Comparative Effects of the Sorghum \u3ci\u3ebmr\u3c/i\u3e-6 and \u3ci\u3ebmr\u3c/i\u3e-12 Genes: II. Grain Yield, Stover Yield, and Stover Quality in Grain Sorghum

Nearly 3 million hectares of grain sorghum [Sorghum bicolor (L). Moench] are harvested in the USA each year. It may be possible to add value to crop and animal systems by enhancing the digestibility of the stover residue by the use of brown midrib (bmr) genes if grain can be maintained. The objectives of this study were to evaluate the effect of bmr-6 and bmr-12 genes on grain yield of sorghum and to evaluate the effect of the bmr genes on stover yield and quality in these genetic backgrounds: ‘Wheatland’, ‘Redlan’, RTx430, Tx623, Tx630, Tx631, and the hybrid AWheatland X RTx430. Plant height, maturity, grain yield and test weight, stover neutral detergent fiber NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), and in vitro NDF digestibility (IVNDFD) were measured in split-plot experiments replicated four times in each of four environments with lines being whole-plots and genotypes being subplots. Brown midrib genes reduced grain yield and residue yield in the lines; however, yield reduction was not observed in the bmr-12 AWheatland X RTx430 hybrid. The bmr-12 near-isolines generally had lowest stover lignin content and highest fiber digestibility, bmr-6 was intermediate, and wild-type counterparts had highest lignin content and lowest fiber digestibility. When all data are considered, the bmr-12 gene appears superior to the bmr-6 gene in terms of potentially adding value to the stover of grain sorghum for use in crop/animal systems. The variable expression of bmr-12 and bmr-6 in different lines indicates that selection of compatible genetic backgrounds will be critical in determining the realized impact on value