The resistance of orchard weed populations to glyphosate

Nowadays, both worldwide and in Serbia, for weed eradication in orchards mostly herbicides based on glyphosate, glufosinate-ammonium, diquat and others are used. Intensive glyphosate application has led to the development of resistant weed species, which has consequently resulted in a decrease in its effectiveness. In our country, areas under orchards amount to 224.000 hectares, which certainly points to a significant herbicide use and a possibility that weed resistant populations have developed. For this reason, seeds of several weed species from areas where glyphosate has been intensively used for years were collected (localities: Inđija, Brestovac, Sabac, Vrsac, Sombor, Glogonjski Rit, Padinska Skela and Surcin). Plants were grown in controlled conditions and in the open field. Plant material was then crushed using liquid nitrogen, and the extraction of shikimic acid was performed using hydrochloric acid (1 g of plant material + 5 ml 1M HCl). 24 hours later the amount of shikimic acid was detected using high-pressure liquid chromatography. The analysis of the obtained results showed that species Amaranthus retroflexus (loc. Sabac), Abutilon teophrasti (loc. Brestovac) and wild Helianthus annuus (loc. G. Rit) have developed a certain degree of glyphosate resistance. .