Multiplication kinetics of Flavescence dor,e phytoplasma in broad bean. Effect of phytoplasma strain and temperature

The multiplication kinetics of the Flavescence dor,e phytoplasma in broad bean after inoculation by the experimental vector Euscelidius variegatus was determined. The number of phytoplasma cells, measured by quantitative real-time PCR in the aerial parts of the plants, increased exponentially over the time. After 22 to 30 days post inoculation, when symptoms appeared, bacterial growth reached a stationary phase. Whatever the time following inoculation there were no statistical differences between numbers of phytoplasma cells in plants infected by Map-FD1 (FD-CAM05) and Map-FD2 (FD92 and FD-PEY05) genotype strains. On the contrary, temperature had an influence on Flavescence dor,e phytoplasma multiplication which was nearly twice as fast in broad beans incubated at 25 A degrees C than in broad beans incubated at 20 A degrees C. At 25 A degrees C, plants expressed symptoms 1 week earlier. In a context of climate change, the consequences of a global warming on the Flavescence dor,e epidemics are discussed.