{"id":{"repo_id":"siu-theses","oai_identifier":"oai:opensiuc.lib.siu.edu:dissertations-1982"},"canonical_url":"https://search.dev.ndltd.org/etd/siu-theses/oai:opensiuc.lib.siu.edu:dissertations-1982","repository":{"repo_id":"siu-theses","name":"Southern Illinois University","base_url":"https://opensiuc.lib.siu.edu/do/oai/"},"display":{"title":"A CHARACTERIZATION OF SELECTION FOR EVOLVED RESISTANCE TO PROTOPORPHYRINOGEN OXIDASE (PPO)-INHIBITING HERBICIDES IN AMARANTHUS TUBERCULATUS","abstract":"Weed management options in agronomic crop production have been severely limited by widespread populations of weeds resistant to herbicides, including waterhemp [<italic>Amaranthus tuberculatus</italic> (Moq.) Sauer (syn. <italic>rudis</italic>)] resistant to foliar applications of herbicides that inhibit protoporphyrinogen oxidase (PPO; EC 1.3.3.4) activity (PPO-R). Herbicides within this site of action (WSSA site of action #14) remain efficacious when soil-applied to PPO-R waterhemp populations. Therefore, the continued use of these herbicides for soil-residual control of PPO-R waterhemp, especially in soybean production, is paramount with limited postemergence herbicides that remain effective. An improved understanding of the selection for PPO-R waterhemp would provide information to help minimize future loss of residual PPO-inhibiting herbicide activity. Five studies, consisting of 14 experiments, were conducted to improve our understanding of the selection for herbicide-resistant individuals. Soil-residual herbicides have been suspected to select for herbicide-resistant individuals; however, this phenomenon has never been observed experimentally in field conditions. This dissertation provides direct evidence from greenhouse and field experiments that significant selection pressure can occur from soil-residual herbicides; however, this selection for resistance could be delayed when using full commercial herbicide rates and effective herbicides from multiple sites of action. Also, the frequency of heterozygous individuals (RS) and PPO-inhibiting herbicide efficacy on RS individuals is a factor in the selection for herbicide resistance; however, current information on the these topics is limited. To provide additional information on RS individuals, a large-scale genotypic and phenotypic screen of multiple PPO-R waterhemp populations was conducted. It was determined that RS individuals were less frequent than expected and PPO-inhibiting herbicide efficacy on RS individuals was population-dependent. Finally, the hormetic effects of soil-residual herbicides have been paradoxically implicated as a means of both mitigating and exacerbating the selection for herbicide resistant biotypes; however, limited information was available on the hormetic effects of soil-residual PPO inhibitors. Greenhouse and growth chamber experiments were conducted to improve understanding of hormesis and soil-residual PPO-inhibiting herbicides. Experiments indicated that PPO-inhibiting herbicides may exert a limited hormetic effect on waterhemp germination below doses that cause a phytotoxic effect of the emerging seedling, indicating this effect may exacerbate the issue of selection for PPO-R waterhemp. Overall, data presented in this dissertation provides important information on the under-studied interaction between PPO-inhibiting herbicides and PPO-R waterhemp to safeguard the sustained efficacy of herbicides within this site of action.","abstract_html":"Weed management options in agronomic crop production have been severely limited by widespread populations of weeds resistant to herbicides, including waterhemp [&lt;italic&gt;Amaranthus tuberculatus&lt;/italic&gt; (Moq.) Sauer (syn. &lt;italic&gt;rudis&lt;/italic&gt;)] resistant to foliar applications of herbicides that inhibit protoporphyrinogen oxidase (PPO; EC 1.3.3.4) activity (PPO-R). Herbicides within this site of action (WSSA site of action #14) remain efficacious when soil-applied to PPO-R waterhemp populations. Therefore, the continued use of these herbicides for soil-residual control of PPO-R waterhemp, especially in soybean production, is paramount with limited postemergence herbicides that remain effective. An improved understanding of the selection for PPO-R waterhemp would provide information to help minimize future loss of residual PPO-inhibiting herbicide activity. Five studies, consisting of 14 experiments, were conducted to improve our understanding of the selection for herbicide-resistant individuals. Soil-residual herbicides have been suspected to select for herbicide-resistant individuals; however, this phenomenon has never been observed experimentally in field conditions. This dissertation provides direct evidence from greenhouse and field experiments that significant selection pressure can occur from soil-residual herbicides; however, this selection for resistance could be delayed when using full commercial herbicide rates and effective herbicides from multiple sites of action. Also, the frequency of heterozygous individuals (RS) and PPO-inhibiting herbicide efficacy on RS individuals is a factor in the selection for herbicide resistance; however, current information on the these topics is limited. To provide additional information on RS individuals, a large-scale genotypic and phenotypic screen of multiple PPO-R waterhemp populations was conducted. It was determined that RS individuals were less frequent than expected and PPO-inhibiting herbicide efficacy on RS individuals was population-dependent. Finally, the hormetic effects of soil-residual herbicides have been paradoxically implicated as a means of both mitigating and exacerbating the selection for herbicide resistant biotypes; however, limited information was available on the hormetic effects of soil-residual PPO inhibitors. Greenhouse and growth chamber experiments were conducted to improve understanding of hormesis and soil-residual PPO-inhibiting herbicides. Experiments indicated that PPO-inhibiting herbicides may exert a limited hormetic effect on waterhemp germination below doses that cause a phytotoxic effect of the emerging seedling, indicating this effect may exacerbate the issue of selection for PPO-R waterhemp. Overall, data presented in this dissertation provides important information on the under-studied interaction between PPO-inhibiting herbicides and PPO-R waterhemp to safeguard the sustained efficacy of herbicides within this site of action.","abstract_has_math":false,"creators":["Wuerffel, Raymond Joseph"],"institution":null,"degree_name":"Doctor of Philosophy","degree_level":"Campus Only Dissertation","degree_discipline":"Plant Biology","degree_department":null,"school":null,"contributors":["Young, Bryan","Lightfoot, David"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2014,"date_issued":"2014-12-01T08:00:00Z","date_published":"2014-12-01T08:00:00Z","updated_at":"2026-07-24T04:34:36Z","subjects":["genotyping","herbicide-resistance","hormesis","soybeans","waterhemp","weed science"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://opensiuc.lib.siu.edu/dissertations/978","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Young, Bryan","Lightfoot, David"]},{"key":"dc:creator","label":"Author","values":["Wuerffel, Raymond Joseph"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"thesis:degree_discipline","label":"Discipline","values":["Plant Biology"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Campus Only Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["genotyping","herbicide-resistance","hormesis","soybeans","waterhemp","weed science"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://opensiuc.lib.siu.edu/dissertations/978"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Weed management options in agronomic crop production have been severely limited by widespread populations of weeds resistant to herbicides, including waterhemp [<italic>Amaranthus tuberculatus</italic> (Moq.) Sauer (syn. <italic>rudis</italic>)] resistant to foliar applications of herbicides that inhibit protoporphyrinogen oxidase (PPO; EC 1.3.3.4) activity (PPO-R). Herbicides within this site of action (WSSA site of action #14) remain efficacious when soil-applied to PPO-R waterhemp populations. Therefore, the continued use of these herbicides for soil-residual control of PPO-R waterhemp, especially in soybean production, is paramount with limited postemergence herbicides that remain effective. An improved understanding of the selection for PPO-R waterhemp would provide information to help minimize future loss of residual PPO-inhibiting herbicide activity. Five studies, consisting of 14 experiments, were conducted to improve our understanding of the selection for herbicide-resistant individuals. Soil-residual herbicides have been suspected to select for herbicide-resistant individuals; however, this phenomenon has never been observed experimentally in field conditions. This dissertation provides direct evidence from greenhouse and field experiments that significant selection pressure can occur from soil-residual herbicides; however, this selection for resistance could be delayed when using full commercial herbicide rates and effective herbicides from multiple sites of action. Also, the frequency of heterozygous individuals (RS) and PPO-inhibiting herbicide efficacy on RS individuals is a factor in the selection for herbicide resistance; however, current information on the these topics is limited. To provide additional information on RS individuals, a large-scale genotypic and phenotypic screen of multiple PPO-R waterhemp populations was conducted. It was determined that RS individuals were less frequent than expected and PPO-inhibiting herbicide efficacy on RS individuals was population-dependent. Finally, the hormetic effects of soil-residual herbicides have been paradoxically implicated as a means of both mitigating and exacerbating the selection for herbicide resistant biotypes; however, limited information was available on the hormetic effects of soil-residual PPO inhibitors. Greenhouse and growth chamber experiments were conducted to improve understanding of hormesis and soil-residual PPO-inhibiting herbicides. Experiments indicated that PPO-inhibiting herbicides may exert a limited hormetic effect on waterhemp germination below doses that cause a phytotoxic effect of the emerging seedling, indicating this effect may exacerbate the issue of selection for PPO-R waterhemp. Overall, data presented in this dissertation provides important information on the under-studied interaction between PPO-inhibiting herbicides and PPO-R waterhemp to safeguard the sustained efficacy of herbicides within this site of action."]},{"key":"dc:title","label":"Title","values":["A CHARACTERIZATION OF SELECTION FOR EVOLVED RESISTANCE TO PROTOPORPHYRINOGEN OXIDASE (PPO)-INHIBITING HERBICIDES IN AMARANTHUS TUBERCULATUS"]}]}],"canonical_facts":{"dc:contributor":["Young, Bryan","Lightfoot, David"],"dc:creator":["Wuerffel, Raymond Joseph"],"dc:description.abstract":["Weed management options in agronomic crop production have been severely limited by widespread populations of weeds resistant to herbicides, including waterhemp [<italic>Amaranthus tuberculatus</italic> (Moq.) Sauer (syn. <italic>rudis</italic>)] resistant to foliar applications of herbicides that inhibit protoporphyrinogen oxidase (PPO; EC 1.3.3.4) activity (PPO-R). Herbicides within this site of action (WSSA site of action #14) remain efficacious when soil-applied to PPO-R waterhemp populations. Therefore, the continued use of these herbicides for soil-residual control of PPO-R waterhemp, especially in soybean production, is paramount with limited postemergence herbicides that remain effective. An improved understanding of the selection for PPO-R waterhemp would provide information to help minimize future loss of residual PPO-inhibiting herbicide activity. Five studies, consisting of 14 experiments, were conducted to improve our understanding of the selection for herbicide-resistant individuals. Soil-residual herbicides have been suspected to select for herbicide-resistant individuals; however, this phenomenon has never been observed experimentally in field conditions. This dissertation provides direct evidence from greenhouse and field experiments that significant selection pressure can occur from soil-residual herbicides; however, this selection for resistance could be delayed when using full commercial herbicide rates and effective herbicides from multiple sites of action. Also, the frequency of heterozygous individuals (RS) and PPO-inhibiting herbicide efficacy on RS individuals is a factor in the selection for herbicide resistance; however, current information on the these topics is limited. To provide additional information on RS individuals, a large-scale genotypic and phenotypic screen of multiple PPO-R waterhemp populations was conducted. It was determined that RS individuals were less frequent than expected and PPO-inhibiting herbicide efficacy on RS individuals was population-dependent. Finally, the hormetic effects of soil-residual herbicides have been paradoxically implicated as a means of both mitigating and exacerbating the selection for herbicide resistant biotypes; however, limited information was available on the hormetic effects of soil-residual PPO inhibitors. Greenhouse and growth chamber experiments were conducted to improve understanding of hormesis and soil-residual PPO-inhibiting herbicides. Experiments indicated that PPO-inhibiting herbicides may exert a limited hormetic effect on waterhemp germination below doses that cause a phytotoxic effect of the emerging seedling, indicating this effect may exacerbate the issue of selection for PPO-R waterhemp. Overall, data presented in this dissertation provides important information on the under-studied interaction between PPO-inhibiting herbicides and PPO-R waterhemp to safeguard the sustained efficacy of herbicides within this site of action."],"dc:identifier":["https://opensiuc.lib.siu.edu/dissertations/978"],"dc:subject":["genotyping","herbicide-resistance","hormesis","soybeans","waterhemp","weed science"],"dc:title":["A CHARACTERIZATION OF SELECTION FOR EVOLVED RESISTANCE TO PROTOPORPHYRINOGEN OXIDASE (PPO)-INHIBITING HERBICIDES IN AMARANTHUS TUBERCULATUS"],"thesis:degree_discipline":["Plant Biology"],"thesis:degree_level":["Campus Only Dissertation"],"thesis:degree_name":["Doctor of Philosophy"]},"updated_at":"2026-07-24T04:34:36Z"}