Know more

Our use of cookies

Cookies are a set of data stored on a user’s device when the user browses a web site. The data is in a file containing an ID number, the name of the server which deposited it and, in some cases, an expiry date. We use cookies to record information about your visit, language of preference, and other parameters on the site in order to optimise your next visit and make the site even more useful to you.

To improve your experience, we use cookies to store certain browsing information and provide secure navigation, and to collect statistics with a view to improve the site’s features. For a complete list of the cookies we use, download “Ghostery”, a free plug-in for browsers which can detect, and, in some cases, block cookies.

Ghostery is available here for free: https://www.ghostery.com/fr/products/

You can also visit the CNIL web site for instructions on how to configure your browser to manage cookie storage on your device.

In the case of third-party advertising cookies, you can also visit the following site: http://www.youronlinechoices.com/fr/controler-ses-cookies/, offered by digital advertising professionals within the European Digital Advertising Alliance (EDAA). From the site, you can deny or accept the cookies used by advertising professionals who are members.

It is also possible to block certain third-party cookies directly via publishers:

Cookie type

Means of blocking

Analytical and performance cookies

Realytics
Google Analytics
Spoteffects
Optimizely

Targeted advertising cookies

DoubleClick
Mediarithmics

The following types of cookies may be used on our websites:

Mandatory cookies

Functional cookies

Social media and advertising cookies

These cookies are needed to ensure the proper functioning of the site and cannot be disabled. They help ensure a secure connection and the basic availability of our website.

These cookies allow us to analyse site use in order to measure and optimise performance. They allow us to store your sign-in information and display the different components of our website in a more coherent way.

These cookies are used by advertising agencies such as Google and by social media sites such as LinkedIn and Facebook. Among other things, they allow pages to be shared on social media, the posting of comments, and the publication (on our site or elsewhere) of ads that reflect your centres of interest.

Our EZPublish content management system (CMS) uses CAS and PHP session cookies and the New Relic cookie for monitoring purposes (IP, response times).

These cookies are deleted at the end of the browsing session (when you log off or close your browser window)

Our EZPublish content management system (CMS) uses the XiTi cookie to measure traffic. Our service provider is AT Internet. This company stores data (IPs, date and time of access, length of the visit and pages viewed) for six months.

Our EZPublish content management system (CMS) does not use this type of cookie.

For more information about the cookies we use, contact INRA’s Data Protection Officer by email at cil-dpo@inra.fr or by post at:

INRA
24, chemin de Borde Rouge –Auzeville – CS52627
31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018

Menu logoprincipal INRA logo gnis Potato dynamics LTD ARVALIS FN3PT GERMICOPA

Potato tuber blemishes: understanding & diagnosis

Black scurf

Fungus, Adelomycete

Latin name : Rhizoctonia solani

Diagnostic characters for visual diagnosis

  • Black scurf patches on tuber correspond to compact masses of mycelium called sclerotia (resting form of the fungus) tightly attached to the tuber skin and which are readily rubbed or scraped off. Sclerotia do not penetrate or damage the tuber skin
  • Sclerotia are raised, dark brown to black, irregular in size and shape, on the surface of the tuber. They are ranging from small, flat, barely visible patches to large, raised lumps
  • Brown strands of R. solani mycelium can sometimes be observed around the sclerotia

                                                                                                                                                                                          

Notes on confirmatory diagnostics

  • Pieces of  sclerotia  from tubers are cut  and transferred to general isolation media (malt Streptomycine, alcaline water agar, etc..) or selective ones (eg modified Ko & Hora medium), then incubated for 2 to 3 days at 20 °C.
  • Mycelium of  R. solani  is colourless  when young, it becames brown at maturity 
  • Observation of the mycelium under the microscope show hyphae portioned into individual cells by a septum,  often branched at 90° angles and which contain more than 3 nuclei per hyphal cell
  • AG3 is the main anastomosis group (AG's) producing sclerotria on potato tubers, but other AG's may be associated with the disease but are less frequent and less aggressive
  •  Identification of anastomosis group is possible by isolates confrontation and microscopic  observation of the hyphal fusion, sequencing of R. solani ITS, using PCR-RFLP

                                                                                                        

Specific references:

Campion et al (2003). European Journal of Plant Pathology, 109, 983-992.

Carling D.E & Leiner R.H (1986). Phytopathology, 76, 725-729.

Castro et al. (1988). Phytopathology  ,78,  1287-1292.  

Fiers et al (2011).  Mycologia, 103(6), 2011, pp. 1230–1244. DOI: 10.3852/10-231

Woodhal et al (2008). Plant Pathology, 57, 897–905 Doi: 10.1111

more symptoms

Possible confusing symptoms :