The Value of Early Root Development Traits in Breeding Programs for Biomass Yield in Perennial Ryegrass (Lolium perenne L.)

Perennial ryegrass ( Lolium perenne L.) is an important forage grass widely used in pastures and lawns, valued for its high nutritive value and environmental benefits. Despite its importance, genetic improvements in biomass yield have been slow, mainly due to complexities in breeding such as its outbreeding nature and the challenges of improving multiple traits simultaneously. This study aims to assess the potential advantages of including early root traits in the perennial ryegrass selection process. Using rhizoboxes to phenotype root traits under glasshouse environment, we collected data on early root morphology and correlated these traits with yield data from three field locations across Europe collected over two years. We employed bivariate models to assess the genetic correlations between early root traits and biomass yield, finding significant positive genetic correlations, particularly for total root length (TRL). Our results demonstrate that early root traits exhibit substantial heritability show potential as predictors of field yield. Incorporating these traits into selection criteria can improve the efficiency of breeding programs, potentially increasing genetic gain by approximately 10%. This study underscores the potential of using early root development traits to enhance perennial ryegrass breeding programs, ultimately contributing to higher biomass yields.