Panicum maximum is an important autotetraploid tropical forage grass. This repository contains R code files, phenotypic data, and supplementary material corresponding to a manuscript submitted to G3 (Genes|Genomes|Genetics). The main objective of the study was to develop predictive models that consider tetraploid allele dosage in a recurrent selection population of P. maximum. We provided bioinformatic and modelling guidelines to allow tetraploid dosage and observed that genomic selection is promising in forage breeding programs.