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

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.

Download Full-text

First Report of Powdery Mildew Caused by Podosphaera xanthii (syn. P. fusca) on Cocklebur in Korea

Plant Disease ◽

10.1094/pdis-10-12-0951-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 842-842 ◽

Cited By ~ 2

Author(s):

H. B. Lee

Keyword(s):

Powdery Mildew ◽

Natural Infection ◽

Morphological Characteristics ◽

Its Region ◽

Xanthium Strumarium ◽

Podosphaera Xanthii ◽

First Report ◽

Rdna Its ◽

Causal Fungus ◽

Powdery Mildew Pathogen

Cocklebur (Xanthium strumarium L., Asteraceae) is an annual broadleaf weed native to the Americas and eastern Asia. The plant is known as one of the worst competitive weeds in soybean fields and also is known to have some phytopharmacological or toxicological properties. In October 2011, a powdery mildew disease was observed on cocklebur growing in a natural landscape at Geomun Oreum located in Jeju Island, South Korea. Initial signs appeared as thin white colonies, which subsequently developed abundant growth on adaxial leaf surfaces. As the disease progressed, brown discoloration extended down infected leaves which withered. Conidia were formed singly and terminally on conidiophores. Primary conidia (20.3 to 28.6 [average 25.1] μm long × 11.1 to 15.2 [14.3] μm wide, n = 30) were ellipsoid with a round apex and truncate base. Conidiophores were straight or slightly curved and 60.1 to 101.7 (97.3) μm long × 8.2 to 13.2 (11.3) μm wide. Chasmothecia were not observed. No fibrosin bodies were observed in the conidia. Morphological characteristics were consistent with descriptions of Podosphaera xanthii (syn. P. fusca) (2,4). To confirm the identity of the causal fungus, the internal transcribed spacer (ITS) region inclusive of 5.8S and 28S rDNA was amplified from white patches consisting of mycelia and conidia on one leaf using ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and LR5F (5′-GCTATCCTGAGGGAAAC-3′), and LROR (5′-ACCCGCTGAACTTAAGC-3′) and LR5F primer sets, respectively. The resulting sequences were deposited in GenBank (Accession Nos. JX502022 and JX964999). A NCBI BLASTn search revealed that the rDNA ITS (JX502022) and 28S (JX964999) homologies of isolate EML-XSPW1 represented 99.6% (512/514) and 100% (803/803) identity values with those of P. xanthii (AB040330 and AB462792, respectively). The rDNA ITS and 28S sequence analysis revealed that the causal fungus clustered with P. xanthii (syn. P. fusca), falling into the Xanthii/Fusca phylogenetic group (2,4). Pathogenicity was confirmed through inoculations made by gently pressing infected leaves onto mature leaves of healthy cocklebur plants in the field in August. The six inoculated leaves were sealed in sterilized vinyl bags to maintain humid conditions for 2 days. Seven days after inoculation, symptoms similar to those observed under natural infection were observed on the inoculated plant leaves. No symptoms developed on the uninoculated control plants. A fungal pathogen that was morphologically identical to the fungus originally observed on diseased plants was also observed on inoculated plants. Erysiphe cichoracearum, E. communis, Oidium asteris-punicei, O. xanthimi, P. xanthii, and P. fuliginea have all been reported to cause powdery mildew on cocklebur (1). P. xanthii was first reported on X. strumarium in Russia (3). To our knowledge, this is the first report of powdery mildew on cocklebur caused by P. xanthii in Korea. The powdery mildew pathogen may represent an option for biocontrol of the noxious weed in the near future. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases , December 11, 2012. (2) H. B. Lee. J. Microbiol. 51:1075, 2012. (3) V. A. Rusanov and T. S. Bulgakov. Mikol. Fitopatol. 42:314, 2008. (4) S. Takamatsu et al. Persoonia 24:38, 2010.

Download Full-text

First Report of Powdery Mildew Caused by Podosphaera xanthii on Papaya in Korea

Plant Disease ◽

10.1094/pdis-06-13-0581-pdn ◽

2013 ◽

Vol 97 (11) ◽

pp. 1514-1514 ◽

Cited By ~ 2

Author(s):

J. H. Joa ◽

B. N. Chung ◽

K. S. Han ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Agricultural Research ◽

Morphological Characteristics ◽

Its Region ◽

Width Ratio ◽

Korean Isolate ◽

Podosphaera Xanthii ◽

First Report ◽

Powdery Mildews ◽

Basal Septum

In March 2013, papaya (Carica papaya L. cv. Sunrise) plants growing in polyethylene-film-covered greenhouses in Agricultural Research Center for Climate Change located in Jeju City, Korea, were observed severely affected by a powdery mildew. Symptoms appeared as circular to irregular white patches on both sides of the leaves. As the disease progressed, the plants were covered with dense masses of the spores, eventually causing senescence and withering of leaves. Voucher specimens were deposited in the Korea University Herbarium (KUS). Hyphae were flexuous to straight, branched, septate, and 5 to 8 μm wide. Conidiophores were 110 to 250 × 10 to 12.5 μm and produced 2 to 5 immature conidia in chains with a crenate outline followed by 2 to 3 cells. Foot-cells of conidiophores were straight, cylindric, slightly constricted at the basal septum, and 55 to 110 μm long. Conidia were hyaline, ellipsoid-ovoid, measured 22 to 38 × 18 to 21 μm with a length/width ratio of 1.2 to 1.8, and had distinct fibrosin bodies. Chasmothecia were scattered or partly clustered, dark brown, spherical, 80 to 100 μm in diameter, and each contained a single ascus. Appendages were mycelioid, 1- to 5-septate, brown at the base and becoming paler. Asci were sessile, 72 to 87 × 52 to 68 μm, had a terminal oculus of 17 to 23 μm wide, and contained 8 ascospores, each 17 to 23 × 12.5 to 15 μm. The morphological characteristics and measurements were consistent with those of Podosphaera xanthii (Castagne) U. Braun & Shishkoff (1). To confirm the identification, the complete internal transcribed spacer (ITS) region of rDNA of KUS-F27269 was amplified with the primers ITS5/P3 and sequenced (3). The resulting 443 bp sequence was deposited in GenBank (Accession No. KF111806). The Korean isolate showed >99% similarity with those of many P. xanthii isolates including an isolate on papaya from Taiwan (GU358450). Pathogenicity was confirmed through inoculation tests by gently pressing a diseased leaf onto young leaves of three asymptomatic, potted seedlings (cv. Sunrise). Three non-inoculated seedlings were used as control. Inoculated plants were isolated from non-inoculated plants in separate rooms in a greenhouse at 26 to 30°C. Inoculated leaves developed symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on the inoculated leaves was identical morphologically to that observed on the original diseased leaves, fulfilling Koch's postulates. Powdery mildews of papaya caused by Podosphaera species including P. caricae-papayae have been reported in North America, South America, Hawaii, Africa, Ukraine, Australia, New Zealand, the Cook Islands, India, Thailand, Taiwan, and Japan (2,4). P. caricae-papayae is currently reduced to synonymy with P. xanthii (1). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on papaya in Korea. Though papaya is a minor crop in Korea, producing about 300 M/T annually in greenhouses, powdery mildew disease is a threat to safe production of the fruits. 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. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, retrieved April 9, 2013. (3) S. Takamatsu et al. Mycol. Res. 113:117, 2009. (4) J. G. Tsay et al. Plant Dis. 95:1188, 2011.

Download Full-text

First Report of Oidium neolycopersici on Greenhouse Tomatoes in Serbia

Plant Disease ◽

10.1094/pdis-02-12-0179-pdn ◽

2012 ◽

Vol 96 (6) ◽

pp. 912-912 ◽

Cited By ~ 1

Author(s):

M. Stevanović ◽

I. Stanković ◽

A. Vučurović ◽

N. Dolovac ◽

E. Pfaf-Dolovac ◽

...

Keyword(s):

Powdery Mildew ◽

Disease Incidence ◽

Morphological Characteristics ◽

Adhesive Tape ◽

Oidium Neolycopersici ◽

Tomato Plants ◽

First Report ◽

Its Sequence Analysis ◽

The World ◽

Plant Pathol

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.

Download Full-text

First Report of Golovinomyces cichoracearum Causing Powdery Mildew on Zinnia elegans in China

Plant Disease ◽

10.1094/pdis-11-20-2333-pdn ◽

2020 ◽

Author(s):

Mo Zhu ◽

Jie Ji ◽

Xiao Duan ◽

YongFang Li

Keyword(s):

Powdery Mildew ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Its Region ◽

Zinnia Elegans ◽

Width Ratio ◽

Post Inoculation ◽

First Report ◽

Golovinomyces Cichoracearum ◽

Length Width

Zinnia elegans, common zinnia, is an annual plant with highly ornamental values. It is widely planted in many nurseries, city parks, universities and home gardens in China. From August to October 2020, powdery mildew-like signs and symptoms were observed on leaves of Z. elegans growing on the campus of Henan Normal University, Henan Province, China. White powdery colonies in circular- or irregularly shaped-lesions were abundant on both surfaces of leaves and covered up to 95 % of the leaf area. Any infected leaves were chlorotic, deformed or senescence. More than 70 % of the monitored Z. elegans plants showed these signs and symptoms. Conidiophores (n = 20) were 100 to 200 × 9 to 13 μm and composed of foot cells, followed by straight cells and conidia. Mycelial appressoria were single and nipple-shaped. The oval-shaped conidia (n = 30) were 22 to 36 × 12 to 18 μm, with a length/width ratio of 1.4 to 2.7, and produced germ tubes from the polar ends of the spore. No chasmothecia were found. Based on these morphological characteristics, the pathogen was initially identified morphologically as Golovinomyces cichoracearum (Braun and Cook 2012). Structures of the pathogen were scraped from infected leaves and total genomic DNA was isolated using the method previously described by Zhu et al. (2019). The internal transcribed spacer (ITS) region of rDNA was amplified by PCR using the primers ITS1/ITS4 (White et al. 1990) and the amplicon was sequenced by Invitrogen (Shanghai, China). The sequence for the fungus was deposited into GenBank under Accession No. MW029904 and was 99.83 % identical (595/596 bp) to G. cichoracearum on Symphyotrichum novi-belgii (HM769725)(Mørk et al. 2011). To perform pathogenicity analysis, leaf surfaces of five healthy plants were fixed in a settling tower and then inoculated by blowing fungal conidia from mildew-infested leaves using pressurized air. Five non-inoculated plants served as a control. The inoculated and non-inoculated plants were separately maintained in two growth chambers (humidity, 60 %; light/dark, 16 h/8 h; temperature, 18 ℃). Eleven- to twelve-days post-inoculation, powdery mildew signs were conspicuous on inoculated plants, while control plants remained healthy. Similar results were obtained by conducting two repeated pathogenicity assays. Thus, based on the morphological characteristics and molecular analysis, the pathogen was identified and confirmed as G. cichoracearum. This pathogen has been reported on Z. elegans in India, Israel, Jordan, Korea, Nepal, Sri Lanka, Switzerland, and Turkey (Farr and Rossman 2020). To our best knowledge, this is the first report of G. cichoracearum on Z. elegans in China. The sudden outbreak of powdery mildew caused by G. cichoracearum on Z. elegans may adversely impact the plant health and ornamental value in China. Therefore, the confirmation of G. cichoracearum infecting Z. elegans expands the understanding of this pathogen and provides the fundamental knowledge for future powdery mildew control.

Download Full-text

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.

Download Full-text

First Report of Alternaria heveae Causing Black Leaf Spot of Rubber Tree in China

Plant Disease ◽

10.1094/pdis-01-14-0065-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 1011-1011 ◽

Cited By ~ 1

Author(s):

Z. Y. Cai ◽

Y. X. Liu ◽

G. X. Huang ◽

M. Zhou ◽

G. Z. Jiang ◽

...

Keyword(s):

Rubber Tree ◽

Morphological Characteristics ◽

Black Spot ◽

Its Region ◽

Post Inoculation ◽

First Report ◽

Leaf Spots ◽

Plastic Bags ◽

Manual Pressure ◽

Tree Leaf

Rubber tree (Hevea brasiliensis Muell. Arg.) is an important industrial crop of tropical areas for natural rubber production. In October 2013, foliar spots (0.1 to 0.4 mm in diameter), black surrounded by a yellow halo, and with lesions slightly sunken were observed on the rubber tree leaf in a growing area in Heikou County of Yunnan Province. Lesion tissues removed from the border between symptomatic and healthy tissue were surface sterilized in 75% ethanol and air-dried, plated on PDA plates, and incubated at 28°C with alternating day/night cycles of light. The pathogen was observed growing out of many of the leaf pieces, and produced abundant conidia. Colonies 6.1 cm in diameter developed on potato carrot agar (PCA) after 7 days, with well-defined concentric rings of growth. Colonies on PCA were composed of fine, dark, radiating, surface and subsurface hyphae. Conidia produced in PCA culture were mostly solitary or in short chains of 2 to 5 spores, long ovoid to clavate, and light brown, 40 to 81.25 × 8 to 20 μm (200 colonies were measured), with 3 to 6 transverse septa and 0 to 2 longitudinal or oblique septa. Morphological characteristics were similar to those described for Alternaria heveae (3,4). A disease of rubber tree caused by Alternaria sp. had been reported in Mexico in 1947 (2). DNA of Ah01HK13 isolate was extracted for PCR and sequencing of the ITS region with ITS1 and ITS4 primers was completed. From the BLAST analysis, the sequence of Ah01HK13 (GenBank Accession No. KF953884), had 97% similarity to A. dauci, 96% identical to A. macrospora (AY154701.1 and DQ156342.1, respectively), indicating the pathogen belonged to Alternaria genus. According to morphological characteristics, this pathogen was identified as A. heveae. Pathogenicity of representative isolate, Ah01HK13 was confirmed using a field rubber tree inoculation method. Three rubber plants (the clone of rubber tree Yunyan77-4) were grown to the copper-colored leaf stage and inoculated by spraying spore suspension (concentration = 104 conidia/ml) to the copper-colored leaves until drops were equally distributed on it using manual pressure sprayer. Three rubber plants sprayed with sterile distilled water were used as controls. After inoculation, the plants were covered with plastic bags. The plastic bags were removed after 2 days post-inoculation (dpi) and monitored daily for symptom development (1). The experiment was repeated three times. The typical 0.1 to 0.4 mm black leaf spots were observed 7 dpi. No symptoms were observed on control plants. A fungus with the same colony and conidial morphology as A. heveae were re-isolated from leaf lesions on inoculated rubber plants, but not from asymptomatic leaves of control plants, fulfilling Koch's postulates. Based on these results, the disease was identified as black spot of rubber tree caused by A. heveae. To our knowledge, this is the first report of A. heveae on rubber tree in China. References: (1) Z. Y. Cai et al. Microbiol Res. 168:340, 2013. (2) W. J. Martin. Plant Dis. Rep. 31:155, 1947. (3) E. G. Simmons. Mycotaxon 50:262, 1994. (4) T. Y. Zhang. Page 111 in: Flora Fungorum Sinicorum: Alternaria, Science Press, Beijing, 2003.

Download Full-text

First Report of Powdery Mildew Caused by Podosphaera xanthii on Calendula officinalis in Italy

Plant Disease ◽

10.1094/pdis-92-1-0174c ◽

2008 ◽

Vol 92 (1) ◽

pp. 174-174 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Powdery Mildew ◽

Its Region ◽

Pathogenicity Test ◽

Podosphaera Xanthii ◽

Calendula Officinalis ◽

First Report ◽

Potted Plants ◽

Blastn Analysis ◽

Voucher Specimens ◽

Pot Marigold

Calendula officinalis L. (Asteraceae) (pot marigold or English marigold) is an ornamental species grown in gardens and as potted plants for the production of cut flower. It was also used in ancient Greek, Roman, Arabic, and Indian cultures as a medicinal herb as well as a dye for fabrics, foods, and cosmetics. During the summer of 2007, severe outbreaks of a previously unknown powdery mildew were observed on plants in several gardens near Biella (northern Italy). Both surfaces of leaves of infected plants were covered with dense, white mycelia and conidia. As the disease progressed, infected leaves turned yellow and died. Mycelia and conidia also were observed on stems and flower calyxes. Conidia were hyaline, ellipsoid, born in short chains (four to six conidia per chain), and measured 27.0 to 32.1 (31.4) × 12.9 to 18.4 (18.2) μm. Conidiophores measured 49 to 77.3 (67.2) × 8 to 13.3 (10.8) μm and showed a foot cell measuring 44 to 59 (51.9) × 9.3 to 12.6 (11.3) μm followed by one shorter cell measuring 15.6 to 18.9 (17.6) × 10.4 to 13.6 (12.2) μm. Fibrosin bodies were present. Chasmothecia were spherical, amber colored, with a diameter of 89 to 100 (94.5) μm. Each chasmothecium contained one ascus with eight ascospores. On the basis of its morphology, the causal agent was determined to be a Podosphaera sp. (2). The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 588 bp showed a 100% homology with the sequence of Podosphaera xanthii (2). The nucleotide sequence has been assigned GenBank Accession No. EU100973. Pathogenicity was confirmed through inoculations by gently pressing diseased leaves onto leaves of healthy C. officinalis plants. Five plants were inoculated. Five noninoculated plants served as control. Plants were maintained in a greenhouse at temperatures ranging from 20 to 26°C. Eleven days after inoculation, typical symptoms of powdery mildew developed on inoculated plants. 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 C. officinalis in Italy. C. officinalis was previously described as a host to Sphaerotheca fuliginea (synonym S. fusca) in Great Britain (4) as well as in Romania (3). 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 and S. Takamatsu. Schlechtendalia 4:1, 2000. (3) E. Eliade. Rev. Appl. Mycol. 39:710, 1960. (4) F. J. Moore. Rev. Appl. Mycol. 32:380, 1953.

Download Full-text

First Report of Powdery Mildew on Spanish Needles (Bidens bipinnata) Caused by Podosphaera xanthii in Korea

Plant Disease ◽

10.1094/pdis-10-12-0966-pdn ◽

2013 ◽

Vol 97 (10) ◽

pp. 1385-1385

Author(s):

H. B. Lee ◽

C. J. Kim ◽

H. Y. Mun

Keyword(s):

Powdery Mildew ◽

Its Region ◽

Broad Host Range ◽

Pathogenicity Test ◽

Podosphaera Xanthii ◽

Tropical Regions ◽

First Report ◽

Rdna Its ◽

Humid Condition ◽

Primer Sets

Spanish needles (Bidens bipinnata L.) is an annual herb that belongs to a genus of flowering plants in family Asteraceae native to United States, and tropical regions around world. The plant produces important flavonoid compounds quercitin and hyperoside that function as anti-allergens, anti-inflammatories, anti-microbials, and anti-cancer agents. Between July and October 2011 and 2012, white superficial mycelia were observed initially on leaf and stem portions, but later progressed to the flower head. Surveys showed that the disease was widespread in Gwangju and most areas of South Korea. Abundant, necrotic, dark brown spots showing chasmothecia were frequently observed in October and were abundant on the adaxial surface of leaves. Chasmothecia were blackish brown to yellow without typical appendages. They ranged from 51.2 to 71.1 (mean 66.8) μm in diameter. Conidia were formed singly and the primary conidia were ellipsoid, rounded at the apex, truncated base, and ranged from 25.4 to 33.2 (mean 27.3) μm long × 10.2 to 12.2 (mean 11.3) μm wide. Conidiophores were erect, 60.1 to 101.3 (mean 98.3) μm long × 6.2 to 9.2 (mean 7.3) μm wide. From extracted genomic DNA, the internal transcribed spacer (ITS) region inclusive of 5.8S and 28S rDNA was amplified with ITS1F (5′-TCCGTAGGTGAACCTGCGG-3′) and LR5F (5′-GCTATCCTGAGGGAAAC-3′), and LROR (5′-ACCCGCTGAACTTAAGC-3′) and LR5F primer sets, respectively. rDNA ITS (GenBank Accession No. JX512555) and 28S (JX512556) homologies of the fungus (EML-BBPW1) represented 99.6% (532/534) and 100% (661/661) identity values with Podosphaera xanthii (syn. P. fusca) AB040349 and P. xanthii (syn. P. fusca) AB462798, respectively. The rDNA sequence analysis revealed that the causal fungus matched P. xanthii (syn. P. fusca), forming a xanthii/fusca group (3,4). A pathogenicity test was performed on three plants in a greenhouse. The treated leaves were sealed in vinyl pack in humid condition for 2 days. Seven days after inoculation, similar symptoms were observed on the inoculated Spanish needles plant leaves. No symptoms were observed on control plants treated with distilled water. Koch's postulates were fulfilled by re-observing the fungal pathogen on the inoculated leaves. Podosphaera (syn. Sphaerotheca) xanthii (or fusca) has been known as an ubiquitous species with a broad host range. So far, five records regarding P. xanthii (=P. fusca) have been found in plants of genus Bidens. P. xanthii has been reported to occur on B. cernua in Belarus and Switzerland. In addition, the powdery mildew species was reported to occur on B. frondosa and B. tripartita in Korea, Russia, and Switzerland (2). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on Spanish needles (B. bipinnata) in Korea. References: (1) U. Braun et al. Schlechtendalia 10:91, 2003. (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/ , 2012. (3) H. B. Lee. J. Microbiol. 51:1075, 2012. (4) S. Takamatsu, et al. Persoonia 24:38, 2010.

Download Full-text

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.

Download Full-text

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.

Download Full-text