Biology and Management of Corn Anthracnose

The fungus Colletotrichum graminicola causes corn anthracnose, a damaging disease in the U.S. Corn Belt and many other locations in the world where corn is grown. The anthracnose syndrome encompasses fungal attack of most corn tissues throughout the plant\u27s development. Anthracnose leaf blight (ALB) and anthracnose stalk rot (ASR) are of particular concern because of their effects on corn yield. Estimated grain yield losses due to anthracnose range from zero to 40%, depending on hybrid, environment, timing of infection, and other stresses. Anthracnose is a not a new disease, having been documented in North America since 1855. It emerged as a disease of economic consequence in the early 1970s in several north central and eastern U.S. states. Widespread epidemics of the 1970s and early 1980s were variously attributed to new biotypes of the fungus, corn hybrids with increased susceptibility, wet cloudy weather that favored the disease, and changes in cultural practice that increased survival of the fungus and availability of infective spores. There is little doubt that the general increase in anthracnose over the last 25 years is associated with regional increases in infected corn stubble remaining on the soil surface as a consequence of conservation tillage. Anthracnose is widespread today in U.S. corn production. In general, modern corn hybrids are less susceptible to both ALB and ASR than were prevalent hybrids of 20 years ago. Yet, sporadic epidemics resulting in yield loss still occur when plants are exposed to abundant spores and favorable weather conditions. Yield losses associated with ASR have been particularly common in plants injured by the European corn borer. In the late 1990s, there is an apparent resurgence of anthracnose as a production problem in some areas

The Basolateral Amygdala γ-Aminobutyric Acidergic System in Health and Disease

The brain comprises an excitatory/inhibitory neuronal network that maintains a finely tuned balance of activity critical for normal functioning. Excitatory activity in the basolateral amygdala (BLA), a brain region that plays a central role in emotion and motivational processing, is tightly regulated by a relatively small population of g-aminobutyric acid (GABA) inhibitory neurons. Disruption in GABAergic inhibition in the BLA can occur when there is a loss of local GABAergic interneurons, an alteration in GABAA receptor activation, or a dysregulation of mechanisms that modulate BLA GABAergic inhibition. Disruptions in GABAergic control of the BLA emerge during development, in aging populations, or after trauma, ultimately resulting in hyperexcitability. BLA hyperexcitability manifests behaviorally as an increase in anxiety, emotional dysregulation, or development of seizure activity. This Review discusses the anatomy, development, and physiology of the GABAergic system in the BLA and circuits that modulate GABAergic inhibition, including the dopaminergic, serotonergic, noradrenergic, and cholinergic systems. We highlight how alterations in various neurotransmitter receptors, including the acid-sensing ion channel 1a, cannabinoid receptor 1, and glutamate receptor subtypes, expressed on BLA interneurons, modulate GABAergic transmission and how defects of these systems affect inhibitory tonus within the BLA. Finally, we discuss alterations in the BLA GABAergic system in neurodevelopmental (autism/fragile X syndrome) and neurodegenerative (Alzheimer’s disease) diseases and after the development of epilepsy, anxiety, and traumatic brain injury. A more complete understanding of the intrinsic excitatory/inhibitory circuit balance of the amygdala and how imbalances in inhibitory control contribute to excessive BLA excitability will guide the development of novel therapeutic approaches in neuropsychiatric diseases

Arsenal of plant cell wall degrading enzymes reflects host preference among plant pathogenic fungi

<p>Abstract</p> <p>Background</p> <p>The discovery and development of novel plant cell wall degrading enzymes is a key step towards more efficient depolymerization of polysaccharides to fermentable sugars for the production of liquid transportation biofuels and other bioproducts. The industrial fungus <it>Trichoderma reesei </it>is known to be highly cellulolytic and is a major industrial microbial source for commercial cellulases, xylanases and other cell wall degrading enzymes. However, enzyme-prospecting research continues to identify opportunities to enhance the activity of <it>T. reesei </it>enzyme preparations by supplementing with enzymatic diversity from other microbes. The goal of this study was to evaluate the enzymatic potential of a broad range of plant pathogenic and non-pathogenic fungi for their ability to degrade plant biomass and isolated polysaccharides.</p> <p>Results</p> <p>Large-scale screening identified a range of hydrolytic activities among 348 unique isolates representing 156 species of plant pathogenic and non-pathogenic fungi. Hierarchical clustering was used to identify groups of species with similar hydrolytic profiles. Among moderately and highly active species, plant pathogenic species were found to be more active than non-pathogens on six of eight substrates tested, with no significant difference seen on the other two substrates. Among the pathogenic fungi, greater hydrolysis was seen when they were tested on biomass and hemicellulose derived from their host plants (commelinoid monocot or dicot). Although <it>T. reesei </it>has a hydrolytic profile that is highly active on cellulose and pretreated biomass, it was less active than some natural isolates of fungi when tested on xylans and untreated biomass.</p> <p>Conclusions</p> <p>Several highly active isolates of plant pathogenic fungi were identified, particularly when tested on xylans and untreated biomass. There were statistically significant preferences for biomass type reflecting the monocot or dicot host preference of the pathogen tested. These highly active fungi are promising targets for identification and characterization of novel cell wall degrading enzymes for industrial applications.</p

Social Preferences and the Efficiency of Bilateral Exchange

Under what conditions do social preferences, such as altruism or a concern for fair outcomes, generate efficient trade? I analyze theoretically a simple bilateral exchange game: Each player sequentially takes an action that reduces his own material payoff but increases the other player’s. Each player’s preferences may depend on both his/her own material payoff and the other player’s. I identify necessary conditions and sufficient conditions on the players’ preferences for the outcome of their interaction to be Pareto efficient. The results have implications for interpreting the rotten kid theorem, gift exchange in the laboratory, and gift exchange in the field

Phyllachora species infecting maize and other grass species in the Americas represents a complex of closely related species

The genus Phyllachora contains numerous obligate fungal parasites that produce raised, melanized structures called stromata on their plant hosts referred to as tar spot. Members of this genus are known to infect many grass species but generally do not cause significant damage or defoliation, with the exception of P. maydis which has emerged as an important pathogen of maize throughout the Americas, but the origin of this pathogen remains unknown. To date, species designations for Phyllachora have been based on host associations and morphology, and most species are assumed to be host specific. We assessed the sequence diversity of 186 single stroma isolates collected from 16 hosts representing 15 countries. Samples included both herbarium and contemporary strains that covered a temporal range from 1905 to 2019. These 186 isolates were grouped into five distinct species with strong bootstrap support. We found three closely related, but genetically distinct groups of Phyllachora are capable of infecting maize in the United States, we refer to these as the P. maydis species complex. Based on herbarium specimens, we hypothesize that these three groups in the P. maydis species complex originated from Central America, Mexico, and the Caribbean. Although two of these groups were only found on maize, the third and largest group contained contemporary strains found on maize and other grass hosts, as well as herbarium specimens from maize and other grasses that include 10 species of Phyllachora. The herbarium specimens were previously identified based on morphology and host association. This work represents the first attempt at molecular characterization of Phyllachora species infecting grass hosts and indicates some Phyllachora species can infect a broad range of host species and there may be significant synonymy in the Phyllachora genus

Does the Order of Invasive Species Removal Matter? The Case of the Eagle and the Pig

Invasive species are recognized as a primary driver of native species endangerment and their removal is often a key component of a conservation strategy. Removing invasive species is not always a straightforward task, however, especially when they interact with other species in complex ways to negatively influence native species. Because unintended consequences may arise if all invasive species cannot be removed simultaneously, the order of their removal is of paramount importance to ecological restoration. In the mid-1990s, three subspecies of the island fox Urocyon littoralis were driven to near extinction on the northern California Channel Islands owing to heightened predation by golden eagles Aquila chrysaetos. Eagles were lured to the islands by an abundant supply of feral pigs Sus scrofa and through the process of apparent competition pigs indirectly facilitated the decline in foxes. As a consequence, both pigs and eagles had to be removed to recover the critically endangered fox. Complete removal of pigs was problematic: removing pigs first could force eagles to concentrate on the remaining foxes, increasing their probability of extinction. Removing eagles first was difficult: eagles are not easily captured and lethal removal was politically distasteful.Using prey remains collected from eagle nests both before and after the eradication of pigs, we show that one pair of eagles that eluded capture did indeed focus more on foxes. These results support the premise that if the threat of eagle predation had not been mitigated prior to pig removal, fox extinction would have been a more likely outcome.If complete eradication of all interacting invasive species is not possible, the order in which they are removed requires careful consideration. If overlooked, unexpected consequences may result that could impede restoration

Ethnic Fragmentation and Police Spending: Social Identity and a Public Good

We present evidence that more ethnically fragmented communities spend, all else equal, more on police services than less fragmented communities. We introduce a model of spending on police services which we use to interpret the data. In this model, we assume that the decision to commit a crime is a rational consideration of the costs and benefits and that spending on police services reduces the attractiveness of committing a crime. We also assume that being a victim of crime affects a loss in utility. However this victimization cost, if victim and perpetrator are a different ethnicity, is greater than or equal to that if the perpetrator is the same ethnicity. A consequence of the model is that a higher level of spending on police services is associated with more ethnically fragmented communities only when agents suffer this differential cost of victimization. These results contribute to our understanding of the stylized fact that spending on police services is increasing at a time in which crime rates are falling. Further, our results provide empirical support for the contention that people have a larger cost of victimization when the perpetrator is a different ethnicity