Gaps and perspectives of pathotype and race determination in Golovinomyces cichoracearum and Podosphaera xanthii

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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Occurrence of Podosphaera xanthii Race 2 on Cucumis melo in Brazil

Plant Disease ◽

10.1094/pdis.2004.88.10.1161a ◽

2004 ◽

Vol 88 (10) ◽

pp. 1161-1161 ◽

Cited By ~ 3

Author(s):

R. F. Kobori ◽

O. Suzuki ◽

R. Wierzbicki ◽

P. T. Della Vecchia ◽

L. E. A. Camargo

Keyword(s):

Cucumis Melo ◽

Fungal Growth ◽

Sao Paulo ◽

Podosphaera Xanthii ◽

São Paulo ◽

Erysiphe Cichoracearum ◽

Summer Squash ◽

Golovinomyces Cichoracearum ◽

Race 1 ◽

Race 2

Powdery mildew is an important disease of melons (Cucumis melo L.) cultivated in greenhouses in Brazil. Currently, there are 5 races of Podosphaera xanthii (formerly known as Sphaerotheca fuliginea) and 2 races of Golovinomyces cichoracearum (formerly known as Erysiphe cichoracearum) described on melons worldwide, but only race 1 of P. xanthii has been reported in Brazil (1). However, typical whitish powdery fungal growth was observed on an experimental hybrid yellow melon resistant to race 1 of P. xanthii during the summer of 2000 in a greenhouse in Bragança Paulista, State of São Paulo. Conidia collected from diseased leaves were spread onto 0.5% water agar medium and maintained at 22°C for 24 h with 12 h of light and 12 h of darkness. Most of the germinated conidia displayed fibrosin inclusion bodies when observed in a solution of 3% potassium hydroxide (KOH), and approximately 1 of 50 also displayed forked germ tubes. These features allowed us to identify P. xanthii as the causal agent. Conidia raised on the susceptible yellow melon ‘Amarelo CAC’ were used to inoculate cotyledons of the differential melon lines (2) ‘Hale's Best Jumbo’ (susceptible to races 1, 2, and 3 of P. xanthii), ‘PMR-45’ (resistant to race 1 and susceptible to races 2 and 3), and ‘PMR-6’ (resistant to races 1 and 2 and susceptible to race 3). Inoculations were performed on 10 plants of each differential line and replicated four times. The presence or absence of symptoms was evaluated 18 days after inoculation. ‘Hale's Best Jumbo’ and ‘PMR-45’ were rated as susceptible while ‘PMR-6’ was rated as resistant, thus indicating the presence of race 2 of P. xanthii in Brazil. During field surveys from 2001 to 2003, this race was found on squash (Cucurbita moschata), summer squash (C. pepo), and melons in São Paulo. References: (1) F. J. B. Reifschneider et al. Plant Dis. 69:1069, 1985. (2) C. E. Thomas et al. Cucurbit Genet. Coop. 7:126, 1984.

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First Report of Podosphaera xanthii Causing Powdery Mildew on Melothria indica in China

Plant Disease ◽

10.1094/pdis-04-21-0716-pdn ◽

2021 ◽

Author(s):

Fei Teng Zhong ◽

Yue Lian Liu ◽

Shili Lu ◽

Jie Chen ◽

Pinling Lin ◽

...

Keyword(s):

Powdery Mildew ◽

Southern China ◽

Morphological Characteristics ◽

Aquatic Organisms ◽

Lateral Position ◽

Molecular Characteristics ◽

Podosphaera Xanthii ◽

The North ◽

Golovinomyces Cichoracearum ◽

Voucher Specimens

Melothria indica Lour. is a wild ornamental plant widely distributed in South China. In November 2020, powdery mildew symptoms with 100% (60 plants) incidence were observed on M. indica climbing on a fence in Zhanjiang (21.17N,110.18E), Guangdong, China. The symptoms were typical for powdery mildew with white colonies on leaf surfaces and stems. Conidiophores appeared in all symptomatic tissues. Chasmothecia were observed only during the late stage of disease. Hyphae were hyaline, branched, and septate. Conidiophores were erect, hyaline, smooth, and had a dimension of 61.5 to 185.6 µm × 8.5 to 14.5 µm (n=20) and a cylindrical, flexuous foot cell, followed by 1 to 5 (−6) shorter cells. Conidia were ellipsoid to ovoid and had a dimension of 24.5 to 38.5 μm×15.5 to 21.8 μm (n=50) with well-developed fibrosin bodies. Germ tubes were in the lateral position. Chasmothecia were gregarious or scattered, subglobose, (64.8–) 65.5 μm to 115.5 (–120.5) μm (n=20) in diameter. The appendages were few, and hyphoid. Ascus one per ascomas, clavate, or subglobose, 56.5 to 78.3 (–90) μm×52.5 to 60.5 (–72) (n=20) μm. Each ascus had eight ascospores that were broadly ellipsoid and sized 13.8 to 18.6 μm×12.5 to 16.5 μm (n=30). The morphological characteristics were consistent with the previous description of Podosphaera xanthii (Castagne) U. Braun & Shishkoff (Braun and Cook 2012). Three voucher specimens, Ms-1, Ms-2, and Ms-3, were deposited in the fungus collection at Aquatic Organisms Museum of Guangdong Ocean University, and were used for molecular analysis. Their internal transcribed spacer (ITS) regions were amplified using primers ITS1/ITS4. Amplicons were sequenced and submitted to GenBank (accession no. MW512919, MW512920, and MW512921). The sequences were identical to each other and 100% similar to two of P. xanthii (Accession No. MT472035 and MN818563). On the basis of the morphological and molecular characteristics, the fungus was identified as P. xanthii. Pathogenicity was examined through inoculation by gently pressing the naturally infected leaves onto healthy ones of three potted M. indica plants with three leaves. Healthy leaves were leaves of three further plants which served as the control. White powdery mildew colonies with an incidence of 100% were similarly observed after 7 days at 28 °C and 80% relative humidity in a greenhouse. The fungal colonies on diseased leaves were morphologically identical to the specimen, and the control plants developed no symptoms. The Koch’s postulates have completed. Golovinomyces cichoracearum is known to cause powdery mildew on M. indica in China (Liu et al. 2015). P. xanthii (synonym:P. fusca p.p.) is the cause of powdery mildew on cucurbits worldwide (Braun and Cook 2000), including M. indica (synonym:M. japonica) in Korea (Kwon et al. 2015) and Japan (Takamatsu et al. 2005), but hitherto not for China. While, the teleomorph of the fungus on cucurbits is seldom found worldwide and in China only in the north (Liu et al. 2011), chasmothecia are recorded for here southern China (21.17N,110.18E).

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Biological control of Podosphaera xanthii the causal agent of squash powdery mildew disease by upregulation of defense-related enzymes

Egyptian Journal of Biological Pest Control ◽

10.1186/s41938-018-0058-8 ◽

2018 ◽

Vol 28 (1) ◽

Cited By ~ 6

Author(s):

Yaser M. Hafez ◽

Asmaa S. El-Nagar ◽

Abdelnaser A. Elzaawely ◽

Said Kamel ◽

Hanafey F. Maswada

Keyword(s):

Biological Control ◽

Powdery Mildew ◽

Causal Agent ◽

Podosphaera Xanthii ◽

Powdery Mildew Disease

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Transformation of the cucurbit powdery mildew pathogen Podosphaera xanthii by Agrobacterium tumefaciens

New Phytologist ◽

10.1111/nph.14297 ◽

2016 ◽

Vol 213 (4) ◽

pp. 1961-1973 ◽

Cited By ~ 18

Author(s):

Jesús Martínez‐Cruz ◽

Diego Romero ◽

Antonio Vicente ◽

Alejandro Pérez‐García

Keyword(s):

Agrobacterium Tumefaciens ◽

Powdery Mildew ◽

Podosphaera Xanthii ◽

Powdery Mildew Pathogen ◽

Cucurbit Powdery Mildew

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First report of powdery mildew caused by Podosphaera xanthii on Cucurbita maxima in Korea

Journal of Plant Pathology ◽

10.1007/s42161-019-00482-5 ◽

2019 ◽

Vol 102 (2) ◽

pp. 599-599 ◽

Cited By ~ 1

Author(s):

In-Young Choi ◽

Young-Joon Choi ◽

Hyeon-Dong Shin

Keyword(s):

Powdery Mildew ◽

Podosphaera Xanthii ◽

Cucurbita Maxima ◽

First Report

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First Report of Powdery Mildew Caused by Podosphaera xanthii on the Invasive Verbena brasiliensis in Texas

Plant Disease ◽

10.1094/pdis-01-20-0022-pdn ◽

2020 ◽

pp. PDIS-01-20-0022

Author(s):

N. C. Luecke ◽

T. Adams ◽

K. M. Crawford

Keyword(s):

Powdery Mildew ◽

Podosphaera Xanthii ◽

First Report

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First Report of Podosphaera xanthii Causing Powdery Mildew on Zinnia elegans in Taiwan

Plant Disease ◽

10.1094/pdis-06-20-1263-pdn ◽

2020 ◽

Author(s):

Yi-Ting Xiao ◽

Yuan-Min Shen ◽

Chao-Jen Wang ◽

Tung-Ching Huang

Keyword(s):

Powdery Mildew ◽

Average Length ◽

Zinnia Elegans ◽

Flowering Plant ◽

Tween 20 ◽

Width Ratio ◽

Podosphaera Xanthii ◽

Bedding Plants ◽

Taichung City ◽

Voucher Specimens

Zinnia elegans L., known as common zinnia, is an annual flowering plant belonging to the Asteraceae family and native to North America. The plant has colorful flowers and is one of the popular ornamental bedding plants for gardening. In March 2020, powdery mildew symptoms were observed in a zinnia floral field with an incidence of >70% in Dacun Township, Changhua County, Taiwan. The symptoms were spotted on the stems, flower petals and leaves which appeared as irregular colonies and white patches on the surfaces. When disease progressed, most of the plant surfaces were covered by the white fungal colonies and became yellowish. Under microscopic examination, hyphal appressoria of the fungus were indistinct or slightly nipple-shaped. The conidiophores were unbranched, erect, straight, smooth to slightly rough, 75.0 to 200.0 × 10.0 to 15.0 µm (n=10), composed of a cylindrical, flexuous foot cell, 40.0 to 100.0 × 8.8 to 15.0 µm (n=10), and following 1 to 5 shorter cells. The conidia were ellipsoid to ovoid, 25.0 to 37.5 × 15.0 to 23.8 µm (n=60), with an average length-to-width ratio of 1.8 and contained fibrosin bodies. No chasmothecia were found. Three voucher specimens (TNM Nos. F0033680, F0033681, and F0033682) were deposited in the National Museum of Natural Science, Taichung City, Taiwan. To confirm the identification, the internal transcribed spacer (ITS) regions of the three specimens were amplified using primer pairs ITS1/PM6 and PM5/ITS4 (Shen et al. 2015) and sequenced from both ends. The resulting sequences were deposited in GenBank under Accession Nos. MT568609, MT568610, and MT568611. The sequences were identical to each other and shared a 100% identity with that of Podosphaera xanthii MUMH 338 on Z. elegans from Japan (Accession No. AB040355) (Ito and Takamatsu 2010) over a 475 bp alignment. Accordingly, the fungus was identified as P. xanthii (Castagne) U. Braun & Shishkoff (Braun and Cook 2012) based on its morphological and molecular characters. Pathogenicity was demonstrated through inoculation by gently pressing naturally infected leaves onto leaves of three healthy potted common zinnia that had been sprayed with 0.02% Tween 20. Additional three non-inoculated plants treated in the same way without inoculating the powdery mildew served as the controls. Powdery mildew colonies were observed on inoculated leaves after 10 days at room temperature, later the diseased leaves became yellowish and deteriorated. The morphological traits of the fungus on the inoculated leaves were similar to those of the first observed. In addition, the ITS sequence from a colony on the inoculated leaves was 100% identical to MT568609-MT568611, fulfilling the Koch’s postulates. All the controls remained symptomless. Z. elegans is known to be a host for different species of powdery mildew in the genus Erysiphe, Golovinomyces, and Podosphaera (Farr and Rossman 2020). In Taiwan, powdery mildew has been briefly reported on zinnia without detailed descriptions (Hsieh 1983). This study confirmed P. xanthii as a causal agent of powdery mildew in Taiwan and the awareness of the disease may benefit the floral industry. To our knowledge, this is the first confirmed report of P. xanthii on Z. elegans in Taiwan.

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