Linking sintering stresses to nano modification in the microstructure of BaLa4Ti4O15 by transmission electron microscopy

High quality factor and a temperature stable resonant frequency make BaLa 4 Ti 4 O 15 (BLT) ceramics attractive materials for microwave applications. Aiming to exploit the effects of external stresses on the development of textured and anisotropic microstructures to optimise MW properties, the influence of applied external pressure during sintering of BLT ceramics is analysed. HRTEM and geometric phase analysis (GPA) showed that stresses applied during sintering, trigger the nucleation and growth of faults hypothesised to be due to the errors in the AO 3 layer (basal plane) stacking sequence of the hexagonal perovskite structure. The results reveal a strong correlation between the high concentration of structural defects and the development of anisotropic microstructures, which tune the properties of BLT. Stresses applied during sintering are therefore a promising tool to design material properties

Morpho-biometrical characterisation of Portuguese Bursaphelenchus xylophilus isolates with mucronate, digitate or round tailed females

Morpho-biometrical studies were conducted on 12 Bursaphelenchus xylophilus isolates collected from maritime pine, Pinus pinaster, in Portugal. The studies were carried out on 20 females and 20 males from each isolate. A wide variation in the female tails, from round, digitate to mucronate was detected in all isolates, confirming the occurrence of mucronate tails in some females of B. xylophilus. The presence of mucronate tailed females in the Portuguese isolates of B. xylophilus clearly makes the identification of B. xylophilus by this morphological character difficult since other non-pathogenic Bursaphelenchus species also have mucronate tailed females. Amplification of satellite DNA of single specimens using species-specific primers confirmed the identity of the mucronate tailed females in the Portuguese isolates as B. xylophilus. The satellite DNA technique was also useful in the identification of juveniles of B. xylophilus from P. pinaster wood samples

Biochemical and Molecular Characterization of Plant-Parasitic Nematodes

Nematologists need correct species identification to carry out research, teaching, extension and other activities. Therefore, nematode taxonomy must be pursued diligently at all levels. The identification of plant-parasitic nematodes is not always easy and that of some species is especially difficult. Most of the information that nematologists use when characterizing and identifying specimens is based on morphological and morphometrical characters. Although these characters are of primary importance, in the last three decades they have been supplemented by biochemical/ molecular characters. Biochemical approaches include the separation of proteins (general proteins and isozymes) by one-dimensional gel electrophoresis, isoelectric focusing, two-dimensional gel electrophoresis, and sodium dodecyl sulphate-capillary gel electrophoresis. Serology has also been found effective in the identification and quantification of nematodes, monoclonal antibodies being a more useful immunological tool than polyclonal antibodies. Identification based on the direct examination of DNA is potentially a more powerful method to characterize inter- and intra-specific variability. The development of techniques such as the polymerase chain reaction, restriction fragment length polymorphism, randomly amplified polymorphic DNA, and amplified fragment length polymorphism has increased the accuracy and speed of nematode characterization/identification. Progress continues to be made and more and more nematologists are using molecular techniques for diagnostic purposes and to assess genetic variation

Root‐lesion nematodes of potato: current status of diagnostics, pathogenicity and management

Root‐lesion nematodes of the genus Pratylenchus are migratory endoparasites with worldwide economic impact on several important crops including potato, where certain species like P. penetrans, P. neglectus and P. scribneri reduce the yield and quality of potato tubers. Morphological identification of Pratylenchus spp. is challenging, and recent advancements in molecular techniques provide robust and rapid diagnostics to differentiate species without need of specialist skills. However, the fact that molecular diagnostics are not available for all Pratylenchus species means that there are limitations in worldwide application. In general, root‐lesion nematodes are difficult to manage once introduced into agricultural land and damage can be related to pathogenicity and population densities. In addition, root‐lesion nematodes interact with fungi such as V. dahliae, resulting in disease complexes that enhance the damage inflicted on the potato crop. Management interventions are often focused on limiting nematode reproduction before planting crops and include the application of nematicides, and cultural practices such as crop rotation, cover crops, biofumigation, and biological control. Understanding the limitations of the available crop protection strategies is important and there are many gaps for further study. This review discusses the status of the diagnosis, distribution, pathogenicity and management of the main species of root‐lesion nematodes, reported to infect potatoes worldwide, and highlights areas for potential future research

First record of Helicotylenchus varicaudatus Yuen, 1964 (Nematoda: Hoplolaimidae) parasitizing Ammophila arenaria (L.) Link in Portuguese coastal sand dunes

A spiral nematode, Helicotylenchus varicaudatus Yuen, 1964, parasitizing Ammophila arenaria (L.) Link, the dominant grass in the Portuguese coastal sand dunes, is reported from Portugal for the first time and raises to seven the number of Helicotylenchus species detected in Portugal. A redescription of the species, with illustrations, and light and scanning electron microscope images of both female and male specimens, is presented. The rDNA containing the internal transcribed spacer regions (ITS) of H. varicaudatus was analysed with ITS-RFLP using the restriction endonuclease Hinf I. Molecular data from the ribosomal small subunit (SSU) (18S) confirmed the identification