Genetic Progress From 50 Years of Smooth Bromegrass Breeding

The first documentation of breeding smooth bromegrass was the single cycle of mass selection practiced by Since its introduction from Eurasia, smooth bromegrass (Bromus two Kansas farmers in the early 1900s to produce the inermis Leyss.) has become an important cool-season forage grass in cultivar Achenbach from “the tallest, best-filled, and North America. The objective of this study was to document breeding progress in smooth bromegrass between 1942 and 1995 in North Amer- lightest colored plants” (Vogel et al., 1996). Although ica. Thirty cultivars or experimental populations were tested at up to there were sporadic breeding efforts at several experiseven sites in the eastern and central USA, with a range of soil types ment stations in the 1910s and 1920s, formal breeding and climates. There have been small genetic changes in forage yield, did not begin in earnest until the late 1930s and early brown leafspot resistance [caused by Pyrenophora bromi (Died) 1940s. This coincided with the widespread value and Drechs.], in vitro dry matter digestibility (IVDMD), and neutral deter- popularity of smooth bromegrass for revegetation of gent fiber (NDF) concentration. Brown leafspot resistance increased drought-damaged grasslands and marginal croplands gradually, averaging 0.21 units decade2 1 . Mean forage yield did not throughout the Great Plains and midwestern regions. change for cultivars developed after 1942, but was 0.54 Mg ha2 1 (7.2%) The initial breeding efforts in smooth bromegrass imhigher for the post-1942 group than in ‘Lincoln’, a direct representative provement capitalized largely on existing natural variaof smooth bromegrass introduced into North America. Selection for increased IVDMD led to an average increase in IVDMD o f9gk g 21 tion among introduced germplasm sources that had be(1.4%), an increase in forage yield of 0.33 Mg ha 21 (5.0%), and a come naturalized land races (Casler and Carlson, 1995). decrease in NDF of 2 8gk g 21 (21.2%) in the post-1942 group . The Many of the cultivars released in the 1940s consisted of slow rate of progress for smooth bromegrass forage yield is due to increases from seed production fields that had consisits complex polyploid inheritance, emphasis on traits other than forage tently given rise to high-yielding forage production yield, and relatively little concentrated attention from public and fields. Of these cultivars, Lincoln was the most widelyprivate breeders. grown, presumably due to its superior performance in regional trials (Thomas et al., 1958). Fifty-five years later, Lincoln remains the most widely grown smooth S