Assessing Trace Element Uptake by Vegetation on a Coal Fly Ash Landfill

Improved methods are required to assess the risks posed by the uptake of potentially toxic elements such as selenium (Se), boron (B), and molybdenum (Mo) by vegetation on contaminated sites. In order to develop such methods and assess risk, vegetation was collected from two sites on a soil-capped coal fly ash landfill near Dunkirk, New York, during June of 1991 and June and August of 1992. The mean concentrations (μg g-1 dry weight) of Se and Mo in the shoots did not exceed, respectively, 0.12 and 18.7 in bird's-foot trefoil (Lotus corniculatus L.), 0.06 and 12.1 in red clover (Trifolium pratense L.), 0.07 and 5.3 in timothy (Phleum pratense L.), and 0.09 and 2.2 in a mixture of grasses. These concentrations were greater than those in the same species harvested concurrently from a non-landfill site. The mean concentrations of B at the landfill ranged from 29 to 53 μg g-1 in the legumes and from 2 to 11 μg g-1 in the grasses, less than those at one non-landfill site but greater than those at another. Within the landfill, the concentration of Se in grasses was not correlated with the concentration of Se in soil and fly ash. The concentration of Se in grasses on both landfill sites was double that of grasses on the non-landfill site despite higher mean concentrations of Se in the upper soil (0–15 cm) on the non-landfill site. Therefore grass roots seem to be accessing Se from the ash by means of mass flow or other mechanisms. Based on our findings of significant variation in trace element uptake among species, harvests, and locations within sites, we recommend that contemporaneous transect sampling of at least two species be used to assess uptake of potentially toxic trace elements on landfills or other sites where contamination may occur.     

Analysis of head and leaf reaction towards <Emphasis Type="Italic">Microdochium nivale</Emphasis>

This research examined the variation in the response of eight commercial wheat cultivars to Microdochium nivale isolates using both in vivo FHB tests (AUDPC and RHW measurements) and in vitro detached leaf assays (LGR). Irrespective of fungal variety, the two Italian cvs Fortore and Norba exhibited the greatest amount of visual disease symptoms (mean AUDPC=2.2 and 2.3, respectively), being significantly more susceptible than the other six cultivars (AUDPC 1.24) (P < 0.05). Irrespective of fungal variety, the Italian cv. Norba and the Irish cv. Falstaff were more susceptible than the other cultivars (except Fatima 2) in terms of RHW (P < 0.05), while the cvs Fortore, GK Othalom and Consort were more resistant than the other five cultivars (P < 0.05). In the detached leaf assay, the Hungarian cv. GK Othalom and the Italian cv. Norba were more susceptible (mean LGR=0.79 and 0.81 mm day^–1, respectively) to M. nivalethan the other six cultivars (mean LGR=0.51–0.72) (P < 0.05). Analysis of the relationship between head and leaf reaction to M. nivaleinfection revealed no significant correlation.     

Patterns of Virulence in Natural Populations of Puccinia coronata on Wild Oat in Israel and in Agricultural Populations on Cultivated Oat in the United States

ABSTRACT Crown rust (Puccinia coronata) in indigenous populations of Avena sterilis has been cited as an example of stability of wild pathosystems that consist of natural mixtures of resistance and virulence. This study confirmed that virulence/avirulence polymorphisms in P. coronata on A. sterilis in Israel are highly diverse and that super races do not dominate. Isolates of P. coronata from Israel in 1991 to 1996 were polymorphic for virulence to 35 of 36 differential oat lines with resistance genes from A. sterilis. On average, isolates of P. coronata were more highly virulent to differentials with Pc genes from A. sterilis accessions from Israel than to differentials with Pc genes from other countries. Isolates from Israel also were more virulent on average to 10 additional differentials with Pc genes derived from A. sativa than to differentials with Pc genes from A. sterilis. Frequencies of virulence were usually higher in collections of P. coronata from Israel than in collections from cultivated oat in the United States, even though several of the Pc genes in the differentials have been used extensively in American oat cultivars. Mean virulence complexity of P. coronata from eight regions of Israel was not correlated with the distribution of resistance among collections of A. sterilis from previous surveys in the same areas, probably because pathogen migration between regions within Israel is sufficient to obscure effects of selection locally.     

Squeezing the turnip with artificial neural nets

ABSTRACT Modeling in epidemiology has followed many different strategies and philosophies. Artificial neural networks (ANNs) comprise a family of highly flexible and adaptive models that have shown promise for application to modeling disease phenomena in general and plant disease forecasting in particular. ANN modeling requires the availability of representative, robust input data and exhaustive testing of model aptness and optimization; meanwhile, ANNs sacrifice much of the biological insight often derived through other model forms. On the other hand, ANNs may extract previously undetected and possibly complex relationships, which can increase prediction accuracy over mainstream statistical methods, usually in an incremental manner.     

Contamination, error, and nonspecific molecular tools

ABSTRACT Random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) are widely used in studies of genetic variation. Although it is recognized that contamination should be avoided in DNA samples, little is known about the potential hazards of low level bacterial contamination of samples from which DNA is extracted for RAPD or AFLP analyses. We found that contamination of Aphanomyces cochlioides cultures with a prokaryote at visibly undetectable levels markedly altered the results of RAPD and AFLP analyses. The contamination resulted in seven contaminant-specific RAPD products and in the suppression of eight products characteristic of uncontaminated A. cochlioides cultures. Prokaryote contamination resulted in 39 contaminant-specific AFLP products, but did not cause suppression of AFLP products. Comparing A. cochlioides samples with outgroup A. euteiches did not clearly indicate the presence of contaminant DNA, because uneven product suppression in RAPD analysis increased the apparent similarity between contaminated samples and A. euteiches and because a high proportion of the contaminant-specific amplified products comigrated with products from A. euteiches in both RAPD and AFLP analyses. Work with organisms that are prone to contamination should employ techniques such as restriction fragment length polymorphism or DNA sequence comparisons rather than relying solely on RAPD or AFLP analyses.     

Can Flush and Lock Solutions Used in Human Medicine Be Applied to Large Animal IV Therapy: A Systematic Review

A recent shortage of prepackaged heparinized saline (HS) syringes has led to the question of whether or not normal saline (NS) can be used to both flush and lock IV catheters in large animal medicine (LAM). Moreover, several known medication incompatibilities exist with IV heparin administration. This is of particular concern in veterinary medicine where limited to no compatibility data exists between “veterinary only” (non-Food and Drug Administration approved) medications and heparin. Most of the literature on this subject is in human medicine where flushing of peripheral IV lines (PIVL) is done safely and effectively with NS. The jugular lines inserted in LAM have characteristics that are more similar to PIVLs versus most central venous access devices used in human patients. In addition, LAM catheters are of larger diameter than those typically used in human medicine thereby reducing the risk of occlusion. Based on the data evaluated, flushing and locking all LAM catheters with of NS is a reasonable alternative method for maintaining IV patency and eliminating problems associated with medication-related incompatibilities or shortages of prepackaged HS syringes.