Freezing Tolerance and Seasonal Color of Experimental Zoysiagrasses

Meyer zoysiagrass (Zoysia japonica Steud.) is the most widely used cultivar in the transition zone of the United States due, in part, to its excellent freezing tolerance. Ten zoysiagrass progeny from crosses between Z. matrella (L.) Merr. x Z. japonica or 'Emerald' [Z. japonica x Z. matrella (L.) Merr. var. pacifica Goudswaard] x Meyer, 'Cavalier' (Z. matrella), and DALZ 0102 (Z. japonica) were evaluated for (i) freezing tolerance, (ii) autumn and spring color, and (iii) a relationship between autumn color and freezing tolerance. Turfgrass cores were sampled from the field near Manhattan, KS, in October, December, or February and exposed to temperatures from -6 to -22 degrees C in the laboratory. Lethal temperatures resulting in death of 50% of tillers (LT50) after 6 wk of recovery in the greenhouse ranged from -0.2 degrees C to -12.2 degrees C. All grasses were equivalent to Meyer in freezing tolerance except Cavalier on three of five sampling dates and one Z. matrella x Z. japonica progeny in December 2007, which were inferior to Meyer. Digital image analysis indicated that five progeny were superior to Meyer in autumn green color retention, but none were superior to Meyer in spring green color. Autumn color in 2007 was positively correlated (r = 0.40 to 0.58, p <= 0.05) with LT50 in December 2007. However, autumn color was also positively correlated with color the following spring (r = 0.31 to 0.72). These progeny demonstrated good freezing tolerance and, in some cases, superior autumn color compared to Meyer.