First Report of Powdery Mildew Caused by Blumeria graminis on Poa pratensis var. anceps Gaud cv. Qinghai in China

Poa pratensis, an important cool-season perennial grass, is widely cultivated for construction of grasslands and ecological management of Qinghai-Tibet Plateau (Dong et al. 2020). Poa pratensis var. anceps Gaud cv. Qinghai (PPAQ) is a variant of P. pratensis (Liu et al. 2009). In June 2016, powdery mildew was observed on PPAQ in an artificial field of PPAQ in Haiyan county of Haibei Tibetan Autonomous Prefecture, Qinghai province, China (36°59′17.76″N, 100°52′54.01″E). Approximately 30 to 50% of leaves (approximate 10 ha) were affected. Initially, irregular white mycelial colonies were observed on the adaxial surface of affected leaves. The colonies increased in number and size, and later covered a large area of leaves and stems. In advanced stages of disease, the colonies covered the whole adaxial surface and white patches appeared on the abaxial surface of affected leaves, and eventually caused leaf death. Conidiophores were unbranched, measuring 160 to 235 × 4 to 13 μm, and borne vertically on hyphae. Each conidiophore produced 4 to 11 conidia in a chain. The conidia were oval, one-celled, and hyaline, measuring 22 to 40 ×10 to 21 μm (n = 50). Chasmothecia were yellow, spherical, and 172 to 240 μm in diameter (n = 20), each of which contained 8 to 17 asci. The appendages were few, and hyphoid. Asci were oblong or ovate, measuring 79 to 115 × 31 to 45 μm (n = 20). Asci were petiolate, containing eight ascospores. Ascospores were round to oval, colorless, one-celled, measuring 17 to 33 × 8 to 14 μm (n = 50). Based on morphological characteristics, the fungal organism was identified as Blumeria graminis (DC.) Speer. To confirm the identification, the internal transcribed spacer (ITS) of 612 bp was amplified from DNA of conidia using ITS5 and P3 primers (Takamatsu et al. 2009). The ITS sequence was deposited in GenBank database (Accession No. MF429949). The ITS showed 95% sequence similarity with those of B. graminis on Poa nemoralis in USA (Accession No. AB273560) and on P. bullbosa in Iran (Accession No. AB273551) (Inuma et al. 2007). Five two-month-old healthy plants were inoculated by spraying a spore suspension (1× 105 conidia ml-1) prepared from conidia brushed from infected plants; five plants sprayed with sterile distilled water served as controls. All the plants were maintained in a growth chamber with a constant temperature of 20°C, a 12 h/12 h light/dark diurnal cycle, and 70% humidity. Two weeks after inoculation, symptoms of powdery mildew were observed on all inoculated plants, whereas the control plants remained symptomless. The same fungus was confirmed by morphological characterization and molecular assays as described above. B. graminis has been reported on P. pratensis in USA (Dugan and Newcombe 2007), Israel (Voytyuk et al. 2009), and China (Zhang et al. 2014), but has not previously been reported on PPAQ. As far as we know, this is the first report of powdery mildew caused by B. graminis on PPAQ in China. These findings indicated that the health of PPAQ was substantially threaten when infected by powdery mildew, therefore, our results also contributed some valuable information how to diagnose this disease on PPAQ in China.

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First Report of Powdery Mildew Caused by Blumeria graminis on Festuca arundinacea in China

Plant Disease ◽

10.1094/pdis-06-14-0567-pdn ◽

2014 ◽

Vol 98 (11) ◽

pp. 1585-1585 ◽

Cited By ~ 1

Author(s):

F.-L. Zhang ◽

Y. Zhang ◽

J. Zhang ◽

K.-D. Xu ◽

K. Liu ◽

...

Keyword(s):

Powdery Mildew ◽

Festuca Arundinacea ◽

Poa Pratensis ◽

Perennial Grass ◽

Morphological Characteristics ◽

The United States ◽

Blumeria Graminis ◽

Its Sequence ◽

Adaxial Surface ◽

First Report

Tall fescue (Festuca arundinacea Schreb), a predominant cool-season perennial grass, is widely used as forage and turf grasses in China. In July 2013, powdery mildew was observed on 10 F. arundinacea lawns (about 0.5 ha in total) in Urumchi, Xinjiang Province, China, with 20 to 30% of the area being infected. Signs of the disease initially appeared as irregular white mycelial colonies on the adaxial surface of infected leaves. As the disease progressed, the colonies covered the whole adaxial surface and white patches appeared on the abaxial surface of infected leaves. Conidiophores were unbranched and cylindrical with swollen bases, measuring 13.3 to 15 × 16.7 to 20 μm, and borne vertically on hyphae. Each conidiophore produced 10 to 18 conidia in a chain. The conidia were oval, one-celled, and colorless, measuring 8.1 to 9.8 × 26 to 29.7 μm. Cleistothecia were black, spherical, and 164.3 to 207.3 μm in diameter, each of which contained 9 to 26 asci. Asci were oblong or ovate, measuring 32.1 to 40 × 85.7 to 96.4 μm. Asci were petiolate, containing eight ascospores. Ascospores were round to oval, colorless, one-celled, measuring 19.1 to 22.5 × 11.7 to 13.6 μm. Based on morphological characteristics of the anamorph and the teleomorph, the fungus was identified as Blumeria graminis (DC.) Speer. Additionally, the internal transcribed spacer (ITS) of 563 bp was amplified from DNA of conidia using ITS1 and ITS4 primers (4). The ITS sequence was deposited in GenBank (Accession No. KF545644). The ITS sequence showed 100% homogeneity with those of B. graminis on Poa pratensis in Swizerland (AB273540) and on P. bulbosa in Iran (AB273551) (1), which further confirmed the identification. Ten 3-week-old healthy plants were inoculated by spraying a spore suspension (1 × 105 conidia ml−1) made from conidia brushed from infected plants, and 10 plants sprayed with sterile distilled water were served as controls. All the plants were placed in the same growth chamber at 20°C, 80% humidity, and 16-h photoperiod. Twenty days after inoculation, typical signs and symptoms of powdery mildew were observed on all the inoculated plants, whereas no symptoms were observed on the controls. Microscopic and ITS analysis showed that the fungus on the inoculated plants is identical to that on diseased field plants. B. graminis on F. arundinacea has been observed in a few European countries (1), Israel (3), and the United States (2). To our knowledge, this is the first report of powdery mildew caused by B. graminis on F. arundinacea in China, which will increase the difficulty to prevent powdery mildew on grasses including cereals. References: (1) U. Braun. The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer Verlag, Jena-Stuttgart-New York, 1995. (2) F. M. Dugan and G. Newcombe. Pacific Northwest Fungi. 2:1-5, 2007. (3) S. O. Voytyuk et al. Biodiversity of the Powdery Mildew Fungi (Erysiphales, Ascomycota) of Israel Vol. 7. Biodiversity of Cyanoprocaryotes, Algae and Fungi of Israel. Koeltz Scientific Books, 2009. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

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Occurrence of Powdery Mildew Caused by Blumeria graminis f. sp. poae on Poa pratensis in China

Plant Disease ◽

10.1094/pdis-09-20-2051-pdn ◽

2020 ◽

Author(s):

Mo Zhu ◽

Jie Ji ◽

Wenqi Shi ◽

YongFang Li

Keyword(s):

Powdery Mildew ◽

Germ Tube ◽

Poa Pratensis ◽

Perennial Grass ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Its Region ◽

Width Ratio ◽

Leaf Surfaces ◽

Length Width

Poa pratensis, known as bluegrass, is a perennial grass and one of the best varieties with highly valued pasture and turf grass uses. It is widely grown on golf courses and used for lawns in squares and parks (Luo et al. 2020). During April and May 2020, powdery mildew-like signs and symptoms were observed on leaves of P. pratensis in Muye Park, Xinxiang city (35.3°N; 113.9°E), Henan Province, China. White or grayish powdery masses in spots- or coalesced lesions were abundant on the adaxial surfaces of leaves and covered up to 90 % of the leaf area. Some of the mildew-infested leaves appeared chlorotic or began senescence. Mildew-infested leaves were collected to microscopically observe the morphological characteristics of this pathogen. Conidiophores were composed of foot cells, followed by one or two cells, and conidia. The ellipsoid- shaped conidia (n = 50) were 25 - 36 × 10 - 15 μm (length × width), on average 30 × 13 μm, with a length/width ratio of 2.3. Foot-cells (n = 15) were 30 - 44 μm long and 7 - 15 μm wide. On leaf surfaces, germinated conidia produced a short primary germ tube and then a long secondary germ tube that finally differentiated into a hooked appressorium. Chasmothecia were not found. Based on these morphological characteristics, the pathogen was initially identified as B. graminis f. sp. poae, the known forma specialis (f. sp.) of B. graminis on P. pratensis (Braun and Cook 2012; Troch et al. 2014). Mycelia of the pathogen were scraped from infected leaves and total genomic DNA was isolated using the method described previously (Zhu et al. 2019). The rDNA internal transcribed spacer (ITS) region was amplified applying primer pairs ITS1/ITS4 (White et al. 1990). The amplicon was cloned and sequenced by Invitrogen (Shanghai, China). The obtained sequence for the pathogen was deposited into GenBank under Accession No. MT892956 and was 100 % identical (549/549 bp) to B. graminis on P. pratensis (AB273530) (Inuma et al. 2007). In addition, the phylogenetic analysis clearly showed that the identified fungus and B. graminis f. sp. poae were clustered in the same branch. To perform pathogenicity analysis, leaf surfaces of eight healthy plants were inoculated by dusting fungal conidia from diseased leaves. Eight non-inoculated plants served as a control. The non-inoculated and inoculated plants were separately maintained in two growth chambers (humidity, 60 %; light/dark, 16 h/8 h; temperature, 18 ℃). Twelve to fourteen days after inoculation, B. graminis signs were visible on inoculated leaves, while control plants remained healthy. The pathogenicity assays were repeated twice and showed same results. Therefore, based on the morphological characteristics and molecular analysis, the pathogen was identified and confirmed as B. graminis f. sp. poae. This pathogen has been reported on P. pratensis in Switzerland and Japan (Inuma et al. 2007). This is, to our best knowledge, the first disease note reporting B. graminis on P. pratensis in China. Because the hybridization of B. graminis formae speciales (ff. spp.). allow the pathogens to adapt to new hosts, P. pratensis may serve as a primary inoculum reservoir of B. graminis to threaten other species, including cereal crops (Klingeman et al. 2018; Menardo et al. 2016). In addition, powdery mildew may negatively affect the yield and quality of grasses. Our report expands the knowledge of B. graminis f. sp. poae and provides the fundamental information for future powdery mildew control.

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First Report of Powdery Mildew Caused by Blumeria graminis f. sp. bromi on Bromus catharticus in China

Plant Disease ◽

10.1094/pdis-09-20-1983-pdn ◽

2020 ◽

Author(s):

Mo Zhu ◽

Jie Ji ◽

Xiao Duan ◽

Wenqi Shi ◽

YongFang Li

Keyword(s):

Powdery Mildew ◽

Sequence Data ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

The United States ◽

Blumeria Graminis ◽

Henan Province ◽

Width Ratio ◽

Causal Organism ◽

First Report

Bromus catharticus, rescuegrass, is a brome grass that has been cultivated for herbage production, and been widely naturalized in many provinces of China, including Henan province. During April and May 2020, powdery mildew was found on leaves of Br. catharticus on the campus of Henan Normal University, Xinxiang city (35.3°N; 113.9°E), Henan Province, China. Abundant white or grayish irregular or coalesced circular powdery colonies were scattered on the adaxial surface of leaves and 70% of the leaf areas were affected. Some of the infected leaves either were chlorotic or senescent. About 60% of the observed plants showed powdery mildew symptoms. Conidiophores (n = 25) were 32 to 45 μm × 7 to 15 μm and composed of foot cells and conidia (mostly 6 conidia) in chains. Conidia (n = 50) were 25 to 35 μm × 10 to 15 μm, on average 30 × 13 μm, with a length/width ratio of 2.3. Chasmothecia were not found. Based on these morphologic characteristics, the pathogen was initially identified as Blumeria graminis f. sp. bromi (Braun and Cook 2012; Troch et al. 2014). B. graminis mycelia and conidia were collected, and total genomic DNA was extracted (Zhu et al. 2019). The rDNA internal transcribed spacer (ITS) region was amplified with primer pairs ITS1/ITS4. The amplicon was cloned and sequenced. The sequence (574 bp) was deposited into GenBank under Accession No. MT892940. BLASTn analysis revealed that MT892940 was 100% identical to B. graminis f. sp. bromi on Br. catharticus (AB000935, 550 of 550 nucleotides) (Takamatsu et al. 1998). Phylogenetic analysis of MT892940 and ITS of other B. graminis ff. spp. clearly indicated least two phylogenetically distinct clades of B. graminis f. sp. bromi and that MT892940 clustered with the Takamatsu vouchers. Leaf surfaces of five healthy plants were fixed at the base of a settling tower and then inoculated by blowing conidia from diseased leaves using pressurized air. Five non-inoculated plants served as controls. The inoculated and non-inoculated plants were maintained separately in two growth chambers (humidity, 60%; light/dark, 16 h/8 h; temperature, 18℃). Thirteen- to fifteen-days after inoculation, B. graminis signs and symptoms were visible on inoculated leaves, whereas control plants remained asymptomatic. The pathogenicity assays were repeated twice with the same results. The observed signs and symptoms were morphologically identical to those of the originally infected leaves. Accordingly, the causal organism of the powdery mildew was confirmed as B. graminis f. sp. bromi by morphological characteristics and ITS sequence data. B. graminis has been reported on Br. catharticus in the United States (Klingeman et al. 2018), Japan (Inuma et al. 2007) and Argentina (Delhey et al. 2003). To our best knowledge, this is the first report of B. graminis on Br. catharticus in China. Since hybridization of B. graminis ff. spp. is a mechanism of adaptation to new hosts, Br. catharticus may serve as a primary inoculum reservoir of B. graminis to infect other species (Menardo et al. 2016). This report provides fundamental information for the powdery mildew that can be used to develop control management of the disease in Br. catharticus herbage production.

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First Report of Powdery Mildew Caused by Golovinomyces sonchicola on Ixeris chinensis in Korea

Plant Disease ◽

10.1094/pdis-11-13-1132-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 999-999 ◽

Cited By ~ 2

Author(s):

J. K. Choi ◽

B. S. Kim ◽

S. H. Hong ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Sequence Similarity ◽

Folk Medicine ◽

Morphological Characteristics ◽

Its Region ◽

Width Ratio ◽

Lateral Part ◽

Potential Threat ◽

First Report ◽

Powdery Mildews

Ixeris chinensis (Thunb.) Nakai, known as Chinese ixeris, is distributed from Siberia to Japan, including Korea, Taiwan, and China. The whole plant has been used in folk medicine in Asia (4). In Korea, the plants of Chinese ixeris have been gathered and used as a wild root vegetable. During summer to autumn of 2011, Chinese ixeris leaves were found to be heavily infected with a powdery mildew in several locations of Korea. Symptoms first appeared as thin white colonies, which subsequently developed into abundant hyphal growth on both sides of the leaves, leading to drying of the leaves. The same symptoms on Chinese ixeris leaves were continuously observed in 2012 and 2013. Voucher specimens (n = 10) were deposited at Korea University Herbarium (KUS). Hyphal appressoria were moderately lobed or nipple-shaped. Conidiophores arose from the lateral part of the hyphae, measured 100 to 270 × 10 to 12.5 μm, and produced 2 to 6 immature conidia in chains with a sinuate outline. Basal parts of foot-cells in conidiophores were curved. Conidia were barrel-shaped to ellipsoid, measured 26 to 36 × 13 to 19 μm (length/width ratio = 1.7 to 2.4), lacked fibrosin bodies, and showed reticulate wrinkling of the outer walls. Primary conidia were ovate with conical-obtuse apex and subtruncate base. Germ tubes were produced on the perihilar position of conidia. Chasmothecia were not observed. The morphological characteristics were typical of the Euoidium type anamorph of the genus Golovinomyces, and the fungus measurements and structures were consistent with those of G. sonchicola U. Braun & R.T.A. Cook (1). To confirm the identification, internal transcribed spacer (ITS) region of rDNA sequences from a representative material (KUS-F26212) was amplified using primers ITS5/P3 and sequenced (3). The resulting 416-bp sequence was deposited in GenBank (Accession No. KF819857). A GenBank BLAST search revealed that the isolate showed >99% sequence similarity with those of G. cichoracearum from Sonchus spp. (e.g., AB453762, AF011296, JQ010848, etc.). G. sonchicola is currently confined to G. cichoracearum s. lat. on Sonchus spp., based on molecular sequence analyses (1). Pathogenicity was confirmed through inoculation by gently pressing a diseased leaf onto leaves of five healthy potted Chinese ixeris. Five non-inoculated plants served as controls. Inoculated plants developed symptoms after 6 days, whereas the controls remained symptomless. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Powdery mildew infections of I. chinensis associated with Golovinomyces have been known in China (2). To our knowledge, this is the first report of powdery mildew disease caused by G. sonchicola on I. chinensis in Korea. Farming of Chinese ixeris has recently started on a commercial scale in Korea. Though no statistical data are available, we postulate the cultivation area in Korea to be approximately 200 ha, mostly growing without chemical controls. Occurrence of powdery mildews poses a potential threat to safe production of this vegetable, especially in organic farming. 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) F. L. Tai. Bull. Chinese Bot. Sci. 2:16, 1936. (3) S. Takamatsu et al. Mycol. Res. 113:117, 2009. (4) S. J. Zhang et al. J. Nat. Prod. 69:1425, 2006.

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First Report of Powdery Mildew Caused by Golovinomyces ambrosiae on Bidens pilosa in China

Plant Disease ◽

10.1094/pdis-05-21-0910-pdn ◽

2021 ◽

Author(s):

Irum Mukhtar ◽

Yunying Cheng ◽

IBATSAM KHOKHAR ◽

Ruanni Chen ◽

Ruiting Li ◽

...

Keyword(s):

Powdery Mildew ◽

Sequence Similarity ◽

Disease Incidence ◽

Folk Medicine ◽

Morphological Characteristics ◽

Primary Source ◽

Flowering Plant ◽

Academic Press ◽

Bidens Pilosa ◽

First Report

Bidens pilosa L., (spanish needle), is a wild, flowering plant of Asteraceae, that is grown in gardens, fields, roadsides, and riverbanks in Fuzhou, China. It is also used in traditional folk medicine for a broad range of ailments in China. In March 2019 and 2020, hundreds of B. pilosa growing along the roadsides, and gardens in the districts of Minhou and Jinshan were observed to be severely affected by a powdery mildew with approximately 80% disease incidence. Symptoms appeared as circular to irregular small white, powdery patches, typically on the adaxial sides of leaves and progressed to coalescent colonies on the leaves. As the disease developed, the infected leaves became wilted and senesced. Mycelia on leaves were superficial and solitary appressoria were slightly to distinctly nipple-shaped. Conidiophores were erect, 120 to 230 × 10 to 12 µm, and produced two to five conidia in chains with a sinuate outline. Foot-cells were erect, cylindrical, and 60 to 110 μm long. Conidia were hyaline, ellipsoid to barrel-shaped, 26 to 40 × 18 to 24 μm, and devoid of distinct fibrosin bodies. Germ tubes were long and produced at the perihilar position of the conidia. No chasmothecia were observed. Morphological characteristics overlapped with Golovinomyces ambrosiae, G. cichoracearum, and G. spadiceus (Braun and Cook 2012) on hosts within the Asteraceae tribe Heliantheae (Takamatsu et al. 2013). For molecular identification, ITS and IGS regions as well as partial LSU of two representative collections (MJU-IM019- MJU-IM020), were amplified using ITS1/ITS4, IGS-12a/ NS1R and LSU1/LSU2 primers (Carbone & Kohn, 1999; Scholin et al. 1994; White et al. 1990), respectively. The resulting sequences were deposited in GenBank (ITS: MW965777, MW965778; LSU: MW965787, MW965788; IGS: MW981256, MW981257). A BLAST search revealed 99 to 100 % sequence similarity to G. ambrosiae sequences (KX987303, AB769421, AB077689, AB769426, AB077643, and AB769425). Phylogenetic analysis of ITS, LSU and IGS also grouped obtained sequences within the G. ambrosiae complex (Qiu et al. 2020). Pathogenicity was confirmed through inoculation by gently pressing infected leaves onto leaves of five healthy, potted, young B. pilosa plants, while five non-inoculated plants served as controls. All plants were maintained in a greenhouse at 25 ± 2°C. Inoculated plants developed symptoms after 7 to 10 days, whereas the control plants remained symptomless. The morphology of the resulting fungus on inoculated plants was identical to that originally observed on diseased plants. Podosphaera spp., have been reported on B. pilosa (Farr & Rossman 2021) from North America, Africa, and Asia. To our knowledge, this is the first report of powdery mildew caused by G. ambrosiae on B. pilosa in China and Asia. Wild populations of B. pilosa may be the primary source of powdery mildew inoculum for commercial Asteraceae members and may warrant consideration in the control of this disease. References: Braun, U., and Cook, R. T. A. 2012. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No. 11. CBS, Utrecht, The Netherlands. Carbone, I., and Kohn, L. M. 1999. Mycologia 91:553. Farr, D. F., and Rossman, A. Y. 2021. Fungal Databases. Syst. Mycol. Microbiol. Lab., USDA ARS, 18 April 2021. Qiu, P. L., et al. 2020. BMC Microbiol. 20:1. Scholin, C. A., et al. 1994. J. Phycol. 30:999. Takamatsu, S., et al. 2013. Mycologia 105:1135. White, T. J., et al. 1990. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA.

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First Report of Stem and Foliage Blight of Chrysanthemum Caused by Phytophthora drechsleri in the United States

Plant Disease ◽

10.1094/pdis-03-21-0631-pdn ◽

2021 ◽

Author(s):

Charles Krasnow ◽

Nancy Rechcigl ◽

Jennifer Olson ◽

Linus Schmitz ◽

Steven N. Jeffers

Keyword(s):

United States ◽

South Carolina ◽

Sequence Similarity ◽

Morphological Characteristics ◽

The United States ◽

Universal Primers ◽

Broad Host Range ◽

Pathogenicity Test ◽

First Report ◽

Foliage Blight

Chrysanthemum (Chrysanthemum × morifolium) plants exhibiting stem and foliage blight were observed in a commercial nursery in eastern Oklahoma in June 2019. Disease symptoms were observed on ~10% of plants during a period of frequent rain and high temperatures (26-36°C). Dark brown lesions girdled the stems of symptomatic plants and leaves were wilted and necrotic. The crown and roots were asymptomatic and not discolored. A species of Phytophthora was consistently isolated from the stems of diseased plants on selective V8 agar (Lamour and Hausbeck 2000). The Phytophthora sp. produced ellipsoid to obpyriform sporangia that were non-papillate and persistent on V8 agar plugs submerged in distilled water for 8 h. Sporangia formed on long sporangiophores and measured 50.5 (45-60) × 29.8 (25-35) µm. Oospores and chlamydospores were not formed by individual isolates. Mycelium growth was present at 35°C. Isolates were tentatively identified as P. drechsleri using morphological characteristics and growth at 35°C (Erwin and Ribeiro 1996). DNA was extracted from mycelium of four isolates, and the internal transcribed spacer (ITS) region was amplified using universal primers ITS 4 and ITS 6. The PCR product was sequenced and a BLASTn search showed 100% sequence similarity to P. drechsleri (GenBank Accession Nos. KJ755118 and GU111625), a common species of Phytophthora that has been observed on ornamental and vegetable crops in the U.S. (Erwin and Ribeiro 1996). The gene sequences for each isolate were deposited in GenBank (accession Nos. MW315961, MW315962, MW315963, and MW315964). These four isolates were paired with known A1 and A2 isolates on super clarified V8 agar (Jeffers 2015), and all four were mating type A1. They also were sensitive to the fungicide mefenoxam at 100 ppm (Olson et al. 2013). To confirm pathogenicity, 4-week-old ‘Brandi Burgundy’ chrysanthemum plants were grown in 10-cm pots containing a peat potting medium. Plants (n = 7) were atomized with 1 ml of zoospore suspension containing 5 × 103 zoospores of each isolate. Control plants received sterile water. Plants were maintained at 100% RH for 24 h and then placed in a protected shade-structure where temperatures ranged from 19-32°C. All plants displayed symptoms of stem and foliage blight in 2-3 days. Symptoms that developed on infected plants were similar to those observed in the nursery. Several inoculated plants died, but stem blight, dieback, and foliar wilt were primarily observed. Disease severity averaged 50-60% on inoculated plants 15 days after inoculation. Control plants did not develop symptoms. The pathogen was consistently isolated from stems of symptomatic plants and verified as P. drechsleri based on morphology. The pathogenicity test was repeated with similar results. P. drechsleri has a broad host range (Erwin and Ribeiro 1996; Farr et al. 2021), including green beans (Phaseolus vulgaris), which are susceptible to seedling blight and pod rot in eastern Oklahoma. Previously, P. drechsleri has been reported on chrysanthemums in Argentina (Frezzi 1950), Pennsylvania (Molnar et al. 2020), and South Carolina (Camacho 2009). Chrysanthemums are widely grown in nurseries in the Midwest and other regions of the USA for local and national markets. This is the first report of P. drechsleri causing stem and foliage blight on chrysanthemum species in the United States. Identifying sources of primary inoculum may be necessary to limit economic loss from P. drechsleri.

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First Report of Powdery Mildew Caused by Golovinomyces biocellatus on Agastache rugosa in Korea

Plant Disease ◽

10.1094/pdis-03-14-0298-pdn ◽

2014 ◽

Vol 98 (9) ◽

pp. 1278-1278 ◽

Cited By ~ 1

Author(s):

S. E. Cho ◽

J. H. Park ◽

S. H. Hong ◽

I. Y. Choi ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Severe Disease ◽

Morphological Characteristics ◽

Control Measures ◽

Control Treatment ◽

Width Ratio ◽

Korean Isolate ◽

Pathogenicity Test ◽

Agastache Rugosa ◽

First Report

Agastache rugosa (Fisch. & C.A. Mey.) Kuntze, known as Korean mint, is an aromatic plant in the Lamiaceae. It is widely distributed in East Asian countries and is used as a Chinese traditional medicine. In Korea, fresh leaves are commonly added to fish soups and stews (3). In November 2008, several dozen Korean mints plants growing outdoors in Gimhae City, Korea, were found to be severely infected with a powdery mildew. The same symptoms had been observed in Korean mint plots in Busan and Miryang cities from 2008 to 2013. Symptoms first appeared as thin white colonies, which subsequently developed into abundant hyphal growth on stems and both sides of the leaves. Severe disease pressure caused withering and senescence of the leaves. Voucher specimens (n = 5) were deposited in the Korea University Herbarium (KUS). Appressoria on the mycelium were nipple-shaped or nearly absent. Conidiophores were 105 to 188 × 10 to 13 μm and produced 2 to 4 immature conidia in chains with a sinuate outline, followed by 2 to 3 cells. Foot-cells of the conidiophores were straight, cylindrical, slightly constricted at the base, and 37 to 58 μm long. Conidia were hyaline, ellipsoid to barrel-shaped, measured 25 to 40 × 15 to 23 μm (length/width ratio = 1.4 to 2.1), lacked distinct fibrosin bodies, and showed reticulate wrinkling of the outer walls. Primary conidia were obconically rounded at the apex and subtruncate at the base. Germ tubes were produced at the perihilar position of conidia. No chasmothecia were observed. The structures described above were typical of the Oidium subgenus Reticuloidium anamorph of the genus Golovinomyces. The measurements and morphological characteristics were compatible with those of G. biocellatus (Ehrenb.) V.P. Heluta (1). To confirm the identification, molecular analysis of the sequence of the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) of isolate KUS-F27200 was conducted. The complete ITS rDNA sequence was amplified using primers ITS5 and P3 (4). The resulting 514-bp sequence was deposited in GenBank (Accession No. KJ585415). A GenBank BLAST search of the Korean isolate sequence showed >99% similarity with the ITS sequence of many G. biocellatus isolates on plants in the Lamiaceae (e.g., Accession Nos. AB307669, AB769437, and JQ340358). Pathogenicity was confirmed by gently pressing diseased leaf onto leaves of five healthy, potted Korean mint plants. Five non-inoculated plants served as a control treatment. Inoculated plants developed symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on inoculated plants was identical morphologically to that observed on the original diseased plants. The pathogenicity test was repeated with identical results. A powdery mildew on A. rugosa caused by G. biocellatus was reported from Romania (2). To our knowledge, this is the first report of powdery mildew caused by G. biocellatus on A. rugosa in Korea. The plant is mostly grown using organic farming methods with limited chemical control options. Therefore, alternative control measures should be considered. 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, USDA ARS, retrieved 17 February 2014. (3) T. H. Kim et al. J. Sci. Food Agric. 81:569, 2001. (4) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

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First Report of Erysiphe cichoracearum Infecting Hedera canariensis var. azorica in Italy

Plant Disease ◽

10.1094/pdis.1999.83.2.198d ◽

1999 ◽

Vol 83 (2) ◽

pp. 198-198

Author(s):

C. Nali

Keyword(s):

New York ◽

Powdery Mildew ◽

Citrullus Lanatus ◽

Ornamental Plants ◽

Morphological Characteristics ◽

Hedera Helix ◽

Cucumis Sativus L ◽

First Report ◽

Erysiphe Cichoracearum ◽

English Ivy

A powdery mildew disease of variegated ivy (Hedera canariensis L. var. azorica) was observed on the Tyrrhenian coast in Tuscany (Italy) in spring 1998. Symptoms began as small, nearly circular reddish spots that later enlarged and coalesced. The hyaline mycelium produced abundant, ellipsoid conidia in long chains that ranged from 20 to 40 μm in length and from 12 to 25 μm in width. Cleistothecia were globose (100 to 120 μm diameter), dark brown (when mature) with a basal ring of mycelioid appendages, and contained several (up to 20) ovate asci, each generally containing two ascospores. Ascospores were hyaline, one-celled, ellipsoid (20 to 35 μm in length and 10 to 20 μm in width). The morphological characteristics of this fungus were those given for Erysiphe cichoracearum DC. Infection also was found on English ivy (Hedera helix L.). It is reported that this species is, occasionally, subject to powdery mildew caused by E. cichoracearum (1). Conidia from infected leaves were shaken onto leaves of melon (Cucumis melo L.), cucumber (Cucumis sativus L.), watermelon (Citrullus lanatus [Thunb.] Matsum. & Nakai), lettuce (Lactuca sativa L.), tomato (Lycopersicon esculentum Mill.), tobacco (Nicotiana tabacum L.) and variegated and English ivy. After 7 days, the disease was observed on cucumber, melon, watermelon, tobacco, and variegated ivy. Examination confirmed that test plants were infected with E. cichoracearum. This is the first report of E. cichoracearum on variegated ivy in Italy. Reference: (1) P. P. Pirone. 1970. Diseases and Pests of Ornamental Plants. The Ronald Press, New York.

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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 Erysiphe macleayae on Macleaya microcarpa in Poland

Plant Disease ◽

10.1094/pdis-03-12-0244-pdn ◽

2012 ◽

Vol 96 (9) ◽

pp. 1376-1376 ◽

Cited By ~ 3

Author(s):

M. J. Park ◽

S. E. Cho ◽

M. Piątek ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Sequence Similarity ◽

Signs And Symptoms ◽

Its Region ◽

Botanical Garden ◽

Central China ◽

Perennial Herb ◽

Width Ratio ◽

First Report ◽

Potted Plants

Macleaya microcarpa (Maxim.) Fedde, also known as smallfruit plume poppy, is a perennial herb belonging to the family Papaveraceae. The plant, together with the better-known species M. cordata (Willd.) R. Br., is native to central China and is now planted worldwide for medicinal purposes. In October 2008 and August 2009, dozens of smallfruit plume poppy planted in the Kraków Botanical Garden, Poland, were found to be severely infected with a powdery mildew. White colonies with abundant sporulation developed on both sides of leaves and young stems, forming circular to irregular patches. Infections caused leaf yellowing and premature defoliation. The damage has been observed every year since 2009. Representative voucher specimens were deposited in the fungal herbarium of the W. Szafer Institute of Botany of the Polish Academy of Sciences (KRAM) and the Korea University herbarium (KUS). Appressoria on the mycelia were lobed, often in pairs. Conidiophores composed of three to four cells arose from the upper part of creeping hyphae, 65 to 120 × 7 to 10 μm, attenuated toward the base, sub-straight or slightly flexuous in foot-cells, and produced conidia singly. Conidia were hyaline, oblong-elliptical to doliiform, 25 to 38 × 12 to 18 μm with a length/width ratio of 1.8 to 2.6; lacked fibrosin bodies; and produced germ tubes on the subterminal position with club-shaped or lobed appressoria. The conidial surface was wrinkled to irregularly reticulate. No chasmothecia were found. The structures described above match well with the anamorph of Erysiphe macleayae R.Y. Zheng & G.Q. Chen (3). To confirm the identity of the causal fungus, the internal transcribed spacer (ITS) region of rDNA from KUS-F24459 was amplified using primers ITS5 and P3 (4) and directly sequenced. The resulting sequence of 553 bp was deposited in GenBank (Accession No. JQ681217). A GenBank BLAST search using the present data revealed >99% sequence similarity of the isolate with E. macleayae on M. cordata from Japan (AB016048). Pathogenicity was confirmed through inoculation by gently pressing diseased leaves onto leaves of three healthy potted plants. Three noninoculated plants served as controls. Plants were maintained in a greenhouse at 25°C. Inoculated plants developed signs and symptoms after 7 days, whereas the control plants remained healthy. The fungus present on the inoculated plants was morphologically identical to that originally observed on diseased plants. The powdery mildew infections of M. cordata associated with E. macleayae have been recorded in China and Japan (2), and more recently in Germany (1,3). To our knowledge, this is the first report of E. macleayae on M. microcarpa globally as well as in Poland. This mildew species was described in China and is endemic to Asia, where chasmothecia of the fungus were found. Only recently have powdery mildews been found on M. cordata in Germany (1,3) and now on M. microcarpa in Poland, indicating the fungus is spreading in Europe. References: (1) N. Ale-Agha et al. Schlechtendalia 17:39, 2008. (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/ , February 7, 2012. (3) A. Schmidt and M. Scholler. Mycotaxon 115:287, 2011. (4) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

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