RELATION BETWEEN NITROGEN NUTRITION AND VIRUS SUSCEPTIBILITY OF MAIZE TO MAIZE-DWARF MOSAIC-VIRUS INFECTION

Two susceptible (Dea SC and Mima SC) and two tolerant (Carmina SC and Florencia SC) maize genotypes to maize dwarf mosaic potyvirus (MDMV-A strain) infection were compared in greenhouse experiments at different levels of nitrogen fertilization. Enhanced nitrogen supply increased the number of diseased plants both in susceptible and in tolerant host-pathogen combinations. By increasing the nitrate nitrogen level both the symptom severity and the virus content increased. When evaluating virus resistance of breeding lines or varieties, it is always necessary to compare the results of greenhouse tests with the field experiments, because of the different nitrogen levels of soils.