Genetic diversity in natural populations of Greenbug, Schizaphis graminum (Rondani) /
Insects often develop new virulent biotypes. It is estimated that 50% of recognized insect biotypes on agricultural crops are of the family Aphididae. Development of biotypes in greenbug, Schizaphis graminum (Rondani), is well documented. Characterizing the extent and distribution of genetic vari...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2001.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=725921631&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Insects often develop new virulent biotypes. It is estimated that 50% of recognized insect biotypes on agricultural crops are of the family Aphididae. Development of biotypes in greenbug, Schizaphis graminum (Rondani), is well documented. Characterizing the extent and distribution of genetic variability in natural populations of greenbug will enhance management practices. Phylogenetic analyses of three mitochondrial (mtDNA) gene fragments were used to examine evolutionary relationships among biotypes and greenbug individuals collected from the field. From these analyses, no clear evolutionary relationship was determined among biotypes or individuals collected from the field. MtDNA haplotype diversity was greater among biotypes (h=0.9) than among greenbugs collected from the field (h=0.78). Microsatellite loci were used to assess genetic diversity in natural populations of greenbugs. There was no population subdivision among greenbugs from three regions of Texas. Fixed heterozygosity was observed at 80% of the microsatellite loci. A common clonal type was observed in 55.7% of greenbug individuals. Forty-four percent of alleles observed were private alleles. The pattern of heterozygosity observed, the lack of regional population subdivision, and gene flow estimates from private alleles indicate significant migration and show that greenbugs in Texas are from parthenogenetic (anholocyclic) lineages. This study helps confirm the belief that greenbug biotypes have not shared an ancestral maternal lineage within the past 0.3-0.6 million years. |
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| Item Description: | Vita. "Major Subject: Entomology". |
| Physical Description: | xi, 109 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 72-84). |