Characteristics of Serially Produced Zoospore Suspensions of Polymyxa betae for Transmission of Beet Necrotic Yellow Vein Virus

Zoospore suspensions of Polymyxa betae were analysed for their potential as inocula to infect sugar beet plants with beet necrotic yellow vein furovirus. The infectivity could be maintained when zoospore suspensions were serially transferred. When zoospore-producing seedlings were individually transferred some of these seedlings lost their infectivity after several passages. Infectivity was first detected in suspensions within I day after inoculation of the plant by zoospores. The suspensions remained infectious for at least 10 h after removal of the plants producing viruliferous zoospores. Both the number of test plants infected and the concentration of virus that developed were greater at 25 C than at 20 C.