Freezing Tolerance and Carbohydrate Changes of Two Agrostis Species during Cold Acclimation

Field trials at two locations in Norway previously demonstrated differences in winter survival between two Agrostis species used for turf, velvet bentgrass (VB; A. canina L.) and creeping bentgrass (CB; A. stolonifera L.). The objectives of this study were to compare freezing tolerance and crown carbohydrate composition of VB and CB. We also compared a direct and two indirect methods of measurements of freezing tolerance. Treatments consisted of: (i) nonacclimated (NA); (ii) acclimation at 2 degrees C for 2 wk (A2); (iii) acclimation at 2 degrees C for 4 wk (A4); and (iv) acclimation at 2 degrees C for 4 wk plus subzero acclimation at -2 degrees C for 2 wk (A4+SZA2). Crowns were harvested for determination of carbohydrates and freezing tolerance. Freezing tolerance (lethal temperature for 50% of the test population [LT50]) was based on whole plant survival (WPS), 2,3,5-triphenyltetrazolium chloride (TTC) reduction, and electrolyte leakage (EL). There was no significant difference in freezing tolerance between VB and CB. The LT50 based on WPS was significantly lower for plants exposed to A2 (-12.7 degrees C), A4 (-14.5 degrees C), and A4+SZA2 (-14.6 degrees C) compared to the NA control treatment (-8.4 degrees C). The concentrations of fructans and sucrose were significantly higher in A2 compared to NA plants of both species, but only fructans continued to increase at A4. The LT50 based on TTC reduction showed better correlation with LT50 based on WPS compared to LT50 values based on EL.