Evaluation of Italian ryegrass (Lolium multiflorum Lam.) populations naturalized in the flooding pampa of Argentina:: I -: Morphological and physiological characters at the juvenile stage

Twenty populations of Italian ryegrass ( Lolium multiflorum) naturalized in the flooding pampa of Argentina and a commercial cultivar were evaluated in two representative soils of the region ( environments). Seeds were sown individually in pots and maintained outdoors to evaluate seedling emergence, growth habit, tillering and leaf characters at the juvenile stage, to determine the degree of genetic determination ( DGD) and resource allocations. Variability in final emergence, growth habit, tiller number, tillering index, leaf width and leaf area per plant was detected among entries, while ( soil x entry) interaction or differences between soils were observed for characters related to emergence and number and size of leaves. The DGD could not be estimated for some characters due to the variance of ( soil x entry) interaction component exceded the genetic component, but it ranged from 14 to 72 for the other attributes. To improve DGD estimations in future experiments, modification of experimental design by increasing the number of environments, replications or plants was discussed for each character.