Relative NaCl tolerance of Kentucky bluegrass, Texas bluegrass, and their hybrids

Government regulations to force water conservation have escalated the use of secondary water high in soluble salts for turfgrass irrigation in the and and semiarid western USA, thus increasing the need for more salt-tolerant turfgrasses. This study was initiated to determine the variability in salt tolerance within and among two Poa species and their hybrids. Two experiments were conducted during 2000 in the greenhouse at Fort Collins, CO, in solution culture to examine the effects of NaCl on leaf firing and shoot and root growth reduction of nine Kentucky bluegrass (KBG; Poa pratensis L.) cultivars representing three ecotypes, three Texas bluegrass (TBG; P. arachnifera Torr.) accessions, and five of their hybrids (P.pratensis X P. arachnifera). In Exp. I, conducted during late winter through spring 2000, overall salt tolerance based on leaf firing and electrical conductivity (EC) of 50% shoot growth reduction (ECshoot 50) placed seven KBG cultivars in the most tolerant group. In Exp. II, conducted during summer though early fall 2000, overall salt tolerance rankings placed 4 KBG and 3 TBG cultivars in the most tolerant group. On the basis of percentage leaf firing and the salinity levels that caused 25 and 50% shoot growth reduction, compact (low, compact growth habit) and aggressive (aggressive, lateral growth habit) KBG ecotypes showed more salt tolerance than common ecotypes in both Exp. I and II. A broad range of variability in leaf firing and shoot and root growth reduction in response to salinity was found to exist within and among these Poa species and their hybrids, indicating that improvement in the salt tolerance of bluegrasses may be possible. Additionally, differences in salt tolerance of KBG and TBG between Exp. I and Exp. II suggested that environmental conditions could affect bluegrass salt tolerance expression.