Salinity slows germination of rough bluegrass

Bermudagrass (Cynodon sp.) greens are overseeded annually with rough bluegrass (Poa trivialis L.) in the coastal southeastern United States, where irrigation water is often saline. Salinity may slow seed germination and delay turf establishment. Cultivar and seed lot differences in sensitivity to salinity may be substantial. Our objective was to determine the effects of salinity on germination of commercially available rough bluegrass cultivars and seed lots. To accomplish this, we examined the effects of salinity (0, 1.8, 3.4, and 5.0 dS.m(-1) established with NaCl in deionized water) on germination of 33 cultivars/seed lots of rough bluegrass in vitro. Fifty seeds of each cultivar/seed lot were placed on pre-moistened germination paper in petri dishes, sealed with parafilm, and placed in growth chambers with 12-hours light/12-hours dark at 20/10 degrees C, respectively. Germination was scored from 4 to 25 days after seed placement. Rough bluegrass germination rate varied among cultivars/seed lots, ranging from less than three seeds/day to nearly seven seeds/day. Salinity slowed rough bluegrass germination rate from about six seeds/day at 0 dS.m(-1) to five seeds/day at 5 dS.m(-1). Increasing salinity reduced early germination of some cultivar/seed lots more than that of others. Impact was substantial in three cultivar/seed lots, where early germination at 5.0 dS.m(-1) was less than 15% of that at 0 dS.m(-1). For most cultivar/seed lots, the reduction in early germination with salinity at 5.0 dS.m(-1) was about 50% of that at 0 dS.m(-1). Final germination was reduced only 3% by increasing salinity. In view of differences in germination rate and response to salinity among seed lots of rough bluegrass cultivars, we suggest the planting of multiple cultivars and seed lots of rough bluegrass to insure rapid establishment.