Mechanism of Schizaphis graminum in transmitting maize dwarf mosaic virus RESISTANCE INDEX SYSTEM OF MAIZE TO DWARF MOSAIC VIRUS Efficiency Evaluation of Two Molecular Markers Linked with Resistance to Maize Dwarf Mosaic Disease Identification and Mapping of a New Resistant Gene to Sugarcane Mosaic Virus in Maize Molecular Tagging of a New Resistance Gene to Maize Dwarf Mosaic Virus Using Microsatellite Markers ANALYSIS OF FACTORS AFFECTING APHID TRANSMISSION OF MAIZE DWARF MOSAIC VIRUS