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ARS Home » Plains Area » Lincoln, Nebraska » Wheat, Sorghum and Forage Research » Research » Publications at this Location » Publication #247847
Title: Efficacy of Singular and Stacked Brown Midrib 6 and 12 in Modification of Lignocellulose and Grain Chemistry

Author
item Sattler, Scott
item Funnell-Harris, Deanna
item Pedersen, Jeffrey

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2010
Publication Date: 2/22/2010
Citation: Sattler, S.E., Funnell-Harris, D.L., Pedersen, J.F. 2010. Efficacy of Singular and Stacked Brown Midrib 6 and 12 in Modification of Lignocellulose and Grain Chemistry. Journal of Agricultural and Food Chemistry. 58:3611-3616.

Interpretive Summary: Brown midrib genes were introduced into the grain sorghum hybrid AWheatland x RTx430 to reduce lignin content and improve digestibility of stalk residues following grain harvest for use as a bioenergy or livestock feedstock. The impact the genes bmr6 and bmr12, which impair the last two steps of lignin synthesis, and the bmr6bmr12 “stacked” double mutant was assessed in a two year field study. In this study, the bmr genes did not significantly reduce grain or stover yield. Stover tissue from bmr6, bmr12, and stacked hybrids had reduced lignin content and increased digestibility compared to the wild-type hybrid. The lignin content of the stacked stover residue was further reduced compared to bmr6 or bmr12, but it had digestibility comparable to bmr12 stover. Analysis of stover carbohydrate composition indicated that bmr12 had modestly increased amounts of cellulose, glucoarabinoxylan and soluble sugars. Together these indicate that bmr12 had broader effects on stover composition than bmr6 or stacked hybrid. Furthermore, fiber and lignin content of grain was modified by bmr genes The bmr12 hybrid had similar fiber and lignin content compared to the wild-type hybrid, while the bmr6 hybrid had 9% greater fiber and 13% greater lignin content than the wild-type hybrid.

Technical Abstract: Near-isogenic versions of the grain sorghum hybrid AWheatland x RTx430 were developed containing brown midrib (bmr) 6 and 12, which impair the last two steps of lignin monomer (monolignol) synthesis, and the bmr6bmr12 double mutant (stacked). The goal of introducing bmr genes into grain sorghum varieties was to reduce lignin content and improve digestibility of lignocellulosic tissues following grain harvest for use as a bioenergy feedstock or for grazing livestock. The impact of bmr genes was assessed in a two year field study. The bmr genes did not have a significant impact on either grain or lignocellulosic tissue yield. Lignocellulosic tissue from bmr6, bmr12 and stacked hybrids had reduced lignin content and increased in vitro dry matter digestibility (IVDMD) compared to wild-type (WT). The lignin content of the stacked lignocellulosic tissue was further reduced compared to bmr6 or bmr12, but it had IVDMD comparable to bmr12 lignocellulosic tissue. Analysis of lignocellulosic tissue carbohydrate composition indicated that bmr12 had modestly increased amounts of cellulose, glucoarabinoxylan and soluble sugars. Together these indicate that bmr12 had broader effects on lignocellulosic tissue composition than bmr6 or stacked hybrid. Furthermore, acid detergent fiber (ADF) and acid detergent lignin (ADL) content of grain was modified by bmr genes The bmr12 hybrid had statistically equivalent ADF and ADL compared to the near-isogenic WT hybrid, while the bmr6 hybrid had 9% greater ADF and 13% greater ADL than the WT hybrid.