Two trials were carried out under greenhouse conditions to compare the development of three ALS inhibitor herbicides resistant (R) wild poinsettia (Euphorbia heterophylla) biotypes (Passo Fundo, Não-Me-Toque and Rio Pardo - RS - Brazil) and one susceptible (S) (Porto Alegre - RS - Brazil) using relative growth rate (RGR) and related indices. The experiment was arranged as a completely randomized design, with three replications, in a 2 x 4 x 4 factorial, where factor A was two growth seasons (fall and spring); factor B, four biotypes of wild poinsettia, and factor C, four assessments of growth indices (first trial at 15, 25, 35 and 45 days after emergence (d.a.e.) and second trial at 23, 33, 43 and 53 d.a.e.). The fall trial showed no interaction between assessment and biotype nor simple biotype effect. The spring trial relative leaf weight (RLW) of Não-Me-Toque biotype was higher than that of the others; leaf area ratio (LAR) of Não-Me-Toque biotype was higher than 23 and 53 d.a.e.; there was no difference of RGR and net assimilation rate (NAR) among biotypes. These results indicate similar R and S biotype productivities and, therefore, their competitive equivalency.
herbicide resistance; relative growth rate; net assimilation rate; leaf area ratio
