Effect of Salinity on Symptom Development of Rapid Blight on Perennial Rye

Abstract

Rapid blight is a new disease of cool season turfgrasses caused by Labyrinthula terrestris. Disease often occurs on turf irrigated with high salinity water and in areas of frequent mowing. The effects of salinity of irrigation water on symptom development were studied in the laboratory using two-week-old seedlings of perennial rye "Brightstar SLT. " Irrigation water was adjusted to 0.5, 0.8, 1.4, 1.8, 2.0, 2.3, 2.8, 4.0, 6.0 and 8.0 dS/m by adding artificial seawater. Plants were inoculated with a 2x10⁵ cells/ml suspension of Labyrinthula terrestris isolated from diseased turf in Arizona. Plants were infected, but not symptomatic, when irrigated with 0.5 dS/m water. At salinities from 0.8 to 8.0 dS/m, symptom development increased as salinity increased. These findings substantiate field observations that rapid blight becomes increasingly more severe as salinity of irrigation water increases.