Hwang, S. F., Ahmed, H. U., Strelkov, S. E., Gossen, B. D., Turnbull, G. D., Peng, G. and Howard, R. J. 2011. Seedling age and inoculum density affect clubroot severity and seed yield in canola. Can. J. Plant Sci. 91: 183–190. Clubroot, caused by Plasmodiophora brassicae, is a serious threat to canola (Brassica napus, B. rapa) production in western Canada because of its long-lived resting spores, high spore production potential, and negative impact on seed yield when inoculum pressure is high. The effect of inoculum density was studied by diluting heavily infested field soil with pathogen-free soil-less potting mix at seven increments, ranging from completely pathogen-free to 100% infested soil, and also by incorporating resting spores into the soil-less mix at concentrations of 1×105 to 1×108 spores cm−3, along with a non-inoculated control. Seed of the susceptible canola cultivar 34 SS 65 was planted in soil of each treatment, grown to maturity, and rated for plant height, seed yield, and clubroot severity (0–3 scale) at harvest. Clubroot severity increased and plant height and seed yield decreased with increasing inoculum density. To assess the effect of seedling age on reaction to clubroot, resting spores of P. brassicae were inoculated onto roots of 1-, 2-, 3- and 4-wk-old seedlings of 34 SS 65. In addition, seed (i.e., 0-wk-old seedlings) was sown into infested soil. Inoculation of young seedlings resulted in higher clubroot severity, shorter plants and lower yield than inoculation of older seedlings. These results indicate that seed treatment fungicides with a long residual period (4 wk or more) may be useful for the management of clubroot.

The impact of cultivar resistance and inoculum density on the incidence of primary infection of canola root hairs by Plasmodiophora brassicae, the causal agent of clubroot, was assessed by microscopy. The incidence of root hair infection in both a resistant and a susceptible cultivar increased with increasing inoculum density, but was two-to threefold higher in the susceptible cultivar; the relationship between root hair infection and inoculum density was also substantially stronger and more consistent in the susceptible cultivar. In the susceptible cultivar, the root hair infection rate peaked between 6 and 8 days after sowing and then declined. In the resistant cultivar, it increased over the 14-day duration of each study. It appears that examination of root hair infection by microscopy in a bait crop of susceptible canola could serve as a useful tool for estimating P. brassicae inoculum levels in soil. In a separate trial, the relationship between inoculum density and clubroot severity, plant growth parameters, and seed yield was assessed under greenhouse conditions. Inoculum density in the susceptible genotype was strongly and positively correlated with clubroot severity and negatively correlated with plant height and seed yield. In addition, a single cropping cycle of the susceptible cultivar contributed significantly higher levels of resting spores to the soil in a greenhouse test than did a cycle of the resistant cultivar, as assessed by quantitative PCR and microscope analysis.

Agricultural and wild ecosystems may interact through shared pathogens such as Macrophomina phaseolina, a generalist clonal fungus with more than 284 plant hosts that is likely to become more important under climate change scenarios of increased heat and drought stress. To evaluate the degree of subdivision in populations of M. phaseolina in Kansas agriculture and wildlands, we compared 143 isolates from maize fields adjacent to tallgrass prairie, nearby sorghum fields, widely dispersed soybean fields and isolates from eight plant species in tallgrass prairie. Isolate growth phenotypes were evaluated on a medium containing chlorate. Genetic characteristics were analysed based on amplified fragment length polymorphisms and the sequence of the rDNA-internal transcribed spacer (ITS) region. The average genetic similarity was 58% among isolates in the tallgrass prairie, 71% in the maize fields, 75% in the sorghum fields and 80% in the dispersed soybean fields. The isolates were divided into four clusters: one containing most of the isolates from maize and soybean, two others containing isolates from wild plants and sorghum, and a fourth containing a single isolate recovered from Solidago canadensis in the tallgrass prairie. Most of the sorghum isolates had the dense phenotype on media containing chlorate, while those from other hosts had either feathery or restricted phenotypes. These results suggest that the tallgrass prairie supports a more diverse population of M. phaseolina per area than do any of the crop species. Subpopulations show incomplete specialization by host. These results also suggest that inoculum produced in agriculture may influence tallgrass prairie communities, and conversely that different pathogen subpopulations in tallgrass prairie can interact there to generate 'hybrids' with novel genetic profiles and pathogenic capabilities.

Late gadolinium enhancement in Brugada syndrome: A marker for subtle underlying cardiomyopathy?, Heart Rhythm, http://dx.doi.org/10. 1016/j.hrthm.2016.12.004 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Pathogenic variability of 14 Septoria tritici isolates from different locations in the USA (California, Oregon, and Texas) was determined on seedlings of two sets of geographically diverse wheat cultivars under greenhouse conditions. Significant isolate effects, cultivar effects, and isolate × cultivar interactions were found, and a substantial amount of variation was accounted for by the interaction terms compared with the main effects of isolate and cultivar. All isolates were pathogenic on the cultivars tested but the degree of virulence on the individual cultivars varied among isolates. Linear contrasts between all homologous combinations (isolate × cultivar combination of same geographic location) and all heterologous combinations (isolate × cultivar combination of different locations) indicated that homologous combinations produced significantly more disease than heterologous combinations. The results demonstrate location‐specific adaptation of S. tritici. Implications of pathogenic variability and local adaptation in S. tritici are discussed.