Abstract
The conditions favouring the infection of cowpea mesophyll protoplasts by Sonchus yellow net virus (SYNV) were determined. When 3 x 106 protoplasts were inoculated with 60 µg SYNV in 40% polyethylene glycol, 3 mM-CaCl2 at room temperature, over 90% of the surviving protoplasts became infected. Infectivity tests showed that the virus could be detected 12 h after inoculation.