Phosphite shifts physiological and hormonal profile of Monterey pine and delays Fusarium circinatum progression.

Fusarium circinatum is the causal agent of pitch canker disease affecting Pinus spp. and Pseudotsuga menziesii worldwide. Under strict quarantine measures, alternative approaches for disease control are necessary. Phosphite (Phi) salts are known for their fungicidal activity and as plant resistance elicitors; however, its potential is yet to be acknowledged in the Pinus-F. circinatum model. The main aim of this study was to assess whether the application of a Phi-based commercial formulation would delay the progression of the pitch canker on Pinus radiata plants, and on the in vitro fungal growth. In vitro assays were performed using different Phi concentrations (1% and 4%) and a non-treated control (0%), and repeated in vivo using inoculated and non-inoculated plants. Plant physiological parameters and hormonal content were evaluated. Phi was effective at inhibiting in vitro mycelial growth in a dose dependent manner. Regardless of fungal inoculation, Phi application induced positive effects on plant performance, despite phytotoxic effects found at 4%. Fusarium circinatum infection led to a reduction in gas exchange and chlorophyll fluorescence (Fv/Fm and φPSII), while proline and hormone (JA, ABA and SA) levels increased. Phi was effective in delaying disease symptom development in a dose dependent manner, concurrent with in vitro observations: gas exchange and chlorophyll fluorescence (Fv/Fm) were unaffected; proline, MDA and ABA decreased; electrolyte leakage and total soluble sugars increased. This suggests a direct (pathogen growth inhibition) and indirect (host defense priming) action of Phi, showing that Phi represents a potential strategy to control F. circinatum infection.

The development of a phosphite-mediated fertilization and weed control system for rice.

Fertilizers and herbicides are two vital components of modern agriculture. The imminent danger of phosphate reserve depletion and multiple herbicide tolerance casts doubt on agricultural sustainability in the future. Phosphite, a reduced form of phosphorus, has been proposed as an alternative fertilizer and herbicide that would address the above problems to a considerable extent. To assess the suitability of a phosphite-based fertilization and weed control system for rice, we engineered rice plants with a codon-optimized ptxD gene from Pseudomonas stutzeri. Ectopic expression of this gene led to improved root growth, physiology and overall phenotype in addition to normal yield in transgenic plants in the presence of phosphite. Phosphite functioned as a translocative, non-selective, pre- and post-emergent herbicide. Phosphite use as a dual fertilizer and herbicide may mitigate the overuse of phosphorus fertilizers and reduce eutrophication and the development of herbicide resistance, which in turn will improve the sustainability of agriculture.

The effect of an additional phosphite stabilizer on the properties of radiation cross-linked vitamin E blends of UHMWPE.

Antioxidant stabilization of radiation cross-linked ultrahigh molecular weight polyethylene (UHMWPE) has been introduced to improve the oxidative stability of total joint implant bearing surfaces. Blending of an antioxidant with UHMWPE resin powder followed by consolidation and radiation cross-linking has been cleared by the FDA for use in both total hips and total knees for designs incorporating two antioxidants, namely vitamin E and Covernox™ (a medical grade version of Irganox™ 1010). The antioxidants in the polymer are expected to protect the polymer during consolidation, during radiation cross-linking, on the shelf before implantation, and in vivo after implantation. To maximize the protection of the polymer afforded by the antioxidant in vivo, a novel approach may be the use of multiple antioxidants, especially to protect the primary antioxidant for a longer period of time. We hypothesized that the addition of a phosphite stabilizer (Irgafos 168™) commonly used in conjunction with hindered phenolic antioxidants in polymer processing could improve the oxidative stability of radiation cross-linked blends of vitamin E. To test our hypothesis, we prepared UHMWPE blends with 0.05 wt% Irgafos and 0.05 wt% vitamin E and compared its cross-link density, wear resistance, tensile properties, and impact strength to control blends containing only vitamin E. Our hypothesis was not supported; the cross-link density of UHMWPE was significantly decreased by the additive without additional benefit to oxidative stability. To our knowledge, this was the first attempt at using multiple stabilizers in medical grade UHMWPE.

Triphenyl phosphite and diisopropylphosphorofluoridate produce separate and distinct axonal degeneration patterns in the central nervous system of the rat.

This study compared the neurotoxic effects of triphenyl phosphite (TPP) in the rat with those seen after exposure to diisopropylphosphorofluoridate (DFP), a compound known to produce organophosphorus-induced delayed neurotoxicity (OPIDN). Animals received either three subcutaneous injections of TPP (1184 mg/kg body wt each dose) administered at 3-day intervals or a single subcutaneous injection of DFP (4 mg/kg body wt). TPP-induced clinical signs were initially observed 2 to 18 days after the last injection and included ataxia, flaccid paresis, stereotyped alternating side-to-side movements, and circling behavior. Axonal and terminal degeneration were present in the cerebellum, vestibular nuclear complex, cochlear nuclei, and superior and inferior colliculi. The subthalamic nucleus, substantia nigra, septal region, hypothalamus, thalamus, hippocampus, and cerebral cortex also contained degenerating axons and terminals. Degeneration was particularly evident in the sensorimotor cerebral cortex, mediodorsal, ventromedial, and medial geniculate thalamic nuclei and in the magnocellular preoptic and medial mammillary nuclei of the hypothalamus. Very light degeneration was present in the gracile fasciculus and nucleus. In contrast, rats injected with DFP showed moderate degeneration in the gracile fasciculus and nucleus but did not display degeneration in any other brain region. Injections of DFP did not produce delayed onset clinical signs. The results indicate that in the rat, different central nervous system cell groups are affected by these two organophosphorus compounds and that TPP affects nuclei and tracts at all levels of the neuraxis, including those associated with higher-order processing and cognitive functions. In addition, the distinct degeneration patterns produced by these two compounds support the view that TPP-induced neurotoxicity should not be considered as a type of OPIDN, but rather as a separate category of organophosphorus-induced neurotoxicity.

Triphenyl phosphite-induced impairment of spatial alternation learning.

Triphenyl phosphite (TPP) is a weak acetylcholinesterase inhibitor and a type II organophosphorus compound-induced delayed neurotoxic agent. The current study examined the cognitive effects of a single 250 mg/kg ip dose of TPP administered to either 3-mo- or 1-yr-old male Sprague-Dawley rats. Starting 4 d after TPP administration, the rats began training on a T-maze spatial alternation task for food reinforcement. Over five sessions of acquisition training, the TPP-treated rats showed significantly lower alternation scores than controls. There was no difference in spatial alternation performance in the first session, when both groups were performing at near-chance levels. In sessions 2-5, the controls improved dramatically to an average of 85.3 +/- 3.2% correct, while the TPP-treated rats did not significantly change, with 69.7 +/- 3.1 percent correct. During sessions 2 and 3 there was a significant TPP treatment-related deficit. This TPP-induced choice accuracy deficit was persistent in that it was seen well after the acute exposure. With continued training the TPP-exposed rats were able to learn the task as well as controls. There were no significant TPP effects on response latency. These data show that acute TPP administration has persistent effects of impairing T-maze learning that do not appear to result from effects on motor function.