scholarly journals First Report of Powdery Mildew of Kenaf Caused by Leveillula taurica in South Africa

Plant Disease ◽  
2001 ◽  
Vol 85 (8) ◽  
pp. 923-923
Author(s):  
W. J. Swart ◽  
J. Terblanche
Keyword(s):  
South Africa ◽  
Powdery Mildew ◽  
Seed Quality ◽  
Leaf Surface ◽  
Hibiscus Cannabinus ◽  
First Report ◽  
Leveillula Taurica ◽  
Abaxial Leaf Surface ◽  
Extensive Growth ◽  
Northwest Province

Kenaf (Hibiscus cannabinus L.) is a fast-growing, bamboo-like annual plant belonging to the Malvaceae. The stem, which ranges from 1.5 to 4 m, presents a source of high-quality cellulose fibers. The plant is being investigated in South Africa with a view to commercial production. In April 2001, at least 50% of 4- to 5-month-old kenaf plants grown from seed in trials near Rustenburg, Northwest Province, South Africa, were observed as having powdery mildew. Signs included extensive growth of white, superficial mycelium and emergent conidiophores on the abaxial leaf surface, followed by partial defoliation. On older leaves, the abaxial leaf surface was completely covered by powdery mildew, and chlorotic and necrotic patches were clearly visible on the adaxial surface. Symptoms were observed on all five planted cultivars (Everglades 41, Cuba 108, El Salvador, SF459, and Tainung 2), and no difference in disease severity was noted among cultivars. Leveillula taurica (Lév.) Arnaud (anamorph Oidiopsis taurica [Lév.] Salmon) was subsequently identified by the presence of endophytic mycelia, often branched conidiophores, and dimorphic conidia borne singly or in short chains (1). In 100 measurements of each type, pyriform conidia averaged 69 ± 5 × 18 ± 2 μm and cylindrical conidia averaged 62 ± 6 × 16 ± 2 μm. The teleomorph was not observed. The source of L. taurica for this reported outbreak is unknown, and powdery mildew was not observed in a field of mature cotton (Gossypium hirsutum L.) growing within 10 m of the kenaf plot. L. taurica was reported on kenaf in Texas in 1992 (2) and in Italy in 1995 (3). The pathogen can cause significant losses in seed yield and reduce seed quality in susceptible kenaf cultivars. Although L. taurica has been reported from Hibiscus sabdariffa in Egypt (4), to our knowledge this is the first report of the pathogen occurring on kenaf in Africa. References: (1) H. J. Boesewinkel. Bot Rev. 46:167, 1980. (2) C. G. Cook and J. L. Riggs. Plant Dis. 79:968, 1995. (3) S. Frisullo et al. Inf. Fitopatol. 45:37–41, 1995. (4) M. Khairy, et al. Phytopathol. Medit. 10:269–271, 1971.

scholarly journals First Report of Powdery Mildew of Greenhouse Pepper Caused by Leveillula taurica in Canada

Plant Disease ◽  
1999 ◽  
Vol 83 (8) ◽  
pp. 781-781 ◽  
Author(s):  
R. F. Cerkauskas ◽  
J. Brown ◽  
G. Ferguson ◽  
S. Khosla
Keyword(s):  
Powdery Mildew ◽  
Leaf Surface ◽  
Morphological Characteristics ◽  
Chili Pepper ◽  
Width Ratio ◽  
Old Field ◽  
First Report ◽  
Leveillula Taurica ◽  
Plastic Bags ◽  
Abaxial Leaf Surface

In 1999, powdery mildew on cvs. Oberon and Triple 4 of greenhouse pepper (Capsicum annum L.) and cv. FireFlame of chili pepper was reported simultaneously in two commercial greenhouses at two separate locations, Leamington and Vineland, geographically separated by 290 km, in southern Ontario. Losses of 10 to 15% each in the 2 and 3.1 ha greenhouse pepper operations were noted. The greenhouse pepper industry in Canada consists of 89.4 ha with sales of $43.6 million (Canadian). Lesions appeared as a white, powdery coating on the abaxial leaf surface only, generally on the lower foliage of pepper plants, while diffuse chlorotic spots were present at corresponding locations on the adaxial surface. In chili pepper, this chlorosis was restricted to interveinal tissue, causing the leaves to have a somewhat netted appearance. In some cases, pale yellow spots appeared on the adaxial portion of the affected foliage during later stages of disease development. No cleistothecia were observed. Pyriform and cylindrical, hyaline, single-celled conidia were present in equal numbers. Both conidia had a network of crests and granules containing tiny, thornlike projections on the surface. These projections were also evident on the lower half of conidiophores. Pyriform conidia ranged in length from 61.6 to 84.0 μm (mean = 70.8, SE = 0.7) and in width from 14.0 to 25.8 μm (mean = 21.1, SE = 0.4, n = 50), with a mean length to width ratio of 3.4. Cylindrical conidia ranged in length from 54.9 to 80.1 μm (mean = 66.3, SE = 0.9) and in width from 15.7 to 24.1 μm (mean = 18.6, SE = 0.3, n = 50), with a mean length to width ratio of 3.1. Short conidial chains borne on conidiophores consisted of a pyriform conidium first followed by cylindrical conidium. Stomatal penetration and extensive endophytic mycelial growth in the mesophyll layer were evident in foliar tissue cleared with glacial acetic acid:EtOH (1:2) and stained with lactophenol cotton blue. To confirm pathogenicity, conidia from infected pepper leaves were dusted onto the water-misted abaxial leaf surface of 41-day-old greenhouse pepper cvs. Cubico and Edison, and onto the similarly treated adaxial leaf surface of 58-day-old field pepper cv. Renegade. Plants were enclosed in plastic bags for 24 h on a bench. Control plants were treated identically but not inoculated. Inoculated plants developed foliar powdery mildew symptoms, including sporulation similar to that of naturally infected plants. Occurrence of the fungus on the abaxial surface of pepper foliage, presence of endophytic mycelium, and the morphological characteristics of the imperfect state confirm the identity of the fungus. This is the first report of Leveillula taurica (Lév.) G. Arnaud on pepper in Canada. Reference: J. Palti. Bot. Rev. 54:423, 1988.

scholarly journals First Report of Puccinia xanthii on Sunflower in North America

Plant Disease ◽  
2002 ◽  
Vol 86 (5) ◽  
pp. 564-564 ◽  
Author(s):  
T. J. Gulya ◽  
L. D. Charlet
Keyword(s):  
South Africa ◽  
North America ◽  
Helianthus Annuus ◽  
Leaf Surface ◽  
Rust Fungi ◽  
First Report ◽  
Abaxial Leaf Surface ◽  
University Of Arizona ◽  
Plant Pathol ◽  
Size And Morphology

Puccinia xanthii Schwein., commonly known as cocklebur rust, is circumglobal on species of Xanthium and Ambrosia. This microcyclic rust has only been observed on oilseed sunflower (Helianthus annuus L.) in Australia (1) and on ornamental sunflowers in South Africa (4). In September 1999, large (4 to 10 mm), raised, chlorotic pustules were observed on the adaxial leaf surface of oilseed sunflower plants (Dekalb 3790) near Hettinger, ND. Telia were associated with the pustules on the abaxial leaf surface. No cocklebur (X. strumarium L.) plants were found in the field, but rust-infected cocklebur plants were collected several kilometers away. Approximately 10% of sunflower plants in the field were affected, and generally only one or two pustules were observed on one or two leaves per plant. In contrast, numerous leaves of cockleur plants were infected with 12 or more pustules. Teliospores from sunflower were brown, two-celled, and averaged 49 × 17 μm, with a distinctly thicker wall at the spore apex and a persistent pedicel averaging 40 μm long. Teliospores from cocklebur were morphologically similar to those from sunflower and averaged 46 × 16 μm. Size and morphology of teliospores from both hosts fit the description of P. xanthii (2). P. xanthii can be distinguished easily from the ubiquitous P. helianthi Schwein. because the latter has smaller telia (1 to 2 mm diameter) and produces wider teliospores (21 to 30 μm diameter). P. xanthii was not found in surveys of 20 other sunflower fields in southwestern North Dakota nor in 45 fields in eastern ND in 1999, nor was P. xanthii found in this or any other sunflower field in 2000 or 2001. To our knowledge, this is the first report of P. xanthii on cultivated or wild sunflower in North America. The relatively few pustules observed on oilseed sunflower agree with the observation that oilseed sunflowers are much less susceptible to P. xanthii (3) than Xanthium spp. References: (1) J. L. Alcorn and J. K. Kochman. Austral. Plant Pathol. Soc. Newsl. 5:33, 1976. (2) G. B. Cummins. Rust Fungi on Legumes and Composites in North America. University of Arizona Press, Tucson, 1978. (3) J. B. Morin et al. Can. J. Bot. 71:959, 1993. (4) Z. A. Pretorius et al. Plant Dis. 84:924, 2000.

scholarly journals First Report of Powdery Mildew of Greenhouse Pepper Caused by Leveillula taurica in British Columbia, Canada

Plant Disease ◽  
2003 ◽  
Vol 87 (9) ◽  
pp. 1151-1151 ◽  
Author(s):  
R. F. Cerkauskas ◽  
A. Buonassisi
Keyword(s):  
British Columbia ◽  
Powdery Mildew ◽  
Morphological Characteristics ◽  
Width Ratio ◽  
Abaxial Surface ◽  
First Report ◽  
Leveillula Taurica ◽  
Abaxial Leaf Surface ◽  
Cotton Blue ◽  
Pepper Leaves

In 2003, powdery mildew of greenhouse pepper (Capsicum annuum L.) was reported simultaneously in two commercial greenhouses at two separate locations near Langley in southern British Columbia. Trace amounts of mildew on the foliage of cv. Zamboni in one operation, and 10 to 80% of the foliage of cv. Triple Four was affected in an organic operation, with losses in fruit yield of 2 to 4 kg/m2, were noted. The greenhouse pepper industry in British Columbia in 2001 comprised 76 ha with sales of $41.3 million (Canadian). Affected areas appeared as a white, powdery coating on the abaxial leaf surface of older foliage while diffuse chlorotic spots were present at corresponding locations on the adaxial surface. In some cases, pale yellow spots appeared on the adaxial portion of the affected foliage during later stages of disease development (2). Hyaline, single-celled pyriform and cylindrical conidia were present in 40:60 proportion, respectively. Both conidia had a network of crests and granules sometimes with tiny thorn-like projections on the surface. These projections were evident also on the lower half of conidiophores. Pyriform conidia ranged in length from 53.8 to 79.5 μm (mean = 68.0, SE = 0.8), and in width from 12.9 to 28.0 μm (mean = 20.1, SE = 0.6, n = 50) with a mean length to width ratio of 3.5. Cylindrical conidia had a length from 48.2 to 84.0 μm (mean = 66.0, SE = 0.9), and in width from 13.4 to 25.2 μm (mean = 18.6, SE = 0.4, n = 50) with a mean length to width ratio of 3.6. Short conidial chains borne on conidiophores consisted of a basal pyriform conidium followed by cylindrical conidium. No cleistothecia were observed. Stomatal penetration and extensive endophytic mycelial growth in the mesophyll layer were evident in foliar tissue cleared with glacial acetic acid/EtOH (1:2) and stained with lactophenol cotton blue. To confirm pathogenicity, a suspension of 2 × 104 conidia/ml from infected pepper leaves was applied onto the abaxial and adaxial leaf surfaces of 60-, 42-, and 28-day-old greenhouse pepper cv. Cubico, tomato cv. Trust, and cucumber cv. Corona, respectively. Plants were maintained in a growth chamber at 25/21°C day/night temperature and 80% relative humidity. Control plants in the same chamber were treated identically but not inoculated. After 21 days, inoculated pepper plants developed foliar powdery mildew symptoms on the abaxial surface, including sporulation similar to that of naturally infected plants. Occurrence of the fungus on the abaxial surface of pepper foliage, presence of endophytic mycelium, and the morphological characteristics of the imperfect state confirm the identity of the fungus (2). To our knowledge, this is the first report of Leveillula taurica (Lév.) G. Arnaud on pepper in British Columbia. The disease was first reported in Ontario, Canada in 1999 (1). References: (1) R. Cerkauskas et al. Plant Dis. 83:781,1999. (2) J. Palti. Bot. Rev. 54:423, 1988.

scholarly journals First Report of Powdery Mildew of Cashew Caused by Oidium anacardii in South Africa

Plant Disease ◽  
2004 ◽  
Vol 88 (11) ◽  
pp. 1284-1284
Author(s):  
W. J. Swart
Keyword(s):  
South Africa ◽  
Powdery Mildew ◽  
Control Treatment ◽  
Pathogenicity Test ◽  
First Report ◽  
Significant Damage ◽  
Kwazulu Natal ◽  
Young Leaves ◽  
Powdery Mildew Fungi ◽  
Extensive Growth

The cashew plant (Anacardium occidentale L.) (family Anacardiaceae) is native to Brazil. It was introduced in East Africa by the Portuguese in the 16th century where it is now widely cultivated, especially in Tanzania, Kenya, and Mozambique. The processed kernels are the most important product derived from the plant, although in Brazil and India, juices, jam, and alcoholic and soft drinks are also made from the pear-shaped edible receptacle. The plant is currently being evaluated in South Africa for commercial production. During May 2002, at least 25% of 5-year-old cashew trees grown from seed in the northern KwaZulu-Natal Province of South Africa were infected with powdery mildew. Signs included extensive growth of white, superficial mycelium bearing upright conidiophores on young shoots with tender leaves, inflorescences, and young receptacles. In severely affected trees, approximately 35% of young shoots and 45% of young receptacles displayed signs of powdery mildew. Severely infected young leaves were brown and deformed in contrast to older leaves that were unaffected. Microscopic examination of diseased tissue revealed hyaline, cylindrical-to-slightly doliform, single-celled conidia (10 to 17.5 × 2.5 to 5 μm) borne in chains. The pathogen was subsequently identified as Oidium anacardii Noack on the basis of morphology (1). No other species of powdery mildew fungi have been reported on cashew. A pathogenicity test was conducted by gently pressing a heavily diseased leaf onto two healthy leaves of each of 10 cashew plants maintained in pots on open benches in the glasshouse at 22 to 25°C and mean relative humidity of 65%. Control treatments entailed pressing an asymptomatic leaf onto each of two healthy leaves per plant. The experiment was conducted three times. After 14 days, at least one powdery mildew colony had developed on 80% of inoculated leaves but were absent from all replications of the control treatment. The source of inoculum for this reported outbreak is unknown, although O. anacardii is known to occur in southern Mozambique less than 100 km from the infected site. Cashew powdery mildew was first officially reported in Tanzania in 1979 where significant crop losses, partially attributable to the pathogen, have been recorded since (3). No significant damage to production has been recorded in Brazil (2). To our knowledge, this is the first report of O. anacardii occurring on cashew in South Africa. References: (1) E. Castellani and F. Casulli. Rivista di Agricoltura Subtropicale e Tropicale 75:211, 1981. (2) F. C. O. Freire et al. Crop Prot. 21:489, 2002. (3) P. J. Martin et al. Crop Prot. 16:5, 1996.

scholarly journals First Report of Powdery Mildew on Euryops pectinatus in Italy

Plant Disease ◽  
2002 ◽  
Vol 86 (8) ◽  
pp. 920-920
Author(s):  
A. Garibaldi ◽  
A. Minuto ◽  
D. Bertetti ◽  
M. L. Gullino
Keyword(s):  
Powdery Mildew ◽  
Leaf Surface ◽  
Northern Italy ◽  
Growth Chamber ◽  
Growth Reduction ◽  
First Report ◽  
Similar Disease ◽  
Commercial Farms ◽  
White Mycelium ◽  
Sphaerotheca Fusca

Euryops pectinatus is grown in Italy for landscape use in parks and gardens. In 2001, severe outbreaks of a previously unknown powdery mildew were observed in commercial farms located in Albenga (northern Italy). All green parts (leaves, stems, and petioles) became covered with a white mycelium. Infections were particularly severe on the upper leaf surface. With progress of the disease, infected leaves turned yellow and died. The presence of powdery mildew infections on leaves and stems only rarely was linked to growth reduction. Conidia were hyaline, cylindric to slightly doliform, did not show fibrosin bodies, borne in chains, and measured 24 to 41 × 12 to 20 μm. Cleistothecia were not observed. The pathogen was identified as Oidium sp. subgen. Fibroidium (1). Pathogenicity was confirmed by gently pressing diseased leaves on leaves of healthy E. pectinatus plants. Inoculated plants were maintained in a growth chamber at 20 to 24°C. After 12 to 14 days, powdery mildew symptoms developed. A similar disease of E. pectinatus was observed in 1999 in California and identified as being caused by Podosphaera (Sphaerotheca) fusca (2). It is possible that the powdery mildew observed in Italy belongs to the same species, also considering that recently the two genera, Podosphaera and Sphaerotheca, have been unified in the genus Podosphaera (1). References: (1) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (2) G. S. Saenz et al. Plant Dis. 84:1048, 2000.

scholarly journals Effect of Fungicide Mobility and Application Timing on the Management of Grape Powdery Mildew

Plant Disease ◽  
2020 ◽  
Vol 104 (4) ◽  
pp. 1167-1174 ◽  
Author(s):  
Brent Warneke ◽  
Lindsey D. Thiessen ◽  
Walter F. Mahaffee
Keyword(s):  
Powdery Mildew ◽  
Leaf Surface ◽  
Quality Standards ◽  
Pinot Noir ◽  
Abaxial Surface ◽  
Phenological Stages ◽  
Application Timing ◽  
Abaxial Leaf Surface ◽  
Detached Leaves ◽  
Grape Powdery Mildew

Grape powdery mildew (GPM) fungicide programs consist of 5 to 15 applications, depending on region or market, in an attempt to achieve the high fruit quality standards demanded by the market. Understanding how fungicides redistribute and targeting redistributing fungicide to critical crop phenological stages could improve fungicide protection of grape clusters. This study evaluated fungicide redistribution in grapevines from major fungicide groups labeled for GPM control. Translaminar and xylem redistribution was examined by placing fungicide-impregnated filter disks on the adaxial or abaxial leaf surface of detached leaves for 10 min and then incubating for 48 h before inoculating the abaxial surface with conidia. Vapor redistribution used Teflon disks sprayed with fungicides and placed on the abaxial leaf surface of detached leaves 48 h before inoculation. Disease development was rated 10 days later. Translaminar movement through calyptra was tested using flowering potted vines. All fungicides tested redistributed through at least one mechanism. Fungicide timing at critical phenological stages (early, mid, and late bloom) was assessed in small plots of cultivar Pinot noir vines. The application of trifloxystrobin, quinoxyfen, or fluopyram at different bloom stages showed that applications initiated at end of bloom resulted in the lowest berry infection probabilities of 0.073, 0.097, and 0.020, respectively. The results of this study suggest that integrating two carefully timed applications of redistributing fungicides initiated at end of bloom into a fungicide program may be an effective strategy for wine grape growers in western Oregon to produce fruit with low GPM infection.

scholarly journals First report of Leveillula taurica causing powdery mildew on cucumber in Mexico

2018 ◽  
Vol 100 (2) ◽  
pp. 353-353
Author(s):  
Hugo Beltrán-Peña ◽  
Alma Rosa Solano-Báez ◽  
Miguel Ángel Apodaca-Sánchez ◽  
Moisés Camacho-Tapia ◽  
Rubén Félix-Gastélum ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
First Report ◽  
Leveillula Taurica

First Report of Powdery Mildew Caused by Leveillula taurica of Field-Grown Sweet Pepper in the Pacific Northwest

2010 ◽  
Vol 11 (1) ◽  
pp. 45 ◽  
Author(s):  
Dean A. Glawe ◽  
Tess Barlow ◽  
Jordan E. Eggers ◽  
Philip B. Hamm
Keyword(s):  
Powdery Mildew ◽  
Economic Impact ◽  
Pacific Northwest ◽  
Sweet Pepper ◽  
Disease Outbreak ◽  
First Report ◽  
Leveillula Taurica ◽  
The Pacific

In August 2009, a grower reported a disease affecting nearly all plants in a drip-irrigated field of sweet pepper cv. Excalibur in Umatilla Co., OR. The fungus was determined to be Leveillula taurica (Lév.) G. Arnaud, previously unreported from this host in Oregon or from field-grown peppers in the Pacific Northwest. This report documents the taxonomic determination of this species and provides information about the disease outbreak, including economic impact. Accepted for publication 18 May 2010. Published 8 July 2010.

First report of Leveillula taurica causing powdery mildew on Tropaeolum majus in Taiwan

2021 ◽  
Author(s):  
Yi-Ting Xiao ◽  
Hiran A. Ariyawansa ◽  
Chao-Jen Wang ◽  
Tung-Chin Huang ◽  
Yuan-Min Shen
Keyword(s):  
Powdery Mildew ◽  
First Report ◽  
Leveillula Taurica ◽  
Tropaeolum Majus

scholarly journals First Report of Powdery Mildew Caused by Leveillula taurica on Cynanchum kashgaricum in China

Plant Disease ◽  
2012 ◽  
Vol 96 (9) ◽  
pp. 1373-1373
Author(s):  
G. He ◽  
B. Xu ◽  
J. G. Song ◽  
L. L. Zhang ◽  
Z. Y. Zhao ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Morphological Characters ◽  
Taklimakan Desert ◽  
Its Sequence ◽  
Endangered Plant ◽  
Voucher Specimen ◽  
First Report ◽  
Leveillula Taurica ◽  
The Family ◽  
In The Wild

Cynanchum kashgaricum Liou f., belonging to the family Apocynaceae, is an endemic herbaceous perennial and extremely endangered plant species, only found in the wild in desert regions of Xinjiang, China (3), and is valuable for sand stabilization. In August 2010, a previously unknown and widespread powdery mildew disease was observed on C. kashgaricum growing in the Taklimakan Desert in Xinjiang, China. Disease symptoms included the appearance of a white mycelial coating on the upper surfaces of leaves, while the corresponding abaxial surfaces of infected leaves became chlorotic. As the disease progressed, the infected leaves turned yellow and necrotic. In this survey, the incidence of affected C. kashgaricum plants was 60%. On the basis of microscopic examination, the morphology of the fungus can be described as follows: the primary conidia of the fungus were lanceolate or clavate, with a pointed apex and rounded base, measuring 40.4 to 82.5 × 11.1 to 24.6 μm, with an irregular surface covered by warts; the secondary conidia varied in shape from subcylindrical to cylindrical, with rounded ends, and had lateral borders that were parallel to each other with rounded or truncate bases, measuring 40.5 to 73.5 × 11.2 to 23.9 μm. The ascomata were nearly gregarious and globe-shaped, of dust-colored appearance, and 113 to 267 μm in diameter; they were immersed in dense mycelial tomentum with numerous asci (usually 10 to 18 per ascoma). Numerous, well-developed appendages were present on the lower half of the ascomata; these appendages were irregularly branched and their length was 0.15 to 0.3 times the diameter of the ascomata. The asci were stalked, long or wide ellipsoidal in shape, and 93 to 140 × 27.6 to 52.9 μm. The asci usually contained two ellipsoidal ascospores 24.5 to 49.5 × 18.3 to 29.5 μm. On the basis of morphologic characteristics, the fungus was identified as Leveillula taurica (2). A voucher specimen of the fungus under the identifier HMTU09021 was deposited in the Mycological Herbarium of Tarim University (HMTU). To verify the identity of the fungus, the internal transcribed spacer (ITS) rDNA was amplified and sequenced, and the sequences were deposited as GenBank Accession No. JN861731. Comparison with sequences in the GenBank database revealed that the ITS sequence showed 100% homology with the sequence of L. taurica on Capsicum annuum (Accession No. GQ167201) and Lepidium latifolium (Accession No. AB044349). Thus, the pathogen was identified as L. taurica on the basis of the anamorphic and teleomorphic morphological characters and the ITS sequence. To our knowledge, while L. taurica infection in plants of the family Apocynaceae has been reported around the world (1), in east Asia only a single report of C. glaucum infection in this genus has occurred, in Afghanistan (1). This is the first report of L. taurica infection of C. kashgaricum. Outbreaks of this powdery mildew could not only threaten growth of the endangered plant but also accelerate local ecological deterioration. References: (1) K. Amano. Host Range and Geographical Distribution of the Powdery Mildew Fungi, 2nd ed. Japan Scientific Societies Press, Tokyo, Japan, 1986. (2) U. Braun. A Monograph of the Erysiphales (Powdery Mildews). Nova Hedwigia Beiheft 89:1, 1987. (3) F. Ying et al. Acta Bot. Boreali-Occidentalia Sin. 23:263, 2003.

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