The objective of this research was to evaluate intra-specific competition ability of purple nutsedge Cyperus rotundus biotypes, using isoenzymes. We sampled weed populations in 66 sites all around São Paulo State - Brazil. Polymorphism was observed in six out of fourteen enzymatic systems studied (aand b-EST, ACP, IDH, MDH, and SKDH). Polymorphism was not observed for ADH, CAT, GDH, AAT, LAP, MADH, PER, and SDH. Using the information of the six polymorphic isoenzymes, it was possible to identify 10 biotypes of Cyperus rotundus and C. flavus, C. iria e C. esculentus species. The two major biotypes were predominant in 48.5% and 21.2% of the sampling sites. The competition ability assay was carried out showing that the most widely spread biotypes were the most competitive ones.
Electrophoresis; weed; biotypes; competition; Cyperus rotundus