Show simple item record

dc.contributor.advisorHarris, Marvin K.en_US
dc.contributor.advisorPeterson, Gary C.en_US
dc.creatorGorena, Roberto Luisen_US
dc.date.accessioned2004-09-30T01:41:20Z
dc.date.available2004-09-30T01:41:20Z
dc.date.created2003-05en_US
dc.date.issued2004-09-30
dc.identifier.urihttp://hdl.handle.net/1969.1/63
dc.description.abstractGreenbug is one of two key insect pests of sorghum, and biotype evolution hinders the long-term usefulness of resistant sorghums. The current study sought to identify plant resistance mechanisms, plant damage characteristics, and greenbug fitness in sorghum/greenbug interactions. Choice tests were conducted to elucidate resistance mechanisms displayed by four sorghum genotypes towards several greenbug biotypes and isolates. Results indicated all three resistance modalities (antibiosis, antixenosis, tolerance) were identified in sorghums, with some genotypes displaying two or more modalities towards some biotypes. This suggests some sorghum genotypes do not select for greenbug biotypes, and the sorghum genotypes cultivated may have relatively long-term resistance. Non-choice tests were used to determine plant damage associated with greenbug feeding. Four sorghum genotype, Johnson grass, and five greenbug biotype combinations were used to elucidate plant characteristics associated with visible plant damage. Fluid loss and plant stunting were significantly associated with visible plant damage, and were also observed in some plants not incurring heavy visible damage. Additionally, some biotypes avirulent to cultivated sorghum caused significant damage to Johnson grass. These results suggest visible plant damage, routinely used in damage studies, reflects underlying causes that could lead to poor agronomic performance. Additionally, Johnson grass may harbor greenbug biotypes not commonly found in sorghum fields. Greenbug colony and individual fitness were determined by reproduction rates of five biotypes on four sorghum genotypes and Johnson grass in non-choice tests. Generally, colony and individual fitness estimates were not different within genotype/biotype combinations. Also, biotypes did best on more susceptible and worst on more resistant sorghum genotypes. Colonies and individuals of all biotypes had lowest fitness on Johnson grass. These results suggest virulent biotypes may have a fitness advantage over avirulent ones, at least in the presence of the cultivated host. The results presented herein reflect the diversity of sorghum/greenbug interactions, and underscore the need for further understanding of the nature of greenbug biotypes, and how they interact with cultivated and non-cultivated host plants.en_US
dc.format.extent1651445 bytes
dc.format.extent232224 bytes
dc.format.mediumelectronicen_US
dc.format.mimetypeapplication/pdf
dc.format.mimetypetext/plain
dc.language.isoen_USen_US
dc.publisherTexas A&M Universityen_US
dc.subjectgreenbugen_US
dc.subjectsorghumen_US
dc.subjectinsect-plant interactionsen_US
dc.subjectbiotypesen_US
dc.titleCharacterization of Schizaphis graminum (Rondani) (Homoptera: Aphididae) biotype evolution via virulence and fitness on Sorghum bicolor (L.) Moench and Sorghum halepense (L.) Persoonen_US
dc.typeBooken
dc.typeThesisen
thesis.degree.departmentEntomologyen_US
thesis.degree.disciplineEntomologyen_US
thesis.degree.grantorTexas A&M Universityen_US
thesis.degree.nameDoctor of Philosophyen_US
thesis.degree.levelDoctoralen_US
dc.contributor.committeeMemberBurd, John D.en_US
dc.contributor.committeeMemberWoolley, James B.en_US
dc.contributor.committeeMemberBernal, Julio S.en_US
dc.type.genreElectronic Dissertationen_US
dc.type.materialtexten_US
dc.format.digitalOriginborn digitalen_US


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record