Évaluation de maladies racinaires du soya dans des champs de la Montérégie en 2014 et 2015

2018 ◽  
Vol 98 (1) ◽  
pp. 25-35
Author(s):  
Yvan Faucher ◽  
Sylvie Rioux ◽  
Nicole Bourget ◽  
Sylvie Thibaudeau ◽  
Brigitte Duval ◽  
...  
Keyword(s):  
Rhizoctonia Solani ◽  
Phytophthora Sojae ◽  
Thielaviopsis Basicola

Un inventaire des maladies racinaires du soya causées par des champignons et des oomycètes a été réalisé en 2014 et 2015 dans 80 champs situés en Montérégie et 4 au Centre-du-Québec. Douze plantules au stade de deux feuilles trifoliées ont été prélevées par champ pour évaluer l’état sanitaire de leurs racines (indice racinaire) selon une échelle de 1 à 5 (1 = belles racines abondantes ; 5 = nécroses et peu de racines), et pour révéler dans ces racines, à l’aide de techniques de mise en culture, la présence de champignons et d’oomycètes pathogènes. L’indice racinaire moyen pour l’ensemble des champs était de 2,6 en 2014 et 3,2 en 2015. Des espèces de Pythium et de Fusarium étaient présentes dans presque 100 % des champs chaque année, alors que Rhizoctonia solani et Thielaviopsis basicola ont été plus abondants en 2015 (88 % des champs) qu’en 2014 (52 %). Phytophthora sojae n’a été isolé d’aucune racine, mais l’a été à partir des sols de 37 % des champs. Les espèces de Fusarium les plus fréquentes étaient F. solani, F. oxysporum et F. equiseti, présentes dans au moins 60 % des champs. La méthode d’analyse « stepwise » a sélectionné trois facteurs pour expliquer la variation de l’indice racinaire, dont deux ont montré des différences significatives entre leurs niveaux, soit le type de semence (indice plus élevé pour non-OGM que pour OGM) et le nombre d’années en culture de soya au cours des quatre dernières années (indice augmentant avec le nombre d’années). Le travail du sol a été le seul facteur sélectionné pour expliquer la variation des Fusarium totaux (somme diminuant avec l’intensité du travail de sol).

A Fungicide Application Decision (FAD) Support System for Postbloom Fruit Drop of Citrus (PFD)

2002 ◽  
Vol 3 (1) ◽  
pp. 16 ◽  
Author(s):  
Natália A. R. Peres ◽  
Soonho Kim ◽  
Howard W. Beck ◽  
Nilton L. Souza ◽  
Lavern W. Timmer
Keyword(s):  
Rhizoctonia Solani ◽  
Support System ◽  
Thielaviopsis Basicola ◽  
Seedling Disease ◽  
Cotton Seedling ◽  
Fungicide Application ◽  
Disease Complex ◽  
Fruit Drop ◽  
Application Decision ◽  
Seedling Diseases

Surveys were conducted to identify fungi associated with postemergence cotton seedling disease in Missouri. Samples consisted of 10 cotton seedlings, 2 to 3 weeks after emergence, with symptoms of seedling diseases collected from a 0.25 ha area in each of 60 fields in 1997 and 1998. Four genera of fungi were cultured from the roots (Fusarium, Pythium, Rhizoctonia, and Thielaviopsis) and three species were identified: Rhizoctonia solani, Thielaviopsis basicola, and Pythiumultimum. Rhizoctonia solani, T. basicola, and P. ultimum were cultured from seedlings in 70%, 47%, and 15% of fields sampled in 1997, respectively, and 55%, 17%, and 5% of fields sampled in 1998, respectively. Repeated tests of pathogenicity confirmed that R. solani AG-4, T. basicola, and P. ultimum were major causal agents of postemergence cotton seedling disease in Missouri. This study provides the first documentation on the distribution and frequency of fungi associated with postemergence seedling disease complex of cotton based on a survey of randomly selected fields. Accepted for publication 10 July 2002. Published 31 July 2002.

Fungi Associated With Postemergence Cotton Seedling Disease in Missouri

2002 ◽  
Vol 3 (1) ◽  
pp. 7 ◽  
Author(s):  
J. A. Wrather ◽  
B. Phipps ◽  
C. S. Rothrock
Keyword(s):  
Rhizoctonia Solani ◽  
Thielaviopsis Basicola ◽  
Seedling Disease ◽  
Cotton Seedling ◽  
Disease Complex ◽  
Seedling Diseases

Surveys were conducted to identify fungi associated with postemergence cotton seedling disease in Missouri. Samples consisted of 10 cotton seedlings, 2 to 3 weeks after emergence, with symptoms of seedling diseases collected from a 0.25 ha area in each of 60 fields in 1997 and 1998. Four genera of fungi were cultured from the roots (Fusarium, Pythium, Rhizoctonia, and Thielaviopsis) and three species were identified: Rhizoctonia solani, Thielaviopsis basicola, and Pythiumultimum. Rhizoctonia solani, T. basicola, and P. ultimum were cultured from seedlings in 70%, 47%, and 15% of fields sampled in 1997, respectively, and 55%, 17%, and 5% of fields sampled in 1998, respectively. Repeated tests of pathogenicity confirmed that R. solani AG-4, T. basicola, and P. ultimum were major causal agents of postemergence cotton seedling disease in Missouri. This study provides the first documentation on the distribution and frequency of fungi associated with postemergence seedling disease complex of cotton based on a survey of randomly selected fields. Accepted for publication 9 July 2002. Published 22 July 2002.

scholarly journals A Comparative Study of Two Components of the Poinsettia Root Rot Complex

1971 ◽  
Vol 30 (1-8) ◽  
pp. 419-453
Author(s):  
Robert S. Perry
Keyword(s):  
Environmental Factors ◽  
Comparative Study ◽  
Rhizoctonia Solani ◽  
Root Rot ◽  
Pythium Ultimum ◽  
Thielaviopsis Basicola ◽  
Disease Symptoms ◽  
Factors Affecting

THE MOST IMPORTANT pathological problem encountered by commercial growers of poinsettias ( Euphorbia piilcheirima Willd.) is caused by a complex of fungi composed of Thielaviopsis basicola (Berk. & Br.) Ferr., Rhizoctonia solani Kuhn, and Pythium ultimum Trow. Collectively these three organisms cause a condition referred to as the poinsettia root rot complex. Since more research has been conducted on P. ultimum and R. solani than on T. basicola, the present research was originally designed to investigate some of the environmental factors affecting the growth of Thielaviopsis and the development of the root rot caused by it. However, another fungus, Chalaropsis thielavioides Peyronel, frequently was obtained in isolations from diseased greenhouse poinsettias. Since C. thielavioides had not been reported as being a part of the poinsettia root rot complex, the author decided to investigate its importance as a pathogen on poinsettias. Numerous similarities between C. thielavioides and T. basicola were evident. The object of this work was to compare the two fungi. Prior to undertaking such a study, the pathogenicity of Chalaropsis on poinsettias had to be established. A comparison of Chalaropsis and two isolates of Thielaviopsis was made to determine the effects of environment on the growth of the fungi and the ability of the two fungi to produce disease symptoms on poinsettias.

Ultrastructure of Melanin Formation in Curvularia sp., Alternaria sp., and Drechslera Sorokiniana

1977 ◽  
Vol 35 ◽  
pp. 398-399
Author(s):  
M. H. Wheeler ◽  
W. J. Tolmsoff ◽  
A. A. Bell
Keyword(s):  
Potassium Phosphate ◽  
Thielaviopsis Basicola ◽  
Wild Type ◽  
Potassium Phosphate Buffer ◽  
Transmission Microscopy ◽  
Electron Transmission ◽  
Melanin Formation ◽  
Before And After ◽  
Alternaria Sp ◽  
Electron Transmission Microscopy

(+)-Scytalone [3,4-dihydro-3,6,8-trihydroxy-l-(2Hj-naphthalenone] and 1,8-di- hydroxynaphthalene (DHN) have been proposed as intermediates of melanin synthesis in the fungi Verticillium dahliae (1, 2, 3, 4) and Thielaviopsis basicola (4, 5). Scytalone is enzymatically dehydrated by V. dahliae to 1,3,8-trihydroxynaphthalene which is then reduced to (-)-vermelone [(-)-3,4- dihydro-3,8-dihydroxy-1(2H)-naphthalenone]. Vermelone is subsequently dehydrated to DHN which is enzymatically polymerized to melanin.Melanin formation in Curvularia sp., Alternaria sp., and Drechslera soro- kiniana was examined by light and electron-transmission microscopy. Wild-type isolates of each fungus were compared with albino mutants before and after treatment with 1 mM scytalone or 0.1 mM DHN in 50 mM potassium phosphate buffer, pH 7.0. Both chemicals were converted to dark pigments in the walls of hyphae and conidia of the albino mutants. The darkened cells were similar in appearance to corresponding cells of the wild types under the light microscope.

Mesure de la colonisation saprophytique en compétition de Rhizoctonia solani Kühn dans les sols et substrats

Agronomie ◽  
1981 ◽  
Vol 1 (6) ◽  
pp. 513-517 ◽  
Author(s):  
Pierre CAMPOROTA ◽  
Reine CAMPOROTA
Keyword(s):  
Rhizoctonia Solani

Sclerotia of the plant pathogen Rhizoctonia solani Kühn as a new source of bioactive compounds

Planta Medica ◽  
2008 ◽  
Vol 74 (09) ◽  
Author(s):  
KA Aliferis ◽  
S Jabaji
Keyword(s):  
Rhizoctonia Solani ◽  
Bioactive Compounds ◽  
Plant Pathogen
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