Hans-Joachim Jung, 411 Borlaug Hall, USDA-ARS, USDA-ARS, 1991 Upper Buford Cir., St. Paul, MN 55108 and Ronald Phillips, 411 Borlaug Hall 1991 Upper Buford Circle, University of Minnesota, University of Minnesota, Department of Agronomy & Plant Genetics, St. Paul, MN 55108.
Ferulate cross linkage of lignin to arabinoxylans in grasses impedes cell wall digestibility. Formation of cross links requires ferulate esters on arabinoxylan. Subsequent lignin deposition is initiated by formation of cross-linked ferulate/monolignol complexes. We hypothesized that selection for severely reduced ferulate ester concentration in seedling leaves could be used to identify Mu-transposon-induced mutants that have improved cell wall digestibility in silage stover because of reduced potential for lignin/arabinoxylan cross linking. A single putative mutant with a 50% reduction in ferulate esters was identified. Four near-isogenic lines derived from the putative mutant were compared to the parental inbred W23 in a field trial with four plots arranged in randomized complete blocks, at two locations in Minnesota for 2 yr. Ferulate ester concentration in seedling leaves was lower in two of the four mutant lines compared to W23. Ferulate cross link concentration will be determined in silage stover. Sporadic small, but inconsistent, differences in plant height, and stem internode number and cross-sectional area were found between W23 and the four mutant lines at silking. At silage maturity, whole plant yield and proportions of leaf blade, sheath, stem, and ear varied inconsistently and sporadically between the parental inbred and the mutant lines. Neutral detergent fiber (NDF) and acid detergent lignin (ADL) concentrations did not differ among the lines for leaf blades, but mutant lines were consistently lower for NDF and ADL in sheaths (2 to 6% and 2 to 7%, respectively) and stems (7 to 16% and 5 to 27%, respectively). In vitro NDF digestibility with rumen microbes was consistently greater for leaf blades, sheaths, and stems in all the mutant lines compared to W23 after both 24-h (7 to 22%) and 96-h (1 to 10%) incubations. Genetic reduction of ferulate esters in seedling maize resulted in improved silage fiber digestibility as hypothesized.