The mitogenic response of bovine peripheral blood mononuclear cells stimulated by concanavalin A (ConA) was suppressed by infectious bovine herpesvirus 1 (BHV-1). Proliferation in response to interleukin-2 (IL-2) by IL-2-dependent lymphocyte cultures was also inhibited by BHV-1. Although inhibition of mitogenesis approached 100%, less than 1 cell in 1,000 was productively infected by BHV-1 in ConA-stimulated cultures. Neither conditioned medium from mitogen-stimulated peripheral blood mononuclear cell cultures nor human recombinant IL-2 reversed suppression by the virus. Infection by BHV-1 did not influence the expression of IL-2 or IL-2 receptor mRNA in ConA-stimulated cultures, nor did it affect the cytolytic capabilities of lymphocytes. The data suggest that the inhibition of T-lymphocyte proliferation is the result of a nonproductive BHV-1 infection.

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Seeds have well-established passive physical and chemical defense mechanisms that protect their food reserves from decay-inducing organisms and herbivores. However, there are few studies evaluating potential biochemical defenses of dormant seeds against pathogens. Caryopsis decay by the pathogenic Fusarium avenaceum strain F.a.1 was relatively rapid in wild oat (Avena fatua L.) isoline “M73,” with >50% decay after 8 days with almost no decay in wheat (Triticum aestivum L.) var. RL4137. Thus, this fungal strain has potential for selective decay of wild oat relative to wheat. To study defense enzyme activities, wild oat and wheat caryopses were incubated with F.a.1 for 2–3 days. Whole caryopses were incubated in assay reagents to measure extrinsic defense enzyme activities. Polyphenol oxidase, exochitinase, and peroxidase were induced in whole caryopses, but oxalate oxidase was reduced, in response to F.a.1 in both species. To evaluate whether defense enzyme activities were released from the caryopsis surface, caryopses were washed with buffer and enzyme activity was measured in the leachate. Significant activities of polyphenol oxidase, exochitinase, and peroxidase, but not oxalate oxidase, were leached from caryopses. Defense enzyme responses were qualitatively similar in the wild oat and wheat genotypes evaluated. Although the absolute enzyme activities were generally greater in whole caryopses than in leachates, the relative degree of induction of polyphenol oxidase, exochitinase, and peroxidase by F.a.1 was greater in caryopsis leachates, indicating that a disproportionate quantity of the induced activity was released into the environment from the caryopsis surface, consistent with their assumed role in defense. It is unlikely that the specific defense enzymes studied here play a key role in the differential susceptibility to decay by F.a.1 in these two genotypes since defense enzyme activities were greater in the more susceptible wild oat, compared to wheat. Results are consistent with the hypotheses that (1) dormant seeds are capable of mounting complex responses to pathogens, (2) a diversity of defense enzymes are involved in responses in multiple plant species, and (3) it is possible to identify fungi capable of selective decay of weed seeds without damaging crop seeds, a concept that may be applicable to weed management in the field. While earlier work on seed defenses demonstrated the presence of passive defenses, this work shows that dormant seeds are also quite responsive and capable of activating and releasing defense enzymes in response to a pathogen.

Depleting the soil weed seedbank is an important integrated weed management strategy that has the potential to foster lasting weed control. Long-term dormancy and decay resistance of weed seeds pose a challenge to weed eradication efforts. Select soil fungi have been shown to cause significant decay of weed seeds. The physical and chemical mechanisms by which seeds in the seedbank defend themselves against pathogens have been well researched. However, very few studies have purposefully investigated the biochemical defence response of seeds. Enzyme-based biochemical seed defences have been detected in dormant and non-dormant seeds, and research supports their function in pathogen defence. This review summarizes current knowledge of the seed defence enzymes polyphenol oxidase, peroxidase, chitinase and oxalate oxidase. The fungal enzymes chitinase, protease and xylanase that function in pathogenesis of seeds in the soil seedbank are also reviewed. Progress in the development and standardization ofin situenzyme analyses fosters our understanding of actual enzyme activity present in soils, while high-throughput microplate techniques promote efficiency and enable greater scope. Application of genomic, proteomic and transcriptomic techniques to glean a deeper and more holistic understanding of the enzymatic interactions of weed seeds and soil fungi in the soil seedbank will support the development of improved integrated weed management strategies.

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The US dairy industry has changed significantly during the past 20 years. The number of dairies declined 63% from 1997 to 2012 owing to the rise in concentrated animal feeding operations and the concomitant decline of small dairy farms. Efficient and cost-effective dairies adhering to the concentrated animal feeding operation business design are praised for their high milk production. However, with a per capita daily manure production of 55 kg, storage and disposal of manure at these large operations pose significant management challenges and environmental risks. Application to surrounding agricultural fields is a common practice for disposing of manure, but the fate and consequences of antibiotics present in dairy waste are issues of great concern. Although antibiotics in the environment promote microbial resistance, their risks to humans and the environment are not completely known. Understanding and predicting the fate of antibiotics from dairy manure in soils is complicated by the variability and complex interactions of soil factors in addition to the diversity of chemicals of emerging concern, their amphoteric structures, and potential antagonistic and synergistic interactions among chemicals of emerging concern. This review explores behavior of the tetracycline (TC) class of antibiotics from dairy manure in the soil environment. TC fate in soils depends significantly on soil pH, ionic strength, and soil organic matter (SOM). Molecular charge and physicochemical properties of TCs at typical soil pHs encourage strong sorption to soils; however, this interaction is complicated by organic matter and metals, and may also encourage development of antibiotic resistance. Furthermore, TC degradation products exhibit distinct properties from their parent compounds that also must be considered. Increased knowledge of the behavior of TC antibiotics in soil is needed to enable mitigation of their potential risks.

In 2012 there were 63% fewer dairies in the United States than there were in 1997 as a result of 21 conglomeration of the dairy industry into concentrated animal feeding operations (CAFOs) at the expense 22 of smaller farms (USDA 2015). Today, 60% of all milk produced in the U.S. comes from 5% of the 23 nation's dairies (operations with ≥ 500 cows) (USDA 2014). Concentrated animal feeding operations are 24 touted as economically efficient agricultural business models, hailed for their increased milk yields. Yet, 25with an average daily manure production of over 27,000 kg for a 500-head dairy, manure storage and 26 disposal are serious management and environmental concerns. A common economical mode of manure 27 disposal is application to nearby agricultural fields. However, a major concern with land-application of 28 dairy manure is the fate of manure-borne hormones, compounds considered chemicals of emerging 29 concern, and the potential threat these hormones pose to humans and the environment. The fate of these 30 chemicals in the soil environment is complicated by multiple edaphic variables including pH, mineralogy, 31 organic matter, microbial activity, and redox status. Estrogens are sorbed by soil organic matter and 32 transformed to non-bioactive, highly soluble conjugated forms or to metabolites that exhibit yet additional 33properties distinct from their parent compounds. However, deconjugation frequently occurs, regenerating 34 endocrine-disrupting free estrogen compounds. It is challenging to fully understand the behavior and 35 predict the fate of estrogenic compounds from dairy manure in soils because of variable and complex 36 interactions with soil factors, as well as possible interactions among the different chemicals of emerging 37 concern. This review focuses on the behavior of naturally occurring estrogen hormones present in dairy 38 manure in the soil environment. Heightened understanding of the fate of these compounds in soil will 39 enhance our ability to reduce their potential risks. 40 41

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