Institutional Repository

The UDSpace Institutional Repository collects and disseminates research material from the University of Delaware.

  • Faculty, staff, and graduate students can deposit their research material directly into UDSpace. Faculty may use UDSpace to fulfill the University of Delaware Faculty Senate Open Access Resolution, and in many cases may use it to fulfill open access requirements from grant funding agencies.
  • Departments can use UDSpace to publish or distribute their working papers, technical reports, or other research material.
  • UDSpace also includes all doctoral dissertations from winter 2014 forward, and all master's theses from fall 2009 forward.

To learn more about UDSpace, and how you can make your research openly accessible to the public, visit our UDSpace Policies website.


Recent Submissions

The Relationship between University Presses and Academic Libraries: Past, Present, and Future
(The Association of College and Research Libraries, 2023) Johnson, Annie
Genome Resequencing Reveals Rapid, Repeated Evolution in the Colorado Potato Beetle
(Molecular Biology and Evolution, 2022-01-19) Pélissié, Benjamin; Chen, Yolanda H.; Cohen, Zachary P.; Crossley, Michael S.; Hawthorne, David J.; Izzo, Victor; Schoville, Sean D.
Insecticide resistance and rapid pest evolution threatens food security and the development of sustainable agricultural practices, yet the evolutionary mechanisms that allow pests to rapidly adapt to control tactics remains unclear. Here, we examine how a global super-pest, the Colorado potato beetle (CPB), Leptinotarsa decemlineata, rapidly evolves resistance to insecticides. Using whole-genome resequencing and transcriptomic data focused on its ancestral and pest range in North America, we assess evidence for three, nonmutually exclusive models of rapid evolution: pervasive selection on novel mutations, rapid regulatory evolution, and repeated selection on standing genetic variation. Population genomic analysis demonstrates that CPB is geographically structured, even among recently established pest populations. Pest populations exhibit similar levels of nucleotide diversity, relative to nonpest populations, and show evidence of recent expansion. Genome scans provide clear signatures of repeated adaptation across CPB populations, with especially strong evidence of selection on insecticide resistance genes in different populations. Analyses of gene expression show that constitutive upregulation of candidate insecticide resistance genes drives distinctive population patterns. CPB evolves insecticide resistance repeatedly across agricultural regions, leveraging similar genetic pathways but different genes, demonstrating a polygenic trait architecture for insecticide resistance that can evolve from standing genetic variation. Despite expectations, we do not find support for strong selection on novel mutations, or rapid evolution from selection on regulatory genes. These results suggest that integrated pest management practices must mitigate the evolution of polygenic resistance phenotypes among local pest populations, in order to maintain the efficacy and sustainability of novel control techniques.
Biology and Management of Peanut Burrower Bug (Hemiptera: Cydnidae) in Southeast U.S. Peanut
(Journal of Integrated Pest Management, 2021-08-06) Aigner, Benjamin L.; Crossley, Michael S.; Abney, Mark R.
Peanut burrower bug, Pangaeus bilineatus (Say), is a piercing-sucking pest of peanut, Arachis hypogaea (L.), that is native to Central and North America. The insect spends most of its life below the soil surface and is not easily detected in the field. Although injury to peanut is sporadic in the Southern USA, the bug has become a serious economic pest for farmers in the region in recent years. During and after peanut seed formation, adult and immature bugs feed directly on seeds through the hull, reducing the quality and value of the crop. The value of peanut is reduced by approximately $209/MT when feeding injury is present on ≥3.5% of kernels by weight. Deep tillage prior to planting and application of granular chlorpyrifos during the growing season are the only tactics currently available for managing P. bilineatus in peanut in the United States. Relatively little research attention has been focused on P. bilineatus, and improved knowledge of the insect’s biology and ecology is needed to develop an integrated pest management (IPM) strategy that significantly reduces financial losses caused by this insect. The purpose of this article is to provide a review of the taxonomic history, biology, pest status, and management of P. bilineatus primarily as it relates to peanut production systems in the Southeast USA.
Multiple cropping alone does not improve year-round food security among smallholders in rural India
(Environmental Research Letters, 2021-06-17) Mondal, Pinki; DeFries, Ruth; Clark, Jessica; Flowerhill, Nicole; Arif, Md.; Harou, Aurelie; Downs, Shauna; Fanzo, Jessica
Achieving and maintaining food and nutrition security is an important Sustainable Development Goal, especially in countries with largely vulnerable population with high occurrence of hunger and malnutrition. By studying a small-scale agricultural system in India, we aim to understand the current state of dietary diversity and food insecurity among the farmer communities. The study landscape has witnessed a steady rise in multiple cropping (i.e. harvesting more than once a year) along with irrigation over the last two decades. Whether this multiple cropping can be expected to improve year-round food security is not well understood. We specifically examine if planting multiple food crops within a year is associated with dietary diversity and food security. We collected information on demographic and economic variables, farming activities and livelihood choices, from 200 unique households for three seasons (monsoon/rainy, winter, summer) during 2016–2018 (n = 600). Based on both a 24 h and a 30 days recall, we calculated several indicators, including the household dietary diversity score, the minimum dietary diversity for women, and household food insecurity access scale. At least 43% of the sample population experiences moderate to severe food insecurity in all seasons. Cereals (mainly rice) remain the most important food item irrespective of the season, with negligible consumption of other nutrient-rich food such as tubers, fish, eggs, and meats. Around 81% of women in all seasons do not consume a minimally diverse diet. Multiple cropping is associated with higher food security only during monsoon, while selling monsoon crops is associated with winter food security. Households practicing multiple cropping consume more pulses (a plant-based protein source) compared to single-cropping or non-farming households (p < 0.05). We find that multiple cropping cannot be used as a cure-all strategy. Rather a combination of income and nutrition strategies, including more diverse home garden, diverse income portfolio, and access to clean cooking fuel, is required to achieve year-round dietary diversity or food security.