Detection and quantification of the air inoculum of Caliciopsis pinea in a plantation of Pinus radiata in Italy

Caliciopsis pinea has been historically described as a secondary pathogen of pines. However, it has recently been associated with severe damages on Pinus radiata in Italy. Our study focused on the description of the seasonal spore dispersal of C. pinea and its relation to meteorological conditions (temperature, leaf wetness, relative humidity and precipitations). For this experiment one infected P. radiata plantation was sampled in Tuscany (Italy). A rotating arm spore trap together with a weather station were installed to sample the aerospora for 24 h every week from May to November 2016. Exposed tapes from spore traps were directly analyzed after DNA extraction by qPCR using specific primers and TaqMan MGB probe. The study shows an irregular occurrence of the inoculum of C. pinea throughout the whole sampling period with peak levels in mid-June and early August. The statistical analysis of the DNA and climatic data clearly show the strong influence of precipitation on the spore production of this pathogen. Furthermore, the very low detection limit of the qPCR experiment shows the efficacy and suitability of rotating arm spore traps for early detection of this pathogen

The role of the topological constraints in the chain dynamics in all-polymer nanocomposites

We investigate all-polymer nanocomposites, formed by linear chains and single-chain polymer nanoparticles (SCNPs), by means of large-scale simulations. To distinguish the role of the soft penetrable character of the SCNPs in the topological constraints from other specific contributions present in experiments, the simulations for different compositions of the mixture are performed at constant density and with identical segmental mobility and monomer excluded volume for the SCNPs and linear chains. Every composition leads to a well-dispersed nanocomposite with fully penetrated nanofillers. Hence, unlike in the case of hard nanofillers, the SCNPs do not exert confinement effects on the linear chains and only contribute to the topological constraints. We discuss the intramolecular dynamics of the linear chains in terms of the tube model. We determine the entanglement length of the linear chains by analyzing their isoconfigurational mean paths (IMP) and the primitive paths (PP) as a function of the concentration and topology of the SCNPs. In the analysis we use different estimators proposed in the literature. The IMP and PP analysis in the nanocomposites with sparse SCNPs yields values of the entanglement length smaller and larger, respectively, than in the reference pure linear melt, though small variations are observed. A more consistent trend is found in the nanocomposites with globular SCNPs, where both the IMP and PP analysis unambiguously reveal that the linear chains are more entangled than in the pure linear melt. Such differences between the effects of SCNPs with different topologies are presumably related to the much higher fraction of threadable loops in the globular SCNPs, with respect to their sparse counterparts, which effectively lead to more topological constraints.We acknowledge financial support from the projects MAT2015-63704-P (MINECO-Spain and FEDER-UE) and IT-654-13 (Basque Government, Spain).Peer Reviewe

Effect of chain stiffness on the structure of single-chain polymer nanoparticles

Polymeric single-chain nanoparticles (SCNPs) are soft nano-objects synthesized by purely intramolecular cross-linking of single polymer chains. By means of computer simulations, we investigate the conformational properties of SCNPs as a function of the bending stiffness of their linear polymer precursors. We investigate a broad range of characteristic ratios from the fully flexible case to those typical of bulky synthetic polymers. Increasing stiffness hinders bonding of groups separated by short contour distances and increases looping over longer distances, leading to more compact nanoparticles with a structure of highly interconnected loops. This feature is reflected in a crossover in the scaling behaviour of several structural observables. The scaling exponents change from those characteristic for Gaussian chains or rings in θ-solvents in the fully flexible limit, to values resembling fractal or 'crumpled' globular behaviour for very stiff SCNPs. We characterize domains in the SCNPs. These are weakly deformable regions that can be seen as disordered analogues of domains in disordered proteins. Increasing stiffness leads to bigger and less deformable domains. Surprisingly, the scaling behaviour of the domains is in all cases similar to that of Gaussian chains or rings, irrespective of the stiffness and degree of cross-linking. It is the spatial arrangement of the domains which determines the global structure of the SCNP (sparse Gaussian-like object or crumpled globule). Since intramolecular stiffness can be varied through the specific chemistry of the precursor or by introducing bulky side groups in its backbone, our results propose a new strategy to tune the global structure of SCNPs.We acknowledge financial support from the projects MAT2015-63704-P (MINECO-Spain and FEDER-UE) and IT-654-13 (Basque Government, Spain).Peer Reviewe

The role of the topological constraints in the chain dynamics in all-polymer nano-composites

Trabajo presentado al SoftComp Annual Meeting, celebrado en Venecia (Italia) del 29 al 31 de mayo de 2017.Peer Reviewe