New and High Virulent Pathotypes of Sunflower Downy Mildew (Plasmopara halstedii) in Seven Countries in Europe

Downy mildew of sunflower, caused by Plasmopara halstedii (Farl.) Berl. et de Toni, is a relevant disease of this crop. High virulent pathotypes have been identified in several countries, while there are few data on the spread of P. halstedii pathotypes in some important sunflower-growing areas of Europe. The goal of this study was to give up-to-date information on the pathotype structure of P. halstedii in Hungary and provide some actual data on the virulence phenotype of the pathogen for six European countries. Infected leaves of different sunflower hybrids and volunteers were collected in seven countries (Hungary, Bulgaria, Serbia, Turkey, Greece, Romania, and Italy) between 2012 and 2019. A universally accepted nomenclature was used with a standardized set of sunflower differential lines for pathotype characterization of isolates. The virulence pattern of the isolates was determined by a three-digit code (coded virulence formula, CVF). A total of 109 P. halstedii isolates were characterized. As a result of our survey, 18 new P. halstedii pathotypes were identified in Europe. Two out of the eighteen pathotypes were detected from the Asian part of Turkey. The detailed distribution of pathotypes in Hungary is also discussed.

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Updated Characterization of Races of Plasmopara halstedii and Entomopathogenic Fungi as Endophytes of Sunflower Plants in Axenic Culture

Agronomy ◽

10.3390/agronomy11020268 ◽

2021 ◽

Vol 11 (2) ◽

pp. 268

Author(s):

Pedro Miranda-Fuentes ◽

Ana B. García-Carneros ◽

Leire Molinero-Ruiz

Keyword(s):

Plant Growth ◽

Downy Mildew ◽

Entomopathogenic Fungi ◽

Genetic Resistance ◽

Axenic Culture ◽

Plasmopara Halstedii ◽

Successful Establishment ◽

Axenic Conditions ◽

Highly Virulent

The management of downy mildew (Plasmopara halstedii) in sunflower, is heavily dependent on genetic resistance, whilst entomopathogenic fungi (EF) can reduce other sunflower diseases. In this work, we characterized P. halstedii from Spain and other countries collected in the past few years. Twenty-three races were identified (the most frequent in Spain being 310, 304, 705 and 715), with an increasing proportion of highly virulent races. Five isolates from countries other than Spain overcame the resistance in RHA-340. In addition, we assessed the efficacy of five EF against downy mildew and their effects on sunflower growth in axenic conditions. None of the entomopathogens reduced disease severity, nor did they have any effect on plant growth when applied together with P. halstedii. In contrast, three EF reduced some of the plant growth variables in the absence of the pathogen. Microbiological and molecular diagnostics suggest that the axenic system and the short experimental time used in this study did not favor the successful establishment of EF in the plants or their potential biocontrol effect. Our results show a shift in P. halstedii racial patterns and suggest that soil as a growth substrate and long infection times are needed for EF effectiveness against downy mildew.

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Isolation and characterization of a mycovirus from Plasmopara halstedii

Canadian Journal of Botany ◽

10.1139/b92-214 ◽

1992 ◽

Vol 70 (9) ◽

pp. 1734-1737 ◽

Cited By ~ 8

Author(s):

D. E. Mayhew ◽

A. L. Cook ◽

T. J. Gulya

Keyword(s):

Molecular Weight ◽

Key Words ◽

Helianthus Annuus ◽

Downy Mildew ◽

Type A ◽

Uv Absorbance ◽

Plasmopara Halstedii ◽

Isolation And Characterization ◽

Virion Surface

A virus was isolated from Plasmopara halstedii, the causal agent of sunflower downy mildew. The virus contained two species of ssRNA with molecular weight (MW) of 1.05 × 106 and 0.53 × 106. One polypeptide with a MW of 37.5 × 103 was associated with whole virus. Purified preparations consisted of two components, the top component consisting primarily of empty shells. The A260/A280 UV absorbance ratio for the bottom component ranged from 1.25 to 1.35. The partially purified virions were isometric, approximately 32 nm in diameter, and had projections of approximately 4 nm on the virion surface. This virus may be related to the type A virus in Sclerophthora macrospora. Key words: mycovirus, downy mildew, Helianthus annuus.

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Races of Isolates of Plasmopara halstedii from Spain and Studies on Their Virulence

Plant Disease ◽

10.1094/pdis.2002.86.7.736 ◽

2002 ◽

Vol 86 (7) ◽

pp. 736-740 ◽

Cited By ~ 30

Author(s):

M. L. Molinero-Ruiz ◽

J. Domínguez ◽

J. M. Melero-Vara

Keyword(s):

Downy Mildew ◽

High Frequency ◽

Fungal Genome ◽

Central Spain ◽

Plasmopara Halstedii ◽

Fungal Isolates ◽

Race 1 ◽

New Race ◽

New System

Plants infected with downy mildew were collected from 1994 to 2000 in sunflower fields in Spain. The race of 102 bulk isolates of Plasmopara halstedii obtained from them was determined by inoculation of sunflower lines traditionally used as differentials for characterization of the pathogen. Nine different races of the fungus were determined. Although race 1 was most common and was the only one found in central Spain, races 4, 6, and 7 were widespread in southern Spain. The results allowed the identification of a new race of the pathogen, race 10, and of a race not previously reported in Europe, race 8. According to the proposal of a new system for characterization of the isolates of P. halstedii in the late 1990s, Coded Virulence Formulae (CVF) were assigned to bulk isolates and single-sporangium (ss) isolates obtained from them. The CVF of the bulk isolates (CVFi) did not always fit with the previous designation. Similarly, ss isolates from the same bulk isolate exhibited different CVF, not only among themselves, but also compared with the CVF of the source isolate. Although a revision of the differential lines used to perform the racial characterization of fungal isolates seems to be needed, the occurrence of a diversity of genotypes in field populations of P. halstedii and a high frequency of recombination and/or mutation of the fungal genome is also suggested.

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Virulence Characterization of Single-Zoospore Isolates of Sclerospora graminicola from Pearl Millet

Plant Disease ◽

10.1094/pdis.1998.82.7.747 ◽

1998 ◽

Vol 82 (7) ◽

pp. 747-751 ◽

Cited By ~ 10

Author(s):

R. P. Thakur ◽

B. Pushpavathi ◽

V. P. Rao

Keyword(s):

Latent Period ◽

Downy Mildew ◽

Pearl Millet ◽

Significant Variation ◽

Disease Incidence ◽

Sclerospora Graminicola ◽

Virulence Pattern ◽

Hybrid Cultivar ◽

Experimental Runs

Sclerospora graminicola, the causal agent of downy mildew in pearl millet, is well-known for variation in its virulence pattern. Nine single-zoospore isolates (Sg 026-Z-1 to Sg 026-Z-9) derived from an oosporic isolate Sg 026 from a pearl millet F1 hybrid cultivar Nath 4209 grown in a farmer's field in a village, Veelad, in Maharashtra state, India, and three controls (Sg 026, Field-1, and Field-2) were evaluated for their virulence in two experimental runs in a greenhouse. The isolates were maintained on pot-grown seedlings of a highly susceptible pearl millet line, 7042S, in a greenhouse through asexual (sporangial) generations. Pot-grown seedlings of six pearl millet potential differential lines/cultivars (7042S, NHB 3, MBH 110, ICMH 451, 843B, and 852B) were spray-inoculated with a sporangial suspension (5 × 105 sporangia ml-1) and maintained in a greenhouse at 25 ± 2°C. Data were recorded for latent period (days) and disease incidence (%), from which a virulence index (incidence × latent period-1) was calculated to quantify disease-causing potential of isolates. Results indicated significant variation in latent period, incidence, and virulence index among isolates. The isolates were classified into four distinct pathotype groups based on their virulence indices on six pearl millet lines. Because of the significant variation for virulence in the S. graminicola population infecting Nath 4209, it is recommended that the hybrid be regularly monitored for downy mildew infection in farmers' fields, and be replaced by a resistant cultivar that is genetically unrelated to the parental lines of Nath 4209. This will help delay or avoid development of downy mildew epidemics and the resulting heavy loss to pearl millet farmers in the region.

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First Report of Cross-Infectivity of Plasmopara halstedii from Marshelder to Sunflower

Plant Disease ◽

10.1094/pdis.2002.86.8.919b ◽

2002 ◽

Vol 86 (8) ◽

pp. 919-919 ◽

Cited By ~ 6

Author(s):

T. J. Gulya

Keyword(s):

Downy Mildew ◽

The Other ◽

Plasmopara Halstedii ◽

Inoculation Method ◽

Fourth Report ◽

Metalaxyl Sensitivity ◽

Virulence Pattern ◽

Treated Seed ◽

Standard Set ◽

Race 4

In May 1999, marshelder (Iva xanthifolia Nutt.) plants with chlorotic upper leaves and abundant white sporulation on abaxial surfaces were observed in roadside ditches near Fargo, ND. Ovoid to elliptical zoosporangia (20 to 30 μm × 15 to 20 μm) that were borne on sporangiophores 400 to 500 μm long and branched monopodially at right angles were recovered from infected marshelder leaves. Dimensions of the zoosporangia and sporangiophores fall within those reported for Plasmopara halstedii (Farl.) Berl. & de Toni (1). Zoosporangia rinsed from marshelder plants were used to inoculate 3-day-old sunflower seedlings. The seedlings were immersed in a suspension of 2 × 104 zoosporangia per ml for 3 h, and planted in a greenhouse maintained at 18 to 24°C with a 16-h photoperiod. Systemic chlorosis, stunting, and sporulation were observed on sunflower plants 12 days after inoculation. Isolates from two individual marshelder plants were inoculated on a standard set of nine sunflower downy mildew differential lines, and were identified as race 3 (virulence pattern 700) and race 4 (virulence pattern 730). The marshelder isolates were evaluated for metalaxyl sensitivity by a soil drench inoculation method. Seed of an oilseed sunflower hybrid commercially treated with metalaxyl (138 g a.i./100 kg of seed) were planted in flats filled with sand and perlite (1:1, vol/vol). Three days after planting, the flats were drenched with a zoosporangial suspension (2 × 104 zoosporangia per ml) for four consecutive days. Both isolates produced 100% infection on plants grown from metalaxyl-treated seed, indicating the isolates were metalaxyl-insensitive. While over 80 species within 35 Compositae genera are reported to be hosts for P. halstedii, this is the fourth report of pathogenicity on sunflower by zoospores originating from other genera, the other three being Ambrosia (ragweed) (4), Dimorphotheca (cape marigold) (2) and Xanthium (cocklebur) (3). The cross-infectivity of the P. halstedii from Ambrosia, Iva, and Xanthium indicates that Compositae weeds may serve as a reservoir of P. halstedii to infect cultivated sunflower, and these weeds may help to perpetuate the metalaxyl-insensitive strain of P. halstedii. References: (1) G. Hall, Mycopathologia 106:205, 1989. (2) E. E. Leppik, Plant Dis. Rep. 49:940, 1965. (3) F. Viranyi, Helia 7:35, 1985. (4) I. Walcz et al. Helia 33:19, 2000.

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Symptoms Development as Tools to Differentiate Dorizontal Resistance in Sunflower

Agrotek ◽

10.30862/agt.v2i6.529 ◽

2018 ◽

Vol 2 (6) ◽

Author(s):

Cipta Meliala ◽

Felicity Fear ◽

Denis Tourvieille de Labrouhe

Keyword(s):

Downy Mildew ◽

Natural Infection ◽

Resistance Mechanism ◽

Good Method ◽

Vegetative Stage ◽

Horizontal Resistance ◽

Symptom Development ◽

Plasmopara Halstedii ◽

Controlled Conditions ◽

Symptom Progression

Downy mildew symptoms caused by Plasmopara halstedii encountered in sunflower plantation are varied. This variation may be related to the resistance mechanism presented by plant to the invasion of the fungus. Our objectives were firstly is to evaluate symptom development after fungus race 710 inoculation on some vegetative stage of susceptible hybrid. Second objective is to evaluate the reaction some sunflower genotypes after fungus inoculation. The study was conducted under controlled conditions or under netting cages in the field. The development of downy mildew symptoms were affected by all factors studied. Shoot inoculation may present a good method to produce downy mildew symptom similar to the natural infection. Downy mildew symptom progression may be used to screen a genotype with a horizontal resistance.

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Spectral characterization of fungal diseases downy mildew, powdery mildew, black-foot and Petri disease on Vitis vinifera leaves

International Journal of Remote Sensing ◽

10.1080/01431161.2021.1929542 ◽

2021 ◽

Vol 42 (15) ◽

pp. 5680-5697

Author(s):

Pâmela A. Pithan ◽

Jorge R. Ducati ◽

Lucas R. Garrido ◽

Diniz C. Arruda ◽

Adriane B. Thum ◽

...

Keyword(s):

Powdery Mildew ◽

Vitis Vinifera ◽

Downy Mildew ◽

Fungal Diseases ◽

Spectral Characterization ◽

Petri Disease ◽

Black Foot

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DISTRIBUTION AND RACE COMPOSITION OF DOWNY MILDEW (Plasmopara halstedii (Farl.) Berl. and de Toni) IN BULGARIA / EXTENSION Y RAZAS DEL MILDIU (Plasmopara halstedii (Farl.) Berl. y de Toni) EN BULGARIA / ÉTENDUE ET RACES DE LA ROUILLE (Plasmopara halstedii (Farl.) Berl. and de Toni) EN BULGARIE

Helia ◽

10.1515/helia.2000.23.33.25 ◽

2000 ◽

Vol 23 (33) ◽

pp. 25-32

Author(s):

P.S. Shindrova

Keyword(s):

Downy Mildew ◽

Resistance Gene ◽

The Other ◽

Plasmopara Halstedii ◽

North West ◽

North East ◽

Race 1 ◽

Race 2 ◽

Production Areas ◽

Number Of Authors

SUMMARY Downy mildew caused by the fungus Plasmopara halstedii is the main disease on sunflower in Bulgaria. In recent years a number of authors have reported the occurrence of new more virulent races of the pathogen. According to other authors these races demonstrate resistance to the fungicides used up to now. This fact is rather alarming and imposes the necessity of annual researches with the aim of following the changes in the downy mildew race variability. In the period 1995-1997 downy mildew isolates were collected from the following locations: Bourgas, Boyanovo, Karnobat, Ognyanovo, Selanovtsi, Kroushari, Lovech, Koubrat, Brashlyan, Sitovo, Tervel, Targovishte, IWS “Dobroudja” and Dobrich. The samples were assessed for virulence on a set of sunflower differential - lines under greenhouse conditions. The obtained results do not reveal a great race variability of downy mildew population in Bulgaria. In the period of study two races of the pathogen were identified: race 1 which infects the differential lines without genes for resistance to the pathogen. It is distributed in all sunflower production areas of the country. The other one is race 2. It is of limited distribution and has been registered in individual fields of north-east and north-west Bulgaria. It attacks the differential lines carrying the resistance gene Pl-1.

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