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Infection Type (infection + type)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Absence of residual effects of a defeated resistance gene in poplar

FOREST PATHOLOGY, Issue 2 2003
K.-S. Woo
Summary In a few plant pathosystems, defeated major genes have been shown to contribute to partial resistance to disease. This hypothesis has never been tested before in a forest tree, but pathogenic variation associated with recent hybridization in poplar rust in the Pacific northwest provided an opportunity. An F2 progeny of 256 poplar clones in the field near Corvallis, Oregon, USA, has been monitored for rust severity and infection type since the advent of the new hybrid rust, Melampsora × columbiana, in the mid-1990s. All 256 clones displayed a susceptible infection type in 1997 and again in 2000, and yet variation in uredinial density (i.e. partial resistance) was still observed. To determine which clones possessed a defeated resistance gene, a greenhouse inoculation was performed with an isolate of M. medusae, one of the parents of M. × columbiana. Clones that would have been resistant to M. medusae, prior to the advent of M. × columbiana, were thus identified. The inoculation resulted in a 1 : 1 segregation (,2=0.772; p=0.38) for resistance, indicating the presence of a major gene. However, the F2 clones possessing the defeated resistance gene displayed the same level of partial resistance in the field in both 1997 and 2000 as their full siblings lacking the gene. Résumé Chez quelques pathosystèmes végétaux, il a été montré que le contournement de gènes majeurs de résistance contribue à une résistance partielle envers la maladie. Cette hypothèse n'a encore jamais été testée chez un arbre forestier, mais le changement de pouvoir pathogène associéà l'hybridation récente de la rouille du peuplier dans le nord-ouest des USA en a fourni l'occasion. Une descendance F2 de 256 clones de peuplier a été suivie au champ près de Corvallis, Oregon, USA, pour la gravité de la rouille et le type d'infection, depuis l'apparition du nouvel hybride Melampsora x columbiana, dans les années 1990. Tous les 256 clones se sont montrés sensibles en 1997 et à nouveau en 2000, et une variation dans la densité des urédies (résistance partielle) a aussi été observée. Pour déterminer quels clones présentaient une résistance contournée, des inoculations ont été réalisées en serre avec un isolat de Melampsora medusae originaire du Kentucky. Des clones qui étaient résistants àM. medusae avant l'apparition de M. x columbiana ont ainsi été identifiés. Les inoculations ont abouti à une ségrégation 1 :1 (,2 = 0,772; P = 0,38) pour la résistance, ce qui indique la présence d'un gène majeur. Cependant, les clones F2 possédant le gène de résistance contourné montraient le même niveau de résistance partielle au champ en 1997 et 2000 que leurs plein-frères qui n'avaient pas ce gène. Zusammenfassung Für einige Pflanzen-Pathosysteme wurde gezeigt, dass unwirksam gewordene Haupt-Resistenzgene immer noch zu einer teilweisen Resistenz beitragen. Für Waldbäume wurde diese Hypothese bisher nie überprüft. Dies wurde jetzt im pazifischen Nordwesten möglich, wo der Pappelrost nach einem rezenten Hybridisierungsereignis stark variierte. An den F2-Nachkommenschaften von 256 Pappelklonen, die unter Freilandbedingungen in der Nähe von Corvallis, Oregon, USA wuchsen, wurde nach dem Auftreten des neuen Hybridrostes (Melampsora × columbiana) ab ca. 1990 die Krankheitsintensität und der Infektionstyp registriert. Alle 256 Klone zeigten einen anfälligen Infektionstyp im Jahre 1997 und dann wieder im Jahre 2000. Dabei wurde eine Variation in der Urediendichte (d.h. partielle Resistenz) beobachtet. Um zu bestimmen, welche Klone ein unwirksam gewordenes Resistenzgen besitzen, wurden Inokulationen im Gewächshaus mit einem Isolat von M. medusae, einem Elter von M. × columbiana, durchgeführt. Damit wurden Klone identifiziert, die vor dem Auftreten von M. × columbiana gegen M. medusae resistent waren. Der Infektionsversuch führte zu einer 1:1 Segregation (,2=0,772; P=0,38) für die Resistenz, was auf das Vorliegen eines Hauptgens hinweist. Die F2-Klone, welche dieses überwundene Resistenzgen besitzen, zeigten jedoch unter Feldbedingungen in den Jahren 1997 und 2000 den gleichen Grad einer Teilresistenz wie ihre Vollgeschwister, welchen dieses Gen fehlt. [source]

Central nervous system infections by members of the Pseudallescheria boydii species complex in healthy and immunocompromised hosts: epidemiology, clinical characteristics and outcome

MYCOSES, Issue 4 2008
A. Serda Kantarcioglu
Summary Infections caused by members of the Pseudallescheria boydii species complex are currently among the most common mould infections. These fungi show a particular tropism for the central nervous system (CNS). We reviewed all the available reports on CNS infections, focusing on the geographical distribution, infection routes, immunity status of infected individuals, type and location of infections, clinical manifestations, treatment and outcome. A total of 99 case reports were identified, with similar percentage of healthy and immunocompromised patients (44% vs. 56%; P = 0.26). Main clinical types were brain abscess (69%), co-infection of brain tissue and/or spinal cord with meninges (10%) and meningitis (9%). The mortality rate was 74%, regardless of the patient's immune status, or the infection type and/or location. Cerebrospinal fluid culture was revealed as a not very important tool as the percentage of positive samples for P. boydii complex was not different from that of negative ones (67% vs. 33%; P = 0.10). In immunocompetent patients, CNS infection was preceded by near drowning or trauma. In these patients, the infection was characterised by localised involvement and a high fatality rate (76%). In contrast, CNS infection in immunocompromised patients was presented as rapidly progressive disseminated lesions at various degrees of evolution. Major risk factors for CNS infection were the aspiration of polluted water in near-drowning episodes in immunologically intact patients and medical immunosuppression in the remaining patient groups. As the therapeutic options were poor, the treatment was difficult in general and the prognosis was poor. [source]

Coherence and correspondence criteria for rationality: experts' estimation of risks of sexually transmitted infections

JOURNAL OF BEHAVIORAL DECISION MAKING, Issue 3 2005
Mary B. Adam
Abstract The aim of this study is to examine both coherence and correspondence criteria for rationality in experts' judgments of risk. We investigated biases in risk estimation for sexually transmitted infections (STIs) predicted by fuzzy-trace theory, i.e., that specific errors would occur despite experts' knowledge of correct responses. One hundred twenty professionals with specific knowledge of STI risks in adolescents were administered a survey questionnaire to test predictions concerning: knowledge deficits (producing underestimation of risks); gist-based representation of risk categories (producing overestimation of condom effectiveness); retrieval failure for risk knowledge (producing lower risk estimates); and processing interference in combining risk estimates (producing biases in post-test diagnosis of infection). Retrieval was manipulated by asking estimation questions that "unpacked" the STI category into infection types or did not specify infection types. Other questions differentiated processing biases from knowledge deficits or retrieval failure by directly providing requisite knowledge. Experts' knowledge of STI transmission and infection risks was verified empirically. Nevertheless, under predictable conditions, they misestimated risk, overestimated the effectiveness of condoms, and also suffered from processing biases. When questions provided better retrieval supports (unpacked format), risk estimates improved. Biases were linked to gist representations, retrieval failures, and processing errors, as opposed to knowledge about STIs. Results support fuzzy-trace theory's dual-process assumptions that different types of errors are dissociated from one another, and separate failures of coherence and correspondence among the same sample of experts. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Histopathology and PR-protein markers provide insight into adult plant resistance to stripe rust of wheat

MOLECULAR PLANT PATHOLOGY, Issue 2 2008
JENNIFER MOLDENHAUER
SUMMARY Stripe rust, caused by Puccinia striiformis f. sp. tritici, is a serious disease of wheat. The spring wheat cultivar Kariega expresses complete adult plant resistance to stripe rust, whereas Avocet S is susceptible. In former studies, quantitative trait loci (QTL) analysis of doubled haploid lines derived from a Kariega × Avocet S cross revealed two major QTL (QYr.sgi-7D and QYr.sgi-2B.1) and two minor QTL (QYr.sgi-1A and QYr.sgi-4A.1) responsible for the adult resistance of Kariega in the field. Avocet S contains none of these QTL. In the present study, stripe rust development was compared, by means of fluorescence and confocal laser scanning microscopy, in flag leaves of Kariega, Avocet S and six doubled haploid (DH) lines, containing all four, none or one QTL. Depending on the QTL present, the infection types of the DH lines ranged from resistant to fully susceptible. No differences in fungal growth were observed during the first 5 days post inoculation (dpi), whereas the mean length of the fungal colonies started to differ at 6 dpi. Interestingly, MP 51 carrying QYr.sgi-7D responded with lignification to the fungal growth without restricting it, whereas MP 35 containing QYr.sgi-2B.1 did not show lignified host tissue, but fungal growth was restricted. RT PCR experiments with sequences of pathogenesis-related (PR) proteins resulted in a slightly stronger induction of PR 1, 2 and 5, known markers for the hypersensitive reaction, and peroxidases in MP 51, whereas a second band for chitinases was detected in MP 35 only. [source]