Trois nouvelles mauvaises herbes resistant aux triazines en France: Amaranthus retroflexus s.l., Chenopodium polyspermum L., Polygonum persicaria L.

Atrazine resistant populations are described for three weed species Amaranthus retroflexus s.l. Chenopodium polyspermum L., Polygonum persicania L.. The behaviour of resistant amaranths leads to think they are hybrids between two closely related species. The resistance has been tested with treatments of seedlings, fluorescence of whole leaves and measure of activity of isolated chloroplasts. The observation of the fluorescence shows that these populations selected with atrazine are triazine resistant.