Genetic progress from 50 years of smooth bromegrass breeding

Since its introduction from Eurasia, smooth bromegrass (Bromus inermis Leys s.) has become an important cool-season forage grass in North America. The objective of this study was to document breeding progress in smooth bromegr ass between 1942 and 1995 in North America. Thirty cultivars or experimenta l populations were tested at up to seven sites in the eastern and central U SA, with a range of soil types and climates. There have been small genetic changes in forage yield, brown leafspot resistance [caused by Pyrenophora b romi (Died) Drechs,], in vitro dry matter digestibility (IVDMD), and neutra l detergent fiber (NDF) concentration. Brown leafspot resistance increased gradually, averaging 0.21 units decade(-1). Mean forage yield did not chang e for cultivars developed after 1942, but was 0.54 Mg ha(-1) (7.2%) higher for the post-1942 group than in 'Lincoln', a direct representative of smoot h bromegrass introduced into North America. Selection for increased IVDMD l ed to an average increase in IVDMD of 9 g kg(-1) (1.4%), an increase in for age yield of 0.33 Mg ha(-1) (5.0%), and a decrease in NDF of -8 g kg(-1) (- 1.2%) in the post-1942 group. The slow rate of progress for smooth bromegra ss forage yield is due to its complex polyploid inheritance, emphasis on tr aits other than forage yield, and relatively little concentrated attention from public and private breeders.