Predicting Dosimetry of Stereotactic Ablative Radiotherapy for the Treatment of Multiple Lung Lesions

PURPOSE/OBJECTIVE(S)

Stereotactic ablative radiotherapy (SABR) has recently been used to treat increasing numbers of lung metastases, either synchronously or over multiple courses of treatment. Selecting the optimal dose and fractionation to balance risk of local failure and treatment toxicity is challenging. This project uses machine learning to provide rapid dosimetry predictions of SABR to multiple lung lesions, allowing exploration of different dose prescription options prior to the radiation (RT) planning process.

MATERIALS/METHODS

A generative adversarial network (GAN) was trained to predict the dosimetry of multi-lesion thoracic SABR treatment from the planning CT scan, target and organ at risk contours, and the prescribed dose-fractionation without the need to carry out treatment planning. RT plans of patients who received at least one SABR treatment for ≥2 lung lesions between 2014-2020 at a single tertiary center were included in the analysis. All prescriptions were converted to their equivalent doses in two Gray fractions (EQD2). SABR treatments received at different timepoints were registered, and EQD2 doses were accumulated with no repair. Model performance was assessed using 5-fold cross validation. Plans were randomly divided into 5 folds, stratified by the number of lesions (no patients crossed folds). Each fold served as the testing set once, with the model trained on the other 4 folds. The model was evaluated on the difference in the volume of lung receiving above 20 Gray (V20) of the predicted dosimetry compared to the true dosimetry.

RESULTS

Treatment plans (n = 103) were included from 81 patients with 280 lesions (62, 23, 8, and 10 plans had 2, 3, 4, and ≥5 lesions respectively). Fifty-five, 18, and 4 patients had a single, 2 and 3 courses of RT respectively. Fifty-two patients were treated for primary lung cancer, 28 patients treated for metastases from other sites, and 1 patient for both. Seven patients (8.6%) developed ≥ Grade 2 pneumonitis. Doses prescribed were 60/8 (n = 136), 55/5 (n = 49), 54/3 (n = 27), 24/1 (n = 21), 35/5 (n = 13), 30/5 (n = 9), and other (n = 25). The mean lung V20 for all patients was 11.3% [1.5%-29.6%]; the mean lung V20 was 9.3%, 12.2%, 13.5% and 20.4% for plans with 2, 3, 4, ≥ 5 lesions respectively. The mean absolute difference (MAD) in lung V20 between the predicted dosimetry and true dosimetry over all 5-folds was 1.9% [0.0%-13.4%]; the MAD in lung V20 between the predicted and actual dosimetry was 1.6%, 2.1%, 2.9% and 2.6% for plans with 2, 3, 4, ≥ 5 lesions respectively.

CONCLUSION

The GAN-based model created in this study can predict the dosimetry of any number of lesions in the thorax treated with SABR. The model can be used to quickly determine the feasibility of SABR treatment for multiple synchronous lesions, or in the retreatment setting. The ability to explore the dosimetry of different prescription options for a given patient prior to RT planning may allow for personalized risk-adapted treatment if combined with local control and toxicity modelling.

Breeding oat for resistance to the crown rust pathogen Puccinia coronata f. sp. avenae: achievements and prospects

Crown rust, caused by Puccinia coronata f. sp. avenae (Pca), is a significant impediment to global oat production. Some 98 alleles at 92 loci conferring resistance to Pca in Avena have been designated; however, allelic relationships and chromosomal locations of many of these are unknown. Long-term monitoring of Pca in Australia, North America and elsewhere has shown that it is highly variable even in the absence of sexual recombination, likely due to large pathogen populations that cycle between wild oat communities and oat crops. Efforts to develop cultivars with genetic resistance to Pca began in the 1950s. Based almost solely on all all-stage resistance, this has had temporary benefits but very limited success. The inability to eradicate wild oats, and their common occurrence in many oat growing regions, means that future strategies to control Pca must be based on the assumption of a large and variable prevailing pathogen population with high evolutionary potential, even if cultivars with durable resistance are deployed and grown widely. The presence of minor gene, additive APR to Pca in hexaploid oat germplasm opens the possibility of pyramiding several such genes to give high levels of resistance. The recent availability of reference genomes for diploid and hexaploid oat will undoubtedly accelerate efforts to discover, characterise and develop high throughput diagnostic markers to introgress and pyramid resistance to Pca in high yielding adapted oat germplasm.

Modification of Enrichment Protocols for TECRA Listeria Visual Immunoassay Method 995.22: Collaborative Study

A collaborative study was conducted to validate new enrichment methods for the TECRA Listeria Visual Immunoassay (TLVIA). These new methods incorporate a newly formulated medium, TECRA Listeria Enrichment Broth, which does not contain the highly toxic antifungal agent, cycloheximide. The new procedures will provide an alternative to the enrichment procedures described in AOAC Method 995.22. Three food types (raw ground beef, lettuce, and ice cream) were analyzed in the United States, and 2 food types (cooked turkey and cooked fish fillets) were analyzed in Australasia. Thirty collaborators participated in the study, 16 in Australasia and 14 in the United States. With the exception of one batch of ground beef, comparison of the proportion of positive test portions (p ≥ 0.05) showed no significant difference between the TLVIA and the reference method for the 5 foods at 3 inoculation levels. For the one batch of naturally contaminated raw ground beef, the TLVIA gave significantly more confirmed positive results than the reference method.

How to differentiate uterine leiomyosarcoma from leiomyoma with imaging

Uterine leiomyomas, the most frequent benign myomatous tumors of the uterus, often cannot be distinguished from malignant uterine leiomyosarcomas using clinical criteria. Furthermore, imaging differentiation between both entities is frequently challenging due to their potential overlapping features. Because a suspected leiomyoma is often managed conservatively or with minimally invasive treatments, the misdiagnosis of leiomyosarcoma for a benign leiomyoma could potentially result in significant treatment delays, therefore increasing morbidity and mortality. In this review, we provide an overview of the differences between leiomyoma and leiomyosarcoma, mainly focusing on imaging characteristics, but also briefly touching upon their demographic, histopathological and clinical differences. The main indications and limitations of available cross-sectional imaging techniques are discussed, including ultrasound, computed tomography, magnetic resonance imaging (MRI) and positron emission tomography/computed tomography. A particular emphasis is placed on the review of specific MRI features that may allow distinction between leiomyomas and leiomyosarcomas according to the most recent evidence in the literature. The potential contribution of texture analysis is also discussed. In order to help guide-imaging diagnosis, we provide an MRI-based diagnostic algorithm which takes into account morphological and functional features, both individually and in combination, in an attempt to optimize radiologic differentiation of leiomyomas from leiomyosarcomas.

Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study

BACKGROUND

Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery.

METHODS

This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy.

RESULTS

Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51-19.97) than planned admissions (OR: 2.32, 95% CI: 1.43-3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8-51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI.

CONCLUSIONS

After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies.

Multiple sclerosis onset after granulocyte macrophage colony-stimulating factor withdrawal

A 51-year old woman with stage III melanoma participated in a phase II clinical trial in which she received subcutaneous rhGM-CSF injections for 3 years. She was in remission by the end of the trial. Seven months after discontinuing GM-CSF she had her first MS event. The unique timeline of rh-GM-CSF injections in a melanoma trial, during which yearly MRI scans showed subtle stable demyelination followed by RRMS onset shortly after discontinuation of treatment, may provide some insight on the role of GM-CSF in MS.

Secreted proteins produced by fungi associated with Botryosphaeria dieback trigger distinct defense responses in Vitis vinifera and Vitis rupestris cells

Grapevine trunk diseases (Eutypa dieback, esca and Botryosphaeria dieback) are caused by a complex of xylem-inhabiting fungi, which severely reduce yields in vineyards. Botryosphaeria dieback is associated with Botryosphaeriaceae. In order to develop effective strategies against Botryosphaeria dieback, we investigated the molecular basis of grapevine interactions with a virulent species, Neofusicoccum parvum, and a weak pathogen, Diplodia seriata. We investigated defenses induced by purified secreted fungal proteins within suspension cells of Vitis (Vitis rupestris and Vitis vinifera cv. Gewurztraminer) with putative different susceptibility to Botryosphaeria dieback. Our results show that Vitis cells are able to detect secreted proteins produced by Botryosphaeriaceae, resulting in a rapid alkalinization of the extracellular medium and the production of reactive oxygen species. Concerning early defense responses, N. parvum proteins induced a more intense response compared to D. seriata. Early and late defense responses, i.e., extracellular medium alkalinization, cell death, and expression of PR defense genes were stronger in V. rupestris compared to V. vinifera, except for stilbene production. Secreted Botryosphaeriaceae proteins triggered a high accumulation of δ-viniferin in V. vinifera suspension cells. Artificial inoculation assays on detached canes with N. parvum and D. seriata showed that the development of necrosis is reduced in V. rupestris compared to V. vinifera cv. Gewurztraminer. This may be related to a more efficient induction of defense responses in V. rupestris, although not sufficient to completely inhibit fungal colonization. Overall, our work shows a specific signature of defense responses depending on the grapevine genotype and the fungal species.

Toxicity of extracellular proteins from Diplodia seriata and Neofusicoccum parvum involved in grapevine Botryosphaeria dieback

Botryosphaeria dieback, esca and Eutypa dieback are three economic major grapevine trunk diseases that cause severe yield reduction in vineyards worldwide. The frequency of disease symptoms has increased considerably over the past decade, and no efficient treatment is currently available to control these diseases. The different fungi associated with grapevine trunk diseases mainly induce necrotic wood and characteristic foliar symptoms. In this context, fungi virulence factors and host invasion are not well understood. We hypothesise that extracellular proteins produced by Diplodia seriata and Neofusicoccum parvum, two causal agents associated with Botryosphaeria dieback, are virulence factors responsible for the pathogenicity. In our previous work, we demonstrated that the total extracellular compounds produced by N. parvum induced more necrosis on Chardonnay calli and triggered a different defence gene expression pattern than those produced by D. seriata. Furthermore, this aggressiveness was not clearly correlated with the production of mellein, a characteristic phytotoxin of Botryosphaeriaceae, in our in vitro calli model. To characterise other potential virulence factors and to understand the mechanisms of host invasion by the fungus, we evaluated the profile, quantity and the impact of extracellular proteins produced by these fungi on Vitis vinifera calli necrosis and defence gene expression. Our results reveal that, under the same conditions, N. parvum produces more extracellular proteins and in higher concentrations than D. seriata. With Vitis vinifera cv. Chardonnay cells, we showed that equivalent concentrations of proteins secreted by N. parvum were more aggressive than those of D. seriata in producing necrosis and that they clearly induced more grapevine defence genes.

Magnetic Resonance Imaging of Asians with Multiple Sclerosis was Similar to that of the West

Magnetic resonance imaging (MRI) of the brain is the most important paraclinical diagnostic test in multiple sclerosis (MS). The appearance of MRI in Asians with MS is not well defined. We retrospectively surveyed the first brain and spinal cord MRI in patients diagnosed to have MS, according to Poser's criteria in seven regions throughout Asia to define the MRI changes among Asians with MS. There were 101 patients with first brain, and 86 with first spinal cord MRI, 66 of whom had both. The brain MRI showed a mean of 17 lesions per patient in T2 weighted images, mostly asymptomatic. Almost all the lesions were in the white matter, particularly in the juxtacortical, deep and periventricular white matter. A third of the lesions were greater than 5 mm, 14% enhanced with gadolinium. There were more supratentorial than infratentorial lesions at a ratio of 7.5: 1. Ninety five percent of the spinal cord lesions were in cervical and thoracic regions, 34% enhanced with gadolinium. The lesions extended over a mean of 3.6 +/- 3.3 vertebral bodies in length. Fifty (50%) of the brain and 54 (63%) of the spinal MRI patients had the optic-spinal form of MS. The MRI of the optic-spinal and classical groups of patients were similar in appearance and distribution, except that the optic-spinal MS patients have fewer brain but longer and more severe spinal cord lesions. In conclusion, the brain and spinal cord MRI of Asian patients with MS was similar to that of the West, although, in this study, Asian MS patients had larger spinal cord lesions.

Extracellular compounds produced by fungi associated with Botryosphaeria dieback induce differential defence gene expression patterns and necrosis in Vitis vinifera cv. Chardonnay cells

Three major grapevine trunk diseases, esca, botryosphaeria dieback and eutypa dieback, pose important economic problems for vineyards worldwide, and currently, no efficient treatment is available to control these diseases. The different fungi associated with grapevine trunk diseases can be isolated in the necrotic wood, but not in the symptomatic leaves. Other factors seem to be responsible for the foliar symptoms and may represent the link between wood and foliar symptoms. One hypothesis is that the extracellular compounds produced by the fungi associated with grapevine trunk diseases are responsible for pathogenicity.In the present work, we used Vitis vinifera cv. Chardonnay cells to test the aggressiveness of total extracellular compounds produced by Diplodia seriata and Neofusicoccum parvum, two causal agents associated with botryosphaeria dieback. Additionally, the toxicity of purified mellein, a characteristic toxin present in the extracellular compounds of Botryosphaeriaceae, was assessed.Our results show that the total extracellular compounds produced by N. parvum induce more necrosis on Chardonnay calli and induce a different defence gene expression pattern than those of D. seriata. Mellein was produced by both fungi in amounts proportional to its aggressiveness. However, when purified mellein was added to the culture medium of calli, only a delayed necrosis and a lower-level expression of defence genes were observed. Extracellular compounds seem to be involved in the pathogenicity of the fungi associated with botryosphaeria dieback. However, the doses of mellein used in this study are 100 times higher than those found in the liquid fungal cultures: therefore, the possible function of this toxin is discussed.

The anticancer antibiotic mithramycin-A inhibits TRPV1 expression in dorsal root ganglion neurons

Activation of peripheral nociceptors by products of inflammation has been shown to be dependent on specific sensory transducing elements such as the capsaicin receptor, TRPV1. The development of high-affinity antagonists to TRPV1 as well as to other receptors capable of detecting noxious stimuli has now become a major focus in analgesic development. Another critical feature of nociception is the relative abundance of a particular pain transducing receptor under normal or pathophysiologic conditions. Increases in expression and/or changes in distribution of nociceptive receptors such as TRPV1 have been correlated with progression of tissue injury and persistence of pain behaviors. Although some details are emerging as to what regulates nociceptor-specific gene expression, compounds that could potentially be used to block or reverse over-expression of nociceptive gene expression are essentially absent. In our efforts to better understand the transcriptional regulation of TRPV1 in sensory neurons, we identified an anticancer agent, mithramycin-A, that decreased TRPV1 expression in primary rat dorsal root ganglion (DRG) neurons. Mithramycin-A dose-dependently (10-50 nM) decreased endogenous TRPV1 mRNA content and appeared to decrease TRPV1-like protein expression in DRG neurons. We also observed that mithramycin-A directed a decrease in the number of capsaicin-responsive DRG neurons without a significant change in the capsaicin-response magnitudes. Interestingly, mithramycin-A also reduced the mRNA encoding Sp1 and Sp4 in DRG neurons, transcription factors previously found to positively regulate TRPV1 expression in sensory neurons. Taken together, we propose that mithramycin-A directs an inhibitory effect on a subpopulation of capsaicin-responsive DRG neurons that utilize Sp1-like factors for TRPV1 expression. Given the therapeutic correlate of mithramycin-A effectiveness in the treatment of certain cancers, small molecule transcriptional inhibitors such as mithramycin-A may serve as useful tools of discovery in pain transduction and possibly future analgesic development.

Clopidogrel resistance is associated with thromboembolic complications in patients undergoing neurovascular stenting

BACKGROUND AND PURPOSE

Antiplatelet drug resistance has been associated with thromboembolic complications in patients after coronary stent placement. It has not been well-studied in patients who have neurovascular stent-placement procedures. This study aimed to analyze the relationship between antiplatelet drug resistance and neurovascular stent-placement complications.

MATERIALS AND METHODS

A prospective data base of all patients treated at our institution was used to identify patients with neurovascular stent-placement procedures. During a 4.5-year period, all patients undergoing neurovascular stent placement were evaluated for aspirin and clopidogrel resistance by using the VerifyNow assay. During an observational phase, all patients received 75 mg of clopidogrel and aspirin (group A). During the intervention phase (group B), patients were given additional clopidogrel on the basis of the clopidogrel resistance assay. We assessed the development of thromboembolic complications within 30 days of the procedure in patients who were resistant-versus-nonresistant to clopidogrel.

RESULTS

Of 96 patients who had neurovascular stent placement, 5.2% were resistant to aspirin and 36.5% were resistant to clopidogrel. Periprocedural thromboembolic complications were seen in 7 patients (7.3%). In a multivariate logistic regression model, clopidogrel resistance, higher diastolic blood pressure, and lack of statin use were significantly associated with periprocedural thromboembolic complication. There was a nonsignificant decrease in thromboembolic complications in patients whose clopidogrel dosage was tailored to the assay.

CONCLUSIONS

In our series, clopidogrel resistance was associated with increased periprocedural thromboembolic complications from neurovascular stent-placement procedures. Targeting the clopidogrel dose to platelet inhibition assays may improve clinical outcomes and requires further study.

Identification of the stem rust resistance gene Pg9 and its association with crown rust resistance and endosperm proteins in 'Dumont' oat

The Canadian oat cultivar 'Dumont' is known to have genes Pc38 and Pc39 for crown rust resistance and genes Pg2 and Pg13 for stem rust resistance. When crossed to a susceptible oat line OT328, 'Dumont' was shown to have an additional dominant gene for crown rust resistance, designated PcX. Tests of segregating progeny indicated that the stem rust resistance gene Pg9 is present and is tightly linked in coupling to PcX. The presence of Pg9 in 'Dumont' was confirmed in crosses involving the cultivar 'Ukraine', which has Pg9 and a crown rust resistance gene tightly linked to it. The association of rust resistance with endosperm proteins in 'Dumont' was investigated. The linkage of gene Pg13 with a 56.6-kDa polypeptide locus (map distance of 10.47 +/- 2.70 cM) was demonstrated using sodium dodecylsulfate - polyacrylamide gel electrophoresis (SDS-PAGE). A 27.9-kDa polypeptide was shown to be associated with the linked PcX/Pg9 loci by SDS-PAGE but appeared to be more reliably separated as an avenin band, designated B4, using acid-PAGE. Another avenin band, designated B2, also was shown to be associated with the PcX/Pg9 loci using acid-PAGE. The loci conditioning the B2 and B4 bands appeared to be tightly linked or allelic and are separated from the linked PcX/Pg9 loci by a map distance of 1.03 +/- 0.36 cM. The association of Pg13 with a 56.6-kDa polypeptide and the tight linkage between PcX/Pg9 and the B2 (in coupling) and B4 (in repulsion) avenin loci offer a useful tool to breeders to detect the presence of these genes in oat breeding.

Mapping of the oat crown rust resistance gene Pc91

Crown rust is an important disease of oat caused by Puccinia coronata Corda f. sp. avenae Eriks. Crown rust is efficiently and effectively managed through the development of resistant oat varieties. Pc91 is a seedling crown rust resistance gene that is highly effective against the current P. coronata population in North America. The primary objective of this study was to develop DNA markers linked to Pc91 for purposes of marker-assisted selection in oat breeding programs. The Pc91 locus was mapped using a population of F7-derived recombinant inbred lines developed from the cross 'CDC Sol-Fi'/'HiFi' made at the Crop Development Centre, University of Saskatchewan. The population was evaluated for reaction to P. coronata in field nurseries in 2008 and 2009. Pc91 mapped to a linkage group consisting of 44 Diversity Array Technology (DArT) markers. DArTs were successfully converted to sequence characterized amplified region (SCAR) markers. Five robust SCARs were developed from three non-redundant DArTs that co-segregated with Pc91. SCAR markers were developed for different assay systems, such that SCARs are available for agarose gel electrophoresis, capillary electrophoresis, and Taqman single nucleotide polymorphism detection. The SCAR markers accurately postulated the Pc91 status of 23 North American oat breeding lines.

Polymorphism of the prion protein gene (PRNP) in two Chinese indigenous cattle breeds

Prion protein (PRNP) gene has been located at position q17 of chromosome 13 in cattle. The polymorphisms of PRNP gene might be associated with BSE susceptibility. In the present work, we investigated the polymorphisms of PRNP gene, including SNP in exon 3, 23-bp indel in promoter region, 12-bp indel in intron 1 in 2 Chinese indigenous cattle breeds of northeast China. Eighty-six animals from Yanbian (34) and Chinese Red Steppes (52) were genotyped at PRNP locus by analyzing genomic DNA. A total of 4 single nucleotide polymorphism (SNP) sites were revealed in the PRNP gene exon 3 of the 2 cattle breeds investigated. Three of these SNPs were non-synonymous mutations that resulted in the amino acid exchanges (K119N, S154N, and M177V), and one is silent nucleotide substitutions (A234G). The two amino acid mutations of S154N and M177V were detected only in Yanbian with a very low frequency (0.0147), and they appears to be absent in Chinese Red Steppes. The average gene heterozygosity (He), effective allele numbers (Ne), Shannon's information index (I) and polymorphism information content (PIC) were 0.3088, 1.5013, 0.3814 and 0.2000 in Yanbian, respectively, being relatively higher than that of Chinese Red Steppes (0.2885, 1.4985, 0.3462 and 0.1873, respectively). In 23-bp indel and 12-bp indel loci, three different genotypes were identified in both Yanbian and Chinese Red Steppes breeds. Based 23- and 12-bp indels, four haplotypes was constructed in the 2 Chinese cattle breeds, of which the 23-bp (-)/12-bp (-) was main haplotypes accounting for more than 50% of the total in both Yanbian and Chinese Red Steppes breeds. These results might be useful in understanding the genetic characteristics of PRNP gene in Chinese indigenous cattle breeds.

Role of muscarinic receptor activation in regulating immune cell activity in nasal mucosa

BACKGROUND

The prevalence of airway inflammatory disorders keeps rising; its pathogenic mechanism is still not fully understood.

OBJECTIVE

The present study aimed to investigate the role of muscarinic receptor (M receptor) in regulating the immune cell activity in nasal mucosa by using surgical removed nasal mucosa from patients with nasal polyposis (NP) as a study platform.

METHODS

Human nasal mucosal sample was collected from inferior turbinectomy of 86 patients with NP or/and allergic rhinitis. Expression of tumor necrosis factor alpha (TNF-alpha), M receptor, OX40 ligand was measured in nasal mucosa by enzyme-linked immunosorbent assay, flow cytometry, and Western blotting assay.

RESULTS

When compared with non-NP (nNP) nasal mucosa, contents of TNF-alpha and TNF-alpha+ cells markedly increased in NP nasal mucosa; immune staining colocalized M3 receptor+ and TNF-alpha+ cells in NP nasal mucosa; exposure of isolated CD4+ T cells to methacholine induced the release of TNF-alpha. We also found CD11c+/M3 receptor+ cells in NP nasal mucosa. Methacholine increased the expression of OX40L in dendritic cells. Staphylococcal (S) aureus and S. enterotoxin B (SEB) were detected in NP nasal mucosa. Exposure of dendritic cells or naïve CD4+ T cells to SEB initiated the expression of M3 receptor at mRNA and protein levels.

CONCLUSIONS

The present data demonstrate that parasympathetic activity has the capacity to activate dendritic cells to release OX40 ligand, the latter induces CD4+ T cells to produce IL-4 and TNF-alpha that may further contribute to the pathogenesis of NP.

Identification and validation of quantitative trait loci for partial resistance to crown rust in oat

Management of oat crown rust disease with host resistance is challenging because major gene resistance is generally short lived. Partially resistant oat cultivars could benefit oat growers by providing more durable resistance. The objective of this study was to validate and discover quantitative trait loci (QTL) affecting crown rust resistance in the partially resistant oat line MN841801-1 using conventional and molecular assessments of disease produced in single-race greenhouse inoculations, single-race polycyclic field tests, and under natural infection in disease-conducive environments. Crown rust was assessed on 150 F(6:9) MN841801-1/'Noble-2' recombinant inbred lines. In total, eight QTL associated with MN841801-1 alleles were detected. Of these, seven matched QTL previously identified while a new QTL (Prq8) was detected on linkage group MN13. Four QTL (Prq1a, Prq2, Prq7, and Prq8) were consistently detected and predicative genetic assays for these QTL should be developed for future validation in additional genetic backgrounds.

Quantitative trait loci in the Ogle/TAM O-301 oat mapping population controlling resistance to Puccinia coronata in the field

Crown rust is the most damaging disease of cultivated oat (Avena sativa) and genetic resistance is the primary means of controlling the disease. Quantitative trait loci (QTL) with major and minor effects have been identified in Ogle1040 and TAM O-301 (most notably, Pc58 and PcNQMG/LGCG from TAM O-301 and OT-27 from Ogle1040) through single-isolate greenhouse and field tests. To map loci and determine the effectiveness of previously identified QTL against naturally occurring pathogen populations in highly disease-conducive environments, the Ogle/TAM O-301 (OT) recombinant inbred line (RIL) population was grown in Texas and Louisiana over 2 years and in Manitoba, Canada. The genetic region characterized by the Pc58 resistance gene complex, particularly Pc58a, accounted for most of the diseased leaf area (DLA) and infection type (IT) variance in all five experiments. Additionally, the genetic region characterized by PcNQMG/LGCG accounted for a portion of the IT variance in three experiments. Although no QTL was detected on OT-27 in this study, all the markers on this linkage group were associated (P < 0.0001) with reducing both IT and DLA using single-marker analysis. Screening with 25 Puccinia coronata isolates from six different states indicated that Pc58abc and Pc58a were highly effective, while characterization using F(2) populations derived from OT RILs containing the two main genetic regions responsible for crown rust resistance in TAM O-301 (Pc58 and PcNQMG/LGCG) and a minor QTL in Ogle (OT-27) indicated that Pc58a, in combination with a locus in Ogle1040, provided high levels of resistance to natural races in Texas. This study provides new information and key loci in OT mapping population and may be useful for effective control of crown rust in North America.

Detached-Leaf Method for Propagating Puccinia coronata and Assessing Crown Rust Resistance in Oat

The crown rust pathogen Puccinia coronata is an obligate biotroph with wind-disseminated propagules and numerous races. These characteristics make propagation of single-race cultures difficult. Genetic studies using single races in field and greenhouse environments are also problematic because pure cultures can easily become contaminated. In this study, we developed an isolated propagation system for P. coronata and tested its ability to assess host resistance. Oat (Avena sativa) leaf sections (10 cm each) were harvested, disinfested, and suspended in sterile plastic boxes by enclosing 3.5-cm linear sections of each leaf end between 4% agar blocks amended with various chemical constituents. The exposed sections (approximately 3 cm) were inoculated with P. coronata urediniospores suspended in water. Boxes were sealed and incubated in a lighted growth cabinet until the pathogen sporulated. Viable spores were produced on leaves in all treatments, whereas 6-benzylaminopurine (BAP) and kinetin treatments sustained the leaves longer and yielded the most viable spores. Based on these data, the BAP treatment was adopted and used for additional studies. Detached leaves of differential oat cultivars produced the same reactions as whole plants screened under standard conditions in a growth chamber. The proposed detached-leaf system should be useful for the propagation of numerous single-race cultures of P. coronata as well as evaluation of host resistance under highly controlled conditions.

Cytopathological evidence for the division of barley yellow dwarf virus isolates into two subgroups

The cytological survey of oat cells in tissue infected with different aphid-specific or aphid-nonspecific isolates of barley yellow dwarf virus (BYDV) was concluded in this study with the examination of the alterations induced by Schizaphis graminum-specific and S. graminum-nonspecific isolates. Cytological alterations were similar with all four isolates examined, except that proliferated membranous inclusions, common with three of the isolates, were absent with S. graminum-nonspecific isolate 6712. Isometric virus-like particles, slender filaments, and single-membraned vesicles containing densely staining fibrils occurred in the cytoplasm with all the isolates. Nuclear alterations consisted of distortion of the outline of the nucleus, followed by aggregation and accumulation of densely staining material within the nucleus. The cytopathological alterations observed in cells infected with isolate 6712 were similar to those found previously with aphid-nonspecific isolates transmitted most efficiently by Rhopalosiphum padi-, and Macrosiphum avenae-specific isolates of BYDV, while the other three isolates differed in the presence of the proliferated, membranous inclusions. Evidence from cytopathology indicates that the six known aphid-specific or nonspecific variants of BYDV may be categorized into two subsections. The general agreement of the cytopathological evidence, with that from serological and cross-protection studies is discussed.

Characterization and mapping of oat crown rust resistance genes using three assessment methods

ABSTRACT Resistance is the primary means of control for crown rust of oat (Avena sativa L.), caused by Puccinia coronata f. sp. avenae, and better knowledge of the genetics of resistance will enhance resistance breeding. Disease data were generated in the field and greenhouse for parents and recombinant inbred lines of the Ogle/TAM O-301 (OT) oat mapping population using (i) a new quantitative assay that employs quantitative real-time polymerase chain reaction (q-PCR) to estimate fungal growth in the host, (ii) digital image analysis, and (iii) visual ratings. The objectives of this study were to evaluate each assessment method's ability to map a major gene from cv. Ogle and potential quantitative trait loci (QTL) contributed by Ogle and TAM O-301. All three assessment methods identified the major gene in Ogle, which was mapped to linkage group OT6. The resolution produced by q-PCR, however, enabled more precise mapping of the major gene. Quantitative analysis indicated that 64% of the phenotypic variation was accounted for using q-PCR, whereas 41 and 52% were accounted for using visual and digital assessments, respectively. Data generated by q-PCR permitted identification of QTL on linkage groups OT32, accounting for 6% of the phenotypic variation, and OT2, accounting for 4% of the variation. QTL on both OT32 and OT2 were conferred by TAM O-301, one of which (OT2) was indiscernible using data from the visual and digital assessments. The new method of precisely phenotyping crown rust resistance provided a more accurate and thorough means of dissecting resistance in the OT mapping population. Similar methods could be developed and applied to other important cereal rust diseases.