Axenic culture of the downy mildew fungus Plasmopara halstedii in Agrobacterium rhizogenes-induced roots of sunflower (Helianthus annuus)

1991 ◽  
Vol 69 (12) ◽  
pp. 2709-2715 ◽  
Author(s):  
G. A. Zahka ◽  
F. Virányi
Keyword(s):  
Comparative Study ◽  
Helianthus Annuus ◽  
Downy Mildew ◽  
Agrobacterium Rhizogenes ◽  
Nutrient Medium ◽  
Axenic Culture ◽  
Root Culture ◽  
Good Source ◽  
Plasmopara Halstedii ◽  
Intact Plants

The downy mildew fungus, Plasmopara halstedii (Farlow) Berlese & de Toni, was cultured axenically in association with sunflower roots derived from petioles inoculated with Agrobacterium rhizogenes. An axenic zoosporangial suspension, obtained from sporulating cotyledons, was added to A. rhizogenes-induced root pieces on agar or in liquid nutrient medium. Roots showed profuse P. halstedii sporulation after 1 week. A comparative study in infection morphology with excised sunflower roots (not induced by A. rhizogenes) of the same cultivar showed no difference, both of which resembled P. halstedii infection in roots from intact plants. The dual-member cultures with A. rhizogenes induced roots were a good source of axenic P. halstedii inoculum, and zoosporangia remained viable for up to 2 monhts in dual-member cultures maintained at 18–20 °C. Noteworthy features were the balanced state of host and parasite and the prolific production of P. halstedii oospores. Key words: downy mildew, sunflower, Plasmopara halstedii, Helianthus annuus, root culture, Agrobacterium rhizogenes.

Host–parasite relationships in dual cultures of Helianthus annuus and Plasmopara halstedii

1987 ◽  
Vol 65 (10) ◽  
pp. 2057-2060 ◽  
Author(s):  
A. Bruce Gray ◽  
W. E. Sackston
Keyword(s):  
Helianthus Annuus ◽  
Downy Mildew ◽  
Culture Medium ◽  
Callus Tissue ◽  
Host Cells ◽  
Downy Mildew Resistance ◽  
Plasmopara Halstedii ◽  
Intact Plants ◽  
Dual Cultures ◽  
Host Parasite

The downy mildew fungus (Plasmopara halstedii) sporulated on callus tissue of sunflower (Helianthus annuus) in dual cultures on tissue culture medium. The fungus was most concentrated in the seven outermost layers of the callus. No haustoria were found inside the host cells. Healthy callus from both susceptible and resistant sunflowers was successfully inoculated with pieces of the dual cultures, giving rise to mycelium but no spores on the fresh callus. Dual cultures developed at comparable rates in both the compatible and incompatible combinations; the downy mildew resistance of intact plants was not expressed in dual cultures under the environmental conditions used.

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

Agronomy ◽  
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.

Colocation of downy mildew (Plasmopara halstedii) resistance genes in sunflower (Helianthus annuus L.)

Euphytica ◽  
1996 ◽  
Vol 91 (2) ◽  
pp. 225-228 ◽  
Author(s):  
Patricia Roeckel-Drevet ◽  
Geneviève Gagne ◽  
Said Mouzeyar ◽  
Laurent Gentzbittel ◽  
Jacqueline Philippon ◽  
...  
Keyword(s):  
Helianthus Annuus ◽  
Downy Mildew ◽  
Resistance Genes ◽  
Plasmopara Halstedii ◽  
Helianthus Annuus L

Development of a polymerase chain reaction diagnostic test for the detection of the biotrophic pathogen Plasmopara halstedii in sunflower

1999 ◽  
Vol 45 (9) ◽  
pp. 797-803 ◽  
Author(s):  
Patricia Roeckel-Drevet ◽  
Jeanne Tourvieille ◽  
Joël R Drevet ◽  
Véronique Says-Lesage ◽  
Paul Nicolas ◽  
...  
Keyword(s):  
Polymerase Chain Reaction ◽  
Helianthus Annuus ◽  
Downy Mildew ◽  
Random Amplified Polymorphic Dna ◽  
Parasitic Fungus ◽  
Sequence Information ◽  
Chain Reaction ◽  
Plasmopara Halstedii ◽  
Polymerase Chain

The obligate parasitic fungus-like organism Plasmopara halstedii (Farl.) Berl. et De Toni, is the causal agent of downy mildew disease in sunflower (Helianthus annuus). New races of this economically important parasite are regularly detected throughout the world. In addition, fungicide-resistant isolates have been reported in Europe and North America. These observations of parasite evolution, as well as the risk of propagation of the disease by infected seeds, means that it is necessary to guarantee the absence of Plasmopara halstedii in seed shipments. We report here the development of a rapid assay that can be used to detect infection by Plasmopara halstedii in plant tissues. Based on the nucleotide sequence information obtained from one cloned random amplified polymorphic DNA fragment, specific oligonucleotides were designed and used as primers for in vitro DNA amplification by polymerase chain reaction. An amplification product was detected on agarose gel stained with ethidium bromide when DNA from various Plasmopara halstedii races was tested, whereas no amplified DNA was detected when DNA from other origins was tested, including DNA from the host plant. The sensitivity of the technique was evaluated. The assay successfully reveals the presence of Plasmopara halstedii in infected sunflower plants prior to sporulation.Key words : diagnosis, polymerase chain reaction, SCAR, downy mildew, Helianthus annuus.

Early stages of infection of resistant and susceptible sunflower seedlings by three races of Plasmopara halstedii

1985 ◽  
Vol 63 (10) ◽  
pp. 1725-1729 ◽  
Author(s):  
A. Bruce Gray ◽  
W. E. Sackston
Keyword(s):  
Helianthus Annuus ◽  
Downy Mildew ◽  
Hypersensitive Reaction ◽  
Red River ◽  
Plasmopara Halstedii ◽  
Helianthus Annuus L ◽  
Red River Valley ◽  
European Race ◽  
Race 2 ◽  
Germ Tubes

Resistance in sunflower (Helianthus annuus L.) to downy mildew (Plasmopara halstedii (Farl.) Berl. et de Toni) is conditioned by a series of Pl. genes. Races 1 (European race), 2 (Red River race), and 3 (a new North American race encountered in the Red River valley in 1980) formed similar infection structures on inoculated seedlings whether susceptible or resistant to races 1 and 2; all cultivars tested were susceptible to race 3. The zoospores encysted and produced germ tubes and appressoria on the roots and hypocotyls. Penetration occurred and mycelium and haustoria developed in both compatible and incompatible host–pathogen combinations. Resistance did not appear to involve a hypersensitive reaction occurring prior to penetration.

Ultrastructure of Plasmopara halstedii containing virus-like particles

1991 ◽  
Vol 49 ◽  
pp. 216-217
Author(s):  
Thomas Freeman ◽  
Thomas Gulya
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Helianthus Annuus ◽  
Downy Mildew ◽  
Systemic Disease ◽  
Disease Symptoms ◽  
Plasmopara Halstedii ◽  
Transmission Electron ◽  
Race 2 ◽  
Standard Techniques

Mycoviruses have been found in more than 100 species of fungi and it is estimated that they may occur in as many as 500 species (Buck, 1986; Hollings, 1978; and Lemke, 1981). Mycoviruses range in size from small, isometric particles (25 nm in diameter) to long, flexuous rods exceeding 2000 nm in length, with the majority being isometric particles ranging in size from 25-50 nm (Buck, 1986). Mycoviruses hae been reported in all groups of fungi, but have been least frequently observed in the Oomycetes.Sunflower (Helianthus annuus) seedlings were inoculated with a North Dakota isolate of race 2 Plasmopara halstedii, the causal agent of sunflower downy mildew. Systemic disease symptoms developed within 14 days and samples were prepared for transmission electron microscopy using standard techniques.

Isolation and characterization of a mycovirus from Plasmopara halstedii

1992 ◽  
Vol 70 (9) ◽  
pp. 1734-1737 ◽  
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.

Lack of genetic variability in French identified races of Plasmopara halstedii, the cause of downy mildew in sunflower Helianthus annuus

1997 ◽  
Vol 43 (3) ◽  
pp. 260-263 ◽  
Author(s):  
Patricia Roeckel-Drevet ◽  
Véronique Coelho ◽  
Paul Nicolas ◽  
Jeanne Tourvieille ◽  
Denis Tourvieille de Labrouhe
Keyword(s):  
Genetic Variation ◽  
Genetic Variability ◽  
Helianthus Annuus ◽  
Downy Mildew ◽  
Random Amplified Polymorphic Dna ◽  
Initial Screening ◽  
Plasmopara Halstedii ◽  
Helianthus Annuus L ◽  
New Races

Downy mildew of sunflower (Helianthus annuus L.) incitated by Plasmopara halstedii is a potentially devastating disease. We report here the finding of two new races of P. halstedii and also two Apron35S fungicide-resistant isolates of race A. Using the random amplified polymorphic DNA (RAPD) technique as an initial screening for genetic variation within P. halstedii French races, genetic variation was not found between isolates within races 1, A, or B, and very few polymorphisms were distinguished between all French races known today.Key words: Plasmopara halstedii, race, genetic variability, RAPD.

Identification of a second linkage group carrying genes controlling resistance to downy mildew (Plasmopara halstedii) in sunflower (Helianthus annuus L.)

2001 ◽  
Vol 103 (6-7) ◽  
pp. 992-997 ◽  
Author(s):  
P. F. Bert ◽  
D. Tourvieille de Labrouhe ◽  
J. Philippon ◽  
S. Mouzeyar ◽  
I. Jouan ◽  
...  
Keyword(s):  
Linkage Group ◽  
Helianthus Annuus ◽  
Downy Mildew ◽  
Plasmopara Halstedii ◽  
Helianthus Annuus L
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