A Coordinated Effort to Manage Soybean Rust in North America: A Success Story in Soybean Disease Monitoring.

Existing crop monitoring programs determine the incidence and distribution of plant diseases and pathogens and assess the damage caused within a crop production region. These programs have traditionally used observed or predicted disease and pathogen data and environmental information to prescribe management practices that minimize crop loss. Monitoring programs are especially important for crops with broad geographic distribution or for diseases that can cause rapid and great economic losses. Successful monitoring programs have been developed for several plant diseases, including downy mildew of cucurbits, Fusarium head blight of wheat, potato late blight, and rusts of cereal crops. A recent example of a successful disease-monitoring program for an economically important crop is the soybean rust (SBR) monitoring effort within North America. SBR, caused by the fungus Phakopsora pachyrhizi, was first identified in the continental United States in November 2004. SBR causes moderate to severe yield losses globally. The fungus produces foliar lesions on soybean (Glycine max) and other legume hosts. P. pachyrhizi diverts nutrients from the host to its own growth and reproduction. The lesions also reduce photosynthetic area. Uredinia rupture the host epidermis and diminish stomatal regulation of transpiration to cause tissue desiccation and premature defoliation. Severe soybean yield losses can occur if plants defoliate during the mid-reproductive growth stages. The rapid response to the threat of SBR in North America resulted in an unprecedented amount of information dissemination and the development of a real-time, publicly available monitoring and prediction system known as the Soybean Rust-Pest Information Platform for Extension and Education (SBR-PIPE). The objectives of this article are (i) to highlight the successful response effort to SBR in North America, and (ii) to introduce researchers to the quantity and type of data generated by SBR-PIPE. Data from this system may now be used to answer questions about the biology, ecology, and epidemiology of an important pathogen and disease of soybean.

Early clinical experience with the E-vita thoracic stent-graft system: a single center study.

AIM: The aim of this study was to evaluate the safety and efficacy of a new endovascular thoracic stent-graft, which was designed to overcome the restrictions of previously used stent-grafts. METHODS: Between May 2004 and March 2008 a prospective evaluation was conducted in 126 consecutive patients (71% men; age 64 [19-86] years). A total of 138 implantations were performed. E-vita stent-grafts were implanted for type-B dissection (N.=56), degenerative aneurysm (N.=25), penetrating aortic ulcer (N.=17), blunt traumatic lesions (N.=10), mobile atheroma (N.=1), suture aneurysms (N.=7) and revisionary surgery following previous endograft implantation (N.=22). All patients eligible for stent-grafting were treated with this system regardless of their clinical status and aortic pathology. The percentage of emergency procedures was 52% (N.=72). Per implantation a mean of 1.3 segments was implanted with an effective total covered length of the aorta of mean 204 mm, median 230 mm (0-450 mm). In 32 of 39 cases with more than one segment, the entire descending aorta was included in the procedure. RESULTS: The 30-day mortality rate was 12.3% (17 patients). All deaths but one were in the group of emergency surgery patients. This results in mortality of 1.5% in the elective and 22% in the emergency procedures. Reversible procedure-induced spinal cord ischemia was observed in 2 cases. Stroke occurred in 2.8% (4 patients). Primary technical success was rated at 77 % (106 procedures) and secondary success at 89 % (124 procedures). CONCLUSION: All forms of thoracic aortic disease can be treated with this new stent-graft. It has proved particularly valuable in cases of difficult conditions in the aortic arch and extended aneurysms. In particular, it is possible to cover the entire thoracic aorta with two or three stent-graft segments, thus considerably reducing the number of connections.

Arabidopsis ecotype variability in camalexin production and reaction to infection by Alternaria brassicicola.

Camalexin production was compared in 24 ecotypes of Arabidopsis thaliana. Detached Arabidopsis leaves were inoculated with Cochliobolus carbonum, an incompatible pathogen of Arabidopsis, to test the ability of each ecotype to produce camalexin. Whole plants were inoculated with Alternaria brassicicola, a crucifer pathogen, to determine if there was a correlation between the ability of an ecotype to produce camalexin and its resistance to A. brassicicola. All ecotypes were capable of producing camalexin, but the amounts produced relative to the Columbia ecotype (used as a standard) varied within and among ecotypes, and among experiments. Different degrees of resistance to A. brassicicola were observed among ecotypes, both macroscopically and microscopically. Extraction of A. brassicicola-inoculated leaves revealed that only four ecotypes (two resistant and two susceptible) produced easily detectable amounts of camalexin in response to this pathogen. TLC plate bioassays suggested that A. brassicicola was relatively insensitive to camalexin, thus casting some doubt on the importance of this compound in defense. These studies suggest that the role of camalexin in disease resistance varies among different Arabidopsis populations in nature, and they provide some clues to other possible determinants of resistance to A. brassicicola.

Effect of Host Plant Resistance and Reduced Rates and Frequencies of Fungicide Application to Control Potato Late Blight.

Field experiments were conducted during 1998 to 2000 to determine the response of commercial potato cultivars and advanced breeding lines (ABL) differing in susceptibility to foliar late blight (caused by Phytophthora infestans) to reduced rates and frequencies of residual, contact fungicide applications. When environmental conditions were most favorable for the development of late blight, the lowest application rate of the fungicides chlorothalonil or fluazinam (33% of the manufacturers' recommended application rate [MRAR]) gave unsatisfactory control of potato late blight. Under conditions moderately conducive for late blight development, effective control was achieved with 33 to 66% MRAR with either fungicide. The Michigan State University advanced selection, MSG274-3, was the least susceptible ABL tested and, during 1998 to 2000, late blight was effectively managed using reduced rates of fungicides. Application rates of chlorothalonil (33 to 100% MRAR) significantly reduced late blight in the cultivar Snowden (5-day application interval) compared with the nontreated control; whereas, late blight was not effectively controlled in Snowden even at 100% MRAR of chlorothalonil at either 10- or 15-day application intervals in 1999 or 2000. The ABL MSG274-3 was the least susceptible of all cultivars and ABL used in this study, and required minimal chemical protection against late blight. The study demonstrates that ABL with reduced susceptibility to late blight can be managed with reduced fungicide rates and longer application intervals, thus offering more economical control of this disease.

Novel procedure for identification of compounds inhibitory to transcription of genes involved in mycotoxin biosynthesis.

A novel assay is described for the identification and isolation of compounds that inhibit the transcription of genes involved in mycotoxin biosynthesis. The thin-layer chromatography-based assay was used to screen plant extracts for compounds that would inhibit the expression of the beta-glucuronidase reporter gene under the control of an aflatoxin biosynthesis gene promoter in Aspergillus parasiticus. The assay was used to track purification of an inhibitory compound, cp2, from extracts of black pepper (Piper nigrum). Cp2 did not inhibit mycelial growth or the expression of the beta-tubulin gene but did inhibit aflatoxin biosynthesis at the transcriptional level. Applications of cp2 to the control of mycotoxins are discussed.

Surgical treatment of active infective aortic valve endocarditis with associated periannular abscess--11 year results.

AIMS: The aim of the study was to evaluate the long-term results of allograft and prosthetic valve replacement in the treatment of infective aortic valve endocarditis with periannular abscess. METHODS: Between March 1988 and March 1996, 65 patients underwent surgery for active aortic valve endocarditis and paravalvular abscess. The indications for surgery were congestive heart failure, systemic emboli and atrioventricular block III. The pre-operative evaluation was performed with transoesophageal echocardiography. Aortic valve replacement was performed with allografts in 47 cases, with mechanical valves in 15, and bioprosthetic valves in three cases. All patients with total ventricular-aortic dehiscence and prosthetic valve endocarditis were treated with allografts. RESULTS: The 30-day mortality rate was 23.5% in the prosthetic group, when compared with 8.5% in the patients treated with allografts. The rate of recurrent valve infections during the 11-year follow-up period was 27.1% in the prosthetic group and 3.2% in the allograft group. The actuarial 11-year survival rate was 82.1% in the allograft group and 64.7% in the prosthetic group. CONCLUSION: Aortic allografts are an effective treatment for infective aortic valve endocarditis with associated periannular abscess. The operative mortality and recurrent infection rates are lower than in the prosthetic group, resulting in a significantly higher survival rate. Diagnosis and surgical management of these cases should be based on pre-operative transoesophageal echocardiography.

Cellular allograft rejection affecting the donor aorta after combined heart-lung transplantation.

BACKGROUND: Infectious pseudoaneurysms of the ascending aorta are a recognized major complication after heart-lung transplantation. METHOD: This report describes an unusual and previously unreported complication, that of cellular allograft rejection, which caused a pseudoaneurysm of the donor's ascending aorta in a patient who underwent combined heart-lung transplantation. Repair was performed by primary suture after mobilization of the aortic segments. RESULT: On histological examination the resected aneurysm showed evidence of proliferative vasculitis with perivascular infiltration of the vasa vasorum by mononuclear cells. The mononuclear cells were identified as CD4+ and CD8+ by immunohistological staining. CONCLUSIONS: This report shows that cellular allograft rejection may affect the donor aorta after heart-lung transplantation and may result in pseudoaneurysm formation, even under triple-drug immunosuppression after ABO-compatible allograft transplantation.

The role of phytoalexins in plant protection.

Plants resist pathogens with combinations of constitutive and induced defences. Of the induced defences, phytoalexin production has received much attention since the phytoalexin concept was introduced over 50 years ago. However, the specific role of phytoalexins in disease resistance is not clear for the majority of host-parasite systems. Much of the research on phytoalexins has relied on the identification of induced antifungal compounds and correlating their presence with resistance. Although an important first step, more definitive studies are needed. Approaches that use in situ localization and quantification have provided good evidence that phytoalexins can accumulate at the right time, concentration, and location to be effective in resistance. Studies on phytoalexin tolerance in pathogenic fungi have also shown a relationship between virulence and the ability of fungi to detoxify phytoalexins. Use of mutants deficient in phytoalexin synthesis and elucidating biosynthetic pathways provide other approaches to evaluating the role of phytoalexins. These approaches will be illustrated using the Arabidopsis-camalexin system and other selected examples. Studies on natural variation in phytoalexin production and the accumulation of phytoalexins under field conditions will be presented as another means of evaluating the role of these compounds in resistance to pathogens and other pests.

Suppression of sclerotinia stem rot of soybean by lactofen herbicide treatment.

ABSTRACT Severity of Sclerotinia stem rot of soybean after treatment with lactofen (Cobra) and other herbicides was assessed in field experiments conducted in Michigan from 1995 to 1997. At sites where disease pressure was high, disease severity was reduced 40 to 60% compared with controls when lactofen was applied at the V3 (1995 and 1996) or R1 (1997) growth stages. Corresponding seed yields were unchanged or up to 20% greater when lactofen was applied at the R1 stage in 1997. Disease severity was not reduced by lactofen treatments in years and at sites where disease pressure was low to medium, and corresponding yields often were reduced by 10%. High levels of glyceollin accumulated in lactofen-injured leaves collected from field plots in 1996 and 1997. High glyceollin content in lactofen-treated leaves was associated with significant reductions in lesion size when leaves were challenge-inoculated with Sclerotinia sclerotiorum.

Camalexin accumulation in Arabis lyrata.

Inoculation of leaves of Arabis lyrata with either a bacterial pathogen Pseudomonas syringae pv. maculicola strain ES4326 or Cochliobolus carbonum, a fungal nonpathogen of A. lyrata, resulted in the accumulation of a compound with similar chromatographic and fluorescent properties to that of camalexin (I), a phytoalexin produced by Arabidopsis thaliana. A. lyrata is closely related to A. thaliana. High resolution electron impact mass spectroscopic and proton NMR analysis confirmed that the compound produced by A. lyrata is camalexin.

Phytoalexin-deficient mutants of Arabidopsis reveal that PAD4 encodes a regulatory factor and that four PAD genes contribute to downy mildew resistance.

We are working to determine the role of the Arabidopsis phytoalexin, camalexin, in protecting the plant from pathogen attack by isolating phytoalexin-deficient (pad) mutants in the accession Columbia (Col-0) and examining their response to pathogens. Mutations in PAD1, PAD2, and PAD4 caused enhanced susceptibility to the bacterial pathogen Pseudomonas syringae pv. maculicola strain ES4326 (PsmES4326), while mutations in PAD3 or PAD5 did not. Camalexin was not detected in any of the double mutants pad1-1 pad2-1, pad1-1 pad3-1 or pad2-1 pad3-1. Growth of PsmES4326 in pad1-1 pad2-1 was greater than that in pad1-1 or pad2-1 plants, while growth in pad1-1 pad3-1 and pad2-1 pad3-1 plants was similar to that in pad1-1 and pad2-1 plants, respectively. The pad4-1 mutation caused reduced camalexin synthesis in response to PsmES4326 infection, but not in response to Cochliobolus carbonum infection, indicating that PAD4 has a regulatory function. PAD1, PAD2, PAD3 and PAD4 are all required for resistance to the eukaryotic biotroph Peronospora parasitica. The pad4-1 mutation caused the most dramatic change, exhibiting full susceptibility to four of six Col-incompatible parasite isolates. Interestingly, each combination of double mutants between pad1-1, pad2-1 and pad3-1 exhibited additive shifts to moderate or full susceptibility to most of the isolates.

Origin of the thiazole ring of camalexin, a phytoalexin from Arabidopsis thaliana.

The principal phytoalexin that accumulates in Arabidopsis thaliana after infection by fungi or bacteria is 3-thiazol-2'-yl-indole (camalexin). Detached noninoculated leaves of Arabidopsis and leaves inoculated with the fungus Cochliobolus carbonum were fed [35S]cysteine (Cys) and [35S]methionine. Inoculated leaves incorporated more than a 200-fold greater amount of radioactivity from [35S]Cys into camalexin, as compared with noninoculated leaves. The amount of radioactivity from [35S]Cys that was incorporated into camalexin from inoculated Arabidopsis leaves was 10-fold greater than the amount of radioactivity that was incorporated into camalexin from [35S]methionine. Additional labeling experiments were performed to determine whether other atoms of Cys are incorporated into camalexin. [14C]Cys and [35S]Cys were incorporated into camalexin with approximately the same efficiency. Cys labeled either with deuterium (D3-Cys[2,3,3]) or 13C and 15N ([U-13C,15N]Cys) was also fed to inoculated leaves of Arabidopsis; camalexin was analyzed by mass spectroscopic analysis. The average ratio of molecular ion intensities of 203/200 for [U-13C,15N]Cys-labeled camalexin was 4.22, as compared with 0.607 for the average 203/200 ratio for unlabeled camalexin. The mass fragment-ion intensity ratios of 60/58 (thiazole ring ion fragment) and 143/142 were also higher for [U-13C,15N]Cys-labeled camalexin, as compared with unlabeled camalexin. The 59/58 and 201/200 ratios were higher for D3-Cys-labeled camalexin as compared with unlabeled camalexin. These data are consistent with the predicted formation of the thiazole ring of camalexin from Cys.

Conidial Germination and Appressorium Formation of Colletotrichum coccodes on Tomato Foliage.

Conidial germination and infection processes of Colletotrichum coccodes were quantified on foliage of processing tomatoes (Lycopersicon esculentum Mill.). The abaxial surface of two opposing terminal leaflets removed from a fully expanded leaf at the 4th to 5th node was inoculated with 10-µl droplets of C. coccodes conidial suspension. Leaflets were incubated for 2 to 24 h in 2-h intervals at 25°C under high relative humidity. Explants with the conidial droplet were fixed, cleared, and preserved for microscopic observation. The percentage of germinated conidia and those with unmelanized and melanized appressoria was determined for each leaf disk. Conidial germination increased linearly with time (R2 = 0.73) (P = 0.001), maximizing (68.3%) 24 h after inoculation. The percentage of germinated conidia with unmelanized appres-soria peaked 6 h after inoculation (38.3%). Melanized appressoria formation followed a linear trend (R2 = 0.74) (P = 0.001), maximizing (62.0%) 24 h after inoculation. Infection vesicles were produced in 2.7% of conidia by 22 h, indicating successful infection.

Structural characterization of 15-hydroxytrichodiene, a sesquiterpenoid produced by transformed tobacco cell suspension cultures expressing a trichodiene synthase gene from Fusarium sporotrichioides.

Tobacco (Nicotiana tabaccum) cell suspension cultures transformed with a gene encoding trichodiene synthase, a sesquiterpene synthase from the fungus Fusarium sporotrichioides, produced a novel sesquiterpenoid derived from the in vivo production of trichodiene. Mass and nuclear magnetic resonance spectroscopic analyses identified the new compound as 15-hydroxytrichodiene. The in vivo hydroxylation of trichodiene by transformant tobacco cell suspension cultures demonstrates that the introduction of a foreign sesquiterpene synthase gene can result in the production of novel sesquiterpenoid metabolites.

Characterization of Novel Sesquiterpenoid Biosynthesis in Tobacco Expressing a Fungal Sesquiterpene Synthase.

The gene encoding trichodiene synthase (Tri5), a sesquiterpene synthase from the fungus Fusarium sporotrichioides, was used to transform tobacco (Nicotiana tabacum). Trichodiene was the sole sesquiterpene synthase product in enzyme reaction mixtures derived from unelicited transformant cell-suspension cultures, and both trichodiene and 5-epi-aristolochene were observed as reaction products following elicitor treatment. Immunoblot analysis of protein extracts revealed the presence of trichodiene synthase only in transformant cell lines producing trichodiene. In vivo labeling with [3H]mevalonate revealed the presence of a novel trichodiene metabolite, 15-hydroxytrichodiene, that accumulated in the transformant cell-suspension cultures. In a trichodiene-producing transformant, the level of 15-hydroxytrichodiene accumulation increased after elicitor treatment. In vivo labeling with [14C]acetate showed that the biosynthetic rate of trichodiene and 15-hydroxytrichodiene also increased after elicitor treatment. Incorporation of radioactivity from [14C]acetate into capsidiol was reduced following elicitor treatment of a trichodiene-producing transformant as compared with wild type. These results demonstrate that sesquiterpenoid accumulation resulting from the constitutive expression of a foreign sesquiterpene synthase is responsive to elicitation and that the farnesyl pyrophosphate present in elicited cells can be utilized by a foreign sesquiterpene synthase to produce high levels of novel sesquiterpenoids.

Monitoring antihypertensive therapy through blood pressure measurements taken casually, at rest, during exercise, and under outpatient conditions.

To ensure a high degree of patient compliance, and thus, therapeutic safety also, an antihypertensive agent should lower blood pressure for 24 h when taken once a day. A placebo-controlled investigation was carried out in 22 patients with essential arterial hypertension, to ascertain whether this was the case with once daily administration of ramipril. Blood pressure was measured at rest, during exercise, and under outpatient conditions (ambulant blood pressure measurement-ABPM). In our study, ramipril had an excellent 24-h effect and was found to be suitable for administration once a day. ABPM represents the most comprehensive and reliable means of monitoring antihypertensive treatment, particularly since it also provides data about nocturnal blood pressure behavior and additionally enables the most distinctive determination of the trough to peak-ratio.

Mechanisms of deposition of epicuticular wax in leaves of broccoli, Brassica oleracea var. capitata L.

Broceeli (Brassika oleraceo L. var. capitata L.) leaf waxes were labelled with [2-14 Cjacetate and examined during synthesis and deposition using microautoradiography. Waxes were viewed with light microscopy and scanning electron microscopy (SEM), including cryo-SEM. In microautoradiography, silver grains resulting from radioactive decay of labelled waxes seemed to be distributed randomly throughout the cuticle. This random distribution supports the hypothesis of diffusion or complex anastomosing pores as the mechanism of epicuriculur wax position. The hypothesis of wax-depositing pores running perpendicular to the leaf surface is not supported.

Comparison of bromine and permanganate as ultrastructural stains for lignin in plants infected by the fungus Colletotrichum lagenarium.

Transmission electron microscopy (TEM) and energy dispersive X-ray microanalysis (EDS) were used to localize manganese from KMnO4, and bromine, as ultrastructural stains for lignin in an herbaceous plant. The Spookie cultivar of pumpkin is susceptible to infection by the fungus Colletotrichum lagenarium and served as a model system to compare the Br and KMnO4 techniques. Bromine was used in a fixation/staining procedure, and in separate experiments, KMnO4 was used as either a fixative or as a postsection stain. The technique for using bromine was modified from the woody plant procedure by adding a paraformaldehyde prefixation step. With the bromine procedure, cell walls were well-preserved, but the cytoplasm was heavily extracted. The KMnO4 procedures produced well-fixed cytoplasm, but with some staining artifacts. With all procedures, EDS dot mapping demonstrated lignin deposition in the cell walls specifically associated with sites of fungal infection. Lignin was also localized in secondary walls of tracheary elements, sites known to be highly lignified. The bromine procedure provided the most specific localization of lignin with a minimum of artifact. The specific applications of these stains provided data on the ultrastructural localization of lignin which contributed to the elucidation of its role in the interactions between pathogenic fungi in both their resistant and susceptible plant hosts.

Phytoalexin Accumulation in Arabidopsis thaliana during the Hypersensitive Reaction to Pseudomonas syringae pv syringae.

Inoculation of leaves of Arabidopsis thaliana (L.) Heynh. with the wheat pathogen, Pseudomonas syringae pv syringae, resulted in the expression of the hypersensitive reaction and in phytoalexin accumulation. No phytoalexin accumulation was detected after infiltration of leaves with a mutant of P. s. syringae deficient in the ability to elicit a hypersensitive reaction; with the crucifer pathogen, Xanthomonas campestris pv campestris; or with 10 millimolar potassium phosphate buffer (pH 6.9). Phytoalexin accumulation was correlated with the restricted in vivo growth of P. s. syringae. A phytoalexin was purified by a combination of reverse phase flash chromatography, thin layer chromatography, followed by reverse phase high performance liquid chromatography. The Arabidopsis phytoalexin was identified as 3-thiazol-2'-yl-indole on the basis of ultraviolet, infrared, mass spectral, (1)H-nuclear magnetic resonance, and (13)C-nuclear magnetic resonance data.