Root-lesion nematodes in cereal fields: importance,distribution, identification,and management strategies

Journal of Plant Diseases and Protection - Root-lesion nematodes of the genus Pratylenchus are among the most important nematode pests that limit production of small-grain cereals. Four...     

The use of invertebrate soil fauna in monitoring pollutant effects

A critical review of biological parameters used to indicate pollutant impact on soil quality was conducted. These parameters mention some soil invertebrates. The value of an indicative organism depends on its life expectancy, life style and specific importance. Nematodes, mites, collembolans, enchytraeids, earthworms, isopods and molluscs are good potential biological indicators. Biological indicators of bioaccumulation and biological indicators of effects (toxicological and ecological) can be distinguished. Bioaccumulation studies are difficult to interpret, as wide variations could be found, depending on taxonomic group, habitat, organ studied, soil type or even pollutant type. Some groups, such as Collembola, require in depth bioaccumulation studies. It is suggested to use a pool of macro-concentrators, including at least some earthworm, isopod and gastropod species. Toxicological indicators have been well studied and their lethal and sublethal pollutant effects are well known. However, studies have focused on only a few species, such as the earthworm Eisenia foetida or the collembolan Folsomia candida. These studies should be extended to other zoological groups, as well as to several species from the same group, to generate a representative test battery. Exposure biomarkers and physiological change studies should be emphasised, as they act as very early warning systems of contamination. Data are currently lacking on how soil biological processes malfunction due to pollution. We need to explore the links between pollutant effects on soil fauna and pollutant effects on soil functioning. Concerning ecological indicators, studies should develop sampling techniques and parameters, which are specific to ecotoxicological goals. Before-after impact control procedures should be carried out, to eliminate the background noise of the study site and only evaluate the influence of pollutants. On the other hand, ecological indices, such as taxonomic diversity or richness, should be used carefully especially concerning chronic pollution. Effects of pollutants on biological cycle studies seem very promising, but need further information on the life history strategies of many species. Furthermore, the pollutant tolerance of rare species should be considered. The different types of biological indicators yield complementary information on pollutant effects. They all need standard procedures. In this context, studies should be extended and diversified, and associate bioaccumulation, toxicological and ecological indicators to provide better information on soil quality.

Résumé

Une liste critique des paramètres biologiques utilisés dans certains travaux pour indiquer l'impact des polluants sur la qualité des sols a été établie. Ces paramètres font référence à un ou plusieurs invertébrés du sol. Le rôle d'organisme indicateur dépend de leurs caractéristiques biodémographiques, de leur mode de vie, de leur taille spécifique. Les nématodes, acariens, collemboles, enchytréides, vers de terre, isopodes et gastéropodes sont potentiellement des indicateurs biologiques. Indicateurs biologiques de bioaccumulation et indicateurs biologiques d'effets (toxicologiques et écologiques) peuvent être distingués. Les études de bioaccumulation sont difficiles à interpréter, car de fortes variations sont observées. Ces variations dépendent du groupe taxonomique étudié, de l'habitat, de l'organe étudié, du type de sol ou bien encore du type de pollution. Certains groupes, comme les collemboles demandent des études plus poussées à ce sujet. Il est suggéré d'utiliser un pool de macro-concentrateurs, avec au moins des espèces de vers de terres, isopodes et gastéropodes. Concernant les indicateurs toxicologiques d'effets, les études les plus nombreuses concernent les effets létaux et sublétaux. Toutefois ces études concernent peu de groupes taxonomiques (essentiellement le vers Eisenia foetida et le collembole Folsomia candida), et devraient être étendues à d'autres groupes zoologiques, ainsi qu'à différentes espèces du même groupe, afin de créer une batterie de tests représentatifs. Les travaux concernant les biomarqueurs et les changements physiologiques devraient être amplifiés, car ils permettent d'obtenir des systèmes d'alarme très précoces concernant l'impact des contaminants. Un manque persistant de données concerne les conséquences de pollutions sur le fonctionnement des écosystèmcs. Il est en effet important désormais d'explorer les liens entre les effets des polluants sur la faune du sol et les effets réels de ces mêmes polluants sur le fonctionnement des sols. Concernant les indicateurs écologiques, les travaux entrepris devraient développer des méthodes d'échantillonnage et des paramètres spécifiques au domaine écotoxicologique. Ainsi, il est préconisé d'entreprendre des études combinant les approches synchroniques et diachroniques. afin d'éliminer le bruit de fond induit par le site d'étude et évaluer uniquement l'influence du polluant. En outre, les indices écologiques, comme la diversité ou la richesse taxonomique, doivent être utilisés avec précautions, particulièrement lors des études de pollution chronique. Par ailleurs, les études concernant les effets de polluants sur les cycles biologiques semblent prometteuses, mais demandent de meilleures connaissances concernant les stratégies de vies des différentes espèces étudiées. De plus, la tolérance aux pollutions des espèces rares devrait être fortement prise en considération. Les différents types d'indicateurs biologiques fournissent des informations complémentaires. Ils demandent tous une standardisation des protocoles. Dans ce contexte, les études devraient être développées et diversifiées et associer les indicateurs de bioaccumulation avec les indicateurs biologiques d'effets pour améliorer l'information sur la qualité des sols.     

Seasonal intestinal coccidiosis in wild bluegill Lepomis macrochirus is associated with a spring bacterial epizootic

Wild bluegill, Lepomis macrochirus Rafinesque, succumb to seasonal mortality in the early spring during cool water temperatures, shown previously to be related to bacteraemia caused by a psychrotrophic bacterium, Pseudomonas mandelii. In the study herein, intestinal coccidiosis in wild bluegill had seasonal prevalence causing heavy intestinal infections and sloughing of intestinal epithelium occurring in late winter/early spring. Infections were predominantly related to two different species, Goussia washuti n. sp., an epicellular coccidium, and a coccidium closely resembling Goussia desseri Molnár 1996, previously only described in percid fish in Europe. In 2019, co‐infections of bacteraemia and intestinal coccidiosis occurred in bluegills. Evaluating coccidium infection intensity by fresh parasite examination and histology, an association was observed in which fish with moderate‐to‐heavy intestinal coccidiosis were 8–12 times more likely to have bacteraemia compared to fish with no or light coccidiosis. The association of these co‐infections suggests that intestinal coccidiosis could contribute to seasonal bacterial epizootics of wild bluegill.     

Identification of potential virulence genes in Erwinia chrysanthemi 3937: transposon insertion into plant-upregulated genes

Erwinia chrysanthemi 3937 is a soft-rotting plant pathogen in Enterobacteriaceae. It attacks a wide range of plant host species. Previously, we identified dozens of E. chrysanthemi 3937 genes induced during plant infection by microarray differential display. Here, we have mutated plant-upregulated and putatively plant-upregulated genes in E. chrysanthemi 3937 using a transposon insertion method. Of 57 mutants produced, 8 were significantly reduced in maceration in African violet leaves. These 8 E. chrysanthemi genes are similar to Escherichia coli purU (formyltetrahydrofolate deformylase; ASAP20623) and wcaJ (undecaprenylphosphate glucosephosphotransferase; ASAP18556), Bacillus subtilis dltA (d-alanine-d-alanyl carrier protein ligase; ASAP19406), Pseudomonas syringae PSPTO2912 (ABC transporter, periplasmic glutamine-binding protein; ASAP15639), Pseudomonas aeruginosa pheC (cyclohexadienyl dehydratase; ASAP19773), P. syringae syrE (peptide synthase; ASAP19989), Vibrio vulnificus VV12303 (unknown protein; ASAP18555), and Yersinia pestis speD (S-adenosylmethionine decarboxylase; ASAP20536). In some of the genes, possible roles in virulence could be postulated based on the functions of their homologues. This work demonstrated that a low proportion of pathogenicity-related genes were among the plant-upregulated genes of E. chrysanthemi 3937. This study and further dissection of these putative virulence genes should lead to new insights into infection mechanisms in pathogens.     

Exophthalmia associated with paranasal sinus osteoma in a Quarterhorse mare.

An 11-year-old Quarterhorse mare developed a paranasal sinus osteoma that extended into the right orbit and led to ipsilateral exophthalmia. Although the tumor was radiographically evident in the paranasal sinuses, ultrasonography was used to demonstrate extension of the tumor into the retrobulbar space, and endoscopy was used to identify its extension into the nasopharynx. Biopsies were obtained using both fine-needle aspiration and paranasal sinus trephination. Despite numerous antemortem diagnostic tests, only postmortem histologic analysis of the mass afforded the diagnosis of osteoma.     

Hyaline mutants from Verticillium dahliae, an example of selection and characterization of strains for host–parasite interaction studies

The objective of the present work was to select stable well-characterized strains of Verticillium dahliae that could be used as biological tools in genetic and plant–microbe interaction studies. Hyaline mutants, known for their stability in pathogenicity were chosen for the study. Diversity in pathogenicity was found among hyaline subclones obtained from a defoliating wild-type clone, but not within those from nondefoliating ones. Most subclones from the defoliating clone had parental pathotypes, but one (V7-2) exhibited weak pathogenicity. This subclone (V7-2), together with a highly virulent one (V7-7) deriving from the same defoliating parent clone (7), were selected for further characterization, because of their differences in pathogenicity. When studied on the basis of their growth requirements, the two subclones expressed marked differences. V7-7 grew better than V7-2 over a wider range of temperature conditions. Both subclones grew similarly in media supplemented with NH₄ as nitrogen source, but in those with NO₃, V7-7 grew more vigorously than V7-2 and only the former could grow when NO₂ was used. In spite of these differences, the two subclones were found to belong to the same vegetative compatibility group, confirming their genetic proximity. These results highlight the physiological and genetic complexity inherent in V. dahliae . In view of their characteristics, the clones obtained in this study should prove to be valuable tools in furthering the understanding of genetic and host– V. dahliae interactions.     

Induced Systemic Resistance (ISR) by Pseudomonas spp. Impairs Pre- and Post-Infection Development of Pythium aphanidermatum on Cucumber Roots

The effect of induced systemic resistance (ISR) by Pseudomonas rhizobacteria on the pre- and post-infection development of Pythium aphanidermatum on cucumber roots was investigated. Cucumber plants (cv. Corona) were grown in vermiculite, roots were split with one side bacterized with Pseudomonas corrugata strain 13 or P. aureofaciens strain 63-28 (bacterized roots) and the other distant side was treated with water (distant, induced roots). For the non-induced control, roots on the bacterized side were treated with buffer instead of the bacterial treatment. Intact, non-split roots were also treated with the bacteria or buffer as a control. Cucumber root tissue from these treatments were harvested and incubated with a zoospore suspension of P. aphanidermatum for three hours. Most of the zoospores in the suspension were stimulated to encyst or germinate. The numbers of germinated zoospores were significantly decreased on distant induced cucumber roots in comparison to non-induced controls. Germination was also reduced on intact bacterized roots, compared to controls. There was less attachment, germ tube production and penetration on roots bacterized or induced by the rhizobacteria compared to non-induced roots. Effects were significantly greater on bacterized roots (roots colonized by bacteria) compared to distant induced roots (roots with the opposite side bacterized). Systemic resistance induced by the two Pseudomonas spp. also reduced pathogen spread on split cucumber roots in planta. Crown infection from induced or bacterized roots was delayed for four to six days in comparison to the non-induced control. Results indicated that Pseudomonas spp. can exert both an indirect influence on P. aphanidermatum zoospore behaviour and infection via induced systemic resistance (ISR) and a local influence via antibiosis or local induced resistance.     

Isolation of a gammaherpesvirus similar to asinine herpesvirus-2 (AHV-2) from a mule and a survey of mules and donkeys for AHV-2 infection by real-time PCR

Equids are commonly infected by herpesviruses, but isolation of herpesviruses from mules has apparently not been previously reported. Furthermore, the genomic relationships among the various equid herpesviruses are poorly characterized. We describe the isolation and preliminary characterization of a mule gammaherpesvirus tentatively identified as asinine herpesvirus-2 (AHV-2; also designated equid herpesvirus-7 (EHV-7)) from the nasal secretions (NS) of a healthy mule in northern California. The virus was initially identified by transmission electron microscopic examination of lysates of cell culture inoculated with NS collected from the mule. A 913 nucleotide sequence of the DNA polymerase gene was amplified using degenerate primers, and comparison of this sequence with those of various other herpesviruses showed that the mule herpesvirus was most closely related to EHV-2 (AHV-2 sequences were not available for comparison). The sequence of a shorter portion (166 nucleotides) of the mule herpesvirus DNA polymerase gene was identical to that of the published sequence of an asinine gammaherpesvirus, previously designated as AHV-4-3 (AY054992). AHV-2 was detected by real-time polymerase chain reaction assay in the NS of approximately 8% of a cohort of 114 healthy mules and 13 donkeys.     

Combined laparoscopic ovariectomy and laparoscopic-assisted gastropexy utilizing a 2-port technique in 10 dogs

A case series was selected retrospectively to evaluate the technique, outcome, and short-term complications associated with a combined laparoscopic ovariectomy (Lap OVX) and laparoscopic-assisted gastropexy (LAG) using a 2-port technique, and to compare it with previously published combined laparoscopic techniques for Lap OVX and LAG in dogs. Medical records of dogs undergoing elective, combined Lap OVX and LAG performed using a 2-port technique between 2017 and 2019 were reviewed. Total surgical time was compared to previously published combined Lap OVX and LAG techniques in dogs. Intraoperative and short-term complications were recorded. Ten dogs [median weight: 29.4 kg (range: 11.4 to 84.1 kg); mean: 37.4] met the inclusion criteria. Median surgical time to complete both the Lap OVX and LAG was 72.5 minutes (range: 47.0 to 120.0 minutes; mean: 77.4 minutes), which was not significantly different than that described in previous studies of combined Lap OVX and LAG (weighted mean average: 67.3 minutes; 95% confidence interval: 46.9 to 87.7, P = 0.3). No intraoperative or postoperative complications were reported. It is concluded that a 2-port technique for combined Lap OVX and LAG is feasible, has few complications, and requires similar time to perform compared to other previously published laparoscopic techniques.