RAPD Marker Variation among Divergent Selections for Fiber Concentration in Smooth Bromegrass

Abstract

Neutral detergent fiber (NDF) is considered the laboratory measure most closely correlated with voluntary intake of forages by ruminant livestock. The objectives of this study were to create smooth bromegrass ( Bromus inermis Leyss.) populations divergent for NDF concentration in four smooth bromegrass germplasm pools and to identify random amplified polymorphic DNA (RAPD) marker changes in these divergently selected populations. Two cycles of divergent phenotypic selection led to significant linear responses in NDF among selection cycles for all germplasm pools. Within‐population variation for RAPD markers was large, reflecting the outcrossing reproduction and the complex inheritance of smooth bromegrass. However, analysis of molecular variance revealed significant genetic differences among selected populations. Analysis of genetic distances showed that each cycle of selection created additional divergence, both among cycles and among germplasm pools. Up to 15 RAPD markers were associated with selection in each population, but only one marker was consistently associated with selection for NDF across all four germplasm pools (linear, homogeneous slopes, no drift). Some of the RAPD markers appear to have utility for marker selection or marker‐assisted selection (MAS) to modify NDF concentration.