Raphanus raphanistrum

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.

Resistance to the synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) in wild radish (Raphanus raphanistrum) appears to be due to a complex, multifaceted mechanism possibly involving enhanced constitutive plant defence and alterations in auxin signalling. Based on a previous gene expression analysis highlighting the plasma membrane as being important for 2,4-D resistance, this study aimed to identify the components of the leaf plasma membrane proteome that contribute to resistance. Key results included: two receptor-like kinases of unknown function (L-type lectin domain-containing receptor kinase IV.1-like and At1g51820-like) and the ATP-binding cassette transporter ABCB19, an auxin efflux transporter, were identified as being associated with auxinic herbicide resistance.

This paper identifies multiple mechanisms: as well as psbA gene mutation there is a non-target site resistance mechanism of enhanced metabolism. Of course, we expect multiple mechanisms of herbicide resistance as evident here in both target site psbA gene mutation and non-target site enhanced metabolism resistance.

Wild radish (Raphanus raphanistrum) is a globally important weed of crops. Two atrazine-resistant wild radish populations (R1 and R2), collected from the Western Australia grain belt, were investigated for resistance to photosystem II (PSII) herbicides.

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.

In an Australian Research Council funded Linkage project with Nufarm as the industry partner, AHRI researcher Danica Goggin combined a transcriptomic and biochemical approach to investigate the diversity of 2,4-D resistance mechanisms in 11 resistant populations of wild radish. All of these wild radish populations had a relatively high level of resistance to 2,4-D and dicamba, although there were differences between populations in the level of resistance.

The synergistic interaction between mesotrione, a hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide, and atrazine, a photosystem II (PS II)-inhibiting herbicide, has been identified in the control of several weed species.

Wild radish, a problem weed worldwide, is a severe dicotyledonous weed in crops. In Australia, sustained reliance on ALS-inhibiting herbicides to control this species has led to the evolution of many resistant populations endowed by any of several ALS mutations. The molecular basis of ALS-inhibiting herbicide resistance in a novel resistant population was studied.

An understanding of weed species incidence and patterns of change in incidence is vital in developing weed management strategies and directing future research endeavours. Weed incidence in fields in the south-west of Western Australia was surveyed in 1997 and repeated in 2008 to determine any changes.