University of Extremadura

About: University of Extremadura is a education organization based out in Badajoz, Spain. It is known for research contribution in the topics: Population & Hyperspectral imaging. The organization has 7856 authors who have published 18299 publications receiving 396126 citations. The organization is also known as: Universidad de Extremadura.

Widespread Phytophthora infestations in European nurseries put forest, semi-natural and horticultural ecosystems at high risk of Phytophthora diseases

Abstract: An analysis of incidence of Phytophthora spp. in 732 European nurseries producing forest transplants, larger specimen trees, landscape plants and ornamentals, plus 2525 areas in which trees and shrubs were planted, is presented based on work conducted by 37 research groups in 23 European countries between 1972 and 2013. Forty-nine Phytophthora taxa were recorded in 670 nurseries (91.5%); within these nurseries, 1614 of 1992 nursery stands (81.0%) were infested, although most affected plants appeared healthy. In forest and landscape plantings, 56 Phytophthora taxa were recovered from 1667 of 2525 tested sites (66.0%). Affected plants frequently showed symptoms such as crown thinning, chlorosis and dieback caused by extensive fine root losses and/or collar rot. Many well-known highly damaging host-Phytophthora combinations were frequently detected but 297 and 407 new Phytophthora-host associations were also observed in nurseries and plantings, respectively. On average, 1.3 Phytophthora species/taxa per infested nursery stand and planting site were isolated. At least 47 of the 68 Phytophthora species/taxa detected in nurseries and plantings were exotic species several of which are considered well established in both nurseries and plantings in Europe. Seven known Phytophthora species/taxa were found for the first time in Europe, while 10 taxa had not been previously recorded from nurseries or plantings; in addition, 5 taxa were first detections on woody plant species. Seven Phytophthora taxa were previously unknown to science. The reasons for these failures of plant biosecurity in Europe, implications for forest and semi-natural ecosystems and possible ways to improve biosecurity are discussed.

The Inhibition of Arginase by Nω-Hydroxy-l-Arginine Controls the Growth of Leishmania Inside Macrophages

Abstract: Polyamine synthesis from l-ornithine is essential for Leishmania growth. We have investigated the dependence of Leishmania infection on arginase, which generates l-ornithine, in macrophages from BALB/c, C57BL/6, and nitric oxide synthase II (NOS II)-deficient mouse strains. We have found that N(omega)-hydroxy-l-arginine (LOHA), a physiological inhibitor of arginase, controls cellular infection and also specifically inhibits arginase activity from Leishmania major and Leishmania infantum parasites. The effect was proportional to the course of infection, concentration dependent up to 100 microM, and achieved without an increase in nitrite levels of culture supernatants. Moreover, when the l-arginine metabolism of macrophages is diverted towards ornithine generation by interleukin 4-induced arginase I, parasite growth is promoted. This effect can be reversed by LOHA. Inhibition of NOS II by N(G)-methyl-l-arginine (LNMMA) restores the killing obtained in the presence of interferon (IFN)-gamma plus lipolysaccharide (LPS), whereas the nitric oxide scavenger 2-(4-carboxyphenyl)-4,4,5,5,-tetramethylimidazoline-3-oxide-1-oxyl (carboxy-PTIO) was without effect. However, exogenous l-ornithine almost completely inhibits parasite killing when added in the presence of LOHA to macrophages from NOS II-deficient mice or to BALB/c-infected cells activated with IFN-gamma plus LPS. These results suggest that LOHA is an effector molecule involved in the control of Leishmania infection. In addition, macrophage arginase I induction by T helper cell type 2 cytokines could be a mechanism used by parasites to spread inside the host.

Delineation of management zones using mobile measurements of soil apparent electrical conductivity and multivariate geostatistical techniques

Abstract: Site-specific management promotes the identification and management of areas within the field, which represent subfield regions with homogeneous characteristics (management zones). However, determination of subfield areas is difficult because of the complex combination of factors which could affect crop yield. One possibility to capture yield variability is the use of soil physical properties to define the management zones as they are related to plant available water. With the aim of characterizing the spatial variability of the main soil physical variables and using this information to determine potential management zones, soil samples were taken from 70 locations in a 33-ha field in Badajoz, southwestern Spain. Firstly, accurate spatial distribution maps of the soil attributes were generated by using regression kriging as the most suitable algorithm in which exhaustive secondary information on soil apparent electrical conductivity (ECa) was incorporated. ECa measurements were carried out with a Veris 3100 operating in both shallow (0–30 cm), ECs, and deep (0–90 cm), ECd, mode. Clay, coarse sand and fine sand were the soil physical properties which exhibited higher correlation with ECa (positively correlated with the finer texture component, clay, and negatively correlated with the coarser ones, coarse and fine sands), particularly with ECs. Thus, this was the secondary variable used to obtain the kriged maps. Later, principal component analysis and fuzzy cluster classification were performed to delineate management zones, resulting in two subfields to be managed separately. This number of subfields was determined using the fuzzy performance index and normalized classification entropy as the way to optimize the classification algorithm.

Serotypes, Virulence Genes, and Intimin Types of Shiga Toxin (Verotoxin)-Producing Escherichia coli Isolates from Healthy Sheep in Spain

Abstract: Fecal swabs obtained from 1,300 healthy lambs in 93 flocks in Spain in 1997 were examined for Shiga toxin-producing Escherichia coli (STEC). STEC O157:H7 strains were isolated from 5 (0.4%) animals in 4 flocks, and non-O157 STEC strains were isolated from 462 (36%) lambs in 63 flocks. A total of 384 ovine STEC strains were characterized in this study. PCR showed that 213 (55%) strains carried the stx(1) gene, 10 (3%) possessed the stx(2) gene, and 161 (42%) carried both the stx(1) and the stx(2) genes. Enterohemolysin (ehxA) and intimin (eae) virulence genes were detected in 106 (28%) and 23 (6%) of the STEC strains, respectively. The STEC strains belonged to 35 O serogroups and 64 O:H serotypes (including 18 new serotypes). However, 72% were of 1 of the following 12 serotypes: O5:H-, O6:H10, O91:H-, O117:H-, O128:H-, O128:H2, O136:H20, O146:H8, O146:H21, O156:H-, O166:H28, and ONT:H21 (where NT is nontypeable). Although the 384 STEC strains belonged to 95 different seropathotypes (associations between serotypes and virulence genes), 49% of strains belonged to only 11. O91:H- stx(1) stx(2) (54 strains) was the most common seropathotype, followed by O128:H- stx(1) stx(2) (33 strains) and O6:H10 stx(1) (25 strains). Three strains of serotypes O26:H11, O156:H11, and OX177:H11 had intimin type beta1; 5 strains of serotype O157:H7 possessed intimin type gamma1; and 15 strains of serotypes O49:H-, O52:H12, O156:H- (12 strains), and O156:H25 had the new intimin, intimin type zeta. The majority (82%) of ovine STEC strains belonged to serotypes previously found to be associated with human STEC strains, and 51% belonged to serotypes associated with STEC strains isolated from patients with hemolytic-uremic syndrome. Thus, this study confirms that healthy sheep are a major reservoir of STEC strains pathogenic for humans.