Spread of glyphosate‐resistant sourgrass (Digitaria insularis): Independent selections or merely propagule dissemination?

The first reports of glyphosate‐resistant (GR) sourgrass (Digitaria insularis) came from Paraguay (2005) and from South and Southeast Brazil, in Paraná (2008), and São Paulo state (2009). The hypothesis of this research is that the evolution of these resistant populations might have occurred indepen...

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Bibliographic Details
Published in:Weed biology and management 2018-03, Vol.18 (1), p.50-59
Main Authors: Takano, Hudson K., de Oliveira, Rubem S., Constantin, Jamil, Mangolim, Claudete A., Machado, Maria de F.P.S., Bevilaqua, Maycon R.R.
Format: Article
Language:English
Subjects:
Digitaria insularis
Evolution
Gene flow
genetic diversity
Genetic structure
Glyphosate
Herbicide resistance
Hypotheses
independent selection
inter simple sequence repeat loci
Low level
Polymorphism
Population genetics
Population studies
Populations
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Summary:The first reports of glyphosate‐resistant (GR) sourgrass (Digitaria insularis) came from Paraguay (2005) and from South and Southeast Brazil, in Paraná (2008), and São Paulo state (2009). The hypothesis of this research is that the evolution of these resistant populations might have occurred independently. To test this hypothesis, a dose–response experiment was conducted in order to confirm resistance and inter simple sequence repeat markers subsequently were evaluated in five sourgrass populations from Paraguay (PY‐R), Paraná (PR‐S and PR‐R), and São Paulo (SP‐S and SP‐R). Resistant populations were confirmed in PY‐R, PR‐R and SP‐R. The resistant populations presented lower polymorphism than susceptible populations, possibly related to the selection pressure exerted by the herbicide. Both similarity matrix and dendrogram provided evidences that the origin of resistance in the populations from Paraguay and Paraná could be the same, which also is explained by their geographical proximity. In contrast, the evolution of GR populations in São Paulo was suggested to occur independently from other locations because resistance evolved in genetically divergent populations. This study’s data provide evidences that GR sourgrass populations from Paraguay and Paraná share a similar genetic background; therefore, it is possible that resistance from Paraguay spread to Paraná through gene flow. The population from São Paulo probably was selected independently because the high values of its genetic structure and low level of gene flow. Independent selections and seed dispersion of GR sourgrass have contributed to the rapid spread of resistance across South America.
ISSN:1444-6162
1445-6664
DOI:10.1111/wbm.12143