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BACKGROUND:Exserohilum turcicum is an important pathogen of both sorghum and maize, causing sorghum leaf blight and northern corn leaf blight. Because the same pathogen can infect and cause major losses for two of the most important grain crops, it is an ideal pathosystem to study plant-pathogen evolution and investigate shared resistance mechanisms between the two plant species. To identify sorghum genes involved in the E. turcicum response, we conducted a genome-wide association study (GWAS). RESULTS:Using the sorghum conversion panel evaluated across three environments, we identified a total of 216 significant markers. Based on physical linkage with the significant markers, we detected a total of 113 unique candidate genes, some with known roles in plant defense. Also, we compared maize genes known to play a role in resistance to E. turcicum with the association mapping results and found evidence of genes conferring resistance in both crops, providing evidence of shared resistance between maize and sorghum. CONCLUSIONS:Using a genetics approach, we identified shared genetic regions conferring resistance to E. turcicum in both maize and sorghum. We identified several promising candidate genes for resistance to leaf blight in sorghum, including genes related to R-gene mediated resistance. We present significant advancements in the understanding of host resistance to E. turcicum, which is crucial to reduce losses due to this important pathogen.

While every field of study presents challenges to the educator, the field of Social Studies and history in particular poses unique obstacles to student success. The issue of scope has been a constant source of anxiety to the history teacher, with new curriculum added with each passing day. Further pressure has been applied to the history teacher in the form of state or locally required common curriculums. This trend, while beneficial in standardizing and guaranteeing curriculum, usually has produced the effect of expanding the content of most classes and programs. Furthermore, the driving force behind most of these new standards has been the need for higher student achievement on standardized tests, forcing teachers to adjust their teaching strategies ("teach to the test"?) and remove favorite or pet topics from their repertoire in order to meet the new requirements. However, it must be noted that most of these challenges are inherent in the teaching of history. Issues such as time constraints and scope of coverage have been a staple for history teachers for years. The greatest obstacle to student success in the field of history education therefore, is not the product of school administrations or government mandates. Getting students to engage in the study of history, to find relevance in the events of the past, and finally to analyze the effects of change over time is perhaps the most difficult thing history teachers are asked to do. So how do history teachers combat student apathy, engage all students, and make history relevant? While there is no complete solution to this dilemma, the author proposes one strategy to increase student engagement through a course with an individualized thematic research and assessment approach that forces students to rewrite historical periods through their own lens. In this way, students construct their own historical understandings. Before examining this approach however, the author revisits the traditional divisions that exist in historical study, and establishes why and how those divisions occur. (Contains 5 notes.)