scholarly journals First Report of Podosphaera xanthii Race 1W Causing Powdery Mildew of Watermelon in California

Plant Disease ◽  
2014 ◽  
Vol 98 (1) ◽  
pp. 158-158 ◽  
Author(s):  
J. Mercier ◽  
M. J. Muscara ◽  
A. R. Davis
Keyword(s):  
Powdery Mildew ◽  
Citrullus Lanatus ◽  
Field Isolate ◽  
Central Valley ◽  
Spore Suspension ◽  
Growth Chamber ◽  
Tween 20 ◽  
Podosphaera Xanthii ◽  
Breeding Lines ◽  
Field Plots

In September and October 2012, powdery mildew was detected on watermelon (Citrullus lanatus var. lanatus) plants of various breeding lines growing in field plots in Davis, California. Plants had partially necrotic leaves, yellowing to brown in color, with white surface mycelium and faint sporulation. No teleomorph was observed. Infected leaves were collected for examination and a spore suspension of the field isolate was made in water with 0.01% Tween 20 to spray inoculate watermelon seedlings of cultivar Dixie Lee with two true leaves. Plants were incubated in a growth chamber (22 to 26°C, 12-h photoperiod) for approximately 10 days, until sporulation was apparent. Microscopic observation of conidial chains showed that they had clearly crenate edges indicative of Podosphaera xanthii (4). To confirm the identity of the pathogen, we used Podosphaera-specific primers PFITS-F (5′-CCAACTCGTGCTGAGTGT-3′) and PF5.8-R (5′-TGTTGGTTTCTTTTCCTCCG-3′) to amplify and sequence the internal transcribed spacer regions of the nuclear rDNA. The 326-bp sequence had 98% homology to the GenBank sequence (accessions JQ340082.1 and AB774158.1) for P. xanthii. Infected ‘Dixie Lee’ leaves were used to make a spore suspension (approximately 5 × 104 conidia/ml) as described above to inoculate watermelon, melon, and squash seedlings (2 to 3 plants per cultivar) in a greenhouse. It caused severe symptoms on all watermelon plants cv. Charleston 76, P8, and Sugar Baby in the form of a powdery mildew with surface mycelium and chains of conidia, with leaves becoming gradually more necrotic and eventually dying, with the appearance of a melting down. Non-inoculated plants did not develop symptoms. The isolate also infected all squash plants ‘Zucchini Elite’ and melon powdery mildew differentials Iran H and ‘Védrantais.’ On these plants, the pathogen produced a powdery mildew (white surface mycelium with sporulation) but did not cause extensive necrosis. All other melon powdery mildew differentials (‘PMR5,’ ‘PMR45,’ WMR29, MR1, PI 124112, and PI 313970) did not develop any powdery mildew. A follow-up test in a growth chamber (22 to 26°C, 12-h photoperiod) with the same set of species and cultivars gave the same results. Based on these results, we conclude that this isolate belongs to race 1W (1,2). The presence of race 1W could have implications in disease management for this crop in the Central Valley of California as most cultivars are not resistant to it and the disease has been shown to cause severe damage in other states (1,3). References: (1) A. R. Davis et al. J. Am. Soc. Hort. Sci. 132:790, 2007. (2) J. D. McCreight. Amer. Soc. Hort. Sci. 131:59, 2006. (3) A. Y. Tetteh et al. Crop Sci. 50:933, 2010. (4) T. A. Zitter. Page 28 in: Compendium of Cucurbit Diseases, The American Phytopathological Society, St. Paul, MN, 1996.

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

Plant Disease ◽  
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.

scholarly journals Outbreak of Cucurbit Powdery Mildew on Watermelon Fruit Caused by Podosphaera xanthii in Southwest Florida

Plant Disease ◽  
2011 ◽  
Vol 95 (12) ◽  
pp. 1586-1586 ◽  
Author(s):  
C. S. Kousik ◽  
R. S. Donahoo ◽  
C. G. Webster ◽  
W. W. Turechek ◽  
S. T. Adkins ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Morphological Characteristics ◽  
The United States ◽  
Tween 20 ◽  
Conidial Suspension ◽  
Podosphaera Xanthii ◽  
Its Sequence Analysis ◽  
Fruit Samples ◽  
Cucurbit Powdery Mildew ◽  
Fruit Surface

Cucurbit powdery mildew caused by the obligate parasite Podosphaera xanthii occurs commonly on foliage, petioles, and stems of most cucurbit crops grown in the United States. (3). However, in the field, fruit infection on cucurbits including watermelon (Citrullus lanatus), is rarely, if ever, observed (2). Consequently, it was atypical when severe powdery mildew-like symptoms were observed on seedless and seeded watermelon fruit on several commercial farms in southwestern Florida during November and December 2010. Severe powdery mildew was also observed on ‘Tri-X 313’ and ‘Mickey Lee’ fruit grown at SWFREC, Immokalee, FL. Infected fruit developed poorly and were not marketable. Powdery mildew symptoms were mainly observed on young immature fruit, but not on mature older fruit. Abundant powdery mildew conidia occurred on fruit surface, but not on the leaves. Conidia were produced in chains and averaged 35 × 21 μm. Observation of conidia in 3% KOH indicated the presence of fibrosin bodies commonly found in the cucurbit powdery mildew genus Podosphaera (3). Orange-to-dark brown chasmothecia (formerly cleisthothecia) containing a single ascus were detected on the surface of some fruit samples. Conidial DNA was subjected to PCR using specific primers designed to amplify the internal transcribed spacer (ITS) region of Podosphaera (4). The resulting amplicons were sequenced and found to be 100% identical to the ITS sequences of P. xanthii in the NCBI database (D84387, EU367960, AY450961, AB040322, AB040315). Sequences from the watermelon fruit isolate were also identical to several P. fusca (synonym P. xanthii), P. phaseoli (GQ927253), and P. balsaminae (AB462803) sequences. On the basis of morphological characteristics and ITS sequence analysis, the pathogen infecting watermelon fruit can be considered as P. xanthii (1,3,4). The powdery mildew isolate from watermelon fruit was maintained on cotyledons of squash (Cucurbita pepo, ‘Early Prolific Straight Neck’). Cotyledons and leaves of five plants each of various cucurbits and beans were inoculated with 10 μl of a conidial suspension (105conidia/ml) in water (0.02% Tween 20). Two weeks after inoculation, abundant conidia were observed on cucumber (Cucumis sativus, ‘SMR-58’) and melon (Cucumis melo) powdery mildew race differentials ‘Iran H’ and ‘Vedrantais’. However, no growth was observed on melon differentials ‘PI 414723’, ‘Edisto 47’, ‘PMR 5’, ‘PMR 45’, ‘MR 1’, and ‘WMR 29’ (2,3). The powdery mildew isolate from watermelon fruit behaved as melon race 1 (3). Mycelium and conidia were also observed on fruit surface of watermelon ‘Sugar Baby’ and a susceptible U.S. plant introduction (PI 538888) 3 weeks after inoculation. However, the disease was not as severe as what was observed in the fields in fall 2010. The pathogen did not grow on plants of Impatiens balsamina or on select bean (Phaseolus vulgaris) cultivars (‘Red Kidney’, ‘Kentucky Blue’, and ‘Derby Bush’), but did grow and produce abundant conidia on ‘Pinto bush bean’. Powdery mildew on watermelon fruit in production fields can be considered as a potentially new and serious threat requiring further studies to develop management strategies. References: (1) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (2) A. R. Davis et al. J. Am. Soc. Hortic. Sci. 132:790, 2007. (3) M. T. McGrath and C. E. Thomas. In: Compendium of Cucurbit Diseases. American Phytopathological Society, St. Paul, MN, 1996. (4) S. Takamatsu and Y. Kano. Mycoscience 42:135, 2001.

scholarly journals Evaluation of Watermelon and Related Species for Resistance to Race 1W Powdery Mildew

2007 ◽  
Vol 132 (6) ◽  
pp. 790-795 ◽  
Author(s):  
Angela R. Davis ◽  
Amnon Levi ◽  
Antonia Tetteh ◽  
Todd Wehner ◽  
Vincent Russo ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Citrullus Lanatus ◽  
Plant Introduction ◽  
The United States ◽  
Common Disease ◽  
Podosphaera Xanthii ◽  
Sphaerotheca Fuliginea ◽  
Wild Type ◽  
Intermediate Resistance ◽  
Cultivated Species

Powdery mildew [Podosphaera xanthii (Castagne) Braun & Shishkoff (syn. Sphaerotheca fuliginea auct. p.p.)] is now a common disease on watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] in the United States. In this study, the entire available U.S. Plant Introduction collection of Citrullus Schrad. ex Eckl. & Zeyh. species was evaluated for resistance to P. xanthii race 1W. The collection consists of four Citrullus species and one Praecitrullus Pangalo species [C. lanatus var. citroides (L.H. Bailey) Mansf., C. colocynthis (L.) Schrad., C. rehmii De Winter, and P. fistulosus (Stocks) Pangalo]. Wild-type accessions tended to be more resistant more often than the cultivated species, C. lanatus var. lanatus. None were immune, eight of the 1573 accessions exhibited high levels of resistance, and another 86 demonstrated intermediate resistance. Stem and leaf disease severity were weakly correlated (r 2 = 0.64, P = 0.001). The majority of accessions having resistance were collected in Zimbabwe. Resistance was found in four species.

scholarly journals Cucurbit Powdery Mildew-resistant Bitter Gourd Breeding Lines Reveal Four Races of Podosphaera xanthii in Asia

HortScience ◽  
2018 ◽  
Vol 53 (3) ◽  
pp. 337-341 ◽  
Author(s):  
Narinder P.S. Dhillon ◽  
Supannika Sanguansil ◽  
Supornpun Srimat ◽  
Roland Schafleitner ◽  
B. Manjunath ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Smallholder Farmers ◽  
Bitter Gourd ◽  
Yield Potential ◽  
Podosphaera Xanthii ◽  
Asian Countries ◽  
Sources Of Resistance ◽  
Breeding Lines ◽  
Race 1 ◽  
Cucurbit Powdery Mildew

Bitter gourd (Momordica charantia L.) is a commercially and nutritionally important market vegetable in Asia cultivated mainly by smallholder farmers. Cucurbit powdery mildew (CPM) caused by Podosphaera xanthii (Px) is a nearly ubiquitous and serious fungal disease of bitter gourd. Five bitter gourd breeding lines (THMC 113, THMC 143, THMC 153, THMC 167, and THMC 170) were selected at the World Vegetable Center for resistance to a local isolate of Px in Kamphaeng Saen, Thailand. We evaluated the resistance potential of these five inbred lines against local isolates of Px at 12 locations in five Asian countries. Plants were inoculated with the respective local Px isolate 15 and 30 days after transplanting and additional Px-infected plants of the inoculated control were interplanted throughout each test. Plants were rated 60 days after transplanting for CPM reaction using a 0 (no evidence of infection) to 5 (>75% infection evident on individual leaves) disease severity scale. THMC 153 and THMC 167 were resistant to the local race of Px in all locations, whereas THMC 143 was observed resistant in all test locations except one in China. THMC 113 was resistant in each location except one in India. THMC 170 was susceptible in three locations in India. The multilocation tests revealed four unique Px races on bitter gourd in different Asian countries and sources of resistance for breeding CPM-resistant bitter gourd cultivars. Six strains of Px isolated from other cucurbits (Cucumis and Cucurbita) and representing five melon CPM races were unable to infect the susceptible M. charantia accession THMC 144 and the five resistant breeding lines, indicating pathotype differences between them and an isolate of M. charantia origin typed as race 1 on melon. THMC 143 and THMC 167, which originated from India, exhibited good yield potential in trials conducted in Thailand, Myanmar, Vietnam, and Bangladesh.

scholarly journals Powdery Mildew Resistant Rootstocks that Impart Tolerance to Grafted Susceptible Watermelon Scion Seedlings

Plant Disease ◽  
2018 ◽  
Vol 102 (7) ◽  
pp. 1290-1298 ◽  
Author(s):  
Chandrasekar S. Kousik ◽  
Mihir Mandal ◽  
Richard Hassell
Keyword(s):  
United States ◽  
Powdery Mildew ◽  
Disease Severity ◽  
Citrullus Lanatus ◽  
The United States ◽  
Bottle Gourd ◽  
Economic Losses ◽  
Podosphaera Xanthii ◽  
Lagenaria Siceraria ◽  
True Leaf

Powdery mildew (PM) is a major foliar disease causing serious economic losses of cucurbit crops grown in the United States. The pathogen Podosphaera xanthii, which causes PM, is known to infect seedlings, stems, foliage, petioles, and fruit of cucurbit crops. In recent years, grafting watermelon on resistant rootstocks for managing soilborne diseases has been gaining popularity in the U.S.A. However, grafting for managing foliar diseases has not yet received adequate attention. Three greenhouse experiments were conducted during the summer months of 2012, 2013, and 2014 to determine if PM-resistant rootstocks could impart resistance to a susceptible watermelon scion. Susceptible watermelon scion ‘Mickey Lee’ seedlings were grafted onto 25 watermelon (Citrullus lanatus, C. amarus, C. mucosospermus) and four bottle gourd (Lagenaria siceraria) rootstocks. Grafted plants were inoculated with a 2 × 104 conidia ml−1 suspension of P. xanthii conidia and disease severity was rated 14 days after inoculation. Mickey Lee grafted on six PM-resistant watermelon rootstocks had significantly (P ≤ 0.05) lower PM severity on cotyledons, 2nd true leaf, and upper leaves (rating for 3rd to 7th or 8th true leaf) compared with Mickey Lee grafted on susceptible watermelon USVL677-PMS or bottle gourd USVL848-PMS rootstocks. However, some of the resistant watermelon rootstocks did not impart significant resistance to the scion. The resistant bottle gourd rootstocks USVL482-PMR and USVL351-PMR provided significantly greater levels of resistance, compared with many of the resistant watermelon rootstocks. Grafting watermelon on resistant rootstocks may help mitigate the effects of PM on susceptible scion seedlings.

scholarly journals Sources of Resistance to Race 2WF Powdery Mildew in U.S. Watermelon Plant Introductions

HortScience ◽  
2011 ◽  
Vol 46 (10) ◽  
pp. 1349-1352 ◽  
Author(s):  
Haiying Zhang ◽  
Shaogui Guo ◽  
Guoyi Gong ◽  
Yi Ren ◽  
Angela R. Davis ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Citrullus Lanatus ◽  
Podosphaera Xanthii ◽  
Sphaerotheca Fuliginea ◽  
Sources Of Resistance ◽  
Foliar Disease ◽  
Breeding For Resistance ◽  
Plant Introductions

Powdery mildew of cucurbits, incited by Podosphaera xanthii (Castagne) Braun & Shishkoff (syn. Sphaerotheca fuliginea auct. p.p.), is an economically important foliar disease. which is now common in watermelon [Citrullus lanatus (Thunb.) Mastum. & Nakai]. This disease occurs in all watermelon-growing areas and can reduce yields by up to 30%. Finding and breeding for resistance to this disease is important to reduce dependence on fungicides and to use in combination with fungicides to limit the spread of fungicide-resistant P. xanthii. This is the first English report that race 2WF of P. xanthii can infect watermelon. It is the prevalent race of watermelon powdery mildew in Beijing.

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

2016 ◽  
Vol 213 (4) ◽  
pp. 1961-1973 ◽  
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

Response of Early, Medium, and Late Maturing Peanut Breeding Lines to Field Epidemics of Tomato Spotted Wilt

1999 ◽  
Vol 26 (2) ◽  
pp. 100-106 ◽  
Author(s):  
A. K. Culbreath ◽  
J. W. Todd ◽  
D. W. Gorbet ◽  
S. L. Brown ◽  
J. A. Baldwin ◽  
...  
Keyword(s):  
High Oleic Acid ◽  
Breeding Programs ◽  
Breeding Lines ◽  
High Oleic ◽  
Tomato Spotted Wilt ◽  
Arachis Hypogaea L ◽  
Early Maturing ◽  
Late Maturity ◽  
Field Plots ◽  
Maturity Groups

Abstract Epidemics of tomato spotted wilt, caused by tomato spotted wilt Tospovirus (TSWV), were monitored in field plots of runner-type peanut (Arachis hypogaea L.) cultivars Georgia Green and Georgia Runner and numerous breeding lines from four different breeding programs as part of efforts toward characterizing breeding lines with potential for release as cultivars. Breeding lines were divided into early, medium and late maturity groups. The tests were conducted near Attapulgus, GA and Marianna, FL in 1997 and in Tifton, GA and Marianna, FL in 1998. Epidemics in some early and medium maturing breeding lines, including some genotypes with high oleic acid oil chemistry, were comparable to those in Georgia Green, the cultivar most frequently used in the southeastern U.S. for suppression of spotted wilt epidemics. No early maturing breeding lines had lower spotted wilt final intensity ratings or higher yields than Georgia Green. However, spotted wilt intensity ratings in some late maturing lines and a smaller number of medium maturing lines were significantly lower than those of Georgia Green. Several of those lines also produced greater pod yields than Georgia Green. Results from these experiments indicated that there is potential for improving management of spotted wilt though development of cultivars that suppress spotted wilt epidemics more than currently available cultivars. There was no indication that differences in spotted wilt ratings corresponded to differences in numbers of thrips adults or larvae.

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