Arabidopsis ethylene receptors have different roles in Fumonisin B1-induced cell death

Ethylene is a central signalling agent in mediating plant defence against pathogens. Mutations to the ethylene receptor ETR1 have been shown to alter susceptibility of plants to mycotoxin-induced cell death. Using Fumonisin B₁ (FB₁) to induce cell death, we demonstrate that the receptor mutant ein4-1 has a reduced rate of necrosis, potentially due to an upregulation of ETHYLENE RESPONSE FACTOR1. Mutations in other ethylene receptors differentially affected the expression of genes in the jasmonic and salicylic acid defence pathways. Together these data indicate that ethylene receptors do not have redundant roles in mediating FB₁-induced cell death.     

Effect of the new pyrazole carboxamide fungicide penthiopyrad on late leaf spot and stem rot of peanut

BACKGROUND: Management of early leaf spot (Cercospora arachidicola Hori.), late leaf spot [Cercosporidium personatum (Berk. & MA Curtis) Deighton] and stem rot (Sclerotium rolfsii Sacc.) of peanut (Arachis hypogaea L.) in the southeastern USA is heavily dependent upon sterol biosynthesis inhibitor (SBI) and quinone outside inhibitor (QoI) fungicides. Effective new fungicides with different modes of action could improve overall disease control and extend the utility of the current fungicides. Penthiopryad is a pyrazole carboxamide fungicide being evaluated for use on peanut. Field experiments were conducted from 2004 to 2007 to determine the effect of a range of rates (0–0.36 kg AI ha^?1) of penthiopyrad on leaf spot and stem rot and the relative efficacy of penthiopyrad and current fungicide standards chlorothalonil, tebuconazole and azoxystrobin. RESULTS: Leaf spot control in plots treated with penthiopyrad at 0.20 kg AI ha^?1 or higher was similar to or better than that for the chlorothalonil standard. The incidence of stem rot for all penthiopyrad treatments was usually less than that for the tebuconazole or azoxystrobin standard treatments. Pod yields for all penthiopyrad treatments were similar to or higher than those for the respective standards. CONCLUSION: Penthiopyrad has excellent potential for management of late leaf spot and stem rot of peanut, and may complement current SBI and QoI fungicides. Copyright © 2008 Society of Chemical Industry     

Field Validation of the Southern Rock Lobster Paralytic Shellfish Toxin Monitoring Program in Tasmania,Australia

Paralytic shellfish toxins (PST) are found in the hepatopancreas of Southern Rock Lobster Jasus edwardsii from the east coast of Tasmania in association with blooms of the toxic dinoflagellate Alexandrium catenella. Tasmania’s rock lobster fishery is one of the state’s most important wild capture fisheries, supporting a significant commercial industry (AUD 97M) and recreational fishing sector. A comprehensive 8 years of field data collected across multiple sites has allowed continued improvements to the risk management program protecting public health and market access for the Tasmanian lobster fishery. High variability was seen in toxin levels between individuals, sites, months, and years. The highest risk sites were those on the central east coast, with July to January identified as the most at-risk months. Relatively high uptake rates were observed (exponential rate of 2% per day), similar to filter-feeding mussels, and meant that lobster accumulated toxins quickly. Similarly, lobsters were relatively fast detoxifiers, losing up to 3% PST per day, following bloom demise. Mussel sentinel lines were effective in indicating a risk of elevated PST in lobster hepatopancreas, with annual baseline monitoring costing approximately 0.06% of the industry value. In addition, it was determined that if the mean hepatopancreas PST levels in five individual lobsters from a site were <0.22 mg STX equiv. kg⁻¹, there is a 97.5% probability that any lobster from that site would be below the bivalve maximum level of 0.8 mg STX equiv. kg⁻¹. The combination of using a sentinel species to identify risk areas and sampling five individual lobsters at a particular site, provides a cost-effective strategy for managing PST risk in the Tasmanian commercial lobster fishery.     

The rapid and accurate determination of germ tube emergence site by Blumeria graminis conidia

The development of appressoria by germinating Blumeria graminis conidia depends on its germ tubes making contact with the host surface. Low angle, low temperature scanning electron microscopy showed that 80% or more of first-formed germ tubes of f. spp. hordei, tritici and avenae conidia emerged from close to the host leaf surface, and so made contact with it allowing them to become functional primary germ tubes. Light microscopy of f. sp.hordei confirmed this result and, in addition, showed that germ tubes frequently emerged close to, and contacted, various hydrophobic and hydrophilic artificial substrata. Geometric models of conidium-substratum interfaces were developed and a “surface point method” was derived to predict the frequency with which contact would result if germ tube emergence was a random phenomenon. However, observed contact frequencies were far higher (c. three to eight times) than predicted. Thus, the germ tube emergence site was determined as a response to substratum contact. In part, this appeared to be a non-specific response. Nevertheless, germ tube contact frequencies were greater on the curved surface of leaf epidermal cells than on planar surface, suggesting that specific recognition of leaf surface characteristics may promote directional emergence. The area of contact required to stimulate directional germ tube emergence was very small: contact with a microneedle tip or with a spiders’ suspension thread was sufficient for many conidia. Similarly, on leaves, the only contact is between the tips of a limited number of conidial wall projections and the edges of epicuticular leaf wax plates. Micromanipulation to roll conidia so that their original site of contact with a leaf was rotated away from it, led to the majority of first-formed germ tubes growing away from the leaf, i.e. emerging close to the site of original contact. The experiments indicated that the site of germ tube emergence is determined within 1 min of deposition. This implicated the release of conidial extracellular materials in recognition of the conidium-leaf surface contact site.     

Outbreak investigation of porcine epidemic diarrhea in swine in Ontario

Porcine epidemic diarrhea virus was first diagnosed in Ontario in January of 2014. An outbreak investigation was conducted and it was hypothesized that feed containing spray-dried porcine plasma contaminated with the virus was a risk factor in the introduction and spread of the disease in Ontario.