Biogeographical patterns and determinants of invasion by forest pathogens in Europe.

A large database of invasive forest pathogens (IFPs) was developed to investigate the patterns and determinants of invasion in Europe. Detailed taxonomic and biological information on the invasive species was combined with country-specific data on land use, climate, and the time since invasion to identify the determinants of invasiveness, and to differentiate the class of environments which share territorial and climate features associated with a susceptibility to invasion. IFPs increased exponentially in the last four decades. Until 1919, IFPs already present moved across Europe. Then, new IFPs were introduced mainly from North America, and recently from Asia. Hybrid pathogens also appeared. Countries with a wider range of environments, higher human impact or international trade hosted more IFPs. Rainfall influenced the diffusion rates. Environmental conditions of the new and original ranges and systematic and ecological attributes affected invasiveness. Further spread of established IFPs is expected in countries that have experienced commercial isolation in the recent past. Densely populated countries with high environmental diversity may be the weakest links in attempts to prevent new arrivals. Tight coordination of actions against new arrivals is needed. Eradication seems impossible, and prevention seems the only reliable measure, although this will be difficult in the face of global mobility.

Fourier transform-infrared spectroscopy as a new method for evaluating host resistance in the Dutch elm disease complex.

Resistance of elms (Ulmus spp.) to the pathogenic fungus Ophiostoma novo-ulmi Brasier depends on chemical and anatomical factors that confine the spread of the pathogen in the vascular system of the host. This study focused on detecting chemical differences in 4-year-old Ulmus minor Mill. seedlings before and after inoculation with a virulent O. novo-ulmi isolate. According to symptom development over 60 days, the trees were divided into resistant (0-33% wilting) and susceptible (67-100% wilting) groups. Histochemical tests and Fourier transform-infrared (FT-IR) spectroscopy analysis were performed on transverse sections of 2-year-old twigs, 2 days before and 40 days after inoculation. Although histochemical tests did not clearly discriminate susceptible from resistant elms, chemical differences between resistant, susceptible and control trees were detected by FT-IR. The average spectrum for resistant tree samples had higher absorbance peaks than the spectra from the susceptible and control samples, indicating increased formation of lignin and suberin. The roles of lignin and suberin in the resistance of the elms against O. novo-ulmi and the usefulness and sensitivity of the FT-IR technique for analyzing metabolic changes caused by pathogens in plants are discussed.

Influence of Plant Age on Symptom Development in Ulmus minor Following Inoculation by Ophiostoma novo-ulmi.

In American and European breeding programs, numerous elm trees from many species (Ulmus spp.) and hybrids have been inoculated annually with the fungus Ophiostoma novo-ulmi (the Dutch elm disease pathogen) in screening tests for resistance. Because trees were inoculated at different ages, it appeared necessary to study the influence of host age on the symptoms shown. Four Ulmus minor trees and one U. minor × U. pumila tree were cloned annually from 1994 to 1999. The replicates obtained (usually n = 6) were inoculated on 17 May 2000 with an O. novoulmi strain. At the end of the season, 2-year-old U. minor trees showed average wilting of 8 ± 3% (ES), significantly less than that of 3-year-old trees (34 ± 5%) (P ≤ 0.01). Elms that were 4, 5, 6, and 7 years old showed wilting values of around 50%. A positive relationship between the symptoms shown and the diameter of the elm xylem vessels was observed, and the implications for elm resistance and breeding are discussed. Breeders and pathologists should use trees of the same age and physiological phase when determining the relative resistance among elm clones. It is concluded that under the growing conditions of this experiment, the optimal age for U. minor screening was 4-year-old plants.

[Acute transverse myelitis: a clinical review and algorithm for diagnostic intervention]. / Mielitis transversa aguda: revisión clínica y algoritmo de actuación diagnóstica.

INTRODUCTION: Under the term of acute transverse myelitis (ATM), there are included a heterogeneous group of diseases, with the nexus common to produce an inflammatory focal injury of the spinal cord, of acute form. In order to try to group all the etiologies that can provoke this affectation, it is nowadays tried to define several groups of pathologies with a common nexus: those ATM associated to some process, or at least predisposed of the ATM, like are certain infections, immunological systemic and/or multifocal processes, and inclusive tumors, but when we did not get to know this triggering factor, then calling them idiopathic ATM. AIM: To know the different classes from existing ATM, creating an algorithm diagnosis that helps to this classification of ordinate form, simplifying the work to the clinicians that faces a ATM, exposing its differential diagnosis, prognosis and possible treatment. DEVELOPMENT: For it we consulted the last guides and works published related to the ATM, mainly from the diagnostic and therapeutic point of view. CONCLUSIONS: Our knowledge of the ATM is being constantly modified with the coming of new diagnostic techniques and theories that try to explain their origin, probably immunological. Unfortunately, the treatment, and therefore the prognosis, has not varied in the same proportion to the knowledge that we are acquiring in the other areas. Without a doubt, it is a way important to walk, but the next future can teach to us more on this disease.

Seasonal changes in wood formation of Ulmus pumila and U. minor and its relation with Dutch elm disease.

Elms containing narrow and scattered vessels have been reported to be more resistant to Ophiostoma novo-ulmi (Dutch elm disease pathogen) than elms with large and contiguous vessels. However, recent measurements in Ulmus pumila and U. minor showed a contrary trend. The pin method was applied to 4-yr-old branches of eight clones planted in Madrid. During 2002, radial growth increments and vessel diameters were measured monthly, and beetle trapping was undertaken weekly. U. minor formed larger vessels at the beginning of the season, coinciding with a peak of captured beetles, but, up to June 15, vessels were larger for U. pumila. The number of vessels per group, the transversal area per vessel group, and the mean theoretical hydraulic conductances were significantly higher for U. minor on most dates. Researchers should take into consideration the seasonal changes in vessel size. The results highlight that seasonal variation of vessel diameters and hydraulic parameters, in combination with beetle abundance, are the main factors that could explain the different susceptibility of both elm species to O. novo-ulmi.