The paired deletion flanking the degron region of SoIAA20 likely provides resistance to 2,4-D by restricting the movement of 2,4-D from the treated tissue to the rest of the plant.
Previous studies have shown a wide range of 2,4-D translocation phenotypes in resistant populations of the agricultural weed Raphanus raphanistrum, but it was hypothesised that enhanced movement out of the apical meristem could contribute to resistance.
The aim of this study was to determine if compounds involved in auxin biosynthesis, transport and signalling are able to synergise with 2,4-D and increase its ability to control 2,4-D-resistant R. raphanistrum populations.
We have previously demonstrated that an aldo-keto reductase (AKR) from Echinochloa colona (EcAKR4-1) can metabolize glyphosate and confers glyphosate resistance. This study aims to investigate if the EcAKR4-1 orthologs from Lolium rigidum also play a role in glyphosate resistance in non-target-site based, glyphosate-resistant (R) L. rigidum populations from Western Australia.
Glyphosate is often tank-mixed with auxinic herbicide 2,4-D for grass and broadleaf weed control. In this paper, the authors examined the possible interaction of 2,4-D and glyphosate in barnyard grass, Echinochloa colona. The results showed that 2,4-D antagonizes glyphosate remarkably in glyphosate resistant populations but only marginally in susceptible populations. This antagonism is related to reduced glyphosate uptake and (to a lesser extent) translocation. As 2,4-D has multiple, unpredictable effects on other herbicides, care must be taken when tank-mixing herbicides with 2,4-D.
Resistance to the auxinic herbicides 2,4-D and dicamba is widespread in Western Australian R. raphanistrum populations, with the resistance mechanism appearing to involve alterations in the physiological response to synthetic auxins and in plant defense. This study aimed to determine whether these alterations cause inhibition in plant growth or reproduction that could potentially be exploited to manage 2,4-D–resistant populations in cropping areas.
Synthetic auxin herbicides, such as 2,4-dichlorophenoxyacetic acid (2,4-D), are widely used for selective control of broadleaf weeds in cereals and transgenic crops.
An overall finding of this study of auxinic herbicide resistance, at least in Raphanus R populations, is that conclusions on mechanisms cannot be made from studying just a few R populations. There are very clear differences between and within resistant populations. This research is ongoing in an attempt to reveal the important mechanisms that can endow resistance to 2,4-D and dicamba in plants.
Arelatively low number of weed species have evolved resistance to auxinic herbicides despite their use for almost 70 years. This inheritance study with two Raphanus raphanistrum populations multiple-resistant 2,4-D and the ALS-inhibiting herbicide chlorsulfuron determined the number of genes and genetic dominance of 2,4-D resistance and investigated the association between traits conferring resistance to the two herbicide modes of action. Levels of 2,4-D phenotypic resistance and resistance segregation patterns were assessed in parental populations, F1 and F2 families.
When used at effective doses, weed resistance to auxinic herbicides has been slow to evolve when compared with other modes of action. Here we report the evolutionary response of a herbicide-susceptible population of wild radish (Raphanus raphanistrum L.) and confirm that sublethal doses of 2,4-dichlorophenoxyacetic acid (2,4-D) amine can lead to the rapid evolution of 2,4-D resistance and cross-resistance to acetolactate synthase (ALS)-inhibiting herbicides.
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