Reactions in Maize Infected with Swedish Isolates of Barley Yellow Dwarf (BYDV)

Nine cultivars of maize (Zea mays L.) were tested for susceptibility to BYDV under three temperature ranges in the greenhouse. Three Swedish isolates of BYDV were used, two specifically transmitted by Rhopalosiphum padi (L.) (39/78) and by Sitobion avenae (Fabr.) (27/77), respectively, and the third by both species (70). The virus isolates were transmitted successfully from different grasses to maize and from infected maize to the susceptible oat cultivar "Sol II" by the respective aphid species. S. avenae showed very high ability to transmit the S. avenae specific isolate to and from maize plants.
The main symptoms that developed on maize were fine chlorotic irregular spots, reddish purple discoloration and malformed leaves.
The relationship between maize cultivar, temperature and percent of infection is discussed. Enzyme-linked Immunosorbent Assay (ELISA) was used with success to detect the virus isolate 27/77 in susceptible and symptomless maize plants.
Electron microscopy of maize (cv. LG ll) infected with the 27/77 isolate of BYDV revealed virus-like particles, about 22 nm in diameter, in the nuclei of companion cells, in the plasmodesmata connecting companion cells with mature sieve tubes, in the lumen of mature sieve tubes and in xylem tracheal elements.