Endothall behavior in Myriophyllum spicatum and Hydrilla verticillata

2,4-D and 2,4-D butoxyethyl ester behavior in Eurasian and hybrid watermilfoil (Myriophyllum spp.)

BACKGROUND

Hybrid watermilfoil is becoming more prevalent in many lakes where the invasive Eurasian (Myriophyllum spicatum, EWM) and native northern watermilfoil (M. sibiricum) co-occur. These Eurasian and northern watermilfoil hybrids (HWM) grow 30% faster and in many cases are less sensitive to 2,4-dichlorophenoxy acetic acid (2,4-D) than either parent. The mechanism(s) impacting 2,4-D tolerance in these hybrids was investigated by comparing the absorption, translocation, metabolism, and desorption of two 2,4-D formulations in EWM and HWM.

RESULTS

2,4-D absorption in EWM and HWM was 5.7 and 7.9 times the external herbicide concentration determined by the plant concentration factor, a metric used to determine herbicide bioaccumulation, and 2,4-D butoxyethyl ester absorption was 35.6 and 52.1 times the external concentration in EWM and HWM, respectively. Herbicide bioaccumulation was greater in HWM than in EWM. Herbicide translocation to HWM roots was limited at 192 HAT and herbicide desorption in HWM was slightly lower than EWM. No differences were found in herbicide metabolism between the two plant species.

CONCLUSION

2,4-D resistance in HWM is not due to non-target-site resistance as no differences in herbicide absorption, translocation, desorption and/or metabolism were identified; therefore, target-site resistance is the most likely resistance mechanism. More research is needed to identify the molecular basis for the 2,4-D-resistant trait in HWM. © 2021 Society of Chemical Industry.

Discovery of novel potential plant growth regulators from Corydalis mucronifera

Three pairs of enantiomers mucroniferals A-C (1-3), with a novel skeleton of 1,4-epoxynaphthalene-2,3-dicarboxylic acid first reported from nature source, were isolated from Corydalis mucronifera. Their structures were elucidated based on extensive spectroscopic data analysis of MS, 1D and 2D NMR, and their absolute configurations were confirmed by single-crystal X-ray diffraction analysis and comparison of the experimental and calculated ECD data. Mucroniferals A-C showed broad-spectrum inhibitory activities on seedling growth of all plants tested (Lepidium apetalum, Raphanus sativus, Lactuca sativa, and Arabidopsis thaliana) with a dose-dependent relationship. Additionally, mucroniferals A and B exhibited significant inhibitory effects on germination of most seeds at concentration of 80 μg/mL, and the inhibition was reversible.

Current Status and Future Prospects in Herbicide Discovery

Herbicides represent about 60% of the pesticides (by volume) used worldwide. The success of herbicides can be attributed in part to a relatively steady discovery of one unique mechanisms of action (MOA) every two years from the early 1950s to the mid-1980s. While this situation changed dramatically after the introduction of glyphosate-resistant crops, evolution of resistance to glyphosate has renewed the agrichemical industry interest in new chemistry interacting with novel target sites. This review analyses recent characterization of new herbicide target sites, the chemical classes developed to inhibit these target sites, and where appropriate the innovative technologies used in these discovery programs.