants were inoculated with sterile distilled water. Then, the pots were kept in a growth chamber at 28°C, 80% relative humidity, and 12 h/12 h light (10,000 lux)/dark. The experiment was repeated two times for each isolate. Two weeks post-inoculation, all inoculated panicles showed similar symptoms with the original samples, whereas no symptoms were observed on the control. The pathogen was re-isolated from inoculated panicles and identified by the method described above to fulfill Koch's postulates. Previous studies reported that F. incarnatum reproduced perithecia to overwinter on rice stubble as the inoculum of Fusarium head blight of wheat in southern China (Yang et al. 2018). To our knowledge, this is the first report of spikelet rot on rice caused by F. incarnatum in China. Further investigation is needed to gain a better understanding its potential geographic distribution of this new pathogen on rice crop.

First Report of Fusarium equiseti Causing Seedling Death on Sugar Beet in Minnesota, USA.

In May 2019, sugar beet (Beta vulgaris L.) seedlings with symptoms of wilting and root tip discoloration and necrosis were found in Moorhead (46.5507° N, 96.4208° W), Minnesota, USA. Roots of infected seedlings were surface sterilized with 10% bleach for 15 seconds, rinsed with sterile distilled water and cultured on water agar (MA Mooragar®, Inc, CA) for 3 days at 23 ± 2°C. Isolates were transferred to carnation leaf agar (CLA) and incubated at room temperature (22°C) under fluorescent light for 14 days. Abundant macroconidia were produced in sporodochia. Macroconidia were 5- to 7-septate, slightly curved at the apex, and ranged from 35 to 110 ×1.2 to 3.8 μm. No microconidia were produced. Chlamydospores with thick, roughened walls were observed in chains or in clumps, and were ellipsoidal or subglobose. Single spore was transferred from CLA to potato dextrose agar (HIMEDIA Laboratories, India) produced abundant white mycelium and was pale brown where the colony was in contact with the media. The morphological features of the isolates were consistent with Fusarium equiseti (Corda) Sacc. (Leslie and Summerell 2006, Li et al. 2015). Genomic DNAs (NORGEN BIOTEK CORP, Fungi DNA Isolation Kit #26200) of two representative isolates were used for polymerase chain reaction (PCR). The second largest subunit of RNA polymerase (RPB2) was amplified by PCR with primers 5f2/7cr (O'Donnell et al. 2010). The amplified PCR product was sequenced and deposited in GenBank (accession number MW048778). A BLAST search in Genbank and the Fusarium MLST database showed 100% sequence alignment to F. equiseti with accession MK077037.1 and NRRL 25795, respectively. Pathogenicity testing was done using three sugar beet seedlings (Hilleshög proprietary material, Hilleshög Seed, LLC, Halsey, OR 97348) at cotyledonary stage grown in a pot (4˝×4˝×6˝) with six replicates. Seedlings were inoculated with F. equiseti conidial suspension (104 conidia ml-1 for 8 minutes) by the root dip method (Hanson, 2006). Mock inoculated plants were dipped in sterile water. Inoculated and control plants were placed in the greenhouse at 25 ± 2°C, and 75 to 85% relative humidity. One week later, inoculated seedlings showed root tip tissue discoloration similar to those observed in the field and non-inoculated seedlings were symptomless. This study was repeated. The fungus was re-isolated from diseased roots and confirmed to be F. equiseti based on morphological characters. Fusarium equiseti was reported on freshly harvested and stored beet in Europe but was not found to be pathogenic (Christ et al. 2011). Strausbaugh and Gillen (2009) reported the association of F. equiseti and root rot of sugar beet but did not report pathogenicity. This pathogen is reported in several crops including edible beans that is grown in rotation with sugar beet in several production areas (Jacobs et al. 2018). The most important Fusarium species reported to cause significant economic damage to sugar beet include F. oxysporum and F. secorum (Secor et al. 2014, Webb et. al. 2012). The presence of another pathogenic Fusarium species in sugar beet will require monitoring to determine how widespread it is and whether current commercial cultivars are resistant. To our knowledge, this is the first report of F. equiseti causing disease on sugar beet seedlings in Minnesota, USA.

First report of stem and root rot of coriander caused by Fusarium equiseti in China.

Coriander (Coriandrum sativum L.) is one of the most important vegetables used as a seasoning in China. During the summer of 2019 and 2020, two-month-old coriander plants with stem and root rot were observed in commercial fields located in Tianjin, China. Symptoms were first observed when temperatures were about 24°C. Diseased plants had chlorotic lower leaves, were stunted, had rotted roots and stems, and eventually wilted and died (Fig. S1). In severe cases, disease incidence was approximately 85%. Plant samples with the same symptoms were collected from five fields by five-point sampling method (4 plants/point; 20 plants/field), out of which twenty plants were arbitrarily selected for pathogen isolation. Root tissue fragments (3 mm2; 3 fragements/plant) at the boundary of the symptomatic area were excised, washed in 1% NaClO for 2 min, rinsed in sterile distilled water (SDW), and incubated on PDA containing 50 mg/liter of streptomycin sulfate. Plates were incubated at 25°C for 5 days in the dark. 25% of the isolates were tentatively identified as Fusarium equiseti according to cultural and morphological characteristics (Leslie and Summerell, 2006). Colonies developed abundant white aerial mycelium with pale brown pigments on PDA. Microconidia were single-celled, hyaline, non-septate and ovoid, and ranged from 4.6 to 17.6 × 1.5 to 3.8 μm (n = 40). Macroconidia were mostly five-septate, slightly curved at apex, and ranged from 13.3 to 34.6 × 2.2 to 4.3 μm (n = 40). Chlamydospores with thick, roughened walls were abundant in clumps or chains, ellipsoidal or subglobose. Diseased-plant samples and pathogen isolates were deposited to China General Microbiological Culuture Collection Center (CGMCC). Species identity was confirmed by amplifying and sequencing the ITS, TEF1-α, mtSSU and RPB2 (Carbone and Kohn 1999; Li et al. 1994; Miller and Huhndorf 2005). BLASTn analyses of ITS amplicon (Genbank No. MT579854), TEF1-α (MT586131), mtSSU (MT587798) and RPB2 (MT648497) genes obtained with cognate sequences available in GenBank showed 99.8% (498 bp out of 499 bp), 100% (493 bp out of 493 bp), 99.7% (625 bp out of 627 bp) and 98.9% (656 bp out of 663 bp) identity to F. equiseti (LS479418 [ITS], KU939020 [TEF1-α], MF667972 [mtSSU] and MG839490 [RPB2]) in NCBI databases, respectively. Pathogenicity tests were conducted with each F. equiseti isolate. Plants were grown in sterilized 10-cm diameter plastic pots containing steamed peat substrate, and three replicated pots (five plants/pot) were included in each treatment. Fifteen-day-old coriander plants were inoculated with 5 mL of 1×106 conidia/mL suspension by root-drenching method. Control plants were inoculated with SDW. Each treatment was incubated in a greenhouse at 29/22°C (12h/12h, light/dark), and watered every other day to keep high humidity. After 4 days, symptoms similar to those observed in the field were observed on inoculated plants (Fig. S2), whereas control plants remained symptomless. Reisolation of F. equiseti from inoculated plants fulfilled Koch's postulates, and identification was confirmed by morphological and molecular methods. To our knowledge, this is the first report of F. equiseti causing coriander stem and root rot in China. This pathogen poses a threat to coriander production, and its accurate identification is necessary to develop effective management strategies.

First Report of Aspergillus flavus Causing Fruit Rot of Grapes (Vitis vinifera) in Pakistan

First Report of <i>Aspergillus flavus</i> Causing Fruit Rot of Grapes (<i>Vitis vinifera</i>) in Pakistan

First Report of Fusarium incarnatum-equiseti Species Complex Causing Fruit Rot of Peach (Prunus persica) in China

Peach (Prunus persica [L.] Batsch; Rosaceae) is an economically important deciduous fruit. China is the largest producer of peaches, providing >50% of world production. Fruit rot is a devastating problem both pre- and postharvest. In May 2019, 882 infected peach fruits covered with white fluffy masses and brown necrotic lesions were observed among 4,500 fruits investigated in a commercial orchard in Jinshan, Shanghai, China. Disease incidence was ∼20%. Infected fruits were collected and kept in separate paper bags. Small sections (5 × 5 mm) were excised from the boundary of necrotic and healthy tissues, surface sterilized with 70% ethanol for 30 s and 5% NaOCl for 90 s, rinsed twice with sterilized distilled water (DW), and aseptically placed onto PDA. After 2 days of incubation at 26°C, sections from new colonies were transferred onto fresh PDA and purified by the single-spore method (Yang et al. 2008). Colonies on PDA had white aerial mycelia at first that turned off-white to light yellow after 5 days. No microconidia were observed. Seven morphologically similar isolates were obtained and representative isolate FQ01 analyzed. Macroconidia were five to seven septate with a tapered and elongated apical cell and prominent foot-shaped basal cells. Apical cells were conically elongated, and basal cells were prominently shaped, 20.1 to 47.2 × 2.5 to 2.9 μm. Macroconidia were produced from monophialides on branched conidiophores. Chlamydospores were abundant in clumps or chains, ellipsoidal to subglobose with thick and roughened walls. The isolated strain was identified morphologically as a member of the Fusarium incarnatum-equiseti species complex (FIESC) (Leslie and Summerell 2006). To confirm identity of FQ01, the internal transcribed spacer (ITS) region and the translation elongation factor 1-α gene (EF1-α) were amplified using primers ITS1/ITS4 (White et al. 1990) and EF1-728F/EF1-986R (Carbone and Kohn 1999), respectively. Total genomic DNA was extracted using the E.Z.N.A. Fungal DNA Mini Kit (Omega Bio-tek) according to the manufacturer’s instructions. Resultant sequences of FQ01 were obtained and submitted to GenBank (MN133053 for ITS and MN133052 for EF1-α). BLASTn analyses showed that sequences shared 99.83% identity with a sequence of F. equiseti for ITS (MH879250.1) and 100% with a sequence of F. equiseti (MK692895.1) for EF1-α. Further BLAST search in the FUSARIUM-ID database indicated that the sequences shared 100% identity with a sequence of FIESC for ITS (FD_01695) and 98.58% with a sequence of FIESC for EF1-α (FD_01627) (Geiser et al. 2004). Pathogenicity tests were conducted on wounded and nonwounded peach fruits with mycelial plugs and conidial suspension, respectively. Ten healthy and surface-sterilized fruits (cv. I9) were wounded using a sterilized needle and inoculated with mycelial discs (6 mm). Ten surface-sterilized nonwounded peach fruits (cv. Qiumi) were sprayed with a 10⁵ conidia/ml suspension. For the control, wounded and nonwounded fruits were inoculated separately using agar plugs and DW, respectively All fruits were enclosed in plastic bags and incubated in a growth chamber at 26°C, 90% relative humidity, and 12 h/12 h light (10,000 lux)/dark. After 5 days, the inoculated sites on wounded fruits had brown and sunken lesions. On nonwounded fruits, brown rot and white fluffy mycelia were observed after 1 week. No symptoms were observed on control fruit. The fungus was reisolated from the lesions of the inoculated plants and verified morphologically. This is the first report of FIESC on peach fruits in China. Owing to the range of mycotoxins produced, members of the FIESC are not only saprophytes and opportunistic plant pathogens but also highly associated with human and animal disease (Leslie and Summerell 2006). The pathogen presents a severe threat to peach quality and production, so further research should be implemented to find effective management strategies to prevent and control it.

First Report of Leaf Spot on Cucumber Caused by Fusarium incarnatum in China

Cucumber (Cucumis sativus L.) is a globally cultivated vegetable crop with great economic and nutritional importance. In May 2019, a new leaf spot disease was observed on cucumber in Jiyang, Shandong Province, China. Disease incidence was estimated at approximately 15% across the survey area. Foliar symptoms began with small pale-yellow lesions, circular to irregular in shape. Subsequently, they developed into large irregular spots, yellow to dark brown, with a gray central area. Finally, the lesions were densely distributed on the leaves. To isolate the pathogen, leaf tissues (5 × 5 mm) were cut from the junction of diseased tissue and healthy tissue, surface disinfected in 75% alcohol for 15 s, soaked in 0.1% mercuric chloride for 1 min, washed with sterile distilled water three times, and cultured on potato dextrose agar (PDA) at 25°C for 3 to 5 days. Seventeen fungal isolates with similar morphological characteristics were obtained and further purified by a single-spore isolation method. The colony of representative isolate SCS6G on PDA was fluffy, white, and showing beige coloration on the reverse side. Macroconidia had three to five septa (more commonly three septa), slightly curved at the apex, ranging from 16.2 to 33.4 × 3.1 to 4.8 µm (n = 100). Microconidia were single celled to one septum, ranging from 6.8 to 17.3 × 2.6 to 4.1 μm (n = 100). Chlamydospores with thick, roughened walls were abundant, singly, in chains or in clumps, ellipsoidal or subglobose. The morphological characteristics and measurements of this fungal isolate were consistent with the descriptions of Fusarium incarnatum (Leslie and Summerell 2006). To validate the species identification, the rDNA internal transcribed spacer (ITS) region (White et al. 1990), β-tubulin gene (Glass and Donaldson 1995), and partial translation elongation factor 1-α (TEF1-α) gene (Cong et al. 2016) were amplified and sequenced. The ITS, β-tubulin, and TEF1-α sequences of isolate SCS6G were submitted to GenBank (MN493639, MN508785, and MN508784, respectively). BLASTn analysis of the sequences showed 99% identity with F. incarnatum (MN317371, KY509037, and KY509036). Furthermore, phylogenetic analysis based on the alignment of the ITS, β-tubulin, and TEF1-α sequences using MEGA7 revealed that the isolate was grouped in the same clade as F. incarnatum. Pathogenicity tests were performed by spraying a conidial suspension (1 × 10⁵ conidia/ml) on 25 healthy cucumber plants at the five-true-leaf stage. Sterile water served as a control. All samples were placed in a dew chamber for 48 h and then kept in a growth chamber at 25°C. All inoculated leaves showed symptoms similar to those observed in the field after 7 days, but no disease occurred on control plants. The same fungus was successfully reisolated from inoculated leaves and reidentified based on morphology and molecular evidence, thus confirming Koch’s postulates. The pathogenicity test was repeated with similar results. To our knowledge, this is the first report of leaf spot caused by F. incarnatum on cucumber in China. This disease may pose a serious threat to cucumber production in China.

First Report of Fusarium incarnatum-equiseti Species Complex Causing Fruit Rot on Muskmelon (Cucumis melo) in China

Muskmelon (Cucumis melo L.) is an economically important fruit crop in China. In September 2018, fruit rot was observed on approximately 20% of muskmelon fruits in Harbin, Heilongjiang Province, China. Brown water-soaked lesions were observed on the fruit side in contact with soil initially, which gradually extended to most of or the entire fruit. Internal decay was observed with white to dark brown mycelium on the fruit surface. Diseased muskmelon tissues were surface disinfested with 1% NaOCl for 3 min, 70% ethanol for 10 s, and then washed three times with sterile water. The disinfested tissues were cut into 1-cm pieces and placed on potato dextrose agar (PDA) amended with streptomycin sulfate (50 mg/liter) and incubated at 25°C for 1 week. Isolations were done on 10 fruit fragments, and the same fungus was obtained. The cultures were purified using the hyphal-tip technique and used for morphological and molecular analyses. Morphological characteristics were observed on 1-week-old PDA cultures grown at 28°C. The aerial mycelium changed from white to light yellow, and the back of the plate turned pale brown with time. Microconidia were single celled, hyaline, nonseptate, ovoid, and 8.5 to 10.6 × 3.2 to 4.4 μm. Hyaline macroconidia (mostly three-septate) were slightly curved at the apex and ranged from 19.4 to 35.2 × 3.8 to 7.7 μm. Chlamydospores with thick, roughened walls were abundant in clumps or chains, ellipsoidal or subglobose. Primers ITS1/ITS4 (White et al. 1990) and EF-1/EF-2 (O’Donnell et al. 2000) were used to amplify and sequence the internal transcribed spacer (ITS1-5.8S-ITS2) and translation elongation factor 1-α (TEF1) region. ITS and TEF1 gene sequences were deposited in NCBI GenBank nucleotide database with accession numbers MH910492 and MH920853, respectively. BLASTn analysis showed 99% nucleotide sequence identity with Fusarium incarnatum-equiseti species complex (FIESC). The TEF1 gene sequence of isolate NEAU-TG1 was compared with sequences in the FUSARIUM-ID database (Geiser et al. 2004), which indicated that the pathogen was most closely (99% identity) related to phylogenetic species within the FIESC. Pathogenicity of these isolates was confirmed by following Koch’s postulates. Ten muskmelon fruits of cultivar Xiangfei were surface disinfested with 2% NaOCl for 2 min and rinsed with sterile distilled water three times. Spores were produced on PDA for 7 days at 28°C and washed with sterile distilled water; the concentrations were adjusted to 1 × 10⁶ spores/ml using a hemocytometer. Ten muskmelon fruits were inoculated by injecting the suspension (2 ml, 1 × 10⁶ spores/ml) and covered with plastic bags for 24 h, and another 10 surface-disinfested fruits treated with sterile distilled water were used as a control. The fruits were placed in a humidified chamber (>95% relative humidity) at 25°C for 48 h after inoculation and kept in a growth chamber at 25°C with 12-h day/night cycle for 8 days. All inoculated fruits showed symptoms identical to those observed in the field. No disease occurred on the controls. The pathogen was reisolated from diseased fruits, and species identification was confirmed by the morphological and molecular method described above. Members of the FIESC can cause disease on plants, such as Allium cepa, Festuca arundinacea, Morchella importuna, and Cucumis trigonus. Furthermore, the members of the FIESC have been reported to produce type A and B trichothecene mycotoxins that cause toxicosis in humans and animals (Leslie and Summerell 2006; O’Donnell et al. 2009). To our knowledge, this is the first report of fruit rot caused by a member of the FIESC on muskmelon in China. This pathogen presents a threat to muskmelon production, and its accurate identification is necessary to develop effective management strategies.

Molecular dynamic simulation to study the effects of roughness elements with cone geometry on the boiling flow inside a microchannel

Present work studies effects of presence of surface roughness elements with cone geometry on the boiling flow behavior of Argon fluid inside microchannels which are affected by different boundary wall temperatures using molecular dynamic simulation method. Firstly, microchannel is simulated with smooth surfaces under boundary wall temperatures of 84 K, 96 K, 108 K, 114 K and 133 K to prepare boiling condition for Argon atoms. Microchannel surfaces are roughened by cone shape of roughness elements and mentioned temperatures are applied on the roughened microchannel walls to be comparable with smooth one. Also, an external driving force of 0.002 eV/Å is applied on the Argon atoms at the entrance of both rough and smooth microchannels for all cases of wall temperatures. Statistical approach is employed to compare results of both microchannels. It is reported that adding roughness elements on the smooth surfaces of microchannel can extend contact surfaces of energy transfer which empowers boiling process of fluid flow. Presence of cone geometry of roughness elements causes fluid flow velocity reduction as much as 0.5–1.5%. Also, it is observed that roughness elements results in enhancement of temperature profiles of fluid. Moreover, it is found that role of roughness element in low time steps is stronger than high time step. Therefore, evolution of boiling process can reduce consequences of roughness on the flow behavior. Finally, due to ignorable consequences of roughness element on the boiling flow behavior, it is concluded that preparing very smooth surfaces is not economical for practical application such as medical micro probes to destroy abnormal or diseased tissues.

Numerical investigation on the suitability of a fourth-order nonlinear k-ω model for secondary current of second type in open-channels

ABSTRACTThis study evaluated a typical nonlinear fourth-order k-ω model and the associated roughness boundary condition for their suitability for simulating secondary current of the second kind in open-channels induced by roughness non-uniformity. Three test cases were simulated: square duct flow, open-channel flow with uniformly roughened bed and smooth side walls, and open-channel flow over roughness patches. The nonlinear model and the roughness boundary condition performed relatively well for the first two cases where the corner effect was dominant. For the third case, with alternate roughness patches, strong pressure gradient was generated at the edge between adjacent patches and the secondary current was greatly over-predicted. Two remedial options were tested: increasing the roughness height for smooth walls to a reasonable value and smoothing the roughness transition with a hyperbolic tangent function. We found the first option works better and the second only marginally improves the results.

First Report of Penicillium brevicompactum Causing Blue Mold Disease of Grifola frondosa in China

HomePlant DiseaseVol. 101, No. 8First Report of Penicillium brevicompactum Causing Blue Mold Disease of Grifola frondosa in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Penicillium brevicompactum Causing Blue Mold Disease of Grifola frondosa in ChinaF. H. Tian, C. T. Li, and Y. LiF. H. TianSearch for more papers by this author, C. T. LiSearch for more papers by this author, and Y. LiSearch for more papers by this authorAffiliationsAuthors and Affiliations F. H. Tian C. T. Li Y. Li , Engineering Research Center of Chinese Ministry of Education for Edible and Medicinal Fungi, Jilin Agricultural University, Changchun, Jilin Province 130118; P.R. China. Published Online:2 Jun 2017https://doi.org/10.1094/PDIS-09-16-1301-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Grifola frondosa (Dicks.) Gray (Maitake) is known for its high nutrition and medicinal properties. In China, it is predominantly grown in the northeastern and southeastern parts. It sustains the livelihoods of many small-scale farmers in Asia and other parts of the world where it is cropped or traded. In May 2015 and June 2016, serious blue mold epidemic occurred on many mushroom farms in Changchun (Jilin Province) and Qingyuan (Zhejiang Province), China. The infected mycelia and fruiting bodies of G. frondosa in cultivated bags became yellow, wilted with yellow water drop secretion, and growth was inhibited, leading to eventual death. The surfaces of the cultivated bags were covered with grayish-green fungal colonies. Once this occurred, the infected mycelia were not able to generate fruiting bodies, and even if fruiting bodies were generated, their growth was stunted or they spread disease to adjacent ones. Samples were collected and sterilized using 0.1% NaClO solution and rinsed three times with sterilized distilled water. It was then plated on four different media, Czapek agar (CA), Czapek yeast autolysate agar (CYA), malt extract agar (MEA), and potato dextrose agar (PDA) supplemented with 0.1M Kanamycin. Colonies on PDA grew slowly, 10 mm in diameter at 25°C and 55 to 60% relative humidity in mold cultivation cabinet within 7 days. The colony was slightly umbonate at center, and radially sulcate. Grayish green conidia were formed on the whole surface of the colonies. Penicilli were most terverticillate. The conidiophore wall was smooth. Metulae were cylindrical, 9.31 to 18.52 × 2.36 to 4.09 μm, in verticils of 3 to 6. Phialides were ampulliform, 8.63 to 18.52 × 2.48 to 4.04 μm, in verticils of 2 to 6. Conidia were spheroidal to ellipsoidal, 3.5 to 4.8 × 3.3 to 4.6 μm, with smooth to roughened walls. The internal transcribed spacer (ITS) region, the second largest subunit of RNA polymerase II (RPB2) gene, and cauliflower (CAL) gene were amplified with primers ITS1/ITS4, RPB2-740F/1365R, and CAL-228F/737R, respectively. Nucleotide alignment showed 99% sequence identity (ITS) with Penicillium brevicompactum (LN808902); 99% sequence identity (RPB2) with P. brevicompactum (LN833569), and 98% sequence identity (CAL) with P. brevicompactum (AY484821). Based on the morphological characteristics, cultural traits, and the sequences of ITS, RPB2, and CAL of the isolation, the fungus was identified as P. brevicompactum. To confirm pathogenicity, modified Koch’s postulates were achieved as following: six repeated bags of G. frondosa for each different growth period were sprayed with 1 ml conidial suspension (106 conidia/ml); another three bags used sterilized water as control. All treatments were maintained at 18 to 19°C and 85 to 90% relative humidity in the same mushroom-growing space. The pathogen was consistently reisolated from the infected fruiting bodies of G. frondosa. All experiments were in triplicate. P. brevicompactum has been reported to the cause of postharvest fruit spoilage (Louw and Korsten 2014) diseases in plants (Valdez et al. 2009) and mushroom production (Qin et al. 2013; Zhu et al. 2016). To our knowledge, this is the first report of P. brevicompactum causing blue mold disease on cultivated G. frondosa. Effective measures need to be adopted to control this pathogen in order to prevent great losses to farmers.

Numerical predictions on fluid flow and heat transfer in U-shaped channel with the combination of ribs, dimples and protrusions under rotational effects

Recently, dimple and protrusion structure has been proved as an effective heat transfer augmentation approach on coolant channel due to its advantage on pressure penalty. A compound heat transfer enhancement technique, the combination of ribs, dimples or protrusions, is applied to a U-shaped square channel similar with the gas turbine blade internal passage. Considering the rotational condition of gas turbine blade on operation, the effect of rotation is also investigated for the coolant channel in order to approximate more to the real operation condition. Thus, the objective of this study is to discuss the effect of rotation on fluid flow and heat transfer performance of turbine blade similar U-shaped channel with the combination structure of ribs, dimples or protrusions. The investigated Reynolds number is 1.25 million and considered rotational number includes 0, 0.4 and 0.6. From the results, the fluid patterns of two-pass channel with compound heat transfer enhancement structure are presented for none-rotating and rotating cases. Meanwhile, spatially Nusselt distributions of roughened walls are obtained to reveal the heat transfer rates. Finally, the area averaged Nusselt number ratio and channel friction penalty are evaluated. The results indicate that rib-protrusion structure seems to be the most effective structure while rib-dimple structure has only slight advantage than ribbed channel. Furthermore, the additional friction penalty by dimple and protrusion structure is tiny. It can also be expected that, the thermal performance of this compound structure can be even improved after a denser arrangement of dimple/protrusion structure and optimal shape design.

First Report of Penicillium polonicum Causing Blue Mold on Stored Onion (Allium cepa) in Serbia.

Penicillium polonicum K. Zaleski is an economically important airborne fungus with a broad host range including cereals, peanuts, onions, dried meats, citrus fruits, and yam tubers (2,4). Secondary metabolites produced by this species include harmful mycotoxins penicillic acid, verucosidin, and nephrotoxic glycopeptides, which may play a role in Balkan Endemic Nephropathy (2,5). In January 2013, decayed onion bulbs (Allium cepa L. cv. Meranto) with blue mold symptoms were found causing significant economic losses at a storage facility in Stara Pazova, Serbia, and were collected. The decayed area of the bulbs was pale yellow to light brown, and tissue was soft and watery. Bluish green sporulation was abundant on the surface and inside the bulb, between decayed scales. Two isolates (designated L1a and L4p) were obtained and further characterized using morphological and molecular methods. Colonies on potato dextrose agar (PDA), Czapek yeast autolysate agar (CYA), malt extract agar (MEA), and yeast extract sucrose agar (YES) media at 25°C after 7 days were blue green, velutinous, with clear exudate present on CYA. Colony reverse color on CYA and YES for both isolates were cream to yellow brown. The mean colony diameter on PDA for L1a was 29.89 ± 0.96 mm, and for L4p was 26 ± 0.37 mm; on CYA 32.56 ± 0.53 mm for L1a and 30.11 ± 2.42 mm for L4p; and on YES 33.86 ± 1.59 mm for L1a and 31.17 ± 1.83 mm for L4p. No growth was observed on CYA when isolates were incubated at 37°C. Conidiophores of both isolates were terverticillate, stipes were septate with smooth to finely roughened walls, and phialides were ampulliform. Conidia were globose to subglobose, smooth-walled, and borne in columns. Conidial dimensions for L4p were 2.72 to 3.82 (3.26) × 2.36 to 3.42 (2.95) μm, and for L1a were 2.87 to 4.39 (3.58) × 2.53 to 3.79 (3.16) μm (n = 50). Both isolates tested positive for the production of cyclopiazonic acid and other alkaloids, as indicated by a violet reaction for the Ehrlich test. Morphological characters of L1a and L4p were in accordance with those described for P. polonicum K. Zaleski (2). Genomic DNA was isolated using CTAB extraction method (1) and molecular identification was completed using gene specific primers for the β-tubulin locus (Bt-LEV-Up4/Bt-LEV-Lo1) via conventional PCR (3). The nucleotide sequences of amplified products (~800 bp) have been assigned to GenBank (KJ570971 and 72). MegaBLAST of obtained sequences showed a 99% similarity with several sequences of P. polonicum deposited in GenBank, which confirmed the morphological identification. Pathogenicity was tested by wound inoculation of 10 surface sanitized onion bulbs cv. Meranto with 50 μl of a 105/ml conidial suspension from isolates grown on PDA. Ten control onion bulbs were wound-inoculated with Tween-treated sterile distilled water. After 30 days incubation in plastic containers, under high humidity at 22°C, typical symptoms of blue mold developed on inoculated bulbs, while non-inoculated controls remained symptomless. Isolates recovered from inoculated bulbs showed the same morphological characteristics as the original isolates, thus completing Koch's postulates. To our knowledge, this is the first report of P. polonicum on stored onion in Serbia. Results from this study indicate that a holistic approach to control this fungus should be implemented that may include one or all of the following: increased sanitation methods to eliminate inoculum, breeding for resistant onion cultivars, and integration of additional control methods to maintain onion quality during storage.

Numerical Calculations on Flow and Heat Transfer in Smooth and Ribbed Two-Pass Square Channels under Rotational Effects

U-shaped channel, which is also called two-pass channel, commonly exists in gas turbine internal coolant passages. Ribbed walls are frequently adopted in internal passage to enhance the heat transfer. Considering the rotational condition of gas turbine blade on operation, the effect of rotation is also investigated for the coolant channel which is close to real operation condition. Thus, the objective of this study is to discuss the effect of rotation on fluid flow and heat transfer performance of U-shaped channel with ribbed walls under high rotational numbers. Investigated Reynolds number is Re=12500and the rotation numbers areRob=0.4and 0.6. In the results, the spatially heat transfer coefficient distributions are exhibited to discuss the effect of rotation and roughened walls. It is found that ribbed walls enhance the heat transfer rate significantly. Under the rotational condition, theNuin the first pass with outward flow is increased while that in the second pass is decreased. Finally, averageNuratio, friction ratio, and thermal performance are all presented to discuss the thermal characteristics.

Penicillium polonicum: Causal agent of onion bulb decay in storage

Penicillium polonicum is an economically important fungal species with a wide host range which includes cereals, peanuts, onions, dried meats, citrus, apple, and yam tubers. Onion bulbs cv. Meranto with blue mold symptoms have been collected, in a storage facility in Stara Pazova during 2013. Fungal isolates were obtained from decayed bulbs and their pathogenicity was proven after wound inoculation of healthy onion bulbs. On differential media the isolates formed velutinous, green blue colonies with a white margin and a characteristic odor. The isolates grew at 5 C while no growth was observed at 37 C. Isolates produced cyclopiazonic acid and other alkaloids. Conidiophores of isolates were terverticillate, stipes were septate with smooth to finely roughened walls, and phialides were ampulliform. Conidia were globose to subglobose, smooth-walled, and borne in columns. The nucleotide sequences of amplified products (~800 bp) for partial β-tubulin gene showed in MegaBLAST search analysis a 99% similarity with several sequences of P. polonicum. Based on morphological and molecular features isolates obtained from stored onion were identified as P. polonicum.

Comparative study of turbulent heat transfer in smooth and scale-rib roughened reciprocating blind ducts with laterally tangent entry jet

This experimental study investigated the performances of heat transfer enhancement (HTE), pressured drop coefficient ( C f ) and relative thermal performance factor ( η th) generated by a lateral entry jet for two reciprocating square blind ducts with smooth and scale-rib roughened walls for piston cooling applications. At each test reciprocating frequency ( f) in the range of 0–2 Hz, the lateral and longitudinal Nusselt number ( Nu) distributions over two opposite duct walls, namely the jet wall and the back wall, are measured at duct (jet) Reynolds numbers Re( Re j ) of 5000(31,850), 10,000(63,690), 15,000(95,540) and 20,000(127,400). The jet-induced flow phenomena in each blind duct interact with the reciprocating and buoyancy forces to exhibit synergistic impacts on HTE performances. This is demonstrated by examining the Nu variations over the reciprocating jet and back walls in response to the changes of Re, pulsating ( Pu) and reciprocating Grashof ( Gr p ) numbers for each blind duct. The individual and interdependent Re, Pu and Gr p effects on heat transfer are comparatively examined to reveal the influences of the scale-rib roughness on HTE performances. Within the parametric conditions tested, the ratios of the averaged Nusselt number ( N u ¯ ) between those measured from the reciprocating and static jet and back walls fall respectively in the ranges of 0.68–0.9 and 0.69–0.89 for the smooth blind duct; and 0.63–0.97 and 0.62–0.99 for the roughened blind duct. Due to the presence of the scale-rib roughness, the ( N u ¯ ) over the roughened reciprocating jet and back walls are respectively raised to 1.04–1.4 and 1.01–1.14 times of the smooth-walled references; while the pressure drop coefficients are raised to about 2–4.2 times of the smooth-walled duct levels. Two sets of N u ¯ correlations over the jet and back walls for the reciprocating blind ducts with smooth and scale-rib roughened walls are generated. Justified by the relative thermal performance factor results, the present wall roughness in the reciprocating blind duct with a lateral entry jet can provide both improvements in HTE effectiveness and the thermal efficiency at Re = 20000.

ICONE19-43177 Experimental Study of Airflow-Mixture by Using PIV

In this paper, it was reported that simulation design study about gas process unit, such as process gas reactor, heat exchangers and heat conditioner, for one of the heat utilization system components development of High Temperature Gas-cooled Reactor (HTGR). In simulating precisely the heat transfer control characteristics of the gas-mixing unit, a good model for turbulent mixing process of some velocity ratios is a key issue. Therefore, we have been proceeding to develop the newly CFD code. This code using algebraic Reynolds stress model has been reasonably predicted about complex turbulent flows such as flow separation in a rectangular duct with 90-degree sharp turn and strong anisotropic flow in straight duct with roughened walls. However, it has not enough been validated for gas-mixing turbulent flow. We have a lack of detailed knowledge and experimental data on the turbulent gas process in the unit. Hence, as the first step to make the air mixing process in gas unit clear, we have made an preliminary experimental study on turbulent mixing using the equipment with flow control door arranged some velocity ratios and a heating core. Flow visualization was carried out by using particle image velocimetry (PIV). As a result of this study, it was obtained representative velocity distribution data and turbulent kinetic energy distributions about separation and gas mixing section in the equipment, which is important for unit performance. Furthermore, it was found that production of turbulence in the unit were strongly formed by unsteadily long separation flow between velocity ratios and small scale vortices induced to the tip of door.