Abstract
ABSTRACT: Greater beggarticks (Bidens pilosa and Bidens subalternans) biotypes have been under selection pressure of ALS-inhibitors since early 90’s in Brazil. The objectives of this work were to investigate whether there are different cross-resistance patterns among ALS-inhibitors herbicides in Bidens spp. biotypes; to understand the geographic distribution of resistance patterns in grains producing regions in Brazil; and evaluate the possibility of multiple resistance to ALS-inhibitors, EPSPs inhibitor and photosystem II inhibitors. Dose-response experiments were carried out with imazethapyr, chlorimuron and diclosulam in three populations. Sensibility to others 34 populations both from Paraná State (PR) and from others Brazilian regions were also evaluated. The dose-response assay revealed cross-resistance with different patterns. One population was resistant to all three herbicides, the second population was tolerant to both imazethapyr and chlorimuron, but not to diclosulam, while a third population was resistant merely to imazethapyr. The results exhibited different cross-resistance patterns, since they can be found in other Bidens spp. populations. However, no relationship was observed between geographic areas where samples were collected and resistance patterns. Conclusively, the most frequent resistance pattern was R2 (resistance to imazethapyr, chlorimuron and diclosulam).
Highlights
Weeds species of the genus Bidens belong to the Asteraceae family, which is originally from South America and can be found in the entire Brazilian territory, especially in Midwestern, Southeastern and Southern regions
In B. pilosa upper third, the branching is dichotomous, whist it is alternate in B. subalternans (Kissmann and Groth, 1999; GromboneGuaratini et al, 2004)
The objectives of this research were: (a) to characterize and map different patterns of crossresistance to acetolactate synthase (ALS) inhibitors in biotypes of Bidens spp. and (b) to evaluate whether reported field control failures are related to the occurrence of multiple resistance cases to ALS inhibitors + atrazine and/or to ALS inhibitors + glyphosate in biotypes collected from soybean-producing areas in Brazil
Summary
Weeds species of the genus Bidens belong to the Asteraceae family, which is originally from South America and can be found in the entire Brazilian territory, especially in Midwestern, Southeastern and Southern regions. These plants are reproduced strictly by seeds and can reach up to 1.2 m. B. pilosa and B. subalternans are the most known weed species among the genus Bidens. The distinction between both species has been challenging for farmers, agronomists and weed scientists due to their similar morphology. In B. pilosa upper third, the branching is dichotomous, whist it is alternate in B. subalternans (Kissmann and Groth, 1999; GromboneGuaratini et al, 2004)
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