Abstract
Roots of two-rowed barley plants naturally infected with yellow mosaic virus were homogenized, after being stored in a refrigerator for 4 months, and filtered successively through 100-. 200-, and 325-mesh screens. The final filtrate was repeatedly centrifuged at 100 and 600 (or 500) rpm for 5-6 minutes alternately and a suspension of fungal spores was obtained. The majority of the fungal spores were resting spores of Polymyxa graminis Led.
Autoclaved soil was inoculated with the fungal spore suspension and barley seeds were sown. More than half of the seedlings became infected showing mosaic symptom. Infection was not obtained when a spore suspension taken from the roots of healthy plants was used.
Barley seedlings were grown on autoclaved soil inoculated with a resting spore suspension of P. graminis obtained from healthy barley roots and the leaves were mechanically inoculated with the virus. The roots of these seedlings showed infectivity. No infectivity was detected in the roots of seedlings grown on soil not inoculated with spore suspension.
Roots of naturally infected barley plants differed in infectivity according to the time of sample collection. The roots of plants showing pronounced mosaic symptom from middle of March to early April showed low infectivity. The roots of plants having obscure symptoms after middle of April showed high infectivity.
The time when the infectivity of the roots increased coincided with the time when P. graminis matured and formed abundant resting spores in the root tissues.
