Browsing by Subject "disease"
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Item Direct and indirect effects of CO2, nitrogen, and community diversity on plant–enemy interactions(Ecological Society of America, 2008) Lau, Jennifer A; Strengbom, Joachim; Stone, Laurie R; Reich, Peter B; Tiffin, PeterResource abundance and plant diversity are two predominant factors hypothesized to influence the amount of damage plants receive from natural enemies. Many impacts of these environmental variables on plant damage are likely indirect and result because both resource availability and diversity can influence plant traits associated with attractiveness to herbivores or susceptibility to pathogens. We used a long-term, manipulative field experiment to investigate how carbon dioxide (CO2) enrichment, nitrogen (N) fertilization, and plant community diversity affect plant traits and the amount of herbivore and pathogen damage experienced by the common prairie legume Lespedeza capitata. We detected little evidence that CO2 or N affected plant traits; however, plants growing in high-diversity treatments (polycultures) were taller, were less pubescent, and produced thinner leaves (higher specific leaf area). Interestingly, we also detected little evidence that CO2 or N affect damage. Plants growing in polycultures compared to monocultures, however, experienced a fivefold increase in damage from generalist herbivores, 64% less damage from specialist herbivores, and 91% less damage from pathogens. Moreover, within diversity treatments, damage by generalist herbivores was negatively correlated with pubescence and often was positively correlated with plant height, while damage by specialist herbivores typically was positively correlated with pubescence and negatively associated with height. These patterns are consistent with changes in plant traits driving differences in herbivory between diversity treatments. In contrast, changes in measured plant traits did not explain the difference in disease incidence between monocultures and polycultures. In summary, our data provide little evidence that CO2 or N supply alter damage from natural enemies. By contrast, plants grown in monocultures experienced greater specialist herbivore and pathogen damage but less generalist herbivore damage than plants grown in diverse communities. Part of this diversity effect was mediated by changes in plant traits, many of which likely are plastic responses to diversity treatments, but some of which may be the result of evolutionary changes in response to these long-term experimental manipulations.Item Facts About New Castle Disease(Minnesota Agricultural Experiment Station, 1953-06) Pomeroy, B. S.; Brandly, C. A.NEWCASTLE DISEASE is a specific, highly contagious disease affecting chiefly chickens and turkeys. Other poultry, as well as various species of wild birds, may be attacked also.Item Mechanistic links between physiology and spectral reflectance enable pre-visual detection of oak wilt and drought stress(Proceedings of the National Academy of Sciences, 2024-02) Sapes, Gerard; Schroeder, Lucy; Scott, Allison; Clark, Isaiah; Juzwik, Jennifer; Montgomery, Rebecca; Guzmán Q., J. Antonio; Cavender-Bares, JeannineTree mortality due to global change—including range expansion of invasive pests and pathogens—is a paramount threat to forest ecosystems. Oak forests are among the most prevalent and valuable ecosystems both ecologically and economically in the United States. There is increasing interest in monitoring oak decline and death due to both drought and the oak wilt pathogen (Bretziella fagacearum). We combined anatomical and ecophysiological measurements with spectroscopy at leaf, canopy, and airborne levels to enable differentiation of oak wilt and drought, and detection prior to visible symptom appearance. We performed an outdoor potted experiment with Quercus rubra saplings subjected to drought stress and/or artificially inoculated with the pathogen. Models developed from spectral reflectance accurately predicted ecophysiological indicators of oak wilt and drought decline in both potted and field experiments with naturally grown saplings. Both oak wilt and drought resulted in blocked water transport through xylem conduits. However, oak wilt impaired conduits in localized regions of the xylem due to formation of tyloses instead of emboli. The localized tylose formation resulted in more variable canopy photosynthesis and water content in diseased trees than drought-stressed ones. Reflectance signatures of plant photosynthesis, water content and cellular damage detected oak wilt and drought 13 days before visual symptoms appeared. Our results show that leaf spectral reflectance models predict ecophysiological processes relevant to detection and differentiation of disease and drought. Coupling spectral models that detect physiological change with spatial information enhances capacity to differentiate plant stress types such as oak wilt and drought.Item A new and effective method to induce infection of Phyllachora maydis into corn for tar spot studies in controlled environments(Plant Methods, 2023) Solórzano, José E.; Issendorf, Shea E.; Drott, Milton T.; Check, Jill C.; Roggenkamp, Emily M.; Cruz, C. D.; Kleczewski, Nathan M.; Gongóra-Canul, Carlos C.; Malvick, Dean K.Background Tar spot of corn is a significant and spreading disease in the continental U.S. and Canada caused by the obligate biotrophic fungus Phyllachora maydis. As of 2023, tar spot had been reported in 18 U.S. states and one Canadian Province. The symptoms of tar spot include chlorotic flecking followed by the formation of black stromata where conidia and ascospores are produced. Advancements in research and management for tar spot have been limited by a need for a reliable method to inoculate plants to enable the study of the disease. The goal of this study was to develop a reliable method to induce tar spot in controlled conditions. Results We induced infection of corn by P. maydis in 100% of inoculated plants with a new inoculation method. This method includes the use of vacuum-collection tools to extract ascospores from field-infected corn leaves, application of spores to leaves, and induction of the disease in the dark at high humidity and moderate temperatures. Infection and disease development were consistently achieved in four independent experiments on different corn hybrids and under different environmental conditions in a greenhouse and growth chamber. Disease induction was impacted by the source and storage conditions of spores, as tar spot was not induced with ascospores from leaves stored dry at 25 degrees C for 5 months but was induced using ascospores from infected leaves stored at -20 degrees C for 5 months. The time from inoculation to stromata formation was 10 to 12 days and ascospores were present 19 days after inoculation throughout our experiments. In addition to providing techniques that enable in-vitro experimentation, our research also provides fundamental insights into the conditions that favor tar spot epidemics. Conclusions We developed a method to reliably inoculate corn with P. maydis. The method was validated by multiple independent experiments in which infection was induced in 100% of the plants, demonstrating its consistency in controlled conditions. This new method facilitates research on tar spot and provides opportunities to study the biology of P. maydis, the epidemiology of tar spot, and for identifying host resistance.