Effect of postinoculation temperature treatments on susceptibility of corn to maize dwarf mosaic and sugarcane mosaic Potyviruses

Four corn genotypes (A632xVa35, Va35, CO255, and Mo17) were inoculated with maize dwarf mosaic Potyvirus-A (MDMV-A), sugarcane mosaic Potyvirus-MB (SCMV-MB), and sugarcane mosaic Potyvirus-A (SCMV-A) in greenhouse. After inoculation plants were divided into three groups and put in three growth chambers at constant temperature of 10, 14, and 24 degrees-C. Four days later each group of plants was transferred to the greenhouse. Number of plants with mosaic symptoms was recorded every 1 or 2 days until the disease incidence did not increase. The average incubation periods were 13.7, 13.1, and 9.0 days, and average disease incidence were 34,35, and 66% at temperature treatments of 10, 14, and 28 degrees-C respectively. Lower temperature treatments altered in different degree the pathogenicity of the three virus strains which manifested in length of incubation period and in percentage of diseased plants. SCMV-MB seemed to be less susceptible to lower temperature than MDMV-A and SCMV-A.