Is there a genetic basis for forage quality of barley for beef cattle?
Surber, Lisa Marie McKinley
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Despite the importance of forage quality to animal performance, barley forage quality has not been used as a selection criterion in barley breeding programs. Our objectives were to: (1) evaluate Steptoe x Morex doubled haploid (DH) and Lewis and Karl recombinant inbred line (RIL) populations for forage quality characteristics; (2) identify QTL for forage quality characteristics; and (3) determine if variation in forage quality characteristics among barley lines is heritable. The 145 DH lines were grown in in 1999 and 2001 under irrigated conditions in Bozeman, MT while 146 RIL lines were grown in 1999 and 2000 under dryland conditions in 2 replications of a randomized complete block design. The experimental unit was entry within block. Forage samples were collected at plant anthesis and at peak forage yield. A 0.15 m clip sample of 1 row was cut at stubble height and dried at 60°C for 48 h. Forage samples were ground to pass a 5-mm screen. In situ DM digestibility (ISDMD) at 48 h was determined. A sub-sample of each line was evaluated for NDF, ADF, N, and NO3-N. At peak forage yield for DH lines, NO3-N was negatively correlated to ISDMD (r = -0.52, P < 0.001). At anthesis, this relationship was weak (r = 0.17, P < 0.001). At peak forage yield for DH lines, the QTL for NO3-N was located at markers on a different region of chromosome 2H than QTL for N and non-NO3-N and this indicates that NO3-N could be selected for independently of other nitrogen components. In the RIL experiment QTL models explained about 41%, of the variation in NO3-N concentration found at locations on chromosomes 3H and 6H. In the DH trial, NDF, N, non-NO3-N, and ISDMD were highly heritable; ADF was moderately heritable; and DM yield, DM, and NO3- N were lowly heritable at anthesis. In the RIL experiment, moderate levels of heritability were seen for NO3-N and ISDMD at the peak forage yield stage of maturity (h2 = 52 and 55%, respectively). This research has provided the identification and mapping of QTL for barley forage quality and will allow deployment of genes for improved forage quality via marker-assisted selection.