First Report of Powdery Mildew of Pumpkin Caused by Golovinomyces cichoracearum in Neelum Valley, Azad Kashmir

During July 2011, a severe powdery mildew outbreak was recorded in pumpkin (Cucurbita moschata Duch.) fields in economically poor areas in the Neelum Valley (Leswa, Mir Pura, Jura, Kundal Shahi, and Bela). Disease symptoms included grayish white circular to irregular patches consisting of epiphytic mycelia and conidia on both surfaces of the leaves of infected vines. Fungal mycelia and conidiophores were also visible in white powdery patches on the main stems, leaves, and petioles of affected plants. Leaves became necrotic with age. Powdery mildew symptoms were more severe on pumpkin vines located in the shade, and severely affected vines collapsed. A voucher specimen (IR00027) has been deposited in First Fungal Culture Bank of the Pakistan (FCBP), Institute of Agriculture Sciences, University of the Punjab, Lahore, Pakistan. For morphological observation, a clear tape strip was used to remove fungal tissue from infected leaves. The tape was mounted on microscope slides with water and examined with a light microscope (2). Conidiophores were unbranched, cylindrical, erect and arose singly on hyphal cells, 110 to 200 × 6 to 12 μm, composed of a foot cell and three to eight barrel-shaped conidia formed in chains with a sinuate edge, followed with a basal septum at the branching point or slightly displaced from the mycelium. Foot cells were 50 to 80 × 6 to 12 μm, and slightly swollen with constriction at the base. Conidia were cylindrical to doliiform, 30 to 50 × 14 to 20 μm and produced in chains. The length/breadth ratio of the conidia was 1.8 to 2.6. Fibrosin bodies were absent in both conidiophores and conidia. No cleistothecia were observed. Identification of the causal agent as Golovinomyces cichoracearum (DC.) V.P. Heluta (synonym Erysiphe cichoracearum) was based on morphology (1). Pathogenicity was determined using field-infected plant leaves transported to a greenhouse. Fresh conidia of field isolates of G. cichoracearum were transferred by a sterile brush from the affected leaves to fully expanded four to five healthy leaves of three 40-day-old vines. For the control, three vines were stroked with a clean sterile brush and control plants were placed 100 m away from the inoculated plants. For disease development 20°C and 80% relative humidity was maintained in the greenhouse. A plastic sheet was placed around each vine for a week and removed later. Inoculated vines developed visible white spots of powdery mildew on the leaves after 10 days in the greenhouse, whereas control plants remained asymptomatic. Fungal colony and conidial morphology on the leaves of inoculated plants were as described above. Previously, G. cichoracearum has been reported on other cucurbits (3) in the plains of Pakistan. To our knowledge, this is the first report of occurrence of G. cichoracearum as a causal agent of powdery mildew on pumpkin in Neelum Valley, Azad Kashmir. References: (1) U. Braun. Beih. Nova Hedwigia 89:1, 1987. (2) J. C. Correll et al. Plant Dis. 71:248, 1987. (3) A. Wahid et al. Pak. J. Agric. Res. 9:209, 1988.

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First Report of Powdery Mildew of Coreopsis Species Caused by Golovinomyces cichoracearum in the Pacific Northwest

Plant Health Progress ◽

10.1094/php-2006-0405-01-br ◽

2006 ◽

Vol 7 (1) ◽

pp. 57

Author(s):

Dean A. Glawe ◽

Gary G. Grove ◽

Mark Nelson

Keyword(s):

Powdery Mildew ◽

Pacific Northwest ◽

Causal Agent ◽

Diagnostic Features ◽

First Report ◽

The Pacific ◽

Powdery Mildew Disease ◽

Golovinomyces Cichoracearum

In 2005, the authors encountered a previously unreported powdery mildew disease of Coreopsis verticillata L. (whorled tickseed) ‘Zagreb’ and C. auriculata L. (lobed tickseed) ‘Nana’ in central Washington and determined the causal agent to be Golovinomyces cichoracearum (DC.) VP Gelyuta. This report documents the occurrence of G. cichoracearum on Coreopsis species in the Pacific Northwest, and describes diagnostic features of the disease and causal agent. Accepted for publication 2 March 2006. Published 5 April 2006.

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First Report of Golovinomyces cichoracearum as the Causal Agent of Powdery Mildew on Symphyotrichum novi-belgii (Synonym Aster novi-belgii) in Denmark

Plant Disease ◽

10.1094/pdis-10-10-0712 ◽

2011 ◽

Vol 95 (2) ◽

pp. 228-228 ◽

Cited By ~ 4

Author(s):

E. K. Mørk ◽

K. Kristiansen ◽

H. J. Lyngs Jørgensen ◽

T. Sundelin

Keyword(s):

Powdery Mildew ◽

Morphological Characteristics ◽

Causal Agent ◽

Spore Density ◽

Healthy Plant ◽

Internal Transcribed Spacer Region ◽

Greenhouse Production ◽

First Report ◽

Potted Plant ◽

Golovinomyces Cichoracearum

Symphyotrichum novi-belgii (L.) G.L. Nesom (synonym Aster novi-belgii L.) is an autumn flowering perennial used in gardens and as a cut flower. During the last 20 years, it has been developed as a potted plant, thereby increasing its economic importance. In Denmark, 7 to 8 million S. novi-belgii plants are produced annually, making it one of the 10 most popular potted plant crops ( http://floradania.dk/index.php?id=165 ). In general, S. novi-belgii is a healthy plant, but it can be severely attacked by powdery mildew both in greenhouse production and outdoors, and diseased plants have been observed in most parts of the country. Infected plants show typical symptoms: leaf surfaces become covered with white mycelium and as the disease progresses infected leaves turn yellow and die. Powdery mildew is regarded the main disease problem in S. novi-belgii and it causes problems year round in greenhouse production. Normally, the disease is controlled by fungicides, but once out of the production system, symptom development in the retail trade will reduce the plant's appeal to customers to a degree that prevents sales. The powdery mildew identified in this study was collected in a small research field at Aarslev, Denmark in September 2004. Since collection, the pathogen has been maintained in a greenhouse on S. novi-belgii and it has been used for disease resistance screening. However, lack of proper identification of the causal agent has hindered the development of powdery mildew resistant cultivars. To identify the pathogen, the internal transcribed spacer region (ITS) of the rDNA was amplified using primers ITS1 and ITS4 (2) and sequenced. The resulting sequence was deposited in GenBank (Accession No. HM769725). BLASTn analysis of the 598-bp fragment showed 99% identity to Golovinomyces cichoracearum (DC.) V.P. Heluta from Rudbeckia laciniata L. (Accession No. AB077622). The powdery mildew colonies were slightly pink with barrel-shaped, hyaline conidia borne in chains of three to four. The length of the conidia was 30 ± 4 μm and the width was 13 ± 1 μm (n = 105). Foot cells of the conidiophores were 101 ± 16 μm long and 12 ± 5 μm wide (n = 50) with a slight constriction at the base. Chasmothecia were not observed. These morphological characteristics confirmed the identification as G. cichoracearum (1). To fulfill Koch's postulates, 10 healthy S. novi-belgii ‘Victoria Fanny’ plants were inoculated in an inoculation tower by shaking infected S. novi-belgii plants over the tower, resulting in a spore density of 47 spores/mm2 on the leaf surface. The infected plants were placed in a growth chamber with 16 h of light (200 μmol·m–2·s–1) and day and night temperatures of 20 and 15°C, respectively. Symptoms developed on all plants after 11 days. Colony morphology on the leaves and the morphological characteristics were as described above. Conidia were washed off the leaves, DNA extracted, and the ITS was amplified by PCR. The resulting PCR product was sequenced and was identical to HM769725. To our knowledge, this is the first report of G. cichoracearum on S. novi-belgii in Denmark. References: (1) U. Braun. The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer Verlag, Jena Germany, 1995. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, New York, 1990.

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First Report of Powdery Mildew on Dipsacus sylvestris Caused by Sphaerotheca dipsacearum in North America

Plant Health Progress ◽

10.1094/php-2006-0607-02-br ◽

2006 ◽

Vol 7 (1) ◽

pp. 54

Author(s):

Frank M. Dugan ◽

Dean A. Glawe

Keyword(s):

North America ◽

Powdery Mildew ◽

Causal Agent ◽

European Species ◽

First Report ◽

Dipsacus Sylvestris ◽

Noxious Weed

Common teasel (Dipsacus sylvestris) is a European species introduced into North America, and is now widely established and regarded as a noxious weed. In October 2005, a powdery mildew was observed on D. sylvestris in two locations in Pullman, Whitman Co., WA. Examination of diseased material confirmed that the causal agent was S. dipsacearum. This report provides the first documentation of S. dipsacearum on D. sylvestris in North America. Accepted for publication 20 April 2006. Published 7 June 2006.

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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 Golovinomyces cichoracearum associated with powdery mildew on Helianthus tuberosus in Korea

Australasian Plant Disease Notes ◽

10.1007/s13314-012-0041-2 ◽

2012 ◽

Vol 7 (1) ◽

pp. 35-37 ◽

Cited By ~ 1

Author(s):

Sung-Eun Cho ◽

Mi-Jeong Park ◽

Ji-Hyun Park ◽

Kyung-Sook Han ◽

Hyeon-Dong Shin

Keyword(s):

Powdery Mildew ◽

Helianthus Tuberosus ◽

First Report ◽

Golovinomyces Cichoracearum

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First Report of Powdery Mildew Caused by Podosphaera xanthii on Cucurbita argyrosperma in Mexico

Plant Disease ◽

10.1094/pdis-11-21-2458-pdn ◽

2021 ◽

Author(s):

José Francisco Díaz-Nájera ◽

Sergio Ayvar-Serna ◽

Antonio Mena-Bahena ◽

Guadalupe Arlene Mora-Romero ◽

Karla Yeriana Leyva-Madrigal ◽

...

Keyword(s):

Powdery Mildew ◽

Microscopic Examination ◽

Disease Incidence ◽

Phylogenetic Analyses ◽

Its Region ◽

Likelihood Method ◽

28S Rrna ◽

Podosphaera Xanthii ◽

Voucher Specimen ◽

First Report

Cucurbita argyrosperma, commonly named as winter or cushaw squash, is highly sought for its seeds, which have important uses in culinary arts. During the autumn 2021, powdery mildew-like signs and symptoms were observed on cushaw squash in several commercial fields located in Cocula, Guerrero, Mexico. Signs were initially appeared as whitish powdery patches on both sides of leaves and then covering entire leaves and causing premature senescence. The disease incidence was estimated to be 80% in about 1000 plants in two fields. The mycelium was amphigenous, persistent, white in color, and occurred in dense patches. A voucher specimen was deposited in the Herbarium of the Colegio Superior Agropecuario del Estado de Guerrero under the accession number CSAEG22. For the morphological characterization by light microscopy, fungal structures were mounted in a drop of lactic acid on a glass slide. Microscopic examination showed nipple-shaped hyphal appressoria. Conidiophores (n = 30) were straight, 100 to 190 × 10 to 12 μm and produced 2 to 6 conidia in chains. Foot-cells were cylindrical, 41 to 78 μm long, followed by 1 to 2 shorter cells. Conidia (n = 100) were ellipsoid-ovoid to barrel-shaped, 29.5 to 39.1 × 19.4 to 22.7 μm, and contained conspicuous fibrosin bodies. Germ tubes were produced from a lateral position on conidia. Chasmothecia were not observed during the growing season. The morphological characters were consistent with those of the anamorphic state of Podosphaera xanthii (Braun and Cook 2012). For further confirmation, total DNA was extracted from conidia and mycelia following the CTAB method (Doyle and Doyle 1990), and the internal transcribed spacer (ITS) region and part of the 28S gene were amplified by PCR, and sequenced. The ITS region of rDNA was amplified using the primers ITS5/ITS4 (White et al. 1990). For amplification of the 28S rRNA partial gene, a nested PCR was performed using the primer sets PM3 (Takamatsu and Kano 2001)/TW14 (Mori et al. 2000) and NL1/TW14 (Mori et al. 2000) for the first and second reactions, respectively. Phylogenetic analyses using the Maximum Likelihood method, including ITS and 28S sequences of isolates of Podosphaera spp. were performed and confirmed the results obtained in the morphological analysis. The isolate CSAEG22 grouped in a clade with isolates of Podosphaera xanthii. The ITS and 28S sequences were deposited in GenBank under accession numbers OL423329 and OL423343, respectively. Pathogenicity was confirmed by gently dusting conidia from infected leaves onto ten leaves of healthy C. argyrosperma plants. Five non-inoculated leaves served as controls. The plants were maintained in a greenhouse at 25 to 35 ºC, and relative humidity of 60 to 70%. All inoculated leaves developed similar signs to the original observation after 10 days, whereas control leaves remained symptomless. Microscopic examination of the fungus on inoculated leaves showed that it was morphologically identical to that originally observed on diseased plants, fulfilling Koch’s postulates. Podosphaera xanthii has been previously reported on C. maxima, C. moschata, and C. pepo in Mexico (Yañez-Morales et al. 2009; Farr and Rossman 2021). To our knowledge, this is the first report of P. xanthii causing powdery mildew on C. argyrosperma in Mexico. This pathogen is a serious threat to C. argyrosperma production in Mexico and disease management strategies should be developed.

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

Plant Disease ◽

10.1094/pdis-11-11-0947-pdn ◽

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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First Report of Powdery Mildew Caused by Golovinomyces cichoracearum on English Daisy (Bellis perennis) in Italy

Plant Disease ◽

10.1094/pdis-92-3-0484a ◽

2008 ◽

Vol 92 (3) ◽

pp. 484-484 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

Powdery Mildew ◽

Its Region ◽

Northern Italy ◽

Flowering Plant ◽

Pathogenicity Test ◽

First Report ◽

Golovinomyces Cichoracearum ◽

Blastn Analysis ◽

Commercial Farms ◽

Voucher Specimens

Bellis perennis (English daisy) is a flowering plant belonging to the Asteraceae and is increasingly grown as a potted plant in Liguria (northern Italy). In February 2007, severe outbreaks of a previously unknown powdery mildew were observed on plants in commercial farms at Albenga (northern Italy). Both surfaces of leaves of affected plants were covered with white mycelia and conidia. As the disease progressed, infected leaves turned yellow. Mycelia and conidia also were observed on stems and flower calyxes. Conidia were hyaline, ellipsoid, borne in chains (as many as three conidia per chain), and measured 27.7 × 16.9 (15.0 to 45.0 × 10.0 to 30.0) μm. Conidiophores measured 114.0 × 12.0 (109.0 to 117.0 × 11.0 to 13.0) μm and showed a foot cell measuring 78.0 × 11.0 (72.0 to 80.0 × 11.0 to 12.0) μm followed by two shorter cells. Fibrosin bodies were absent. Chasmothecia were not observed in the collected samples. The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 415 bp obtained showed an E-value of 7e–155 with Golovinomyces cichoracearum (3). The nucleotide sequence has been assigned the GenBank Accession No. AB077627.1 Pathogenicity was confirmed through inoculations by gently pressing diseased leaves onto leaves of healthy B. perennis plants. Twenty plants were inoculated. Fifteen noninoculated plants served as a control. Plants were maintained in a greenhouse at temperatures ranging from 10 to 30°C. Seven days after inoculation, typical symptoms of powdery mildew developed on inoculated plants. The fungus observed on inoculated plants was morphologically identical to that originally observed. Noninoculated plants did not show symptoms. The pathogenicity test was carried out twice. To our knowledge, this is the first report of powdery mildew on B. perennis in Italy. The disease was already reported in other European countries (2). Voucher specimens are available at the AGROINNOVA Collection, University of Torino. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) U. Braun The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer Verlag, Jena, Germany, 1995. (3) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000.

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First Report of Powdery Mildew Caused by Golovinomyces ambrosiae on Verbena bonariensis in Korea

Plant Disease ◽

10.1094/pdis-02-21-0349-pdn ◽

2021 ◽

Author(s):

In-Young Choi ◽

Ho-Jong Ju ◽

Kui-Jae Lee ◽

Hyeon-Dong Shin

Keyword(s):

Powdery Mildew ◽

Large Subunit ◽

Morphological Characteristics ◽

Morphological Characterization ◽

Control Measures ◽

Width Ratio ◽

Infected Leaf ◽

Voucher Specimen ◽

First Report ◽

Pcr Products

Verbena bonariensis L., named as purple-top vervain or Argentinian vervain, is native to tropical South America. It is cultivated worldwide as an ornamental plant. During summer and autumn of 2020, over 50% of the leaves of V. bonariensis were found infected with powdery mildew in a flower garden in Seoul (37°35'19"N 127°01'07"E), Korea. White, superficial mycelia developed initially on the leaves and subsequently covered surfaces of leaves and stems, are resulting in leaf discoloration, early defoliation, and shoots distortion. Heavily infected plants lost ornamental value. A representative voucher specimen was deposited in the Korea University herbarium (KUS-F32168). Morphological characterization and measurements of conidiophores and conidia were carried out using fresh samples. Microscopic observation showed that aAppressoria on the superficial hypha were nipple-shaped, but rarely found or nearly absent. Conidiophores (n = 30) were cylindrical, 110 to 220 × 10 to 12 µm, and produced 2 to 5 immature conidia in chains with a sinuate outline, followed by 2 to 3 short cells. Foot-cells of conidiophores were straight, cylindrical, and 46 to 90 μm long. Conidia (n = 30) were hyaline, ellipsoid to doliiform, 28 to 40 × 18 to 24 μm with a length/width ratio of 1.3 to 2.0, and contained small be like oil-like drops, but without distinct fibrosin bodies. Primary conidia were apically rounded and sub-truncate at the base. Germ tubes were produced at perihilar position of the conidia. Chasmothecia were not observed. These morphological characteristics were typical of the conidial stage of the genus Golovinomyces (Braun and Cook 2012, Qiu et al. 2020). To identify the fungus, rDNA was extracted from the voucher sample. PCR products were amplified using the primer pair ITS1F/PM6 for internal transcribed spacer (ITS), and PM3/TW14 for the large subunit (LSU) of the rDNA (Takamatsu and Kano 2001). The resulting sequences were registered to GenBank (MW599742 for ITS, and MW599743 for LSU). Using Blast’n search of GenBank, sequences showed 100% identity for ITS and LSU with G. ambrosiae (MT355557, KX987303, MH078047 for ITS, and AB769427, AB769426 for LSU), respectively. Thus, based on morphology and molecular analysis, the isolate on V. bonariensis in Korea was identified as G. ambrosiae (Schwein.) U. Braun & R.T.A. Cook. Pathogenicity tests were carried out by touching an infected leaf onto healthy leaves of disease-free pot-grown plants using a replication of five plants, with five non-inoculated plants used as controls. After 7 days, typical powdery mildew colonies started to appear on the inoculated leaves. The fungus on inoculated leaves was morphologically identical to that originally observed in the field. All non-inoculated control leaves remained symptomless. On different global Verbena species, tThere have been many reports of Golovinomyces powdery mildews including G. cichoracearum s.lat., G. longipes, G. monardae, G. orontii s.lat., and G. verbenae (Farr and Rossman 2021). In China, G. verbenae was recorded on V.erbena phlogiflora (Liu et al. 2006). Golovinomyces powdery mildew has not been reported on Verbena spp. in Korea. Powdery mildew has been reported on V. bonariensis in California, but identity of the causal agent had not been reported. To our knowledge, this is the first report on the identity of the powdery mildew caused by G. ambrosiae on V. bonariensis in Korea. Since heavily infected plants lost ornamental value, appropriate control measures should be developed.

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First Report of Powdery Mildew Caused by Podosphaera spiraeae on Japanese Spiraea in China

Plant Disease ◽

10.1094/pdis-09-13-0944-pdn ◽

2014 ◽

Vol 98 (4) ◽

pp. 571-571 ◽

Cited By ~ 1

Author(s):

H. H. Xing ◽

C. Liang ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Width Ratio ◽

Pathogenicity Test ◽

Voucher Specimen ◽

First Report ◽

Powdery Mildews ◽

White Spots ◽

Length Width ◽

Qingdao City ◽

Leaf Distortion

Japanese spiraea (Spiraea japonica L.f.), belonging to Rosaceae, is widely planted for its ornamental value in China. Since July 2011, powdery mildew infections on leaves and stems of Japanese spiraea have been noticed in some parks and gardens of Chengyang District in Qingdao City, China (GPS coordinates 36°31′04.22″ N, 120°39′41.92″ E). Symptoms first appeared as white spots covered with mycelium on both side of the leaves and young stems. As the disease progressed, abundant mycelial growth covered the whole shoots and caused growth reduction and leaf distortion with or without reddening. A voucher specimen was deposited in the herbarium of Qingdao Agricultural University (Accession No. HMQAU13013). Hyphae were flexuous to straight, branched, septate, 5 to 7 μm wide, and had nipple-shaped appressoria. Conidiophores arising from the upper surface of hyphal cells produced 2 to 5 immature conidia in chains with a crenate outline. Foot-cells of conidiophores were straight, 60 to 125 × 7 to 9 μm, and followed by 1 to 2 shorter cells. Conidia were ellipsoid-ovoid to doliiform, measured 25 to 32 × 12 to 15 μm with a length/width ratio of 1.8 to 2.6, and had distinct fibrosin bodies. Chasmothecia were not found. The structures and measurements were compatible with the anamorphic state of Podosphaera spiraeae (Sawada) U. Braun & S. Takam. as described before (1). The identity of HMQAU13013 was further confirmed by analysis of nucleotide sequences of the internal transcribed spacer (ITS) regions amplified using the primers ITS1/ITS4 (4). The resulting 564-bp sequence was deposited in GenBank (Accession No. KF500426). A GenBank BLAST search of complete ITS sequence showed 100% identity with that of P. spiraeae on S. cantoniensis (AB525940). A pathogenicity test was conducted through inoculation by gently pressing a diseased leaf onto five healthy leaves of a potted Japanese spiraea. Five non-inoculated leaves served as controls. The plants were maintained in a greenhouse at 22°C. Inoculated leaves developed typical symptoms of powdery mildew after 5 days, but the non-inoculated leaves remained symptomless. The fungus presented on the inoculated plant was morphologically identical to that originally observed on diseased plants, fulfilling Koch's postulates. Powdery mildew of S. japonica caused by P. spiraeae has been recorded in Japan, Poland, and Switzerland (2,3). To our knowledge, this is the first report of powdery mildew caused by P. spiraeae on Japanese spiraea in China. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No.11. CBS, Utrecht, 2012. (2) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ September 10, 2013. (3) T. Kobayashi. Index of Fungi Inhabiting Woody Plants in Japan. Host, Distribution and Literature. Zenkoku-Noson-Kyoiku Kyokai Publishing Co. Ltd., Tokyo, 2007. (4) S. Matsuda and S. Takamatsu. Mol. Phylogenet. Evol. 27:314, 2003.

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