Effects of temperature and CO2 on phytoplasma multiplication pattern in vector and plant.

Multiplication patterns of two phytoplasmas, chrysanthemum yellows and 'flavescence dore?e' were characterized over time in insect vectors and plant hosts under different climatic (temperature, T, and CO2) conditions. Acquisition and transmission experi- ments were run in parallel in two phytotrons (P1 and P2). Euscelidius variegatus and daisy were used as chrysanthemum yellows hosts, Scaphoideus titanus and broad bean as 'flavescence dore?e' hosts. Phytoplasma concentration was measured three times in insects and four in plants, at different days after acquisition and inoculation, respectively. Latent period in the vector was also evaluated for both phytoplasmas under the two conditions. On average, phytoplasma multiplication was faster under cooler condi- tions in insects (P1, 18-22°C; CO2 400 ppm) and under warmer conditions in plants (P2, 22-26°C; CO2 800 ppm). An influence of T and CO2 concentrations was observed for chrysanthemum yellows latency in the vector only. Results suggest that T and CO2 influence on phytoplasma multiplication is host-dependent.