Effect of Genetic Modifiers on the Phenotypic Expression of the Maize Brown Midrib-3 (bm3) Mutant.

Effect of Genetic Modifiers on the Phenotypic Expression of the Maize brown midrib-3 (bm3) Mutant Authors: Calli M. Anibas, Natalia de Leon, Shawn Kaeppler Department of Agronomy, University of Wisconsin, Madison, WI, USA Grown for its diverse functionality as a grain and biomass source, maize is one of the most heavily produced crops around the world. Improving the productivity and biochemical composition of maize creates a more sustainable crop. The brown midrib-3 (bm3) mutant which disrupts the formation lignin within maize plants, reduces biomass recalcitrance and improves overall digestibility as a forage. However, dependent upon the background to which the mutant is introduced, substantial variation exists in productivity and overall plant morphology. The purpose of this research is to evaluate the hypothesis that plant performance is impacted by the overall penetrance of this large-effect gene in differing genetic backgrounds and seek endogenous variants that may interact with this major gene affecting its phenotypic expression. Two inbreds that demonstrated distinct responses to the bm3 introduction, W64Abm3 and W182Ebm3, were crossed and individual derived F2 families were subsequently selfed to create 135 F3:F4 families for this evaluation. Hybrids were then created by crossing the resulting F3:F4 families by the W64Abm3 and W182Ebm3 and their corresponding isogenic wild-type (W64A and W182E). A replicated field trial was conducted to evaluate the 540 generated hybrids to for overall forage yield, digestibility and other important agronomic traits. Variation across genotypes was observed for digestibility, forage yield, dry matter content, plant and ear height and flowering times. Delayed flowering, biomass reduction, and improved digestibility were seen across bm3 mutants when compared to their wild-type counterparts with W182E backgrounds impacted more severely than their W64A counterparts. Investigation further into these results is being done through the use of genetic mapping to identify possible QTLs across the RILS and their crosses with the four testers. Funding Acknowledgements: United States Department of Agriculture (USDA) Hatch WIS01639 and Forage Genetics International