Freezing tolerance of six cultivars of buffalograss

Freezing tolerance is an important trait that determines geographical adapt ation of a turfgrass. This study was conducted to assess the relative freez ing tolerance, seasonal changes in freezing tolerance (LT50), and winter su rvival of six cultivars of buffalograss [Buchloe dactyloides (Nutt.) Engelm .]. The cultivars 91-118, Tatanka, Texoka, Stampede, UCR-95, and 609 were g rown in the field at Fort Collins, CO. From September 1998 to April 1999 an d from October 1999 to May 2000, stolons were sampled monthly from each plo t and subjected to laboratory freezing tests. Survival and recovery followi ng the freezing test indicated that all cultivars had similar LT50 in Septe mber and gradually increased in winter hardiness during fall. However, the capacity to acclimate and the maximum freezing tolerance were significantly different among the cultivars. Ranking of grasses for mean LT50 (degreesC) was Tatanka (-18.1) = 91-118 (-18.0) less than or equal to Texoka (-17.1) < 609 (-14.4) < Stampede (-12.4) < UCR-95 (-9.2) during midwinter in 1998-1 999 and Texoka (-21.7) = 91-118 (-21.6) = Tatanka (-21.0) < 609(-15.8) = St ampede(-15.1) < UCR-95 (-14.0) during midwinter in 1999-2000. Following fre ezing treatments, Tatanka and 91-118 maintained a higher relative shoot and root regrowth than other cultivars. Root regrowth was reduced by freezing to a greater extent than shoot regrowth for all cultivars. Field winter sur vival, a measure of winter hardiness, in 1998, 1999, and 2000 was generally in agreement with laboratory test results, showing that Stampede, 609, and UCR-95 were more susceptible to winterkill than 91-118 and Tatanka. The di fferences in freezing tolerance among the cultivars tested indicates substa ntial intraspecific variation that may be used for breeding improvement.