Undesirable physical seed mixture in commercial seed lots of several Brachiaria species is a cause of growing concern in Brazil. Such a mixtures often result in the contamination of cultivated areas by species which are difficult to erradicate in conseqüence of their aggressivity and of the low selectivity of available herbicides. The obtention of contamination-free seed lots is, therefore, of great interest and so are the techniques for the precise identification of Brachiaria species, which would allow the improvement of quality control by commercial enterprises. This paper reports an attempt of evaluating the discriminatory potential of the eletrophoretic technique applied to four enzymatic systems present in seedlings of four Brachiaria species, namely, B. brizantha cv. Marandu, B. decumbens cv. Basilisk, B. humidicola “cv. common”, and B. plantaginea. Fifty coleoptiles of each species, obtained from seeds germinated in the dark at 30°C, were used in each treatment. Polyacrilylamide gels, at 7.0% and 7.5%, were used as supporting gels. The banding pattern resulted from the electrophoresis of the isozymes Glutamate dehydrogenase and Glucose-6-phosphate dehydrogenase allowed the differentiation of B. plantaginea and B. humidicola between themselves and these from B. brizantha and B decumbens, but not the differention between the later species. However, when the isozymes α- and β-esterase were used, a clear distinction of the four species studied was possible.
Weed; seed; varietal mixture; quality control