Current status of community resources and priorities for weed genomics research.

Weeds are attractive models for basic and applied research due to their impacts on agricultural systems and capacity to swiftly adapt in response to anthropogenic selection pressures. Currently, a lack of genomic information precludes research to elucidate the genetic basis of rapid adaptation for important traits like herbicide resistance and stress tolerance and the effect of evolutionary mechanisms on wild populations. The International Weed Genomics Consortium is a collaborative group of scientists focused on developing genomic resources to impact research into sustainable, effective weed control methods and to provide insights about stress tolerance and adaptation to assist crop breeding.

Phytoremediation of quinclorac and tebuthiuron-polluted soil by green manure plants.

Quinclorac and tebuthiuron are residual herbicides that may remain in the soil longer than for the cropping season. The objective of this research was to evaluate the use of green manure plants to remediate soils treated with quinclorac and tebuthiuron. Soils were separately treated with 14C-quinclorac and 14C-tebuthiuron at 266.4 and 132 g ha-1, respectively. After 21 days, four green manure plants, namely Crotalaria spectabilis, Canavalia ensiformis, Stizolobium aterrimum, and Lupinus albus, were separately sown in the treated soils. Overall, all four species absorbed more 14C-tebuthiuron [C. ensiformes (22.49%), S. aterrimum (16.71%), L. albus (15%), and C. spectabilis (4.48%)] than 14C-quinclorac [C. ensiformis (13.44%), L. albus (10.02%), S. aterrimum (6.2%), and C. spectabilis (1.75%)]. Quinclorac translocation in all four plants was greater in young leaves compared to old leaves, cotyledons, or roots, and 14C-tebuthiuron translocation in all four plant species was greater in old leaves and cotyledons compared to young leaves or roots. Regardless of the differences in translocation between the two herbicides, the four green manure plants are capable to remediate soils that have been treated with quinclorac and tebuthiuron. However, C. ensiformis is more efficient for the remediation of tebuthiuron-treated soil compared to the other plants.

Quantification of the fate of mesotrione applied alone or in a herbicide mixture in two Brazilian arable soils.

The effects of mesotrione, S-metolachlor, and terbuthylazine, applied in mixture, on soil biodegradation remain insufficiently researched. However, herbicide mixtures have been a common practice in agricultural systems in the last years. Understanding the fate of soil-applied herbicides may help on planning weed management tactics towards more sustainable and efficient weed control. Therefore, this study evaluated the fate of mesotrione alone and in mixture with S-metolachlor and terbuthylazine when applied to two contrasting arable Brazilian soils. Mineralization and degradation experiments were conducted using 14C-mesotrione alone or in mixture. From the 49-day laboratory incubation data, increased mineralization half-life of mesotrione was observed for the mixture of herbicides, ranging from a 4-day increase for the sandy loam soil to a 1-day increase in the sandy clay texture soils. Mesotrione degradation rate had a twofold increase in the sandy loam compared to the sandy clay soil. Two metabolites can be identified from mesotrione degradation, 4-methyl-sulfonyl-2-nitrobenzoic acid (MNBA) and 2-amino-4-methylsulfonyl benzoic acid (AMBA). Indices for the score of ubiquity in groundwater indicated mesotrione possesses leaching potential for both soils. Applying mesotrione alone or in mixture did not influence the amount of bound residues from mesotrione. However, mesotrione degradation rate was influenced by soil texture regardless if applied alone or in mixture. Mesotrione biotransformation was relatively quick, indicating that this herbicide has low persistence and, consequently, low residual effect on crops and weeds when present in similar soils to this present study.