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Horseweed (Conyza Canadensis) Has Evolved in Glyphosate Resistance in China
Sheng Qiang, Xiaoling Song, Jiajun WuWeed Research Laboratory, Nanjing Agricultural University
Nanjing ,China , 210095
ABSTACT Horseweed (Conyza canadensis), an invasive alien weed, is one of main weeds in orchards in China. Glyphosate has been used for the controlling annual and perennial weeds in orchards for more than 25 years in China. We firstly report that horseweed has evolved in glyphosate resistance in China. The seeds of 45 populations were collected from different orchards with different glyphosate application history. The pot seedlings with 5-7 leaves were treated with glyphosate dosage at 35, 70, 140 280, 560, 1120, 2240, 4480 and 8960 (ai )g ha-1. The dosage dependence response curve of each population was set up by Log-logistic dose response regression equation. The ED50 value of each population was calculated and compared with 10 typical susceptible and resistant populations from America. The results showed that the different population had different glyphosate-resistant level which increased with prolonging of glyphosate application years. Two populations with the highest resistance level at 8.28 and 7.95 fold were found in Ningpo, Zhejiang Province where glyphosate was ever applied twice a year for more than fifteen years.
Supported By:
Editors:
Mark
E. Whalon
Robert M. Hollingworth
Area Editors:
Plant Pathology
Margaret Tuttle McGrath
Herbicide
Jonathan Gressel
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Theresa A. Baker