Productivity and Quality of Brown Midrib (bmr) Sorghum Varieties to Producers in Central America

Abstract

The improved dry matter digestibility of the brown midrib (bmr) sorghum cultivars is attributed to constitutive deficiencies of the lignin biosynthesis pathways which results in lower lignin concentrations. The lower lignin concentrations are expressed only in a homozygous recessive genotypes and it is phenotypically identified by a brown to tan vascular coloration present in the mid-rib of the leaf blades. Utilizing this trait increases forage consumption and productivity of both dairy and beef production. There is a need to extend this trait into more forage production systems, including those in Central America where forages constitute a major portion of the ruminants’ diets.

To achieve this goal, the bmr12 gene was incorporated via conventional breeding, into 16 lines derived from commonly used Central American sorghum varieties. These experimental lines were tested for agronomic performance during 2010 and 2011 in the Central American region. In addition, grain and biomass composition were estimated using near-infrared reflectance spectroscopy (NIRS) whereas the dry biomass digestibility was evaluated using an in vitro approach.

The combined analysis indicated the bmr trait increased in vitro dry matter digestibility and reduced acid detergent lignin and acid detergent fiber levels. This combination results in improved sorghum forage quality. Furthermore, negative traits typically associated with bmr mutants such as plant height reduction, delayed flowering, and lodging problems were not observed and the bmr trait had no effect on grain composition.

Additionally, post hoc tests identified CI0947bmr as the best experimental line for dry both biomass and grain yield across multiple environments. Stability analysis, identified CI0947bmr as the most stable genotype for both traits. Finally, the “which-won-where” biplot analysis graphically identified CI0947bmr as the best bmr inbred for Honduras, Guatemala and Nicaragua across several environments.