Ecology, epidemiology

• Storage, source of inoculum 

As previously suggested, the two nepoviruses responsible for the short-knot , GFLV and to a lesser extent ArMV, are transmitted by nematodes belonging to the genus Xiphinema: X. index for GFLV and X. diversicaudatum for ArMV. These nematodes, which belong to the order Nemathelminths or roundworms, are able to survive for a long time in the soil (up to 1.5 meters deep which makes them not very vulnerable to nematicides), even in the absence of food. , and therefore contribute to the conservation of these two viruses. They therefore easily survive on pieces of poorly extracted roots when uprooting vines (up to 4 to 5 years).

Rather polyphagous and living in the rhizosphere of plants and in particular of the vine, they feed by pricking the roots thanks to their oral stylet and thus infect the vine. It should also be noted that their actions on the roots can lead to the formation of root galls. Once transmitted to the vine, it multiplies and migrates into the latter. 

• Transmission and dissemination of the virus

Contaminated plant material is the main source of transmission and spread of this virus. Indeed, if the latter is infected and it is used to produce scions or rootstocks, their use during grafting will ultimately result in a more or less significant proportion of contaminated plants. Subsequently, their marketing to many producers will contribute to the dissemination of knot short over long distances and to a more or less large number of new plots. Indeed, these two viruses pass easily from the rootstock to the graft and vice versa, whatever the grafting method used.

The vector nematodes also contribute to the dissemination of the short knot in the plots, but their movement capacity being reduced (<1.5 m / year), their extension remains limited. It can be amplified if the plot is on a slope. In fact, during heavy rains, the runoff that occurs entrains soil particles and viruliferous nematodes over significant distances, contributing to a more rapid and significant spread of the disease. It should be noted that the use of soil recovered from soil harboring viruliferous nematodes can also lead to the dissemination of the knot grass to other healthy plots.

Finally, let us point out that no transmission is possible by aerial vector (aphids, whiteflies, psyllids ) or by the material used for pruning; on the other hand, it can take place by the seed.