Given the importance of glyphosate use in GR crops and others cropping systems, the aim of this study was to evaluate glyphosate efficacy on three sourgrass biotypes with suspected resistance.
Sourgrass seeds of each biotype were sown in polystyrene trays filled with substrate.
The glyphosate dose-response experiments showed significant differences between the sourgrass biotypes (based on confidence intervals), confirming the resistance of the BA and MT biotyp es.
Sourgrass is the weed species with the most cases of glyphosate resistance in Brazil (Gazola, Belapart, Castro, Cipola Filho, & Dias, 2016).
The low weed control level of the MT and BA biotypes, and the control failures exhibited by the GO biotype are of concern, since sourgrass can recover from severe damages caused by glyphosate.
When sourgrass presents resistance to glyphosate, it has high RF values.
Glyphosate resistance was confirmed in MT and BA sourgrass biotypes collected in fields cultivated with GR crops, and they presented a high resistance level to this herbicide.
Detection of sourgrass (Digitaria insularis) biotypes resistant to glyphosate in Brazil.
Mean values of the distance between vascular bundles distances, parenchymal thickness and xylem/phloem relation of glyphosate resistant and susceptible biotypesof sourgrass
. Biotype Vascular bundles Parenchymal Xylem/phloem distance thickness relation ([micro]m) ([micro]m) Resistant 116,50 b 67,18 b 2,32 a Susceptible 130,27 a 74,93 a 2,05 b Means followed by different letters in the columns are significantly different by Tukey's test at 5% probability.