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Abstract
Greenbug, Schizaphis graminum, biotypes (Rondani) were obtained from laboratory colonies maintained by USDA-ARS, Stillwater, Oklahoma, as well as Texas and three locations in Nebraska. Since the outbreak of greenbug in Great Plains, ten biotypes have been defined based on their ability to damage different host plants and resistant to insecticides. The biotypes are morphologically indistinguishable.
Several polymerase chain reaction (PCR) techniques were used to characterize seven greenbug biotypes. PCR procedures amplified DNA with 34 of the 100, 10 base primers tested. Results of four primers (RAPD-PCR) produced unique amplification products and separated all biotypes by distinct size differences in amplified fragments, and also produced unvarying patterns in field-collected biotype E from Texas and Nebraska.
Amplified mitochondrial DNA (mtDNA) was cloned, sequenced, aligned, and subjected to nucleic acid analysis using endonuclease restriction enzymes. Ten restriction sites, derived from two regions, identified one, two, or three biotypes individually or in combinations.
Nucleotide sequences of amplified DNA segments (742 base pairs) were obtained from all seven greenbug biotypes. There were more nucleotide differences in the ND$\sb4$ (23%) and cytochrome b-ND1 region (8%) than ND1-large rRNA region (3%).
The average percentage sequence divergence estimates among the seven greenbug biotypes is P = 4.84%. Biotype H was the most changed of all biotypes. The amount of sequence divergence found in mitochondrial data suggests a long divergence ($>$2.4 million years) rather than recent origin.
