Spread of Maize Dwarf Mosaic Virus from Johnsongrass to Corn

Abstract

. plants to the east and west of these Knoke, J. K., Louie, R., Madden, L. V., and Gordon, D. T. 1983. Spread of maize dwarf mosaic mares in eah row were surveye virus from johnsongrass to corn. Plant Disease 67:367-370. resulting in 200 10-plant samples per plot. Spread of maize dwarf mosaic virus (MDMV) from introduced virus-infected johnsongrass to Disease incidence was recorded as the adjacent susceptible corn in experimental plots was evaluated during 1979 and 1980. The proportion of plants in each sample that relationship between MDM incidence in corn and distance from the source was adequately showed disease symptoms. Straight-line described by the model Y = a(exp(-bD)), where Y is disease incidence at distance D from the distances from the johnsongrass to the source, b is the spread coefficient, and a is the scaling factor. In both years, b was significantly center of each 10-plant sample were greater than zero, demonstrating that MDMV spread to the corn test plots. In control plots with no calculated. For regression analysis, intentionally placed virus source, b values and disease incidence were lower than in test plots. For a incidence data in each plot were grouped single planting in 1979, the steepness of the gradient of disease incidence from the source (quantified in 1-m intervals, eg, all observations by b) decreased with time as fewer plants remained uninfected. For two successive plantings in 1980, no significant difference in b values was observed. MDMV spread also was not related to 20-21 m from johnsongrass were prevalent wind direction. No spread of maize chlorotic dwarf virus (MCDV) to corn was observed averaged to calculate incidence at 20.5 m. by symptomatology even though 90 and 50% of the johnsongrass plants were infected in 1979 and In 1980, PAG 246006 and Agway 1980, respectively, as indicated by enzyme-linked immunosorbent assay. The leafhopper vector of XP708 were each machine-planted in MCDV, Graminella nigrifrons, was also present during both years. The presence of MDMV in the four plots on 11 June, 15 July, 8 August, control plots indicates that there were virus sources other thanjohnsongrass or that MDMV moved and 4 September. The sweet corn hybrid more than 400 m from johnsongrass to the control plots. Agway XP708 is susceptible to MDMV and MCDV, whereas the dent corn