wild radish

Herbicides that inhibit HPPD have become very important. In North America, corn-selective HPPD herbicides have long been used and cases of HPPD herbicide-resistant weeds reported. 

The paper “Non-target site resistance to PDS-inhibiting herbicides in a wild radish Raphanus raphanistrum population” is the work of AHRI PhD student Huan Lu.

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.

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.

Rice is a major field crop of paramount importance for global food security. However, the increased adoption of more profitable and resource-efficient direct-seeded rice (DSR) systems has contributed to greater weed infestations, including weedy rice, which has become a severe problem in several Asian regions. In this study we have developed a conceptually novel method to protect rice plants at high doses of clomazone and triallate.

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.

Herbicides have been the primary tool for controlling large populations of yield depleting weeds from agro-ecosystems, resulting in the evolution of widespread herbicide resistance. In response, nonherbicidal techniques have been developed which intercept weed seeds at harvest before they enter the soil seed bank.