Effects of Maize Dwarf Mosaic Virus on Mechanically Inoculated Maize1

Abstract

Effects of maize dwarf mosaic virus (MDMV) on maize (Zea mays L.) were determined by growing selected inbred lines with diallel crosses among them in an area free of johnsongrass (Sorghum halepense L.). Mechanical inoculation with MDMV produced significant effects on grain yield and several other plant traits but the differences were small compared to those observed under natural infection. Two inbred lines, T8 and VaLE8, did not react the same under conditions of natural and mechanical inoculation. Inoculated plants had more gray leaf spot, caused by Cercospora zeae‐maydis (Tehon and Daniels), than uninoculated plants. In paired‐row plots, maximum reduction was 34% for yield and 14% for plant height. Significant mean effects ou yield and moisture content of grain and days to silk were related to time of inoculation. One inbred line, H84, showed severe symptoms when inoculated 10 days after planting but showed mild symptoms when inoculated later. No cross that included Oh07B was measurably affected by MDMV. The most productive hybrid was Oh07B ✕ Oh43, a cross between a very resistant and a very susceptible inbred line. Resistance was dominant in Oh07B, but the intermediate resistance of T8 and VaLE8 was recessive to susceptibility in Oh43 and Pa9l.Stunting, leaf discoloration, barrenness, and severe loss of yield were not induced by mechanical inoculation and subsequent infection with MDMV. We concluded that MDMV is only a moderately destructive virus of maize; therefore, other agents must be contributing to the severely damaging syndrome in maize‐johnsongrass associations.