Fig. 2. Indirect responses of particle size reduction index (PSRI) to divergent selection for neutral detergent fiber (NDF) concentration in four smooth bromegrass populations. Means are over four replicates, three locations, 3 yr, and two harvests. Solid lines represent linear selection responses (b) and dashed lines represent effects of drift (d). R2 = 0.99, 0.94, 0.97, and 0.99 for Alpha, WB19e, Lincoln, and WB88S, respectively.