First report of Golovinomyces sp. causing powdery mildew infection on Dyschoriste nagchana in Western Ghats of India

Dyschoriste nagchana Nees (Acanthaceae) is a perennial plant grows naturally in wet grassland, but is now often also found in secondary bushland and grassland, including lawns. In January2019, severe powdery mildew symptoms were observed on the leaves and stem of D. nagchana (Fig.1, a). The infection was found to be very severe at that time on plant and because of severe infestation premature leaf fall was also observed. The occurrence of powdery mildew in its anamorphic form on D. nagchana. was first observed in the ranges of hills in Western Ghats pertaining to district Satara viz Yavateshwar (17°41’02.91”N 73°56’58.15”E and Elevation 3419ft) and Varoshi (17°52’04.42” N 73°45’03.12” E and Elevation 2834ft). later on, disease incidence was noticed from different areas of said district.

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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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Heterocentron subtriplinervium (Melastomataceae) – the first report of naturalisation of a potential invasive alien species in Asia from India

Acta Botanica Hungarica ◽

10.1556/034.62.2020.1-2.1 ◽

2020 ◽

Vol 62 (1-2) ◽

pp. 1-6

Author(s):

A. P. Balan ◽

A. J. Rubi ◽

R. Prakashkumar

Keyword(s):

Alien Species ◽

Western Ghats ◽

Invasive Alien Species ◽

First Report ◽

Western Ghats Of India ◽

First Time ◽

The Western Ghats

Heterocentron subtriplinervium (Link et Otto) A. Braun et C. D. Bouche, a potential invasive alien species is reported here for the first time for Asia from the Western Ghats of India. The plant is probably introduced deliberately into gardens for ornamental purpose from where it escaped and become naturalised in the Western Ghats. This species is a potential weed, which quickly conquers areas wherever introduced displacing the indigenous flora. A detailed description, illustration, photograph and relevant notes are provided for easy identification in the field.

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

Plant Disease ◽

10.1094/pdis-03-21-0545-pdn ◽

2021 ◽

Author(s):

Irum Mukhtar ◽

Ruiting Li ◽

IBATSAM KHOKHAR ◽

Ruanni Chen ◽

Yunying Cheng ◽

...

Keyword(s):

Powdery Mildew ◽

Disease Incidence ◽

Large Subunit ◽

Mainland China ◽

Lsu Rdna ◽

Podosphaera Xanthii ◽

Powdery Mildew Fungus ◽

Potential Threat ◽

First Report ◽

Plant Pathol

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

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First Report of Canola Powdery Mildew Caused by Erysiphe polygoni in Argentina

Plant Disease ◽

10.1094/pdis.2004.88.10.1163c ◽

2004 ◽

Vol 88 (10) ◽

pp. 1163-1163 ◽

Cited By ~ 5

Author(s):

S. Gaetán ◽

M. Madia

Keyword(s):

Powdery Mildew ◽

Buenos Aires ◽

Disease Incidence ◽

Fungal Growth ◽

The United States ◽

Climatic Conditions ◽

Width Ratio ◽

Infected Leaf ◽

First Report ◽

Erysiphe Polygoni

Canola (Brassica napus) is a developing oleaginous crop grown commercially in the Buenos Aires and Santa Fe provinces of Argentina. During the autumn of 2003, typical signs of powdery mildew were observed on canola plants in experimental field plots in Buenos Aires. Average disease incidence was 42% on 3- to 6-month-old canola cultivars developed in the following countries: Argentina (Eclipse, Impulse Master, Mistral, and Nolza); Australia (Oscar and Rainbow); Canada (Sentry); France (Cadillac, Camberra, and Capitol); and Sweden (Maskot, Sponsor, and Wildcat). The range of incidence on these cultivars was 35 to 93%. Other cultivars exhibited an apparent high level of resistance or escaped disease. These included: Charlton (Argentina); 46CO3, Dunkeld, Insignia, Mystic, Monty, Outback, Rivette, and Surpass 400 (Australia), and Caviar (France). Climatic conditions in Buenos Aires, especially rainfall, from March to May 2003 were apparently favorable for powdery mildew development. On susceptible cultivars, fungal growth was observed on leaves, stems, and pods that resulted in premature senescence of the tissues. The mycelium, with multilobed hausthoria, was white to gray, dense or fine, and in patches or covering the entire adaxial leaf surfaces. Appressoria were lobed and conidiophores were straight. Foot cells were cylindrical, straight, measured 35 to 42 × 7 to 10 μm, and were followed by two cells. Conidia were produced singly, cylindrical to ovoid, and measured 36 to 40 × 18 to 20 μm. The conidial length-to-width ratio was 2.0. No fibrosin bodies were observed in the conidia and conidia germinated at the ends. Cleistothecia were not observed. On the basis of mycelial, conidial, and hausthoria characteristics observed on six leaves for each affected cultivar, the fungus was identified as Erysiphe polygoni DC (1). Pathogenicity was confirmed on 5-week-old canola plants of cvs. Eclipse, Impulse, Master, Mistral, and Maskot by gently pressing (1 min) one adaxial infected leaf with abundant sporulation onto one adaxial healthy leaf. The experiment, which included five inoculated plants and three noninoculated control plants for each cultivar, was conducted in a greenhouse at 22 to 24°C and maintained at 75% relative humidity with no supplemental light. Inoculated and control plants were covered with polyethylene bags for 48 h after inoculation. Powdery mildew developed on all inoculated plants of all cultivars after 12 to14 days. The control plants did not develop disease. The experiment was repeated with similar results. E. polygoni has a worldwide distribution (2); however, the results suggest that this fungus may be a threat to the main cultivars being grown in Argentina (Eclipse, Impulse, Master, Mistral, and Nolza), since high levels of disease incidence, as much as 70%, were observed. Under propitious environments, this pathogen could cause severe yield losses in commercially grown canola in Argentina. To our knowledge, this is the first report of canola powdery mildew caused by E. polygoni in Argentina. References: (1) H. J. Boesewinkel. Rev. Mycol. Tome 41:493, 1977. (2) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St.Paul, MN, 1989.

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First Report of Powdery Mildew Caused by Podosphaera euphorbiae-hirtae on Euphorbia tithymaloides in California

Plant Disease ◽

10.1094/pdis-05-12-0461-pdn ◽

2012 ◽

Vol 96 (12) ◽

pp. 1822-1822

Author(s):

S. Rooney-Latham ◽

J. F. Bischoff

Keyword(s):

Powdery Mildew ◽

Disease Incidence ◽

Its Region ◽

Virgin Islands ◽

California Department ◽

First Report ◽

Food And Agriculture ◽

Trace Back ◽

Ventura County ◽

The Uk

Euphorbia tithymaloides (Euphorbiaceae; known as ‘Jacob's ladder,’ ‘Devil's Backbone’) is a perennial, succulent spurge, grown primarily as a border plant in ornamental landscapes. In June 2011 and February 2012, the California Department of Food and Agriculture Plant Pest Diagnostics Lab, Sacramento, CA, received an unusual powdery mildew sample on greenhouse-grown E. tithymaloides from a Ventura County, CA nursery. Disease incidence at the nursery was 100%. White mycelial patches were present on the stems and on both sides of the leaves. Over time, heavily infected branches defoliated and brownish, roughened, scabby lesions developed on the stems. Hyphae were thin-walled, up to 8 μm wide and developed nipple-shaped appressoria. Ellipsoid-ovoid conidia measured 21.0 to 32.5 × 13 to 18 μm (avg. 26.4 × 13.9 μm, n = 20) and formed in chains. The rDNA internal transcribed spacer (ITS) region was amplified with primers PFITS-F and PF5.8-R (4). The 387-bp sequence (GenBank JX006103) was 99% similar (346/347 bp) to Podosphaera euphorbia-hirtae (AB040306) from Acalypha australis (Euphorbiaceae) (3). Based on ITS similarity and culture morphology, the fungus was identified as P. euphorbiae-hirtae U. Braun & Somani (1,3). Pathogenicity was confirmed through inoculation by gently pressing diseased leaves from the nursery onto the youngest leaves of three plants each of E. tithymaloides cultivars ‘Nano’ and ‘Variegated.’ Leaves of an equal number of control plants were pressed with healthy leaves. Plants were incubated in a dew chamber for 48 h after which they were transferred to a 22°C growth chamber with a 12-h photoperiod. The experiment was repeated once. White powdery mildew colonies formed after 7 days on ‘Variegated’ and 13 days on ‘Nano’. Conidia measured 27.5 to 35.0 × 11 to 15 μm (avg. 30.5 × 12.6 μm, n = 30) which was within the range of P. euphorbia-hirtae. No symptoms developed on the control plants. P. euphorbiae-hirtae has been reported in Asia and the UK on E. tithymaloides and in Asia on A. australis (2). An asexual Oidium stage on Euphorbiaceae in Asia, Africa, Australia, Florida, Puerto Rico, Cuba, and the U.S. Virgin Islands may correspond to P. euphorbiae-hirtae (2). To our knowledge, this is the first report of P. euphorbiae-hirtae in California. Following the 2011 and 2012 detections, all E. tithymaloides plants in the Ventura County, CA nursery were destroyed. A regulatory trace back survey found that the plants were shipped from a Florida supplier, which was also shown to have an outbreak of P. euphorbiae-hirtae. The original source of the Florida E. tithymaloides plants was a 2010 shipment from Costa Rica. The host range of P. euphorbiae-hirtae is restricted to three landscape species in the Euphorbiaceae. References: (1) U. Braun. Beih. Nova Hedwigia 89:143, 1987. (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/index.cfm May 1, 2012. (3) T. Hirata. et al. Can. J. Bot. 78:1521, 2000. (4) R. Singh et al. Plant Dis. 93:1348, 2009.

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First Report of Golovinomyces orontii Causing Hydrangea macrophylla Powdery Mildew in Qinghai-Tibet Plateau, China

Plant Disease ◽

10.1094/pdis-11-20-2359-pdn ◽

2021 ◽

Author(s):

Taijun Fang ◽

Wenjun Shang ◽

luchao bai ◽

Nuyi Ya ◽

Jiezhuoma Duo ◽

...

Keyword(s):

Powdery Mildew ◽

Disease Incidence ◽

Tibet Plateau ◽

Single Spore ◽

Universal Primer ◽

Bootstrap Analysis ◽

First Report ◽

Golovinomyces Orontii ◽

Hydrangea Macrophylla ◽

Qinghai Tibet Plateau

Hydrangea macrophylla (Thunb.) Ser. (Hydrangeaceae) is the most popular hydrangea species grown in home gardens and landscapes in China. Plants of H. macrophylla with symptoms of powdery mildew were found in a commercial wholesale nursery in Huzhu, Haidong (36°49'11.87" N, 101°57′03.36″E, alt. 2490 m), in May 2020, with disease incidence reaching 80%. Symptoms included yellowing and necrosis of leaves. Upon microscopic observation, masses of conidia and mycelium were observed covering the symptomatic tissues. Fungal isolates displayed nipple-shaped hyphal appressoria, often poorly developed, conidiophores erect, arising laterally or from the upper surface of hyphal mother cells, and positioned almost centrally or towards one end of the cells, up to about 160 μm long (n = 30), with foot cells straight or flexuous, 32 to 86 × 8 to 13 μm (n = 50), followed by one to three shorter cells about 11 to 24 × 10 to 15 μm (n = 50), forming catenescent conidia in usually predominantly chains, conidia doliiform to limoniform, hyaline, 24 to 35 × 13 to 25μm (n = 50). Conidial germination was of the Euoidium type. Chasmothecia were not observed. To confirm fungal classification, single spores were isolated and cultured on detached leaf bioassay following the protocol described in Farinas et al. (2019). Total DNA was extracted directly from single-spore cultures using a Chelex extraction method (Walsh et al. 1991). The rDNA internal transcribed spacer (ITS) regions were amplified by polymerase chain reaction (PCR) utilizing the universal primer pairs ITS1/ITS4 (White et al. 1990). The sequences (726-727 bp) were deposited in GenBank (accessions no. MT568633, MT757924 and MT757925). The ITS sequences showed 99.9-100% identity with a sequence of Golovinomyces orontii reported on Papaver rhoeas (AB769466) in Switzerland. Based on the ITS rDNA phylogenetic tree, the sequences retrieved from the specimen clustered within a strongly supported clade with G. orontii (AB769466), confirming the identity of the pathogen (Takamatsu 2013). Cladistic trees were constructed using the neighbor-joining method with the Kimura 2-parameter substitution model in MEGA 6.0. Branch robustness was assessed via bootstrap analysis with 1,000 replicates. To confirm pathogenicity, eight H. macrophylla plants were sprayed until run-off with a suspension containing 1 × 105 conidia/ml. Four plants were used for fulfilling Koch’s postulates and four plants were used as mock-inoculated controls sprayed only with sterile distilled water. Inoculated and non-inoculated plants were covered with plastic bags separately and maintained overnight in a greenhouse at 25 ± 2°C and 50 to 60% relative humidity. Typical powdery mildew colonies developed on inoculated plants 10 to 15 days after inoculation, which were morphologically identical to those originally observed on the diseased plats, whereas the control plants remained symptomless. To our knowledge, this is the first report of powdery mildew caused by G. orontii on H. macrophylla in Qinghai-Tibet Plateau, China (Braun and Cook 2012).

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First Report of Powdery Mildew Caused by Erysiphe buhrii on Gypsophila paniculata in Korea

Plant Disease ◽

10.1094/pdis-03-14-0237-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 1013-1013 ◽

Cited By ~ 4

Author(s):

I. Y. Choi ◽

B. S. Kim ◽

S. E. Cho ◽

J. H. Park ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Host Range ◽

Disease Incidence ◽

Width Ratio ◽

Korean Isolate ◽

Pathogenicity Test ◽

Cut Flower ◽

Voucher Specimen ◽

First Report ◽

Gypsophila Paniculata

Gypsophila paniculata L. (baby's breath, family Caryophyllaceae), native to Central and Eastern Europe, is commonly cultivated as a commercial cut flower crop in greenhouses in Korea. Since 2011, baby's breath cv. Cassiopeia has been observed affected by a powdery mildew with nearly 100% disease incidence at the stage of harvesting in Iksan City. Powdery mildew colonies first appeared as thin white patches on stems and both sides of the leaves. As disease progressed, plants were covered with dense masses of spores, followed by senescence and reduction of quality of cut flowers. A voucher specimen was deposited in the Korea University Herbarium (Accession KUS-F27313). Appressoria were well-developed, multilobed or moderately lobed, and single or opposite in pairs. Conidiophores were straight, 95 to 150 × 7 to 10 μm, and composed of 3 to 4 cells. Foot-cells were cylindric or slightly sinuous at the base and 37 to 53 μm long. Singly produced conidia were cylindrical to oblong-elliptical, 35 to 56 × 12.5 to 18 μm with a length/width ratio of 2.1 to 3.6, devoid of fibrosin bodies, and with angular/rectangular wrinkling of outer walls. Germ tubes were in the perihilar position on conidia, and ended with lobed appressoria. No chasmothecia were found. These structures are typical of the Pseudoidium anamorph of the genus Erysiphe. Specific measurements and host range were consistent with those of E. buhrii U. Braun (2). To confirm identification, the complete internal transcribed spacer (ITS) region of rDNA of isolate KUS-F27313 was amplified with primers ITS1/ITS4, and sequenced directly. The resulting 725-bp sequence was deposited in GenBank (KJ530705). A GenBank BLAST search of the Korean isolate showed 99% similarity with E. buhrii on Acanthophyllum sp. (Caryophyllaceae) from Iran (AB128924). Pathogenicity was confirmed through inoculation by gently dusting conidia onto leaves of five healthy, potted baby's breath cv. Cassiopeia. Five non-inoculated plants served as controls. Inoculated plants were isolated from non-inoculated plants in separate rooms in a greenhouse at 25 ± 2°C. Inoculated plants developed signs and symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Pathogenicity test was repeated twice. The powdery mildew disease caused by E. buhrii on baby's breath has been recorded in the former Soviet Union (Armenia, Kazakhstan, Ukraine), Romania, Turkey, Iran, Mongolia, and Argentina (1,3). Also, a fungus occurring on baby's breath was recorded as Oidium sp. from Japan (4). To our knowledge, this is the first report of powdery mildew caused by E. buhrii on baby's breath in Korea. Powdery mildew infections pose a serious threat to production of this cut flower crop. References: (1) K. Amano. Host Range and Geographical Distribution of the Powdery Mildew Fungi. Japan Scientific Societies Press, Tokyo, 1986. (2) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No. 11. CBS, Utrecht, 2012. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, Retrieved February 18, 2014. (4) M. Satou et al. Ann. Phytopathol. Soc. Jpn. 62:541, 1996.

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

Plant Disease ◽

10.1094/pdis-06-20-1368-pdn ◽

2020 ◽

Author(s):

Hugo Beltrán-Peña ◽

Ruben Felix-Gastelum ◽

Moises Camacho-Tapia ◽

Kamila C. Correia ◽

Gabriel Herrera-Rodriguez ◽

...

Keyword(s):

Powdery Mildew ◽

Urban Areas ◽

Disease Incidence ◽

Phylogenetic Analyses ◽

Morphological Characteristics ◽

Podosphaera Xanthii ◽

Monitoring And Control ◽

Voucher Specimen ◽

First Report ◽

Initial Symptoms

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

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

Plant Disease ◽

10.1094/pdis.2001.85.12.1292b ◽

2001 ◽

Vol 85 (12) ◽

pp. 1292-1292 ◽

Cited By ~ 3

Author(s):

J. J. Marois ◽

M. T. Momol ◽

J. W. Kimbrough ◽

R. C. Hochmuth ◽

W. Dankers

Keyword(s):

New York ◽

Powdery Mildew ◽

Disease Incidence ◽

Control Measures ◽

Oidium Neolycopersici ◽

Razor Blade ◽

First Report ◽

White Mycelium ◽

Repeated Applications ◽

Greenhouse Tomatoes

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

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

Plant Disease ◽

10.1094/pdis-07-21-1427-pdn ◽

2021 ◽

Author(s):

In-Young Choi ◽

Ho-Jong Ju ◽

Kui-Jae Lee ◽

Hyeon-Dong Shin

Keyword(s):

Powdery Mildew ◽

Large Subunit ◽

Pcr Amplification ◽

Echinacea Purpurea ◽

The United States ◽

Infected Leaf ◽

Podosphaera Xanthii ◽

Powdery Mildew Fungus ◽

First Report ◽

Perennial Plant

Salvia farinacea Benth. (Lamiaceae) is an herbaceous perennial plant, native to Mexico and southern parts of the United States. This plant is cultivated worldwide for its ornamental value. In November 2019, hundreds of S. farinacea ‘Blue Bedder” grown in a flower garden in Jeju (33°30'57"N 126°32'50"E), Korea have been found to be infected with a powdery mildew fungus. The disease severity was estimated to be 100%. Likewise in October 2020, a similar situation with this plant was also observed in a flower garden in Seoul (37°35'19"N 127°01'07"E), Korea. Leaves, stems and inflorescence of plants were covered by white, thin mycelial felt, bearing an abundance of conidiophores and conidia. Eventually, infected plants lose their ornamental value. Two voucher specimens have been deposited in the Korea University Herbarium (KUS-F31478 and F32164). Fresh materials were examined. Hyphal appressoria were nipple-shaped, but rarely found. Conidiophores (n = 30) were straight, 95 to 160 × 10 to 12 μm and produced 2 to 7 immature conidia in chains with a crenate outline. Foot-cells were cylindric and 36 to 60 μm long. Conidia (n = 30) were ellipsoid-ovoid to barrel-shaped, 32 to 38 × 18 to 24 μm, and contained conspicuous fibrosin bodies. Dark brown chasmothecia were found partly embedded in the mycelial felt on leaves, mostly hypophyllous, spherical, and 82 to 100 µm diameter, with a single ascus in each. Appendages were few, mycelioid, 1- to 4-septate, brown near the base when mature, but paler above. Asci were broadly ellipsoid to subglobose, 56 to 68 × 50 to 62 μm, sessile and 8-spored. Ascospores were colorless, oval to subglobose, and 14 to 18 × 12 to 15 µm. These characteristics were consistent with those of Podosphaera xanthii (Castagne) U. Braun & Shishkoff (Braun and Cook 2012). For further confirmation, genomic DNA was extracted from chasmothecia from KUS-F31478 and F32164. PCR amplification was performed 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). Obtained sequences were deposited to the GenBank under the accession numbers MZ359847 and MZ359859 for ITS, MZ359858 and MZ359861 for LSU. For ITS regions 99.80-100% similarity was found with sequences MT131256 (Salvia farinacea), MT131254 (Mazus pumilus) and MT131252 (Erigeron bellioides) of P. xanthii, whereas it was 99.90% with sequences of this fungus on Echinacea purpurea (MT826247 and MT826245) for 28S rDNA gene. Pathogenicity tests were carried out by touching an infected leaf onto healthy leaves of disease-free 30 days old potted ‘Blue Bedder’ using replication of five plants, with five non-inoculated plants used as controls. The typical signs of powdery mildew started to develop on the inoculated leaves in 7 to 10 days, and microscopic examination revealed the morphological identity with the fungus observed from the field. All non-inoculated control plants remained symptomless. Hitherto Golovinomyces powdery mildews on Salvia spp. were reported globally (Farr and Rossman 2021). However, Podosphaera elsholtziae on Salvia sp. and P. xanthii on S. farinacea were reported from China and Taiwan (Zheng and Yu 1987, Yeh et al. 2021). To our knowledge, this is the first report of P. xanthii on S. farinacea in Korea. The occurrence of Podosphaera powdery mildew on S. farinacea could pose a serious threat to the beauty of this plant, causing premature senescence of young leaves and gray to purplish discoloration of the leaves.

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