Divergent recurrent selection for seedling tiller number in Altai wildrye

Seedling tiller number is a possible selection criterion to improve seedling establishment of Altai wildrye, Leymus angustus (Trin.) Pilger, an important grass for autumn grazing of beef cattle in semiarid environments. Forty-two half-sib families selected for high seedling tiller number (HTN) and eighteen half-sib families selected for low seedling tiller number (LTN) by four cycles of divergent recurrent selection were compared with four controls, Altai wildrye cultivars Prairieland, Eejay and Pearl, and crested wheatgrass (Agropyron desertorum (Fisch. Ex Link) Schultes), cultivar Nordan, on dryland and irrigated sites at Swift Current, Saskatchewan, Canada. Seedling tiller count, seedling height, tiller weight and seedling dry-matter yield (DMY) were determined on two plants per plot and DMY was determined for each plot for 2 years post-establishment. HTN half-sib families had more, tighter and shorter tillers than LTN half-sib families. There was a negative correlation (r = -0.42, P<0.01, n=60) between seedling DMY and tiller number. HTN half-sib families had higher DMY in post-establishment years at the dryland site only. Seedling tiller number in Altai wildrye may be related to DMY at sites at which resource availability delays seedling establishment, but selection for HTN will not increase seedling DMY owing to concomitant changes in carbon allocation.