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?