Potential role of almond in sharka epidemics : susceptibility under controlled conditions to the main types of plum pox potyvirus and survey for natural infections in France

UMR BGPI - Equipe 6International audienceThe changes in cropping conditions of almond and the development of efficient tools for the detection and characterization of plum pox potyvirus (PPV) populations have led us to reassess the potential susceptibility of this species to sharka disease and its role as a virus reservoir. The susceptibility of almond cv. Ai' to nine isolates, representative of the known diversity among PPV populations, was assessed under controlled conditions. Most isolates were able to infect almond, by graft or aphid inoculation, causing generalized stable infections without any obvious sharka symptoms. These infected almonds were found to constitute a potential source of virus for aphid vectors, mainly in the case of M isolates. Surveys were carried out in the south of France, in foci of M and D strains of PPV, to evaluate the presence of natural infections of almond. No typical symptoms were observed and the virus was never detected. It can be assumed that the actual limited prevalence of PPV in France does not lead to a sufficiently high inoculum pressure to allow almond trees to be infected