BACKGROUND Poa annua is a widespread winter annual weed species in California. Recently, poor control of this species with glyphosate was reported by growers in an almond orchard in California with a history of repetitive glyphosate use. The objectives of this research were to evaluate the level of glyphosate resistance in a developed S4 P. annua line (R) and identify the mechanisms of resistance involved. RESULTS Whole‐plant dose–response experiments confirmed glyphosate resistance in R, which required 18‐fold more glyphosate to achieve a 50% growth reduction compared with a susceptible line (S), results that were supported by the lower shikimate accumulation observed in R compared with S. No differences in glyphosate absorption, translocation, or metabolism were observed, suggesting that non‐target‐site mechanisms of resistance are not involved in the resistance phenotype. A missense single nucleotide polymorphism was observed in EPSPS coding position 106 in R, resulting in a leucine to proline substitution. This polymorphism was observed exclusively in P. supina EPSPS homeologs. A seven‐fold increase in the number of copies of EPSPS alleles was observed in R compared with S. CONCLUSIONS We report the first case of glyphosate resistance associated with both EPSPS duplication and target‐site mutation at position 106, leading to high levels of glyphosate resistance in the allotetraploid weed species Poa annua L. Data obtained in this research will be useful for the development of diagnostic tools for rapid glyphosate resistance identification, monitoring and containment. © 2018 Society of Chemical Industry

It is important to determine the three-dimensional nonuniform deformation of articular cartilage in its native environment. A new magnetic resonance imaging (MRI)-based technique (cartilage deformation by tag registration (CDTR)) has been developed, which can determine such deformations provided that the compressive load-displacement response of the knee reaches a quasi-steady state during cyclic loading. The objectives of this study were (1) to design and construct an apparatus to cyclically compress human cadaveric knees to physiological loads in a MRI scanner, (2) to determine the number of load cycles required to reach a quasi-steady-state load-displacement response for cyclic loading of human cadaveric knees, and (3) to collect sample MR images of undeformed and deformed states of tibiofemoral cartilage free of artifact while using the apparatus within a MRI scanner. An electropneumatic MRI-compatible apparatus was constructed to fit in a clinical MRI scanner, and a slope criterion was defined to indicate the point at which a quasi-steady-state load-displacement response, which would allow the use of CDTR, occurred during cyclic loading of a human knee. The average number of cycles required to reach a quasi-steady-state load-displacement response according to the slope criterion defined herein for three cadaveric knee joints was 356+/-69. This indicates that human knee joint specimens can be cyclically loaded such that deformation is repeatable according to MRI requirements of CDTR. Sample images of tibiofemoral cartilage were obtained for a single knee joint. These images demonstrate the usefulness of the apparatus in a MRI scanner. Thus the results of this study are a crucial step toward developing a MRI-based method to determine the deformations of articular cartilage in whole human cadaveric knees.

There is a need to align the mechanical axis of the tibia with the axis of loading for studies involving tibiofemoral compression to interpret results and to ensure repeatability of loading within and among specimens. Therefore, the objectives of this study were (1) to develop a magnetic resonance imaging (MRI)-based alignment method for use with apparatuses applying tibiofemoral joint compression, (2) to demonstrate the usefulness of the method by aligning cadaveric knees in an apparatus that could apply tibiofemoral joint compression, and (3) to quantify the error associated with the alignment method. A four degree-of-freedom adjustable device was constructed to allow determination and alignment of the mechanical axis of the tibia of cadaveric knee joints with the axis of loading of an apparatus applying tibiofemoral joint compression. MRI was used to determine the locations of bony landmarks in three dimensions defining the mechanical axis of the tibia relative to an initial orientation of the four degree-of-freedom device. Adjustment values of the device were then computed and applied to the device to align the mechanical axis of the tibia with the axis of a compressive loading apparatus. To demonstrate the usefulness of the method, four cadaveric knees were aligned in the compressive loading apparatus. The vectors describing the mechanical axis of the tibia and the loading axis of the apparatus before and after adjustment of the four degree-of-freedom device were computed for each cadaveric knee. After adjustment of the four degree-of-freedom device, the mechanical axis of the tibia was collinear with the loading axis of the apparatus for each cadaveric knee. The errors in the adjustment values introduced by inaccuracies in the MR images were quantified using the Monte Carlo technique. The precisions in the translational and rotational adjustments were 1.20 mm and 0.90 deg respectively. The MR-based alignment method will allow consistent interpretation of results obtained during tibiofemoral compressive studies conducted using the apparatus described in this paper by providing a well-defined loading axis. The alignment method can also be adapted for use with other apparatuses applying tibiofemoral compression.

Almonds [Prunus dulcis (Mill.) D.A. Webb] are grown on nearly 650,000 hectares in California and generate nearly $4.9 billion in export revenue annually, primarily to the European Union (EU). To facilitate harvest operations, broad-spectrum herbicides, such as glyphosate and/or glufosinate, are commonly used to control vegetation prior to harvest. The current minimum preharvest interval (PHI) for glyphosate and glufosinate herbicides registered in the US are three and 14 days, respectively. The maximum residue limit (MRL) for glyphosate and glufosinate in almonds in the EU is 0.1 mg kg−1 however, a recent study recommended the glyphosate MRL be reduced to 0.05 mg kg−1. Laboratory and field experiments were conducted to evaluate herbicide transfer from soil to almonds and the effect of longer PHIs on glyphosate and glufosinate residues in harvested almonds. After harvest operations, almonds were dissected into hulls, shells, and kernels for analysis of glyphosate, glufosinate, and their metabolites using LC-MS/MS. In the field experiment, glyphosate and glufosinate were detected at 0.121 to 0.291 mg kg−1 in almond hulls and shells. Glyphosate and primary metabolites were below the LOD in almond kernels at all PHIs. Glufosinate was below the LOD but the metabolite 3-(methylphosphinico)propionic acid (MPP) was detected at 0.03 – 0.075 mg kg−1 in kernels from some replicate plots. There were no significant differences in either herbicide or any metabolite among PHI treatments. The lab experiment showed decreasing residue levels from hull to shell to kernel; furthermore, rinsing kernels resulted in a 71% and 46% reduction in [14C]-glyphosate and glufosinate, respectively which suggest much of the herbicide residue may be associated with dust on the kernel surfaces. The results of these experiments indicate very low levels of herbicide transfer from soil to almonds and increasing the PHI within the tested range did not reduce the already low amounts of herbicide or metabolites in almonds.

California is the top producer of almonds [Prunus dulcis (Mill.) D.A. Webb] worldwide, generating over $6 billion in revenue in 2020; the European Union (EU) is the primary importer of California almonds. Weed control in almond orchards is an important part of the preharvest process because weeds can interfere with harvest equipment and host diseases. Glyphosate and glufosinate are broad spectrum herbicides commonly used for preharvest weed control. Global differences in maximum residue limits (MRLs) and regulated compounds can pose a challenge for growers who rely on broad spectrum herbicides such as glyphosate and glufosinate for preharvest weed control. The EU MRL for glyphosate and total glufosinate is currently 0.1 mg kg-1. The United States MRL for total glyphosate is 1 mg kg-1 and total glufosinate is 0.5 mg kg-1. An 8-week field experiment, from spray to harvest, was conducted in an 8-hectare commercial orchard to evaluate the potential contribution of the preharvest herbicide treatment to low levels of herbicide residue in almonds. Then, the same batch of almonds were followed through a commercial processing facility to evaluate the potential movement of herbicide residues from soil, debris, and hulls to almond kernels during processing. Glyphosate was not detected in any almond kernel samples at the end of processing. 3-(methylphosphinico)propionic acid (MPP), a glufosinate metabolite, was detected in kernels at the end of processing at about 0.1 mg kg-1, which is above the EU MRL for total glufosinate. Almonds sampled directly from the tree, without any contact with soil, were found to have elevated MPP residues. This indicates glufosinate or MPP translocation may be a factor in low level glufosinate residues detected in almonds in some EU exports.