Glyphosate resistance in Conyza species is dependent on

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

Conyza spp. on roadsides

C. bonariensis C. canadensis C. albida

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

Glyphosate. Resistant C. bonariensis

Vineyard

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

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

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

Response of C. bonariensis (pop. 1 b) grown at different temperatures to glyphosate (0. 72 kg ae/ha) 1 b Control 340/ 280/ 220/ 160/ 100

Linear correlation between plant age and plant response to glyphosate (0. 36 kg ae/ha)

Effect of glyphosate on shoot fresh weight of different C. bonariensis populations RI 5. 7 3. 4 1. 3 -- ED 50 0. 32 0. 20 0. 07 0. 06

Effect of glyphosate on plant survival of different C. bonariensis populations Population ED 50 RI 18 b 0. 5 - 1 b 1. 8 3. 6 AH 18. 3 36. 6 15 A 17. 3 34. 6

Response of C. bonariensis to glyphosate (X=0. 72 kg ae/ ha) b 1 b 18 AH AH A 15

C. bonariensis seedlings before treatment

Effect of glyphosate on C. bonariensis seedlings. Seedling were treated at 14 DAP and harvested 21 DAT RI 30 28 2 -- ED 50 0. 147 0. 138 0. 010 0. 005

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

In vivo shikimate accumulation in C. bonariensis plants treated with glyphosate (0. 18 kg ae/ha)

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

* * * 14 C * distribution in treated plants

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

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