First Report of Oidium neolycopersici on Greenhouse Tomatoes in Serbia

In September 2011, tomato (Solanum lycopersicum L. ‘Big Beef’) plants showing typical symptoms of powdery mildew were collected in a greenhouse in the vicinity of Padinska Skela (District of City of Belgrade) in Serbia. Numerous circular, white colonies of powdery mildew were observed predominantly on the adaxial surface of the leaves, the petioles, and the stems. The foliage of infected plants turned yellow and necrotic, which was followed by rapid defoliation. Disease incidence was estimated by counting plants with powdery mildew symptoms in a random batch of 100 plants in four replicates and estimated to be extremely high, approaching 90%. Tomato plants (‘Novosadski Jabučar’) were inoculated with conidia released from diseased tomato leaves positioned above the tomato leaves and maintained at 25°C with a 14-h photoperiod. Healthy tomato plants from the same lot, which were not exposed to the conidia shower, were used as negative control. The first white fungal colonies appeared on the leaves of the inoculated plants within 4 to 7 days after inoculation, while no fungal growth was observed in the control plants. To determine the morphological characteristics of the pathogen, surface mycelium was removed with small strips of clear adhesive tape and examined using light microscopy. Microscopic observation revealed mycelium with lobed appressoria and hyaline, ellipsoid-ovoid or doliform conidia (32.5 to 47.5 × 17.5 to 25 μm) with no distinct firosin bodies and which produced sub-terminal germ tubes. Conidia were produced on the unbranched, erect conidiophores (82.5 to 150 μm) consisting of a cylindrical foot-cell followed by one to three short cells. No chasmothecia were found. On the basis of morphological characteristics, the pathogen was identified as Oidium neolycopersici (4), which was confirmed by internal transcribed spacer (ITS) sequence analysis. Total DNA was extracted directly from the whitish spots of superficial mycelium on the leaves with a DNeasy Plant Mini Kit (Qiagen, Hilden, Germany) following the manufacturer's instructions. PCR amplification and sequencing were performed with primers ITS1F and ITS4 (1). The nucleotide sequence of the representative isolate 809-11 (Accession No. JQ619840) shared 100% identity with 16 O. neolycopersici isolates deposited in GenBank from different parts of the world. Tomato powdery mildew caused by O. neolycopersici is present in many European (4) and other countries around the world (3) and is becoming economically very important as majority of the tomato cultivars have shown to be susceptible (2). To our knowledge, this is the first report of O. neolycopersici in Serbia. Because tomato is a very popular and widely grown vegetable in Serbia, the presence of a new and potentially harmful disease could endanger greenhouse as well as open field tomato production. References: (1) J. H. Cunnington et al. Australas. Plant Pathol. 32:421, 2003. (2) T. Jankovics et al. Phytopathology 98:529, 2008. (3) H. Jones et al. Mol. Plant Pathol. 2:303, 2001. (4) L. Kiss et al. Mycol. Res. 105:684, 2001.

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First Report of Powdery Mildew (Pseudoidium neolycopersici) on Croton (Codiaeum variegatum var. pictum) in China

Plant Disease ◽

10.1094/pdis-09-14-0892-pdn ◽

2015 ◽

Vol 99 (2) ◽

pp. 288-288 ◽

Cited By ~ 3

Author(s):

X.-M. Liu ◽

Y.-X. Wei ◽

H. Zhang ◽

F.-X. Zhou ◽

J.-J. Pu

Keyword(s):

Powdery Mildew ◽

Southern China ◽

Disease Incidence ◽

Morphological Characteristics ◽

Oidium Neolycopersici ◽

Tomato Plants ◽

First Report ◽

Pseudoidium Neolycopersici ◽

Codiaeum Variegatum ◽

Pathogenicity Tests

Croton (Codiaeum variegatum (Linn.) var. pictum (Lodd.)) is an ornamental plant commonly grown in southern China. In March 2014, severe powdery mildew infections were observed on crotons in gardens of Hainan University (20.1°N and 110.3°E), Haikou, Hainan province. Disease incidence was estimated in a random batch of 100 plants in three replicates, with the average value approaching 80%. Symptoms first appeared as white circular patches on the adaxial surface and expanded to the abaxial surface, petioles, and stems. The top leaves were the most affected. Upper surfaces of the infected leaves were covered by white, dense mycelia. As the disease progressed, infected leaves turned purple on the lower surfaces and curly before becoming necrotic and abscising from the plant. Powdery mildew was more severe in shaded environments, especially during rainy or foggy weather in early spring. Two hundred conidiophores and conidia were observed microscopically. The conidiophores were straight or occasionally flexuous, 62.3 to 127.6 × 6.2 to 10.2 μm, consisting of two to three straight cells. Conidia were born in solitary on the top of conidiophores. Conidia were hyaline, ellipsoidal, 26.4 to 42.2 × 11.7 to 23.4 μm (average 32.5 × 16.5 μm), contained no distinct fibrosin bodies, and produced a subterminal germ tube. The wrinkling pattern of the outer walls of older conidia was angular or reticulated. Appressoria were single and multilobed. Cleistothecia were not observed. Based on morphological characteristics, the fungus was identified as Oidium neolycopersici (2), which was recently renamed Pseudoidium neolycopersici (L. Kiss) (3). The identity was confirmed by sequence analysis. Genomic DNA was extracted from the foliar powdery mildew colonies using Chelex-100 (Bio-Rad, Shanghai, China). The rDNA internal transcribed spacer (ITS) region was amplified with primers ITS1 and ITS4 (5). The ITS sequence of the representative isolates C01 (GenBank Accession No. KJ890378.1) and four other powdery mildew samples collected from crotons in Hainan University was 100% identical to that of P. neolycopersici isolates from tomato plants such as JQ972700 and AB163927. Inoculations were made by gently pressing diseased leaves onto leaves of five healthy plants of croton and tomato (‘Money maker’). Five non-inoculated croton and tomato plants served as controls. Inoculated and non-inoculated plants were maintained in an incubator at 25°C with a 12-h photoperiod. After eight days, typical powdery mildew symptoms developed on 93% of the inoculated plants, while no symptom developed on the non-inoculated plants. The pathogenicity tests were repeated three times. The same fungus was always re-isolated from the diseased tissue according to Koch's postulates. The pathogenicity tests further confirmed that the pathogen from crotons is P. neolycopersici (Basionym. Oidium neolycopersici (KJ890378.1)), which is commonly known as the tomato powdery mildew. P. neolycopersici is also a pathogen of Normania triphylla (1) and papaya (4). To our knowledge, this is the first report of P. neolycopersici infecting croton. The avenue of this pathogen entering gardens of Hainan University remains unknown. The gardens are located far away from tomato farms. Also no symptom of powdery mildew on croton was observed during surveys in other locations in Haikou. The origin of the pathogen warrants additional research. References: (1) D. Delmail et al. Mycotaxon 113:269, 2010. (2) L. Kiss et al. Mycol. Res. 105:684, 2001. (3) L. Kiss et al. Mycol. Res. 115:612, 2011. (4) J. G. Tsay et al. Plant Dis. 95:1188, 2011. (5) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

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First Report of Powdery Mildew Caused by Erysiphe diffusa, Oidium neolycopersici, and Podosphaera xanthii on Papaya in Taiwan

Plant Disease ◽

10.1094/pdis-05-11-0362 ◽

2011 ◽

Vol 95 (9) ◽

pp. 1188-1188 ◽

Cited By ~ 6

Author(s):

J.-G. Tsay ◽

R.-S. Chen ◽

H.-L. Wang ◽

W.-L. Wang ◽

B.-C. Weng

Keyword(s):

Powdery Mildew ◽

Morphological Characteristics ◽

Its Region ◽

Podosphaera Xanthii ◽

Oidium Neolycopersici ◽

First Report ◽

Plastic Bags ◽

The World ◽

Golovinomyces Cichoracearum ◽

Powdery Mildew Fungi

Powdery mildew can be found in most papaya (Carica papaya L.) fields during the winter and spring seasons in Taiwan. It usually causes severe yellowing of the leaf lamina and petiole and serious defoliation. Three types of powdery mildew fungi were isolated from papaya leaves in Chiayi City (23.28°N, 120.28°E) at the beginning of 2008. Conidia of the first one were single, globose, hyaline, and 24 to 36 × 14 to 18 μm (average 30.2 × 15.6 μm) without fibrosin bodies and with straight or occasionally flexuous conidiophores at the base. The second one had short pseudo-chains of two to four conidia which were ellipsoidal to ovoid, hyaline, and 24 to 40 × 12 to 16 μm (average 29.7 × 13.4 μm) without fibrosin bodies. The third type had chains of ellipsoidal conidia that were hyaline, 24 to 28 × 12 to 16 μm (average 26.3 × 14.4 μm) and contained fibrosin bodies. To confirm the identity of the three fungi, the internal transcribed spacer (ITS) region of rDNA was amplified using the primer pairs G1 (5′-TCC GTA GGT GAA CCT GCG GAA GGA T-3′)/Ed2 (5′-CGC GTA GAG CCC ACG TCG GA-3′), G1 (5′-TCC GTA GGT GAA CCT GCG GAA GGA T-3′)/On2 (5′-TGT GAT CCA TGT GAC TGG AA-3′), and S1 (5′-GGA TCA TTA CTG AGC GCG AGG CCC CG-3′)/S2 (5′-CGC CGC CCT GGC GCG AGA TAC A-3′). The alignment of obtained sequences (GenBank Accession Nos. GU358452, 507 bp; GU358451, 580 bp; and GU358450, 455 bp) showed a sequence identity of 100, 99, and 99% with the ITS sequences of Erysiphe diffusa, Oidium neolycopersici, and Podosphaera xanthii (GenBank Accession Nos. FJ378880, EU909694, and GQ927254), respectively. On the basis of morphological characteristics and ITS sequence similarities, these fungi were identified as E. diffusa (Cooke & Peck) U. Braun & S. Takam., O. neolycopersici L. Kiss, and P. xanthii (Castagne) U. Braun & S. Takam., respectively (1,3). Single colonies on papaya leaves infected with powdery mildew were identified in the laboratory and maintained on papaya leaves as inoculum. Pathogenicity was confirmed through inoculations by gently pressing a single colony of each fungus onto leaves of healthy papaya seedlings (cv. Horng-Fe). Five seedlings were inoculated for each fungus and then covered with plastic bags for 2 days. Five noninoculated seedlings served as control. After inoculation, treated plants were maintained separately from the control in different rooms of a greenhouse at 25°C under natural daylight conditions. Seven days after inoculation, typical symptoms of powdery mildew were observed on inoculated plants, but not on noninoculated plants. The same species from diseased lesions following artificial inoculation with each fungus were identified with light microscopy. Papaya was previously described as a host to O. caricae Noack in many tropical and subtropical areas of the world including Taiwan (2). However E. cruciferarum, Golovinomyces cichoracearum, Oidiopsis sicula, O. caricae, O. caricae-papayae, O. caricicola, O. indicum, O. papayae, Ovulariopsis papayae, P. caricae-papayae, P. macularis, P. xanthii, and Streptopodium caricae were reported to infect papaya (4). To our knowledge, this is the first report of papaya powdery mildew caused by E. diffusa and O. neolycopersici in the world and the first report of the three fungi found on papaya in Taiwan. References: (1) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (2) H. S. Chien and H. L. Wang. J. Agric. Res. China 33:320, 1984. (3) L. Kiss et al. Mycol. Res. 105:684, 2001. (4) J. R. Liberato et al. Mycol. Res. 108:1185, 2004.

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First Report of Powdery Mildew Caused by Oidium neolycopersici on Tomato in China

Plant Disease ◽

10.1094/pdis-92-9-1370c ◽

2008 ◽

Vol 92 (9) ◽

pp. 1370-1370 ◽

Cited By ~ 3

Author(s):

C. W. Li ◽

D. L. Pei ◽

W. J. Wang ◽

Y. S. Ma ◽

L. Wang ◽

...

Keyword(s):

Powdery Mildew ◽

Average Length ◽

Pathogenic Fungus ◽

Fruit Size ◽

Morphological Characteristics ◽

Conidial Suspension ◽

Oidium Neolycopersici ◽

First Report ◽

Its Sequence Analysis ◽

Tomato Powdery Mildew

Tomato powdery mildew can cause remarkable reduction in fruit size and quality (4). In March of 2008, powdery mildew appeared as circular, white colonies on leaves, petioles, and stems of tomato plants grown in greenhouses in Shangqiu, Henan Province, China. The pathogenic fungus had unbranched conidiophores with an average length of 58.4 μm and width of 5.1 μm. Conidia were hyaline, elliptical, and were borne singly. Average length and width of conidia were 30.6 and 15.1 μm, respectively. Germ tubes were straight and formed at the ends or very close to the ends of conidia. Chasmothecium was not found in the collected samples. Different tomato cultivars and species, including Lycopersicon esculentum Mill (cvs. Moneymaker, Micro-Tom, Zaofen, Fenguo, and Zhongza series), L. peruvianum cv. LA2172, and L. hirsutum cv. G1.1560, were inoculated with a conidial suspension with a concentration of 5 × 104 conidia/ml. Plants developed powdery mildew symptoms as early as 4 days after inoculation. Susceptible symptoms developed on all L. esculentum cultivars, while L. peruvianum LA2172 and L. hirsutum G1.1560 displayed complete resistance, which is similar to the results of Bai et al 2004 (1) and Lindhout and Pet 1990 (3). Morphological characteristics of the pathogen on susceptible genotypes were similar to those from naturally infected plants. On the basis of the characteristics of the asexual stage, the pathogen was identified as an isolate of Oidium neolycopersici L. Kiss, which was confirmed by internal transcribed spacer (ITS) sequence analysis. PCR amplification and sequencing of the ITS region were performed with primers ITS1 and ITS4. The nucleotide sequence was assigned GenBank Accession No. EU486992, which had a 100% homology with 10 ITS sequences of O. neolycopersici in GenBank (Accession Nos. EU047559 to 047568) (2). In Asia, the spread of this pathogen has been recently reported in Japan (2). To our knowledge, this is the first report of tomato powdery mildew in China. Voucher specimens are available at the Specimen Center in the Department of Life Science, Shangqiu Normal University. References: (1) Y. Bai et al. Mol. Plant-Microbe. Interact. 18:354, 2005. (2) T. Jankovics et al. Phytopathology 98:529, 2008. (3) P. Lindhout and G. Pet. Tomato Gen. Coop. Rep. 40:19, 1990. (4) J. M. Whipps et al. Plant Pathol. 47:36, 1998.

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First Report of Powdery Mildew on Greenhouse Tomatoes Caused by Oidium neolycopersici in Michoacan, Mexico

Plant Disease ◽

10.1094/pdis-91-12-1684c ◽

2007 ◽

Vol 91 (12) ◽

pp. 1684-1684

Author(s):

G. Rodríguez-Alvarado ◽

J. García-López ◽

R. Rodríguez-Fernández ◽

S. P. Fernández-Pavía ◽

E. Garay-Serrano

Keyword(s):

Powdery Mildew ◽

Disease Incidence ◽

Morphological Characteristics ◽

Severe Infection ◽

The United States ◽

Oidium Neolycopersici ◽

Razor Blade ◽

First Report ◽

Tomato Seedlings ◽

Greenhouse Tomatoes

During June and July of 2007, powdery mildew-infected tomato (Lycopersicum esculentum Mill. cv. Reserve) plants were observed in a commercial greenhouse with an open hydroponic system in Morelia County. Disease incidence increased from 0.5% to more than 90% in 1 month. Infected plants showed leaves with irregular areas of dense, white mycelium covering most of the upper surface. Microscopic analysis showed hyaline, septate hyphae with lobed appressoria. Conidia were ellipsoid to ovoid and 30 to 45 (38) μm × 15 to 20 (16) μm. Conidiophores were erect, 80 to 120 (103) μm, consisted of a foot cell 42 to 67 (56) μm, and two to three short cells. Conidia were produced singly. On the basis of the observed morphological characteristics, the fungus was identified as Oidium neolycopersici L. Kiss (1). Pathogenicity tests were conducted on fourth true-leaf tomato seedlings cv. Reserve under greenhouse conditions (22 ± 5°C). Inoculation was performed by transferring conidia from infected leaves to the leaves of uninfected tomato seedlings with a single-edged razor blade. Powdery mildew symptoms began to develop 7 days after inoculation. Symptoms and morphological characteristics were similar to those observed in the commercial greenhouse. Noninoculated plants remained healthy throughout the experiments. To our knowledge, this is the first report of O. neolycopersici causing powdery mildew on tomato in Michoacan, Mexico. This disease has been reported from Canada, Europe, Japan, the United States (2), and Venezuela (3) on greenhouse and field tomato crops. The observed high incidence and severe infection indicates that this disease may become an important problem in greenhouse tomatoes in Mexico. References: (1) L. Kiss et al. Mycol. Res. 105:684, 2001. (2) L. Kiss et al. Plant Dis. 89:491, 2005. (3) J. O. Montilla et al. Plant Dis. 91:910, 2007.

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First Report of Leaf Spot Disease Caused by Colletotrichum gloeosporioides on Chinese Bean Tree in China

Plant Disease ◽

10.1094/pdis-03-12-0261-pdn ◽

2013 ◽

Vol 97 (1) ◽

pp. 138-138 ◽

Cited By ~ 1

Author(s):

B. Z. Fu ◽

M. Yang ◽

G. Y. Li ◽

J. R. Wu ◽

J. Z. Zhang ◽

...

Keyword(s):

Leaf Spot ◽

Colletotrichum Gloeosporioides ◽

Disease Incidence ◽

Phylogenetic Analyses ◽

Morphological Characteristics ◽

Leaf Spot Disease ◽

First Report ◽

Spot Disease ◽

Rdna Its ◽

Its Sequence Analysis

Chinese bean tree, Catalpa fargesii f. duciouxii (Dode) Gilmour, is an ornamental arbor plant. Its roots, leaves, and flowers have long been used for medicinal purposes in China. During July 2010, severe outbreaks of leaf spot disease on this plant occurred in Kunming, Yunnan Province. The disease incidence was greater than 90%. The symptoms on leaves began as dark brown lesions surrounded by chlorotic halos, and later became larger, round or irregular spots with gray to off-white centers surrounded by dark brown margins. Leaf tissues (3 × 3 mm), cut from the margins of lesions, were surface disinfected in 0.1% HgCl2 solution for 3 min, rinsed three times in sterile water, plated on potato dextrose agar (PDA), and incubated at 28°C. The same fungus was consistently isolated from the diseased leaves. Colonies of white-to-dark gray mycelia formed on PDA, and were slightly brown on the underside of the colony. The hyphae were achromatic, branching, septate, and 4.59 (±1.38) μm in diameter on average. Perithecia were brown to black, globose in shape, and 275.9 to 379.3 × 245.3 to 344.8 μm. Asci that formed after 3 to 4 weeks in culture were eight-spored, clavate to cylindrical. The ascospores were fusiform, slightly curved, unicellular and hyaline, and 13.05 to 24.03 × 10.68 to 16.02 μm. PCR amplification was carried out by utilizing universal rDNA-ITS primer pair ITS4/ITS5 (2). Sequencing of the PCR products of DQ1 (GenBank Accession No. JN165746) revealed 99% similarity (100% coverage) with Colletotrichum gloeosporioides isolates (GenBank Accession No. FJ456938.1, No. EU326190.1, No. DQ682572.1, and No. AY423474.1). Phylogenetic analyses (MEGA 4.1) using the neighbor-joining (NJ) algorithm placed the isolate in a well-supported cluster (>90% bootstrap value based on 1,000 replicates) with other C. gloeosporioides isolates. The pathogen was identified as C. gloeosporioides (Penz.) Penz. & Sacc. (teleomorph Glomerella cingulata (Stoneman) Spauld & H. Schrenk) based on the morphological characteristics and rDNA-ITS sequence analysis (1). To confirm pathogenicity, Koch's postulates were performed on detached leaves of C. fargesii f. duciouxii, inoculated with a solution of 1.0 × 106 conidia per ml. Symptoms similar to the original ones started to appear after 10 days, while untreated leaves remained healthy. The inoculation assay used three leaves for untreated and six leaves for treated. The experiments were repeated once. C. gloeosporioides was consistently reisolated from the diseased tissue. C. gloeosporioides is distributed worldwide causing anthracnose on a wide variety of plants (3). To the best of our knowledge, this is the first report of C. gloeosporioides causing leaf spots on C. fargesii f. duciouxii in China. References: (1) B. C. Sutton. Page 1 in: Colletotrichum: Biology, Pathology and Control. CAB International. Wallingford, UK, 1992. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990. (3) J. Yan et al. Plant Dis. 95:880, 2011.

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First Report of Powdery Mildew (Oidium sp.) on Pincushion Flower (Scabiosa columbaria) in New York

Plant Disease ◽

10.1094/pdis-93-3-0316b ◽

2009 ◽

Vol 93 (3) ◽

pp. 316-316 ◽

Cited By ~ 1

Author(s):

T. Jankovics ◽

L. Kiss ◽

R. E. Niks ◽

M. L. Daughtrey

Keyword(s):

New York ◽

Powdery Mildew ◽

The Netherlands ◽

Morphological Characteristics ◽

The United States ◽

Its Sequences ◽

Herbarium Specimens ◽

Chelidonium Majus ◽

Oidium Neolycopersici ◽

First Report

Scabiosa columbaria (Dipsacaceae) is a popular perennial ornamental in the United States. It is native to Europe and was introduced to North America by nursery trade only recently. In the spring of 2006, symptoms of powdery mildew infection were observed on overwintered plants of S. columbaria cv. Butterfly Blue in a nursery in Cutchogue, NY. White powdery mildew mycelia with abundant sporulation were observed on upper and lower leaf surfaces. The portions of leaves with powdery mildew colonies often showed purplish discoloration. Conidia were cylindric to doliiform, measured 20 to 33 × 10 to 15 μm, and were produced singly on 60 to 130 μm long conidiophores consisting of a foot-cell measuring 20 to 50 × 6 to 10 μm, followed by one to three, 12 to 40 μm long cells. Hyphal appressoria were lobed or multilobed. The teleomorph stage was not found. On the basis of these characteristics, the pathogen was identified as an Oidium sp. belonging to the subgenus Pseudoidium. Recently, an anamorphic powdery mildew fungus with similar morphological characteristics, identified as Erysiphe knautiae, was reported on S. columbaria cv. Butterfly Blue in Washington (2). E. knautiae is a common powdery mildew species of dipsacaceous plants such as Scabiosa spp. and Knautia spp. in Europe and Asia (1). To determine whether the fungus reported here was E. knautiae, DNA was extracted from its mycelium, and the internal transcribed spacer (ITS) region of the ribosomal DNA was amplified and sequenced as described earlier (4). No ITS sequences are available in public DNA databases for E. knautiae, thus, we determined this sequence in a specimen of E. knautiae collected from Knautia arvensis in The Netherlands. Herbarium specimens of the Oidium sp. infecting S. columbaria in New York and E. knautiae from the Netherlands were deposited at the U.S. National Fungus Collections under accession numbers BPI 878259 and BPI 878258, respectively. The ITS sequence from Oidium sp. infecting S. columbaria in New York (GenBank Accession No. EU377474) differed in two nucleotides from that of E. knautiae infecting K. arvensis in the Netherlands (GenBank Accession No. EU377475). These two ITS sequences were also more than 99% similar to those of some newly emerged anamorphic powdery mildew fungi: Oidium neolycopersici and other Oidium spp. infecting Chelidonium majus, Passiflora caerulea, and some crassulaceous plants (3,4). Thus, it is unclear whether the fungus reported here was E. knautiae known from Eurasia or an Oidium sp. that has acquired pathogenicity to S. columbaria. To our knowledge, this is the first report of powdery mildew on S. columbaria in New York. References: (1) U. Braun. Beih. Nova Hedwigia 89:1, 1987. (2) D. A. Glawe and G. G. Grove. Online publication. doi:10.1094/PHP-2005-1024-01-BR. Plant Health Progress, 2005. (3) B. Henricot. Plant Pathol. 57:779, 2008. (4) T. Jankovics et al. Phytopathology 98:529, 2008.

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First Report of Powdery Mildew Caused by Podosphaera xanthii on Cuphea hyssopifolia (Lythraceae) in Mainland China

Plant Disease ◽

10.1094/pdis-03-21-0545-pdn ◽

2021 ◽

Author(s):

Irum Mukhtar ◽

Ruiting Li ◽

IBATSAM KHOKHAR ◽

Ruanni Chen ◽

Yunying Cheng ◽

...

Keyword(s):

Powdery Mildew ◽

Disease Incidence ◽

Large Subunit ◽

Mainland China ◽

Lsu Rdna ◽

Podosphaera Xanthii ◽

Powdery Mildew Fungus ◽

Potential Threat ◽

First Report ◽

Plant Pathol

Cuphea hyssopifolia (Mexican heather) is a popular evergreen perennial shrub used for ornamental and medicinal purposes. Due to its high ornamental value, it is often used as a ground cover in parks and gardens in China. During February and March 2019 & 2020, powdery mildew was observed on C. hyssopifolia in the districts of Minhou and Jinshan of Fuzhou, China. Disease incidence was 70% but of low severity with only a few older leaves showing yellowing and wilting. Sparse irregular patches of white superficial powdery mildew observed on both sides of mature and young leaves. The powdery mildew fungal appressoria that occurred on epigenous hyphae, were indistinct to nipple-shaped, hyaline, and smooth. Conidiophores were erect, smooth, 80 to 210 × 10 to 12 µm, and produced two to eight crenate-shaped conidia in chains. Foot-cells of conidiophores were straight, cylindric, and 30 to 65 × 10 to12 µm. Conidia were hyaline, smooth, ellipsoid-ovoid to barrel-shaped, 25 to 38 × 16 to 20 µm with distinct fibrosin bodies. Germ tubes were simple to forked and produced from the lateral position of the germinating conidia. No chasmothecia were observed on the surface of infected leaves. Based on the morphology of the imperfect state, the powdery mildew fungus was identified as Podosphaera xanthii (Castagne) U. Braun & N. Shishkoff (Braun and Cook 2012). To confirm fungal identification, total DNA was extracted (Mukhtar et al., 2018) directly from epiphytic mycelia on infected leaves collected from both districts. Internal transcribed spacer (ITS) regions and the partial large subunit (LSU) rDNA were amplified using primers ITS1/ITS4 and LSU1/LSU2 (Scholin et al. 1994, White et al. 1990), respectively. The sequences were deposited in GenBank (ITS: MW692364, MW692365; LSU: MW699924, MW699925). The ITS and LSU sequences were 99 to 100 % identical to those of P. xanthii in GenBank, (ITS: MT568609, MT472035, MT250855, and AB462800; LSU: AB936276, JX896687, AB936277, and AB936274). Koch’s postulates were completed by gently pressing diseased leaves onto leaves of five healthy potted C. hyssopifolia plants that were held in a greenhouse at 24 to 30°C without humidity control. Five non-inoculated plants served as controls. Inoculated plants developed symptoms after 6 to 10 days, whereas the controls remained symptomless. The morphology of the fungus on the inoculated leaves was identical to that observed on the originally diseased leaves. Previously, Podosphaera sp. has been reported on C. rosea in the United Kingdom (Beales & Cook 2008) and P. xanthii on C. hyssopifolia in Taiwan (Yeh et al. 2021). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on C. hyssopifolia in mainland China. Our field observations suggest that the P. xanthii infections would be a potential threat to the health of C. hyssopifolia in China. References: Beales, P. A., and Cook, R. T. A. 2008. Plant Pathol. 57:778. Braun, U., Cook, R. T. A. 2012. The Taxonomic Manual of the Erysiphales (Powdery Mildews). CBS Biodiversity Series 11: CBS. Utrecht, The Netherlands. Mukhtar, I., et al. 2018. Sydowia.70:155. Scholin, C. A., et al. 1994. J. Phycol. 30:999. White, T. J., et al. 1990. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA. Yeh, Y. W., et al. 2021. Trop. Plant Pathol. 46:44.

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First Report of Powdery Mildew on Tomato Caused by Oidium neolycopersici in Venezuela

Plant Disease ◽

10.1094/pdis-91-7-0910b ◽

2007 ◽

Vol 91 (7) ◽

pp. 910-910 ◽

Cited By ~ 1

Author(s):

J. O. Montilla ◽

M. S. González ◽

D. Renaud

Keyword(s):

Powdery Mildew ◽

Leaf Surface ◽

Distinct Species ◽

Oidium Neolycopersici ◽

First Report ◽

Physalis Peruviana ◽

Infected Tomato ◽

White Mycelium ◽

Foliar Tissue ◽

Plant Pathol

During 2004 and 2005, a powdery mildew was observed in tomato (Lycopersicon esculentum Mill. cv. Rio Grande) fields in several states in Venezuela. Symptoms included development of patches of dense white mycelium, predominantly on the upper leaf surface. Leaves in the middle and lower canopies were the most affected. Similar symptoms sometimes were observed on stems. The foliage of infected plants turned yellow and showed necrosis followed by desiccation and rapid defoliation. Microscopic examination revealed the presence of typical structures of the Oidium genus. Hyphae were hyaline and septate. Conidiophores were unbranched, erect, measured 51 to 108 (80) μm, and consisted of 3 or 4 cells. Conidia were hyaline, ellipsoidal to ovoidal, and measured 16 to 43 (30) × 12 to 22 (16) μm. Conidia were produced singly, without fibrosin bodies. Conidial polar germination was common. Appressoria were lobed. The sexual stage was not found. The fungus was identified as Oidium neolycopersici, recently recognized as a distinct species (1,2). Conidia from infected tomato leaves were shaken onto leaves of 10 plants of L. esculentum and L. pimpinellifolium (Jusl.) Mill. and five plants of a weed (Physalis peruviana L.). Noninoculated plants served as a control. Symptoms that developed on all inoculated plants were similar to those of plants naturally infected. Within 7 to 8 days, symptoms in L. esculentum consisted of small colonies that quickly covered large portions of foliar tissue. L. pimpinellifolium showed small and localized symptoms after 10 days and P. peruviana showed symptoms after 15 days. To our knowledge, this is the first report of O. neolycopersici in Venezuela. References: (1) H. Jones et al. Mol. Plant Pathol. 2:303, 2001. (2) L. Kiss et al. Mycol. Res. 105:684, 2001.

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First Report of Powdery Mildew on Leucophyllum frutescens Caused by Podosphaera xanthii in Mexico

Plant Disease ◽

10.1094/pdis-06-20-1368-pdn ◽

2020 ◽

Author(s):

Hugo Beltrán-Peña ◽

Ruben Felix-Gastelum ◽

Moises Camacho-Tapia ◽

Kamila C. Correia ◽

Gabriel Herrera-Rodriguez ◽

...

Keyword(s):

Powdery Mildew ◽

Urban Areas ◽

Disease Incidence ◽

Phylogenetic Analyses ◽

Morphological Characteristics ◽

Podosphaera Xanthii ◽

Monitoring And Control ◽

Voucher Specimen ◽

First Report ◽

Initial Symptoms

Leucophyllum frutescens (Scrophulariaceae family), commonly known as Texas sage or cenizo, is an evergreen shrub native to southwestern United States and northern Mexico. This plant is commercially sold as a native, drought-tolerant ornamental. During the spring of 2019 and 2020, typical symptoms of powdery mildew were found on cenizo plants growing as ornamentals in urban areas in the municipality of Ahome, Sinaloa, Mexico. Disease incidence was 95% from a sampled population of 120 plants. Initial symptoms of powdery mildew developed as irregular white colonies on upper leaf surfaces which expanded as infections progressed. In severe infections, leaves became distorted, exhibiting premature defoliation. Microscopic examination showed nipple-shaped appressoria. Conidiophores (n= 30) were hyaline, cylindrical, erect, 89.4 to 134.2 μm long, and forming catenescent conidia. Foot-cells were cylindrical, 35.7 to 65.3 × 10.2 to 13.5 μm, followed by 1–3 shorter cells. Conidia (n= 100) were hyaline, ellipsoid to ovoid, 27.9 to 40.5 × 13.8 to 18.9 μm, containing distinct fibrosin bodies. Germ tubes were simple to forked and laterally produced from the middle of conidia. Chasmothecia were not found during the sampling period on the infected leaves. Based on morphological characteristics, the fungus was identified as Podosphaera xanthii (Braun and Cook 2012). A voucher specimen (accession no. FAVF219) was deposited in the Herbarium of the Faculty of Agronomy of El Fuerte Valley at the Autonomous University of Sinaloa (Juan Jose Rios, Sinaloa, Mexico). To further confirm the identification, total DNA was extracted, and the internal transcribed spacer (ITS) region was amplified by PCR using the primers ITS5/ITS4 (White et al. 1990) and sequenced. The resulting 503 bp sequence (GenBank accession no. MT624793) had 100% coverage and 100% identity to those of P. xanthii (MT568609–MT568611, MT472035, MT309699, MT250855, MT242593). A phylogenetic tree using the maximum parsimony (MP) and maximum likelihood (ML) methods and including published ITS sequences for Podosphaera species was obtained. Phylogenetic analyses revealed that ITS sequence from FAVF219 isolate was grouped into a clade with P. xanthii. Pathogenicity was demonstrated by gently dusting conidia from infected leaves onto 50 leaves of five healthy plants. Five non-inoculated plants served as controls. All plants were covered with polyethylene bags for 48 h to maintain high humidity and were maintained in a greenhouse at temperatures ranging from 20 to 35ºC. All inoculated plants developed similar symptoms to the original observations after 19 days, whereas no symptoms of powdery mildew were observed on control plants. The fungus present on the inoculated plants was morphologically identical to that originally observed on diseased plants, fulfilling Koch’s postulates. This fungus has been reported infecting members of the Cucurbitaceae in Mexico (Félix-Gastélum et al. 2017; Farr and Rossman 2020). However, to our knowledge, this is the first report of P. xanthii causing powdery mildew on a member of Scrophulariaceae, specifically L. frutescens in Mexico and worldwide. Further studies for monitoring and control strategies of powdery mildew on Texas sage are required.

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First Report of Powdery Mildew on Greenhouse Tomatoes Caused by Oidium neolycopersici in Florida

Plant Disease ◽

10.1094/pdis.2001.85.12.1292b ◽

2001 ◽

Vol 85 (12) ◽

pp. 1292-1292 ◽

Cited By ~ 3

Author(s):

J. J. Marois ◽

M. T. Momol ◽

J. W. Kimbrough ◽

R. C. Hochmuth ◽

W. Dankers

Keyword(s):

New York ◽

Powdery Mildew ◽

Disease Incidence ◽

Control Measures ◽

Oidium Neolycopersici ◽

Razor Blade ◽

First Report ◽

White Mycelium ◽

Repeated Applications ◽

Greenhouse Tomatoes

In December 1999, typical signs of powdery mildew-dense white mycelium in irregular patterns often covering almost the entire upper surface of leaves-were observed in production greenhouses on tomato cv. Tradiro. Microscopic observations revealed mycelium with lobed appressoria and large, approximately cylindrical conidia that measured 38 to 45 × 16 to18 μm. Short germ tubes were at one end of the conidium and ended in a lobed appressorium. Conidiophores were straight with cylindrical foot-cells (≈40 to 42 μm), followed by two short cells (14 to18 μm). Based on these characteristics the fungus was identified as 0idium neolycopersici Kiss et al. (2) (formerly O. lycopersicum Braun [1]). Disease-free tomato cv. FL47 plants were inoculated at the fourth true-leaf stage with conidia by transferring fungal colonies collected from plants in production greenhouses with a single-edged razor blade to the adaxial surface of the test plants (six plants and three leaves per plant). Plants were grown in the greenhouse at 20 to 25°C. Powdery mildew, exhibiting the same morphological features, was observed 12 days later on inoculated tomato leaves. Powdery mildew on tomatoes in Suwannee Valley area greenhouses in Florida was quite common and severe in 1999 to 2000. Secondary cycles of the disease were observed, resulting in disease incidence up to 50 to 60% in some greenhouses, requiring repeated applications of sulfur for its management. This disease is expected to become a significant problem in greenhouse tomatoes, requiring regular disease control measures. This powdery mildew has not yet been observed in field-grown tomatoes in Florida. The pathogen has been reported in Connecticut on tomatoes grown under greenhouse and field conditions (3). To our knowledge, this is the first report of O. neolycopersici on greenhouse-grown tomatoes in Florida. References: (1) U. Braun. The Powdery Mildews (Erysiphales) of Europe. Gustav Fisher Verlag, New York, 1995. (2) L. Kiss et al. Mycol. Res. 105:684, 2001. (3) J. A. LaMondia et al. Plant Dis. 83:341, 1999.

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