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.

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.

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

2021 ◽  
Vol 7 (7) ◽  
pp. 549
Author(s):  
Rita Bán ◽  
Attila Kovács ◽  
Nisha Nisha ◽  
Zoltán Pálinkás ◽  
Mihály Zalai ◽  
...  
Keyword(s):  
Downy Mildew ◽  
European Countries ◽  
Actual Data ◽  
Plasmopara Halstedii ◽  
Virulence Phenotype ◽  
Virulence Pattern ◽  
Few Data

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.

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

Plant Disease ◽  
2002 ◽  
Vol 86 (7) ◽  
pp. 736-740 ◽  
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.

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.

Symptoms Development as Tools to Differentiate Dorizontal Resistance in Sunflower

Agrotek ◽  
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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