Tolerance of Cool-Season Turfgrasses to Rapid Blight Disease

Abstract

Forty‐nine different cool‐season grass cultivars representing 24 species were tested for their tolerance to the causal agent of rapid blight, Labyrinthula spp. Seeds of each grass were sown in 7.6‐cm pots and grown in the greenhouse. Plants were watered daily with deionized water for three weeks, then with artificial sea water at a concentration of 3.5 deciSiemens per meter. Experimental design was a randomized split‐plot with four replications where treatment (inoculated or non‐inoculated) was the main‐plot factor and cultivars were the sub‐plot factor. The entire experiment was replicated twice. Bulk inoculum of five Labyrinthula isolates was prepared by growing isolates on modified serum seawater agar for four days, adding colonized agar plugs to serum broth and vortexing. Cell counts of the bulk inoculum at 1.4 × 105 per ml were used for each inoculation. Plants in each pot were inoculated with 1 ml of inoculum placed on leaf tissue in the form of droplets from a syringe after wounding by trimming with scissors. Plants were rated for percent of diseased foliage. A high degree of susceptibility was observed in cultivars of rough bluegrass (Poa trivialis L.), colonial (Agrostis capillaris L.) and velvet bentgrasses (Agrostis canina L.), and perennial ryegrass (Lolium perenne L.) while certain cultivars of alkaligrass (Puccinellia distans (Jacq.) Parl.), slender creeping red fescue (Festuca rubra spp. littoralis (G. F. W. Meyer) Auquier), and creeping bentgrass (Agrostis stolonifera L.) appear to have moderate levels of tolerance.

Salinity and Salinity Tolerance Alter Rapid Blight in Kentucky Bluegrass, Perennial Ryegrass, and Slender Creeping Red Fescue

“…The KB ‘North Star’ and PRG ‘Hawkeye’ and ‘Peregrine’ had lower AULCC than other cultivars of the same species. Species and cultivar differences in these experiments were similar to those found in another study (19). The simple correlation between AULCC due to rapid blight at 2.5 dS/m reported in this paper and % disease in an earlier study (19) was 0.74 (excluding Barcrown II which was not examined previously).…”

“…The relationship between salinity and rapid blight tolerance differed in magnitude between run 1 and 2 because salinity was less in run 2 than run 1, however both had high R 2 . The correlation between salinity tolerance and rapid blight tolerance observed in this study among 12 cultivars of 3 species and earlier research that found rapid blight tolerance among 49 cultivars representing 24 cool‐season grass species to be generally related to their reported salinity tolerance (19), suggests that mechanisms of grass tolerance to salinity and to rapid blight may be similar.…”

“…Several perennial ryegrasses were susceptible to rapid blight, although as a group they are rated as moderate to highly tolerant of salinity (3). Substantial variation in rapid blight tolerance also occurred among cultivars of Kentucky bluegrass (19). Kentucky bluegrass has shown a wide range in salinity tolerance as well (7,10,22,23).…”

Labyrinthula terrestris: a new pathogen of cool‐season turfgrasses

“…Both field and greenhouse studies indicate that susceptibility of cool‐season turfgrasses to rapid blight generally increases as salt tolerance of specific varieties within a species decreases (Kopec et al ., 2004; Peterson et al ., 2005). In these studies, salt‐sensitive varieties of perennial ryegrasses and bentgrasses were significantly more susceptible to rapid blight when irrigated with water of 3.5–4.0 dS/m (approximately 2240–2560 p.p.m.…”

“…Rapid blight is most severe on salt‐sensitive varieties of turfgrasses referred to as ‘cool‐season’ turfgrasses such as rough bluegrass ( Poa trivialis ), perennial ryegrass ( Lolium perenne ), annual bluegrass ( Poa annua ) and colonial bent ( Agrostis tenuis ) (Peterson et al ., 2005). Early symptoms of disease include patches of turf that appear water‐soaked, slightly sunken and darker than healthy turf.…”