Identification of field resistance to HPPD-inhibiting herbicides in wild radish (Raphanus raphanistrum)

Abstract

The control of multiple-resistant wild radish (Raphanus raphanistrum L.) populations in no-till Australian wheat crops has relied upon 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides over the last decade. Two R. raphanistrum populations identified as putatively resistant to pyrasulfotole + bromoxynil in an initial large-scale screening trial were characterized and confirmed to be 5- to 8-fold (comparison of LD50 values) less sensitive than the susceptible control population to the HPPD inhibitor pyrasulfotole when plants were treated at the four-leaf stage. The two pyrasulfotole-resistant populations exhibited up to 4-fold resistance to the co-formulated herbicide mixture pyrasulfotole + bromoxynil and up to 9- and 11-fold cross-resistance to mesotrione and topramezone post-emergence, respectively. A small-plot trial was conducted in the field from which of one of the populations suspected of resistance was originally collected. Pyrasulfotole + bromoxynil or topramezone + bromoxynil applied post-emergence delivered reduced R. raphanistrum control (79-87%), whereas mesotrione applied pre-emergence was >99% effective. We report here the first case of field resistance to HPPD-inhibiting herbicides in R. raphanistrum, caused by 12 years of continuous reliance on that mode of action. The mitigation of herbicide resistance in continuous no-till cropping requires a constant optimization of the herbicide technology via alternation and mixtures of multiple sites of action, use of pre-emergence herbicides, and ensuring post-emergence herbicides are applied to most sensitive plant growth stages.

Multiple Metabolic Enzymes Can Be Involved in Cross-Resistance to 4-Hydroxyphenylpyruvate-Dioxygenase-Inhibiting Herbicides in Wild Radish

“…55 Recently, two wild radish populations with a 12 year use history of HPPD-inhibiting herbicides showed relatively high levels of resistance (about 10-fold) to mesotrione, pyrasulfotole, and topramezone. 16 Because the resistance in the R wild radish population investigated in our study was not directly selected by HPPD-inhibiting herbicides and the resistance level is modest, the identified NTSR genes can be different from those involved in a higher level of resistance in other wild radish populations.…”

“…7−14 Recently, resistance to HPPDinhibiting herbicides has been reported in three Australian wild radish (Raphanus raphanistrum) populations: one with no history of HPPD-inhibiting herbicide usage 15 and two with longterm exposure to the herbicides. 16 Herbicide resistance can be target-site-and/or non-targetsite-based. Target-site resistance (TSR) is endowed by mutation(s) or overproduction of a target protein.…”

“…As a result of their high efficacy, crop selectivity, low toxicity, and broad-spectrum weed control, these herbicides are now being globally used in major grain crops maize (Zea mays), wheat (Triticum aestivum), and rice (Oryza sativa) and recently in genetically modified (GM) soybean (Glycine max) . Despite their considerable usage, especially in maize crops in the Americas, resistance evolution to HPPD-inhibiting herbicides has thus far been identified in a limited number of weed species, such as waterhemp (Amaranthus tuberculatus) and Palmer amaranth (Amaranthus palmeri). − Recently, resistance to HPPD-inhibiting herbicides has been reported in three Australian wild radish (Raphanus raphanistrum) populations: one with no history of HPPD-inhibiting herbicide usage and two with long-term exposure to the herbicides …”

Exploring chemical control of 2,4-D–resistant wild radish (Raphanus raphanistrum) with auxin-related compounds

“…Replacing 2,4-D with an alternative auxinic herbicide (MCPA, mecoprop, halauxifen) was also ineffective, and in any case would likely lead to a resistance problem even if the treatments were initially successful (Vencill et al 2012). Chemical control of 2,4-D-resistant R. raphanistrum is likely to be more successful when two (or more) different modes of action are mixed, as demonstrated in Busi et al (2022). Nonchemical R. raphanistrum control tactics that have shown promise in field-based studies are centered around depletion of the soil seedbank by (1) using minimal tillage, leaving the seeds exposed to harsh conditions and ant predation over summer; (2) incorporating a pasture phase in which slashing and cutting are timed to minimize flowering and seed set; (3) collecting weed seeds at harvest; and (4) avoiding introduction of weed seeds from contaminated farm equipment, stock feed, or grain (Cheam et al 2008).…”