ABSTRACT
In the framework of a research programme on integrated control of Polymyxa graminis Led., vector of the barley yellow mosaic virus (BYMV) on winter barley in Western Europe, the plant-bait technique is optimised and standardised for identification of factors affecting inoculum potential and multiplication of this obligate parasite.
Barley seedlings are grown in glass tubes on a soil/sand mixture watered with half-strength Hoagland solution, at saturation during the second and third week and sparsely otherwise. The assay is performed in controlled environmental cabinets with a photoperiod of 12 h at 13 000 lux. Root infection is assessed, with the help of a microscope, in roots boiled in lactophenol with cotton blue, or in homogenates of roots treated with KOH.
The highest levels of thalli (zoosporangial or cystosoral) and of cystosori are observed after four and seven weeks, respectively, when the plants are grown at night/day temperatures of 15–20°C, compared to 10–15, 20–25 or 25–30°C.
Serial dilutions of infested soil with sterilised sand permit comparison of inoculum potential in soils.
