Effects of Azoxystrobin on Mycotoxin Production in a Carbendazim-Resistant Strain ofFusarium sporotrichioides

Carbendazim-resistant (RS) and control (CS) strains ofFusarium sporotrichioides Sherb., previously developed in our laboratory, were exposed to graded concentrations of azoxystrob in in broth media under shake-culture conditions for 2, 3, 4 and 8 days. Azoxystrobin concentrations were 0, 1, 10 and 100 mg 1^-1 broth and cultures were incubated at a constant 25°C. Mycelial growth was significantly affected by strain (P<0.01), azoxystrobin concentration (P<0.001) and incubation time (P<0.001). Combined results for the four incubation times showed that CS yielded higher mycelial mass than RS (P<0.01) only in the absence of azoxystrobin. At fungicide additions of 1, 10 and 100 mg P^-1 mycelial growth was reduced (P<0.001) with minimal strain differences (P>0.05) at all three doses of azoxystrobin. Significant (P<0.05 or better) strain-fungicide interactions were recorded in trichothecene production following exposure to azoxystrobin. At 4 and 8 days of incubation, the 10 mg 1^-1 addition of azoxystrobin stimulated T-2 toxin synthesis (P<0.05) only in RS cultures. In contrast, T-2 toxin enhancement in CS cultures occurred only on day 8 but at a lower level of azoxystrobin (1 mg1^-1). Thus, the stimulation of T-2 toxin synthesis depended upon strain and azoxystrobin level. Production of diocetoxyscirpenol (DAS) was affected by a more complex set of interactions. Overall means showed that, in comparison with initial values (on day 2 or 3), DAS output maximized significantly(P<0.05) on day 4 in RS cultures and on day 8 in CS. Marked strain effects were observed on exposure to the 10 mg 1^-1 level of azoxystrobin. At this level, DAS production was enhanced in RS only after 4 (P<0.01 ) and 8 (P<0.05) days of incubation, while in contrast, CS reduced DAS production. As with T-2 toxin, DAS production in CS was stimulated (P<0.05 or better) only at low exposure levels of azoxystrobin. In the case of neosolaniol (NEO), however, the main effect of strain was significant (P<0.05), with CS producing consistently more of the mycotoxin than RS on day 4 of the experiment. At this point, the NEO:T-2 toxin ratio was also higher in CS (0.63) than in RS (0.12), a feature reported by us previously. In conclusion, the present investigation has shown for the first time that the development of resistance to one fungicide can affect trichothecene production inF. sporotrichioides on exposure to a second fungicide. These results have been incorporated into a new classification scheme for fungicide efficacy which is also presented in this paper. http://www.phytoparasitica.org posting Oct. 7,2001.     

Important emerging bacterial zoonotic infections affecting the immunocompromised

The immunocompromised are at particular risk for infection with zoonotic diseases. Persons can be temporarily immunocompromised due to pregnancy or developmental stage (i.e. infants); longer-term or permanent states of immunosuppression can occur as a result of immunosuppressive treatment following cancer or organ transplant, or from infectious diseases, such as AIDS. The focus of this review article is on emerging bacterial zoonotic diseases that are of particular concern among the immunocompromised. Factors that affect disease emergence can include factors such as human demographics and behavior; technology and industry; economic development and land use; international travel and commerce; microbial adaptation and change; and breakdown of public health measures. The immunocompromised need to take precautions when engaging in seemingly normal activities such as food preparation; caring for companion animals; and recreational or occupational activities. The immunocompromised are not only more susceptible to infection, but often suffer more serious sequelae as a result of infection. This review article provides an overview of the major foodborne, respiratory, and vector-borne bacterial pathogens that affect the immunocompromised. The major categories of immunodeficiency are described. In addition, measures that can be taken to prevent infection, including the role of health education, are discussed.     

A small animal clinician's guide to critical appraisal of the evidence in scientific literature.

There is a tremendous amount of medical literature available to the clinician. The challenge is to identify information that is useful and relevant for the patient population of interest. This article provides an overview of important considerations when critically appraising a report, such as selection of the study population, features of the study design used, potential sources of bias, and evaluation of the statistical evidence.     

Neutral sugars in melanins synthesized by actinomycetes from Brazilian soils

 Nine actinomycete melanins synthesized under various culture conditions, eight of them by actinomycete samples isolated from Brazilian topsoils under savanna (cerrado) vegetation and one from an ATCC sample, were subjected to a two-step hydrolysis procedure and the sugars released qualitatively and quantitatively determined by capillary gas-liquid chromatography (GLC). Humic acids (HAs) extracted from these soils, analysed previously, were used for comparison. The neutral sugars glucose, galactose, mannose, xylose, arabinose, ribose, rhamnose and fucose and the alcohol sugar inositol were present in varying amounts in most of the melanins analysed. The same sugars were present in the HAs used for comparison, except for ribose. Some qualitative and quantitative differences observed in the two types of macromolecules would be expected, considering their origins. The results indicate that the actinomycete melanins have a qualitative sugar distribution pattern similar to that of the HAs from Brazilian tropical soils and of HAs reported for soils from other climatic regions. The possible participation of actinomycete melanins in the formation of soil humic substances is discussed. Received: 4 April 1997     

Detection and quantification of Fusarium oxysporum f. sp. cucumerinum in environmental samples using a specific quantitative PCR assay

The rapid and reliable identification and quantification of pathogens is essential for the management of economically important plant diseases. Fusarium oxysporum f. sp. cucumerinum is the soil borne fungus responsible for Fusarium vascular wilt of cucumber. In this study, we report the development of a specific and reliable real-time quantitative PCR assay and the development of an ultra-sensitive diagnostic pseudo-nested PCR assay. The capacity of the PCR assays to accurately identify and quantify Fusarium oxysporum f. sp. cucumerinum was experimentally tested by the development of standard curves from serial dilutions of copy numbers in a range of complex environmental DNA samples. The amplification efficiency, sensitivity and reproducibility of the qPCR assays were not significantly affected by the presence of any of the non-target background DNA tested. In quantitative real-time PCR, as few as 100 copies could be reliably quantified, and in simple and pseudo-nested PCR as little as 10 pg and 10 fg, respectively, could be detected. This rapid and sensitive qPCR method can be used to facilitate investigations into plant–pathogen interactions, epidemiology, and disease management practices.     

Comparison of bread wheat varieties with different breeding origin under organic and low input management

In recent years needs have increased to investigate the necessity of breeding cereals for organic agriculture. The aims of this study were (1) to compare 37 bread wheat (Triticum aestivum L.) varieties with different breeding origin under low input conventional and certified organic farming conditions in Austria and Hungary for 3 years, (2) to identify traits highly sensitive to management systems that could be separated according to their suggested selecting environments and (3) to find evidence for the distinctness of organic wheat breeding. According to the results, seven out of the 15 traits assessed during this study showed significant management × genotype interaction meaning that these traits could be the basis of selection for different management systems. Heading date, sensitivity to leaf rust and powdery mildew had high repeatabilities. For economic reasons, it is therefore reasonable to select for these traits in conventional fields even if the selection target is organic agriculture. However, the present study suggests that selection for the other four traits (grain yield, test weight, leaf-inclination and vigorous growth during booting) should be done later in the target environment. The study compared groups of varieties developed by different breeding strategies (organic, conventional and combined strategies). The results of multivariate analyses showed that the organic breeding was distinct from the other two breeding strategies, but the combined and conventional breeding resulted in similar groupings. It is concluded that the selecting environment has measurable effects on the performance of bread wheat varieties under organic and low input growing conditions.