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 Logo Principal

Encyclop'Aphid : l'encyclopédie des pucerons

Encyclop'APHID

Viruses

It has been little over 100 years that viruses have been known to exist in plants and humans The viruses have become important research models for molecular biology. Their nucleic acids are the most well known, as they carry a restricred amount of genetic information that is relatively easy to study and manipulate The phytopathogenic viruses are endowed with an impressive aptitude for penetrating the plant cell and inserting foreign genetic information.

The viral diseases of plants

The viruses are obligatory parasites, proliferating to the detriment of their host. They disturb the physiological processes of the plant's organs and tissues. The symptoms are signalled by changes to colour, tissue deformation and necroses. These disturbances can lead to substantial yield losses (including fall in the number of seeds and their weight) and decline in quality (modification of appearance of fruit, texture and so on).

Aphid vectors of viruses

The alate aphids create indirect contacts between plants that are fixed and distant from each other. When they move around, they feed on plants by sucking up the sap, and viruses are ingested with it if the plant is contaminated. In this way they transmit and propagate the highly numerous viral species in the environment. There are several thousand different associations involving a species of aphid, a virus and a plant. A single species of aphid can transmit numerous different viruses: Myzus persicae, for example, transmits over 100 viral species. Just one virus can infect several plant species: many wild and cultivated Poaceae, for instance, can harbour barley yellow dwarf virus (BYDV). Finally a single virus can be transmitted by several species of aphid: the situation for example for BYDV with Rhopalosiphum padi, Sitobion avenae and Metopolophium dirhodum.

Transmission effectiveness

The effectiveness of transmission is linked to the insect’s host-seeking behaviour. When the aphid lands on a plant, it makes a brief trial attack, piercing superficially to taste if the potential host is suitable. If it is, the aphid stays still, thrusts its stylets in as far as the phloem and has a lengthy feed. Otherwise it flies off again in search of another plant. But it can extract a virus as easily in a trial run as during the real feeding action. The viruses and the mode of transmission are specific to one type of piercing and sucking attack.

The principal phases of transmission are:

  • Acquisition: the vector takes up a virus from a diseased plant.
  • Latent period: lapse of time between virus acquisition and the exact moment the vector will be able to infect a healthy plant. It then becomes infectious. The latent period concerns the vector.
  • Retention: lapse of time during which the vector remains infectious after a contaminating meal.
  • Inoculation: the infectious vector’s act of injecting the virus into the plant.
  • Incubation: lapse of time between inoculation and external manifestation of symptoms on the plant.

Several modes of transmission have ben defined: non-persistent, persistent and semi-persistent, according to whether the virus is circulative or non-circulative in the aphid.