1. Glyphosate resistance in Conyza species is dependent on environmental conditions Gadi Ben-Ami, Tz. Whitefish, Moshe Sibony and Baruch Rubin R H Smith Institute of Plant Science and Genetics in Agriculture, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel

2. Conyza spp. on roadsides

3. C. bonariensis C. canadensis C. albida

4. Glyphosate Introduced early 70’s Excellent and inexpensive herbicide Widely used all over the world (not only in agriculture) Applied in over-doses

5. Glyphosate- Resistant C. bonariensis

6. Vineyard

8. Glyphosate Introduced early 70’s Excellent and inexpensive herbicide Widely used all over the world (not only in agriculture) Applied in over-doses Over 100 populations of Conyza spp. were collected and examined

9. Glyphosate (kg ae/ ha) C. Canadensis C. bonariensis Dose response 34/28 Cº O 28/22C º  22/16C º  16/10C º

10. Linear correlation between temperature regime and response of C. bonariensis and C. canadensis to glyphosate (based on ED 50 values)

11. Response of C. bonariensis (pop. 1b) grown at different temperatures to glyphosate ( 0.72 kg ae/ha ) 16 0 / 10 0 34 0 / 28 0 28 0 / 22 0 22 0 / 16 0 Control 1b

12. Linear correlation between plant age and plant response to glyphosate (0.36 kg ae/ha)

13. RI ED50 5.7 0.32 3.4 0.20 1.3 0.07 -- 0.06 Effect of glyphosate on shoot fresh weight of different C. bonariensis populations

14. RIED 50 Population -0.518b 3.61.81b 36.618.3AH 34.617.315A Effect of glyphosate on plant survival of different C. bonariensis populations

15. b1 b18 AH b1 b18 AH A15 Response of C. bonariensis to glyphosate (X=0.72 kg ae/ ha)

16. C. bonariensis seedlings before treatment

17. Effect of glyphosate on C. bonariensis seedlings. Seedling were treated at 14 DAP and harvested 21 DAT RI ED 50 30 0.147 28 0.138 2 0.010 -- 0.005

18. AH O 15a  1b  18b  Cotton RR In vitro shikimate accumulation in C. bonariensis leaf discs (4 mm) following exposure to glyphosate for 18 h in light

19. In vivo shikimate accumulation in C. bonariensis plants treated with glyphosate (0.18 kg ae/ha)

20. ** 14 C-glyphosate absorbed in C. bonariensis plants 24 HAT (A) and % translocated to other plant parts

21. * 14 C distribution in treated plants

22. Glyphosate Significant effect of plant age and temperature Confirmed resistance in Conyza bonariensis

23. How to combat GR? Use alternative herbicide. Which one? Use mixtures. With which herbicides?