The use of phosphonates in agriculture. Chemical, biological properties and legislative issues

Impact of Spray Concentration and Application Frequency to Modulate Phosphonic Acid Residues in Container-Grown Grapevines

This study investigated the translocation and persistence of inorganic phosphonate in container-grown vines of Vitis vinifera L. cv. Riesling after foliar and soil applications over two consecutive years. Phosphonate concentrations were monitored in leaves, petioles, grape canes, shoot tips, inflorescences, and berries during the season, applying an identical total amount of 3 or 4 sprays of 0.54 or 0.4% (w/v, aq) phosphonate, respectively. The overall uptake of inorganic phosphonate into the leaves was either identical (year 1) or substantially lower (year 2) when spraying 3 times (0.54%) instead of 4 times (0.4%) as expressed by the area under the concentration vs time curve. Residues found in leaves at the end of the vegetation period were also lower when spraying 3 times. Across both years, residues in berries were also significantly lower when applying the 0.54% phosphonate solution (20.2-30.9 mg/kg) 3 times as compared with the 4× application of 0.4% phosphonate (38.5-40.6 mg/kg). Soil applications resulted in a comparably low overall uptake but still yielding measurable residues in berries (6.0 ± 1.2 mg/kg). Further data on grape cane, shoot tips, and inflorescences supported the hypothesis that phosphonate residues in the plant and, ultimately, in the berries and the resulting products might be significantly reduced when spraying 3 times (0.54%) instead of 4 times (0.4%).

Thalassobellus suaedae gen. nov., sp. nov., a marine bacterium of the family Flavobacteriaceae isolated from a halophyte Suaeda japonica

Two Gram-stain-negative, facultative anaerobic, rod-shaped and non-gliding bacteria, designated as HL-DH10T and HL-DH14, were isolated from the halophyte Suaeda japonica in a mudflat, Republic of Korea. Based on the results of 16S rRNA gene pairwise analysis, the two isolates were the members of the family Flavobacteriaceae, and Aestuariibaculum suncheonense SC17T was the most closely related to strains HL-DH10T and HL-DH14 with 96.3% and 95.4% sequence similarity, respectively. The average nt identity and digital DNA-DNA hybridization values between strains HL-DH10T and HL-DH14 and other related species were all less than 79.2% and 21.9%, respectively. The genomic DNA G+C contents of strains HL-DH10T and HL-DH14 were 32.0% and 31.5%, respectively. Cells of these strains showed optimal growth at 25 °C, pH 6.5-7.0 and 2.5-4.0% (w/v) sea salts. The major respiratory quinone was menaquinone-6. The major cellular fatty acids were iso-C15:0 (14.0-16.0%), iso-C15:1 G (10.0-12.0%), iso-C17:0 3-OH (12.4-13.9%), iso-C15:0 3-OH (11.8-14.9%) and anteiso-C15:0 (9.4-10.6%). The polar lipids consisted of phosphatidylethanolamine, an unidentified aminophospholipid, two to three unidentified aminolipids and three unidentified lipids. The comprehensive phylogenetic, genomic, phenotypic and chemotaxonomic results indicate that strains HL-DH10T and HL-DH14 are considered to represent a novel genus of Flavobacteriaceae. Hence, we propose the novel genus Thalassobellus suaedae gen. nov., sp. nov. The type strain is HL-DH10T (=KCCM 90512T=JCM 36598T).

Disentangling the Regulatory Response of Agrobacterium tumefaciens CHLDO to Glyphosate for Engineering Whole-Cell Phosphonate Biosensors

Phosphonates (PHTs), organic compounds with a stable C-P bond, are widely distributed in nature. Glyphosate (GP), a synthetic PHT, is extensively used in agriculture and has been linked to various human health issues and environmental damage. Given the prevalence of GP, developing cost-effective, on-site methods for GP detection is key for assessing pollution and reducing exposure risks. We adopted Agrobacterium tumefaciens CHLDO, a natural GP degrader, as a host and the source of genetic parts for constructing PHT biosensors. In this bacterial species, the phn gene cluster, encoding the C-P lyase pathway, is regulated by the PhnF transcriptional repressor. We selected the phnG promoter, which displays a dose-dependent response to GP, to build a set of whole-cell biosensors. Through stepwise genetic optimization of the transcriptional cascade, we created a whole-cell biosensor capable of detecting GP in the 0.25-50 μM range in various samples, including soil and water.

The Role of Phosphate-Solubilizing Microbial Interactions in Phosphorus Activation and Utilization in Plant-Soil Systems: A Review

To address the issue of phosphorus limitation in agricultural and forestry production and to identify green and economical alternatives to chemical phosphorus fertilizers, this paper reviews the utilization of phosphorus in plant-soil systems and explores the considerable potential for exploiting endogenous phosphorus resources. The application of phosphate-solubilizing microorganisms (PSMs) is emphasized for their role in phosphorus activation and plant growth promotion. A focus is placed on microbial interactions as an entry point to regulate the functional rhizosphere microbiome, introducing the concept of synthetic communities. This approach aims to deepen the understanding of PSM interactions across plant root, soil, and microbial interfaces, providing a theoretical foundation for the development and application of biological regulation technologies to enhance phosphorus utilization efficiency.

Supramolecular Binding of Phosphonate Dianions by Nanojars and Nanojar Clamshells

Despite the widespread use of phosphonates (RPO32-) in various agricultural, industrial, and household applications and the ensuing eutrophication of polluted water bodies, the capture of phosphonate ions by molecular receptors has been scarcely studied. Herein, we describe a novel approach to phosphonate binding using chemically and thermally robust supramolecular coordination assemblies of the formula [RPO3⊂{cis-CuII(μ-OH)(μ-pz)}n]2- (Cun; n = 27-31; pz = pyrazolate ion, C3H3N2-; R = aliphatic or aromatic group). The neutral receptors, termed nanojars, strongly bind phosphonate anions by a multitude of hydrogen bonds within their highly hydrophilic cavities. These nanojars can be synthesized either directly from their constituents or by depolymerization of [trans-CuII(μ-OH)(μ-pz)]∞ induced by phosphonate anions. Electrospray-ionization mass spectrometry, UV-vis and variable-temperature, paramagnetic 1H and 31P NMR spectroscopy, single-crystal X-ray diffraction, along with chemical stability studies toward NH3 and Ba2+ ions, and thermal stability studies in solution are employed to explore the binding of various phosphonate ions by nanojars. Crystallographic studies of 12 different nanojars offer unprecedented structural characterization of host-guest complexes with doubly charged RPO32- ions and reveal a new motif in nanojar chemistry, nanojar clamshells, which consist of phosphonate anion-bridged pairs of nanojars and double the phosphonate-binding capacity of nanojars.

Whole Genome Sequencing Reveals Novel Insights about the Biocontrol Potential of Burkholderia ambifaria CF3 on Atractylodes lancea

Root rot caused by Fusarium spp. is the most destructive disease on Atractylodes lancea, one of the large bulks and most common traditional herbal plants in China. In this study, we isolated a bacterial strain, CF3, from the rhizosphere soil of A. lancea and determined its inhibitory effects on F. oxysporum in both in vitro and in vivo conditions. To deeply explore the biocontrol potential of CF3, we sequenced the whole genome and investigated the key pathways for the biosynthesis of many antibiotic compounds. The results revealed that CF3 is a member of Burkholderia ambifaria, harboring two chromosomes and one plasmid as other strains in this species. Five antibiotic compounds were found that could be synthesized due to the existence of the bio-synthesis pathways in the genome. Furthermore, the synthesis of antibiotic compounds should be confirmed by in vitro experiments and novel compounds should be purified and characterized in further studies.

Ligand-Free Iron-Catalyzed Construction of C-P Bonds via Phosphorylation of Alcohols: Synthesis of Phosphine Oxides and Phosphine Compounds

An efficient method for the construction of C-P(V) and C-P(III) bonds via the iron-catalyzed phosphorylation of alcohols under ligand-free conditions is disclosed. This strategy represents a straightforward process to prepare a series of phosphine oxides and phosphine compounds in good to excellent yields from the readily available alcohols and P-H compounds. A plausible mechanism is also proposed. We anticipate that this mode of transforming simple alcohols would apply in chemical synthesis widely.

A review of organophosphonates, their natural and anthropogenic sources, environmental fate and impact on microbial greenhouse gases emissions - Identifying knowledge gaps

Organophosphonates (OPs) are a unique group of natural and synthetic compounds, characterised by the presence of a stable, hard-to-cleave bond between the carbon and phosphorus atoms. OPs exhibit high resistance to abiotic degradation, excellent chelating properties and high biological activity. Despite the huge and increasing scale of OP production and use worldwide, little is known about their transportation and fate in the environment. Available data are dominated by information concerning the most recognised organophosphonate - the herbicide glyphosate - while other OPs have received little attention. In this paper, a comprehensive review of the current state of knowledge about natural and artificial OPs is presented (including glyphosate). Based on the available literature, a number of knowledge gaps have been identified that need to be filled in order to understand the environmental effects of these abundant compounds. Special attention has been given to GHG-related processes, with a particular focus on CH4. This stems from the recent discovery of OP-dependent CH4 production in aqueous environments under aerobic conditions. The process has changed the perception of the biogeochemical cycle of CH4, since it was previously thought that biological methane formation was only possible under anaerobic conditions. However, there is a lack of knowledge on whether OP-associated methane is also formed in soils. Moreover, it remains unclear whether anthropogenic OPs affect the CH4 cycle, a concern of significant importance in the context of the increasing rate of global warming. The literature examined in this review also calls for additional research into the date of OPs in waste and sewage and in their impact on environmental microbiomes.

Plant Resistance Inducers Affect Multiple Epidemiological Components of Plasmopara viticola on Grapevine Leaves

Plant resistance inducers (PRIs) harbor promising potential for use in downy mildew (DM) control in viticulture. Here, the effects of six commercial PRIs on some epidemiological components of Plasmopara viticola (Pv) on grapevine leaves were studied over 3 years. Disease severity, mycelial colonization of leaf tissue, sporulation severity, production of sporangia on affected leaves, and per unit of DM lesion were evaluated by inoculating the leaves of PRI-treated plants at 1, 3, 6, 12, and 19 days after treatment (DAT). Laminarin, potassium phosphonate (PHO), and fosetyl-aluminium (FOS) were the most effective in reducing disease severity as well as the Pv DNA concentration of DM lesions on leaves treated and inoculated at 1 and 3 DAT; PHO and FOS also showed long-lasting effects on leaves established after treatment (inoculations at 6 to 19 DAT). PRIs also prevented the sporulation of Pv on lesions; all the PRI-treated leaves produced fewer sporangia than the nontreated control, especially in PHO-, FOS-, and cerevisane-treated leaves (>75% reduction). These results illustrate the broader and longer effect of PRIs on DM epidemics. The findings open up new perspectives for using PRIs in a defense program based on single, timely, and preventative field interventions.

An alternative C-P cross-coupling route for the synthesis of novel V-shaped aryldiphosphonic acids

The synthesis of phosphonate esters is a topic of interest for various fields, including the preparation of phosphonic acids to be employed as organic linkers for the construction of metal phosphonate materials. We report an alternative method that requires no solvent and involves a different order of addition of reactants to perform the transition-metal-catalyzed C-P cross-coupling reaction, often referred to as the Tavs reaction, employing NiCl2 as a pre-catalyst in the phosphonylation of aryl bromide substrates using triisopropyl phosphite. This new method was employed in the synthesis of three novel aryl diphosphonate esters which were subsequently transformed to phosphonic acids through silylation and hydrolysis.